California Columbus Day Firestorm

Although October is usually known for Atlantic hurricane activity and sometimes a second peak of severe weather that can occur as summer wanes, this month is also the height of the California wildfire season, which typically runs from spring to late fall. Unfortunately, it should be no surprise that this western wildfire season has been one of the worst on record – in May, I briefly mentioned that it could likely get ugly. So far, the U.S. budget for fighting wildfires has topped out at $2.35B, which does not include the recent fire-fighting efforts. Year to date, the wildfires have burned 8.5 million acres across 51,000 fires.

National Interagency Fire Center Stats https://www.nifc.gov/fireInfo/nfn.htm

California has had nearly five years of extreme drought followed by record rains last winter, producing a bumper crop of grasses and fine fuels on top of drought-dried, diseased and stressed heavier fuels. Fuel analysis ahead of the Columbus Day firestorm were at all-time record dry levels. Like many previous firestorms, when this situation is combined with the Santa Ana/Diablo wind events that occur every year and the right weather conditions, any fire ignitions that occur will cause fire explosions that race along the landscape.

Columbus Day firestorm cause
The Oakland Hills, CA fire of 1991 had been the seminal fire event that changed the insurance industry’s perspective on wildfire loss, much like Andrew did with hurricane loss. However, the Columbus Day firestorm will no doubt be viewed as a considerable event in a growing list of large wildfires that have impacted the insurance industry in recent decades. There are very few natural catastrophic events that result in such destruction as a wildfire, although the effects of an EF 5 tornado are similar. However, the damage from wildfires is often worse since everything is reduced to ash, with virtually nothing being recoverable. With EF 5 tornado damage, some personal belongings can usually be salvaged. This is often not the case in fires, which make them a different beast entirely.

 

The exact cause of most of the Columbus day fires are still under investigation, it is most likely they were either human triggered or a result of sparking from down power-lines due to the high winds that occurred.  No thunderstorms were in the area so that can be ruled out at this time.

The weather conditions that created the firestorm are often referred to Diablo winds, which follow the same type of pattern as Santa Ana winds – the northern and southern California areas simply use different names for the same weather phenomenon. The increased fire conditions start when a big ridge of high pressure sets up over the Great Basin in the inter-mountains west from Utah to Nevada. This causes air to flow from east to west across California, from high elevation to sea level. It is at this point that the first law of thermodynamics takes over. As the air is compressed when moving from a higher elevation to a lower elevation, it heats up. During this movement of air, the moisture in the air does not change much, but with a rising temperature, a large disparity between the temperature and the moisture in the air is created and pushes the relative humidity to very low levels. As the air gets compressed, it moves faster, forced over mountains and pushed through canyons.

How hot, dry downslope winds form, like the Diablos and Santa Anas. Source: The Washington Post

Leading up to Monday’s firestorm, the pressure at Reno, NV at 9:00 p.m. on Sunday, October 8 was at 1020 mb, and the pressure at Napa, CA was even lower at 1008 mb. This difference in pressure was the catalyst for the Diablo winds, which in some places gusted to 79 mph.

Notice how fast the winds picked up in the evening hours on October 8th. This is scary as most people were in bed when these fires broke out so they have little to no warning to leave.

As of Thursday morning, 22 wildfires were burning across northern California, which is an increase from the 14 that were originally reported on Monday. Looking ahead, until there is a major North American weather pattern change, the Diablo/Santa Ana wind events could occur every few days. With a La Nina building in the Pacific Ocean, the long-term prospects for rain are slim across the state, particularly in the south. A large subtropical ridge is forecasted to be in the area until at least next week, as moisture-laden storms rumble ashore over the Pacific Northwest and keep California dry. Currently, the National Weather Service has a Red Flag Warning in effect until Thursday the 12th until 5 pm PDT, which means that critical fire weather conditions are either occurring now or will be shortly. The combination of strong winds, low relative humidity, and warm temperatures can contribute to extreme fire behavior.

Although the wind is not expected to be as strong as observed earlier in the week, this warning is due to the increasing north to northeast wind and low humidity that will generate critical fire weather conditions again. New and existing fires could rapidly spread during this time period.

Measuring insured loss of Columbus Day Firestorm
The latest figures from the Associated Press suggest that the Columbus Day firestorm destroyed at least 3,500 homes and businesses. PCS has issued two separate catastrophe bulletins which cover the Atlas Fire near Napa, CA and the Tubbs Fire near Santa Rosa, CA. However, these are just two of the most destructive fires across the region. For example, the Canyon Fire 2 near Anaheim Hills is now 60% contained, but burned 26 structures, damaged another 36, and continues to threaten 3,500 structures. Therefore, the wildfire losses will be more far-reaching than PCS has reported, since it only designates losses of $25m or more. For the latest information on these fires and their containment levels, please see Cal Fire Incident Information, which gets updated as often as needed.

Where and how to get fire information

Current location of active fires according to Cal Fire

 

This is an area in North Santa Rosa around Coffey Park. As shown many of these structures were burned to the ground. Zillow suggest many of these structures are worth at least $400. Locations outside of town in the foothills are easily double in value. It should be noted this is just the home value not counting the total loss of the contents of these structures.

If the AP estimate of at least 3,500 homes burned is correct, then as a combined event, this will be one of the largest wildfire insured loss events in U.S. history, if not the largest. Below is a chart illustrating some of the most damaging North American wildfires and the estimated insured losses if they were to occur today.

List of the largest damaging wildfires in the USA in recent time, ranked by # of buildings destroyed. The Oakland hills fire of 1991 was 2,900 structures. So, in aggregate, the ongoing Columbus Day Fires now exceed 1991 Oakland Hills fire. Notice how many of the CA wildfire have occurred in October.  Note most fires with over 2,000 structures are over $2 billion in insured loss.

 

BMS iVision has a direct feed of the current fire perimeters. These perimeters use the IRWIN (Integrated Reporting of Wildland-Fire Information) system. Perimeters are collected in the field by a variety of means, including infrared flights, and by using a GPS unit to map the perimeter. BMS clients can use these maps to see if any risks are exposed to the fires.

With the understanding that the Tubbs and Atlas Fires had a large impact on the expensive Napa/Santa Rosa areas, it is assumed that the losses will be much higher than past fires such a the Oakland hills fire of 1991 because of the effects on commercial property. At least 14 commercial wineries, a Hilton hotel, a Kmart, a McDonalds and even the historic Fountaingrove Round Barn have been destroyed by the fires.   Many other commercial properties have been destroyed and if not destroyed will have business interruption. Smoke related clean up that could also work its way into the insured losses from this event even if the structure did not have damage.

Catastrophe Model can’t come fast enough
Many areas of California have a long and active wildfire history. Typically, about 10,000 wildfires are ignited in California every year. Of those, only about 20 cause property losses and fewer still cause losses large enough to be designated a catastrophe. But when conditions are right, the losses can be truly catastrophic, as we saw with the Columbus Day firestorm. Many areas of the state are characterized by narrow valleys surrounded by steep, hilly terrain. The interface between wildland areas and development, exposed residents and businesses is increasing the wildfire risk. In the last several decades, the combination of firefighting technology, fire suppression policies, environmental regulation, and development trends has led to increased fuel loads, greater occupancy of remote areas and greater potential for catastrophic wildfires. This is a trend occurring all across the country.

The risk for wildfire is increasing across all 50 states, with the costly wildfire outbreaks in Texas, Tennessee, and Colorado being recent examples, yet the insurance industry still lacks the access to a full probabilistic wildfire loss model for the entire U.S. For years, the insurance industry has had access to assess the wildfire hazard from various sources and, of course, there are several tools built into the catastrophic loss models that help with accumulation management. Some catastrophic modeling companies have developed loss models for California only as a result of the high losses that occurred after the devastating fires that hit southern California in October and early November 2007. However, limited updates have been made since the initial release.

The good news is that modeling companies are currently working on U.S.-wide probabilistic wildfire loss models. However, as we have shown, wildfires can be very complex, with embers traveling several miles and igniting new fires. The models that are in development will need to incorporate the newest landfire fuel databases that seem to change constantly with growing vegetation across the U.S. These models need to have fire-spread algorithms and account for human fire suppression decision-making through stochastic simulations of man-made fire breaks. They should also model the possibility that a wildland-urban interface fire will transform into an urban conflagration, such as we saw in the Santa Rosa area.

To understand wildfire behavior, the models will need to include historical data on average hourly wind speed and direction based on weather stations, but those might not address the varied microclimates that can occur in a complex terrain. Of course the models will need to account for a wide-range of residential and commercial constructions, including the presence of mitigating factors, such as fire-resistant roofing and siding materials, which are becoming more and more popular.

Several million dollar homes in the Fountaingrove area northeast of Santa Rosa were destroyed. Notice the lack of defensible space around many of these structures.

Also, as we have seen in past wildfires, defensible space and vegetation control have a huge impact on site-specific loss. In fact, fire-wise communities, resilience efforts and research by the IBHS are helping to minimize wildfire loss.

BMS Tropical Update 10/07/2017 11 AM CDT

Last night at 11:30 PM EDT, the NHC upgraded Nate to hurricane status about 18 hours ahead of when it was originally predicted to become a Category 1 storm. This is now the first time since 2012 that more than nine hurricanes have developed in one season. This is also the first time since 1893 that nine Atlantic named storms have consecutively reached hurricane status (Franklin-Nate). But, it should be noted that, obviously, vastly different systems are now in place than in the 19th century, which means weaker systems likely were missed before satellite and aircraft observation.

Since Nate is now a hurricane, there is no doubt it will continue to strengthen and be a Category 2 storm as it makes landfall around Gulfport or Biloxi, MS.  There is even a possibility that Nate could be a major hurricane at landfall if it undergoes rapid intensification over the next 12 hours. However, this is more difficult to predict with a fast-moving storm like Nate. Regardless, a stronger storm at landfall will increase the insured losses expected from this event, as yesterday’s estimates were based on a weak hurricane or tropical storm at landfall.

Nate continues to improve its satellite presentation as it cruises north/northwest this morning. With winds at 90 mph, Nate has maintained its gradual strengthening overnight. Nate is located 180 miles south/southeast from the mouth of the Mississippi River. Intense thunderstorms have wrapped all the way around the center, and distinct spiral bands have developed both northwest and southeast of the center. Strong outflow is noted in all directions, which indicates low wind shear. It will be a race against time to see how much Nate can intensify before it moves onshore and weakens.

Nate’s Landfall Impacts
The general landfall area continues to narrow with an expected location between New Orleans, LA and Mobile, AL with the consensus of a landfall location near Gulfport or Biloxi, MS. The main question continues to be: how much strengthening can happen in the next 12-15 hours before landfall?  Nate is already close to a Category 2 hurricane.

Wind Impacts
What we do know is based on observations from the hurricane hunter – the overall wind structure is quite lopsided. This is likely due to Nate’s fast forward motion of 26 mph. This will cause Nate to have a small core of hurricane-force winds only to the northeast of its center.

Cross section of Nate showing pressure and wind. The wind profile clearly shows that the stronger winds are to the right side of the storm with weaker winds on the left side of the storm center. This is likely due to Nate’s rapid forward motion.

There will be little, if any, hurricane force winds to the west of the storm which would be good for New Orleans and cities to the west side of the landfall location. Tropical storm-force winds will extend well east into Alabama, and possibly the Florida panhandle, as Nate makes landfall around 7 pm CDT.  This is also much sooner than expected based on Nate’s rapid forward motion.

Because of Nate’s swift forward motion east of its center, locations further inland could experience higher winds, versus a typically slower-moving storm, as Nate will be further inland before it weakens over land.

As with all landfilling hurricanes, weak tornadoes are the primary threat away from the center of the storm. However, due to the incredibly warm, moist nature of hurricanes, hail is not expected to be an issue.

BMS iVision allows clients to run risks to better understand various impacts from Nate. This is the 3 sec gust wind speed, which shows only coastal areas will see the strongest winds. However, tropical storm-force winds will be widespread, particularly along the eastern side of the storm. Given current fwd speed (26 mph), concerned about higher inland wind potential in southeast as well.

 

BMS iVision allows clients to run risks to better understand various impacts from Nate. This is the 1 minute wind speed, which shows only coastal areas will see the strongest winds. However, tropical storm-force winds will be widespread, particularly along the eastern side of the storm. Given current fwd speed (26 mph), concerned about higher inland wind potential in southeast as well.

Surge Impacts
As with any northward moving hurricane, the onshore winds will cut across a wide swath of the Northern Gulf Coast from southeast Louisiana to the Florida panhandle. These onshore winds will pile water up against the coastline, resulting in storm surge flooding. As I mentioned yesterday, the slope of the Gulf Coast is quite flat, meaning that it doesn’t take much storm surge to cause issues. The factor that could limit the amount of storm surge is Nate is an extremely fast-moving system, meaning that it won’t have prolonged winds along the shore, thus limiting the storm surge. Currently, Mobile Bay seems to be the target for the highest storm surge amounts, which could be close to nine feet. One unfortunate coincidence is that the moon is full and high tide will occur around midnight locally, which coincides with landfall and peak storm surge, maximizing coastal surge.  At this time this does not look to be a big surge event for New Orleans as higher impacts should be greater in MS and AL coastal locations.

NHC Potential Storm Surge Flooding Map. These will get updated here: http://www.nhc.noaa.gov/refresh/graphics_at1+shtml/091740.shtml?wsurge#contents

Rainfall Flooding Impacts
Rainfall will be heavy as this system moves onshore, especially near the center, but could extend well east of the center to the Florida peninsula. As with the surge, the fast motion of the storm precludes any extreme impacts from rainfall, but flooding should be expected whenever 3-8″ of rain occurs. Also note that the heavy rain will continue north into the Appalachians.

Forecasted rainfall over the next 5 days. This shows up to 8″ of rain is now forecasted for parts of the eastern slopes of the Appalachian Mountains. This could create isolated flash flooding.

Insured loss
Over the last few days, I have provided a few analogs that were from tropical storms like Lee in 2012 to Cindy in 2005 and even Isidore in 2002. All of these analog events resulted in insured losses of under $300 million. However, with Nate now likely a Category 2 at landfall, a comparison to a higher analog storm such as Ethel in 1960 seems more appropriate, which today would be closer to a billion dollar insured loss event. Fortunately, it’s highly unlikely Nate will be worse than Opal was in 1995, which today could be close to a 3 billion dollar insured loss event. The intensity at which Nate makes landfall will dictate the amount of insured loss, but an insured loss closer to a billion dollars is more credible with a stronger storm at landfall.

Next Tropical Trouble

A strong suppressed Kelvin wave is forecast to push across the Atlantic this week. After Nate, there is a good chance of a lull in activity until late Oct.  There is a chance that  something manages to spin up in the sub-tropics, which are less impacted by suppressed Kelvin wave passages.  Overall Nate looks to be the last U.S. landfalling hurricane at least for the next two weeks.

 

BMS Tropical Update 10/06/2017 12 PM CDT

Nate’s overall structure is finally beginning to improve, based on satellite imagery and observation from a hurricane hunter aircraft. Strong thunderstorms have developed over/near the center of the system, and organized outflow is developing in the upper levels. Banding structures are now beginning to organize around the system. This is a marked change from late yesterday afternoon when thunderstorms were disorganized and weak. The storm is now over the warm waters of the western Caribbean and further intensification is expected.

Nate’s track forecast continues to wobble around, but the general expectation remains consistent. The storm will either make landfall on, or barely miss, the Yucatan Peninsula today before tracking north-northwest into the Gulf of Mexico. A turn north and then northeast is expected on Saturday before a landfall somewhere between Lake Charles, LA and Panama City, FL around 1 am Sunday morning. The storm’s remnants will then race northeast and bring heavy rains to the Mid-Atlantic and parts of New England.

Nate’s Forecasted Intensity
The biggest question mark continues to be just how strong Nate will be at landfall. I focused on this in yesterday’s update, but it is worth discussing again since intensity is key to the overall insured impact at landfall.

As I have been showing, warm waters and low wind shear are the only two factors that suggest strengthening may occur. Dry air and land interaction with the Yucatan Peninsula are the two opposing factors that may cause Nate to be weaker as it moves into the southern Gulf of Mexico. It appears that the dry air will be the primary inhibiting factor in terms of Nate’s intensity prior to landfall in the U.S. The last several runs of the models show dry air wrapping into the system from the west and south as it moves closer to New Orleans tomorrow. If this dry air can wrap into the inner core of the system, it will keep a lid on Nate’s intensity. However, if an inner core can organize today before the dry air really kicks in, and if interaction with the Yucatan doesn’t disrupt this inner core, the storm may be able to continue strengthening despite the dry air.

The majority of ensembles suggest that Nate will have a pressure of 988 – 999 mb at landfall, which is what we would see in a weak hurricane or tropical storm.

Nate is expected to make landfall in 48 hours, so note the pressure forecast from the ensembles during this forecast time period.

Nate’s Forecasted Landfall

The last few model runs of the GFS suggest that land interaction with the Yucatan will be less of a factor as the track has shifted back to the east over the last 24 hours. This may cause Nate to be stronger than forecasted this afternoon, as it tracks close to the Yucatan but not over the Yucatan.

Notice over the last 12 hours a shift in Nate’s track (Green Line) versus what the NHC had forecasted (Red Line).  This may allow Nate to track between the Yucatan and Cuba and would limit land interaction.

 

Last night’s multi-model European, American, and Canadian ensemble’s strike probabilities for Nate.

The landfall location currently appears to be near Gulfport, MS, as the models shift back east away from a New Orleans landfall.  However, the range of possible landfall locations fall somewhere between Lake Charles, LA and Panama City, FL just before midnight on Sunday morning. I would not be surprised if the models continue to shift a landfall location to the Florida Panhandle.

Landfall Impacts
Nate’s impact will extend well away from the center regardless of the inner core’s organization, especially to the east side of the storm. I expect to see strong thunderstorm activity in Nate’s outer bands as it makes landfall, with the heaviest storms moving onshore along Florida’s entire west coast, hundreds of miles east of the center. Gusty winds, heavy rains, and tornadoes will be concerns in these outer bands.

This simulated satellite forecast from the ECMWF shows strong thunderstorm activity in Nate’s outer bands moving onshore in Florida.

Even the weakest of hurricanes can cause storm surge along the northern Gulf Coast. Note in the image below the wide expanse of onshore winds from New Orleans all the way east to the Big Bend of Florida. Even if these onshore winds barely reach tropical storm-force, they will pile up water along the coast. Due to the very flat slope of the Gulf Coast, even a small rise in water level is enough to cause flooding concerns.

The extent of the storm surge will depend on the storm’s intensity, but coastal locations vulnerable to storm surge flooding will likely see at least some level of storm surge. Mobile Bay, AL, Gulf Port, MS, Biloxi, MS and Pensacola, FL are all expected to see at least three feet in storm surge, with some isolated locations expected to see six feet.  Also worth noting that landfall will be close to High Tide, which means water levels will be even higher usual.

NHC Potential Storm Surge Flooding Map. These will get updated here: http://www.nhc.noaa.gov/refresh/graphics_at1+shtml/091740.shtml?wsurge#contents

Several inches of rain may also cause freshwater flash flooding, but the storm’s fast forward motion should preclude any devastating flooding like we saw with Harvey. The map below shows total rainfall for the next 5 days across the U.S. Note the swath of higher totals along Nate’s forecasted path all the way up into New England, where the storm’s remnant low will enhance rainfall associated with a cold front.

Forecasted rainfall over the next 5 days. This shows up to 8″ of rain is now forecasted for parts of the eastern slopes of the Appalachian Mountains. This could create isolated flash flooding.

 

BMS iVision allows clients to run risks to better understand various impacts from Nate. This is the 3 sec wind gust in MPH, which shows only coastal areas will see the strongest winds. However, tropical storm-force winds will be widespread, particularly along the eastern side of the storm.  Given current fwd speed (21 mph), concerned about higher inland wind potential in southeast as well.

 

Potential For Insured loss

The insured loss will depend on the intensity at which Nate makes landfall. It is likely that only minor insured losses will occur if Nate makes landfall as a Category 1 hurricane along the Gulf Coast (under $1B in insured loss). The best analog in recent memory would be Hurricane Cindy 2005 which made landfall over the Mississippi River delta as a Category 1 hurricane, tracking north-northeast with a second landfall just west of Biloxi, MS.  Cindy caused roughly $200M (in 2016 dollars) in insured loss across Louisiana, Mississippi and Alabama. Another analog might be Isidore 2002, which, in 2016 dollars, would have caused $279M in insured loss. Arlene 2005 made landfall as a tropical storm in a similar area but did not cause a PCS loss event.

 

BMS Tropical Update 10/05/2017 10 AM CDT

Tropical Depression 16 has been upgraded as of this morning to Tropical Storm Nate, but it remains poorly organized as it interacts with the Central American coastline. Nate’s center is now just off the Nicaraguan coast. A well-defined core has not yet emerged at this stage, and any banding features are weak and transient. Unfortunately, environmental conditions are favorable for that to change in the coming days.

Forecasted Intensity
Water temperatures remain extremely warm in the western Caribbean Sea, as well as in the southern Gulf of Mexico. Tropical systems need ocean temperatures above 80F to develop and thrive, and the water in Nate’s path is well over that mark in the range of 84F to 87F.

Current Sea Surface Temperature analysis suggests waters warm enough to support rapid intensification. However, warm water is just one ingredient that is needed.  Temperatures above are in degrees Celsius.

Wind shear over the next few days will be light. Nate is expected to be located over the western Caribbean Sea by tomorrow, between Honduras and the Yucatan Peninsula. Wind shear values in this area, excluding those generated by the storm’s circulation, are near zero. Nate will have little to no trouble with wind shear as it moves northwest, and this combined with the warm water in its path leads me to believe that strengthening will occur.

The amount of land interaction that Nate has with the Yucatan Peninsula as it moves north will be critical in determining how strong Nate will be when it enters the southern Gulf of Mexico. Another potential inhibiter to Nate’s future intensity could be a bit of dry air it encounters as it approaches the Yucatan Peninsula and moves into the Gulf of Mexico. Notice the dry air stretching from Guatemala to the NE Gulf.

Current water vapor showing the amount of water in the air. The brown in the image above shows dry air in the path of Nate in the central Gulf of Mexico.

 

This is the 700 mb water vapor from the American Model initialization. This shows dry air is even at lower levels of the atmosphere, which is also backed up by the water vapor image above.

This is the dry air inhibiting development of the tropical wave near Florida this morning, and it may put a lid on how strong Nate can become as it enters the Gulf of Mexico.

Therefore, the intensity forecast remains even more uncertain than the track forecast at this time. If the storm can put together an inner core and keep the dry air at bay, intensification into a mid-grade hurricane is possible. If the storm’s inner core doesn’t become organized, or if dry air is able to work into the core, the system will likely remain either a strong tropical storm or a weak hurricane until landfall. However, as discussed yesterday, weaker systems tend to strengthen right up until landfall in the Gulf of Mexico, which appears to be possible with Nate.  Some model guidance is still suggesting that a Category 2 hurricane is possible at landfall.

However, given the inhibiting factors of the Yucatan Peninsula, the dry air and some increase in wind shear that is forecasted right before landfall, today there is a much lower possibility of Nate becoming a major hurricane prior to landfall, and it is more likely that it will be a weak hurricane or even a tropical storm at landfall.

Forecasted Landfall

Nate’s forecasted path has shifted slightly west over the last 24 hours, although there remains some uncertainty as to exactly where the storm will make landfall.  At this point, anyone from the Big Bend region of Florida over to western Louisiana should be watching this system closely.  The current model consensus takes the center of the storm near New Orleans, which is a perfectly reasonable scenario.

 

Current morning run of the American GFS model ensemble plot. The black line is the NHC OFCL forecast, which is east of most of the model guidance from this model.

 

Current morning run of the European ECMWF model ensemble plot. The black line is the NHC OFCL forecast, which is east of most of the model guidance from this model.  Since the GFS and ECMWF are all west of the NHC official forecast, I think the NHC will keep adjusting the landfall location west.

Regardless of landfall location, the model guidance on the timing of Nate’s northward track is now in better agreement with it making landfall on the Gulf Coast on Sunday morning. It should then weaken as it races northeast across the Appalachian Mountains early next week as a much weaker tropical system, bringing some much needed rain to the area. The fast movement of the system at this time is not conducive to a large inland flood threat.

Current rainfall forecast suggesting that the upward eastern slopes of the Appalachian Mountains will receive the most rain into early next week.  The amounts are all less than 5″ at this time.

Insurance Industry Impacts
Until we know Nate’s strength as it moves into the Gulf of Mexico, it is too early to determine storm surge impacts and potential insured loss. However, even a weak tropical storm such as Tropical Storm Lee that made landfall near New Orleans in 2011 caused insured loss along the Gulf Coast and inland states.

 

BMS Tropical Update 10/04/2017 9 AM CDT

Despite the lull in new activity since September 16, the hurricane season is not over yet. This is not a surprise, as even the very active year of 2005 had periods of inactivity. As I last talked about in my September 25 update, the next area to watch for tropical development is the southwest Caribbean Sea. Just as expected, the NHC is now expected to label an area of low pressure in the Southwest Caribbean Sea Tropical Depression 16 (TD 16) at 11 AM EDT.

 

The NHC is expected to send aircraft reconnaissance into this developing area of low pressure later today, and if they find strong enough winds within the embedded thunderstorm activity, it could become Tropical Storm Nate later today.

As I talked about back on September 18th, the Main Development Region (MDR) tends to shut down as October approaches and new named storm development becomes more likely to form in the western Caribbean. In fact, if you look at the landfall locations for all U.S. hurricanes during the month of October since 1851, the Gulf of Mexico coastline and Florida’s west coast have been heavily favored areas.

Landfall locations for all continental U.S. hurricanes during October since 1851. West coast of Florida gets hit fairly often. Source; CSU

Future Track of TD 16
There is growing consensus that TD 16  will track northward into the Gulf of Mexico this weekend. In fact, some of the guidance suggests a hurricane could be in the Gulf of Mexico by this weekend with a landfall as early as Sunday morning.  The model guidance is suggesting a landfall location across the eastern Gulf of Mexico, so the Texas coastline has a very low probability of landfall at this point. Florida’s panhandle has the highest probability, which goes along with the climatology shown above.

Last nights multi-model European, American, and Canadian ensemble, strike probabilities for TD 16.

It is too early to provide insured loss guidance, but we know that Hurricane Hermine caused $205 million in insured loss to the region last year.

Future Intensity of TD 16
The key to how intense TD 16  becomes will be how much land interaction it sees as it moves northward over the next few days. What’s more troublesome with the current ensemble guidance above is that many of the members are showing a track of free reign over very warm water with little land interaction.

The average sea surface temp in the area Nate is expected to develop is 84 °F a major concern for hurricane development.

The area Nate is developing is some of highest tropical cyclone heat potential in the world right now.

This would mean a stronger storm as it tracks northward. A major hurricane cannot be ruled out at this time, although most of the early guidance is keeping this area of low pressure from becoming anything more than a tropical storm or minimal hurricane as it tracks into the Gulf of Mexico this weekend.

However, the ingredients for rapid strengthening are there, with a low wind shear environment and plenty of ocean heat content and warm sea surface temperatures.

The other key to the future intensity at landfall might be just how strong the storm has become as it enters the Gulf of Mexico. Stronger hurricanes often tend to weaken just before landfall, as the shallow continental shelf allows for colder water upwelling ahead of a hurricane and deprives it of an important energy source. Lili 2002 is the most extreme example of this, where it went from Category 4 to Category 1 in only 12 hours. There are certainly exceptions to this rule though, such as Camille 1969, Eloise 1975 and Frederic 1979, which were all major hurricanes that strengthened right up until landfall.

If a weaker hurricane is in the Gulf of Mexico, however, strengthening is almost always common right up until landfall, much like we saw already this year with Harvey.

BMS Tropical Update 9/25/2017 12 PM CDT

Maria is weakening at a greater pace than previously thought, and it will now likely have little impact on the insurance industry as it stays a safe distance from land and begins to race across the Atlantic on Wednesday. This is great news and should provide the insurance industry with a much needed break before the next area of tropical trouble shows up in the southwest Caribbean late next week.

Maria Final Forecast
Today’s main weather story continues to be Maria which is a weak Category 1 hurricane 315 miles southeast of Cape Hatteras, NC.  She is moving north at a slow 7 mph  towards the North Carolina coast. Satellite imagery shows Maria’s inner core being ripped apart by dry air and wind shear. A large, cloudless area now exists where you’d typically expect intense thunderstorm activity to be. Dry air being forced into Maria’s inner core by strong winds aloft (wind shear) is the culprit, and its weakening influence won’t let up anytime soon.

Notice the lack of deep convection on in the center of Maria and on the west side of the center.

Another factor, as discussed yesterday, is that Maria is tracking over the cold wake of Hurricane Jose, which has also clearly helped in Maria’s deterioration.

Sea Surface Temperatures off the North Carolina are below 26 degrees C (78.8 F) which is not conducive of tropical convection. This is a direct result of the cold wake left from Hurricane Jose last week. Over the next 12 hours Maria will be moving over this colder water which will further weaken Maria into a tropical storm.

The confidence in Maria’s track forecast continues to improve with there now being very little probability of landfall (less than 20%). However, a weakening ridge of high pressure over New England will guide Maria close enough to the Outer Banks that I expect some of these coastal communities could see tropical storm-force winds (40+ mph). However, with Maria rapidly falling apart, it is also very possible that these conditions will not be experienced. The biggest hazard at this time is the strong onshore wind that will pile up water on the ocean side of the northern Outer Banks and on the bay side of the southern Outer Banks. Storm surge of a couple feet in both of these areas is expected. Maria’s impact should be limited to the coastal areas, however, as the inland areas of North Carolina likely won’t even see rain over the next few days.  At this time I don’t expect that Maria to cause enough PCS loss for North Carolina to be designated as a loss state, but her Puerto Rico impacts have already placed her in the record books.

As Maria moves slowly northward, it will continue to weaken and perhaps even stall just east of the Outer Banks as the steering currents weaken. An approaching upper level trough that is currently moving across the central plain states should then shoot the storm rapidly out to sea at the end of this week.

Next Tropical Trouble
The southwest Caribbean certainly seems to be the next area to watch for tropical development. The following is a look at the ECMWF Probability of Tropical Depression formation for Thursday, October 5.

The long range ECMWF ensemble are sniffing out a general area low pressure in the Western Caribbean Sea late next week.

In the meantime, enjoy the lull in tropical activity. I’ll provide new updates if I feel there is any threat to the insurance industry.

BMS Tropical Update 9/24/2017 10 AM CDT

Maria Still Has A U.S. Landfall Threat

I just wanted to provide a quick weekend update on Hurricane Maria and discuss the final end game that will play out this week as it slowly tracks northeast of the Bahamas.  Maria is currently located 300 miles northeast of Great Abaco Island and moving north at 9 mph as a Category 2 hurricane.  Maria is expected to maintain a north to northwest direction of travel until Wednesday of this week.  As suggested in my last update, the National Hurricane Center’s (NHC) cone of uncertainty has expanded to cover the Outer Banks of North Carolina, which means a U.S. landfall is still possible.

Track Guidance

Although the NHC cone of uncertainty is highlighting the risk of landfall along the North Carolina coastline, it seems that there is a 50/50 split in the number of ensemble members from the GFS and ECMWF that have Maria making landfall as opposed to not making landfall.  The landfall probability is currently as high as 50%.  As I mentioned back on September 18th, the end game forecast for Maria would be complicated due to Hurricane Jose, which has now dissipated into open ocean 200 miles southeast of Nantucket, Massachusetts.  Jose has no doubt spared the U.S. from yet another major hurricane landfall this season.

 

 Ensemble Guidance

The ensemble guidance below has been trending to the west with a higher and higher likelihood of landfall.   This trend needs to be watched carefully for a possible landfall on Wednesday this week.  However, after Wednesday, a large scale upper level trough is expected to push Maria out across the north Atlantic.

 

GFS (American) ensemble forecast showing a 40% chance that Maria could track over the Outer Banks of NC before a sharp right turn out to sea.

 

ECMWF (European) ensemble forecast showing several forecasts that track inland to North Carolina before a sharp right turn out to sea. Currently there is a 60% chance of landfall along the Outer Banks.

Intensity

As mentioned, Jose likely has steered Maria away from a southeast U.S. landfall as a major hurricane.  Jose’s slow track will likely also help in decreasing Maria’s intensity later this week, as Maria is expected to follow a similar track to Jose over cooler waters.  Jose has also caused upwelling in these waters, and this is making it more difficult for Maria to maintain its intensity.  I expect fluctuations in Maria’s intensity over the next 36 hours until it reaches some of that colder water.  Also, around Wednesday of this week, wind shear should start to increase from the upper level trough, which should decrease Maria’s intensity.  At this time, I expect Maria to only be a Category 1 hurricane as it moves toward the North Carolina coastline on Wednesday of this week.   It should be noted, however, that Maria is a large cyclone and the associated tropical storm-force winds could eventually reach the North Carolina coastline even if Maria does not make landfall.  It should also be noted that the strongest winds will be on the right side of the storm as it tracks towards North Carolina, so those winds would likely stay off shore.

Insured Loss

A few worst-case scenarios at this time might be Alex 2004 (which did not trigger a PCS Event) and Ophelia 2005, which triggered a $35 million insured loss event.  More recently in 2014, Arthur made landfall on the Outer Banks as a Category 2 hurricane.  Arthur is also the first Category 2 hurricane to make landfall in the U.S. and not be registered as a PCS insured loss event.  At this stage, it’s difficult to understand what type of insured losses to expect from Maria if it tracks close enough to the North Carolina coastline.  Given the current forecast, it should be expected that tropical storm-force winds may be experienced along coastal sections.  Hurricane conditions may be experienced on the Outer Banks, but this will depend on how close Maria tracks to the Outer Banks.  However, as noted above, the strongest winds would still be to the right of the storm center and away from the coastline.  I do expect some areas of the Outer Banks to experience storm surge of up to 8 feet, which could flood some parts of the Outer Banks.

Expected storm surge at Duck Pier, NC showing a storm surge as high as 6 feet.

Next Tropical Troubles

It is that time of year where the African originated storms shut down, and given the current surge of dust off Africa, this seems to likely be the case for at least the near future.

Dust and dry air off Africa now dominate the region

Without any new named storm development since September 16th and with Maria expected to dissipate out to sea later this week after a close interaction with the North Carolina coast, we will have a lull in this very busy season.  Even the busy 2005 hurricane season had a lull, so this season is likely not done yet.  I expect the next area of tropical trouble to develop off the Central American coastline in the western Caribbean later next week, maybe around October 6th.

ECMWF Normalized sea level pressure forecast valid for October 2nd showing Maria off the coast of Nova Scotia, and possible new development off the coastline of Honduras and Nicaragua.

This is one of the very few areas that has not seen tropical activity this season.  The waters here are very warm and the wind shear is low, so the conditions are ripe for more tropical trouble here yet this season.

Current Sea Surface Temperature Anomaly Not the normal to colder than normal along the southeast coastline.

In the meantime, enjoy the lull in this 2017 Atlantic Hurricane Season once Maria turns out to sea later this week .

BMS Tropical Update 9/20/2017 4 PM CDT

2017 Atlantic Hurricane Season Records Continue To Fall

The 2017 Atlantic hurricane season, which has already been memorable, continues to create long-lasting memories which will likely be talked about for decades. The newest talking point is Maria’s landfall at 6:35 this morning near Yabucoa, Puerto Rico. Maria arrived as a top end major Category 4 hurricane with maximum sustained winds of 155 mph and a pressure of 917 mb. Maria will likely be the strongest storm in terms of pressure to make landfall in Puerto Rico since 1928 – in terms of wind, it’s the second strongest. It is also the third most intense (by pressure) U.S. hurricane on record to make landfall behind Hurricane Camille, and the  Labor Day 1935 hurricane.

The statistics and images coming out of Puerto Rico indicate that Maria will likely be one of the largest natural catastrophes the island has ever experienced in terms of insured loss. But, I won’t dive into the devastation that has already occurred on the island, which is being covered extensively, but rather focus on the uncertainty of Maria’s long-term impact on the U.S. mainland.

Maria’s U.S. Mainland Threat

The geography of Puerto Rico has had a tremendous impact on Maria’s current intensity. The infrared satellite imagery above shows that the storm’s interaction with the high mountains has resulted in weakening, with a clear eye no longer visible. Unfortunately, this makes the storm no less dangerous, as winds well over 100 mph continue to beat the island. Torrential rainfall will remain as well, with totals nearing two feet in the higher terrain. Flash flooding and mudslides will be major issues for the next few days as Maria begins to move away from the island.

As Maria moves today toward the northwest, this weakening could influence the future track of the storm over the next week which, at this point, is still uncertain. A wobble south toward Hispaniola would result in a weaker system that may allow for a track farther west in the long term. The current forecast track takes the storm just north of Hispaniola, where the effect of land interaction would be minimal, thus keeping Maria on a more northwest track away from the East Coast of the U.S. next week.

The other complicating factor is the continued influence of Tropical Storm Jose, as discussed in my Monday update. Jose has already been a named storm for 15 days, which ties it for the 10th longest named storm since the beginning of the satellite era. Jose is still a large storm and, if it were not for Maria, would be a front-page news story. However, as I previously suggested, its insured impact has been minimal and similar to that of a nor’easter.

Currently Jose is doing another small loop off the New England coastline and is expected to continue to weaken over colder water as it moves back to the west later this week.

Reposting this image as the general ideas still holds from Monday thinking on overall pattern driving the northward turn of Maria.

Maria is expected to follow this weakness in the upper level ridge that Jose has created. However, the exact movement is a bit uncertain based on Maria’s trajectory away from Hispaniola and how far west Jose actually tracks. The general model guidance currently keeps Maria away from the East Coast. I do, however, expect the western edge of the National Hurricane Center’s cone of uncertainty to be very close to the coastline of North Carolina and Massachusetts as the five-day forecast cone expands northward over the next few days.

Right now, the forecast models have a bias that sometimes curve hurricanes northward  moving the hurricane to the northeast. If there is an error, it would result in a greater correction to the west with each model run.

Current long range track ensemble guidance from the American (GFS) and European (ECMWF) models. Most ensemble members keep Maria off the East Coast of the U.S. Some members however offer up landfall options all along the Northeast Coast of the U.S.

Currently, there is a 30% chance of U.S. landfall in New England per the American(GFS) ensemble model and a lower 10% chance from the ECMWF ensemble model. It should be noted, however, that cooler water temperatures and increasing wind shear will result in weakening of Maria as the storm moves northwest and then north this weekend. It would likely only be a Category 1 hurricane north of North Carolina.

Next Area Of Tropical Troubles

This is the next area to watch. This is the forecast valid for Oct 6th suggesting low pressure will be across the Western Caribbean

The next area to watch will be the western Caribbean, as the longer range models are suggesting tropical cyclogenesis in early October.

BMS Tropical Update 9/18/2017 12 PM CDT

Although there are no current threats to the U.S. mainland, I would like to provide a brief update on the thoughts that were discussed in Friday’s Tropical Update.

Below are a few key points about each tropical system:

Tropical Depression (TD) Lee:
TD Lee is currently 1060 miles west of the Cabo Verde Islands and is a weak tropical depression. It has weakened significantly since being named a tropical storm on Saturday morning and is now battling dry air and wind shear. Lee is expected to dissipate over the next 24 hours and will not likely be a threat to the insurance industry.

Hurricane Jose
Jose is currently 265 miles east-southeast of Cape Hatteras, NC and is moving north at 9 mph. It is currently a Category 1 hurricane.

Jose continues to show signs of weakening on satellite imagery as dry air is wrapped into the circulation. It will likely continue to weaken as it moves over increasingly cold water, as discussed on Friday. It should turn into a subtropical system later this week.

The outer bands of Jose will arrive on the coast between Boston and Cape Hatteras on Tuesday morning. These bands will feature breezy conditions and light/moderate rain. Overall, there should be minimal impact on Tuesday as rain bands continue to rotate onshore.

The one area of concern that’s been a given since the beginning loop early last week are the large waves that will continue to pound all ocean facing beaches in Delaware, New Jersey, Long Island, Rhode Island, and Massachusetts. Beach erosion will be an issue for the typically at-risk areas. Additionally, astronomically high tides will fuel coastal flooding concerns for low-lying areas as persistent onshore winds push a slight storm surge into eastern Massachusetts and the Long Island Sound. Waves and surge will gradually subside on Thursday as the storm weakens.

Beyond Thursday, Jose will become trapped between two upper level systems. As a result, it will linger off the New England coast as it weakens due to the cold waters in the region. In the long range, there is a chance that its remnant moisture could loop around back into coastal New England and play a role in Maria’s long-term forecast, as discussed in more detail below.
At this time, the threat of major insured loss from Jose is low.

Hurricane Maria

Hurricane Maria, which was Invest 96L when discussed on Friday, was my biggest concern due to its track toward the Windward Islands. It is now 60 miles east of Martinique as a Major Category 3 with sustained winds of 120 mph.  Rapid intensification is still expected today and it looks like Maria could have a small eye suggesting a tight central core with very strong winds.

These continued signs of intensification are likely due to  warm waters not affected by Irma up-welling.  Richard Dixon @catinsight has put together a nice little graphic showing that there is currently little overlap across the Caribbean islands between the hurricane-force winds from Hurricane Irma and the forecasted wind swath for Maria. The overlap could occur near Puerto Rico, which will likely be impacted by Maria as a major hurricane on Wednesday of this week.


In the long range forecast, Maria still has some uncertainty not only in intensity but also with its future track. These go hand and hand. There is a chance that Maria could be weakened by the high topography of Puerto Rico, depending on its track over the island. Parts of the various ensemble model guidance from last night showed Maria moving west and dissipating over the high mountains of Hispaniola and Southern Cuba. Some model guidance also points to a Florida landfall or potentially even a track into the Gulf of Mexico. Many more ensemble members point Maria up the eastern seaboard, with impacts spreading all the way to the mid-Atlantic. Finally, the storm could recurve out to sea before impacting land. So, which of these scenarios is most likely in the long range?

All the ensemble runs from last night showing all the possible tracks for Maria. Currently there is only a 5-10% of landfall given the ensembles Map provided by Allan Huffman and models.americanwx.com

To understand that question we need to look at the bigger atmospheric pattern. The upper level forecast map from the ECMWF for Thursday shows a complex and highly amplified pattern over North America.

ECMWF forecast for this Saturday with highlights of the different features that will determine Maria’s future track.

The jet stream will be in what’s called a meridional flow pattern with high amplitude waves. This pattern is being driven by the recurvature of Typhoon Talim, which was previously discussed, and tends to cause a trough of low pressure to form along the East Coast 6-10 days later. However, it would appear that the blocking high pressure over the Great Lakes will attempt to stay in place. Jose will stand in the way from the high building back to the East. Therefore, this will likely create a weakness in the ridge. How quickly Jose can either leave the scene or weaken will have a huge impact on how quickly the ridge can rebuild, and thus will play a role in Maria’s track over the long range.

It appears at this point that Jose will be around until this weekend, which should attract Maria up to the east of the Bahamas. Maria will likely follow the path of least resistance around the Bermuda high and the weakness Jose has produced within the high pressure along the western part of the Atlantic Ocean. This would keep Maria away from the U.S. coastline. Although it currently looks like Maria will stay away from East Coast of the U.S., there is still some uncertainty in the long range. The overall forecast pattern is complex with several moving puzzle pieces that will come together later this week.

The insured impact from Maria will be high in the short-term as it will be a major hurricane when it interacts with some of the Caribbean islands yet to see impacts this year. Puerto Rico will likely take a direct hit from Maria.  The last such major hurricane was Hurricane Hugo 1989.


The insured impact in the long-term is unknown at this time, given the uncertainty in the forecast.  Currently there is only a 5 – 10% chance Maria would make U.S. landfall given the current ensemble forecasts.

Other Tropical Troubles

There is nothing else to worry about at this time off the coast of Africa.  Lots of dust and dry air and little convection over Africa.

Current Dust Layer from http://tropic.ssec.wisc.edu/

The next tropical development could occur near the coast of central America later next week, but this is with low confidence and little model support in the long range. However, this is an area to watch as October approaches, when the Main Development Region (MDR) tends to shut down and new named storm development tends to form in the western Caribbean as climatology suggests below.

Source: http://www.nhc.noaa.gov/climo/

BMS Tropical Update 9/15/2017 12 PM CDT

More Tropical Troubles

First and foremost, I had previously mentioned several times I thought the Atlantic Basin would shut down for a few weeks due to the suppression phase of the Madden-Julian Oscillation (MJO). Unfortunately, the MJO is currently in a weakened state and the large-scale subsidence is not strong enough to overcome other climate forces that are allowing for new named storm formation in the Main Development Region (MDR). In this case, it could be tied to a convectively coupled Kelvin Wave which is likely enhancing the development of new named storms in the MDR.

Data suggesting a Convectively Coupled Kelvin Wave could be the climate forcer that is allowing for development in the MDR.

So, with the understanding that the insurance industry is still in the early stages of tallying the losses from Harvey and Irma, there might be a need to inquire about additional capacity for the remainder of the year. Therefore, I want to provide a bit more detail on what to expect in terms of tropical troubles for the remainder of the month.

Jose End Game

Hurricane Jose has been on the radar since it first tracked off of Africa on September 4th and passed just north of the Leeward Islands on September 9th. It then tracked into the Bermuda Triangle where it has done a large loop. Jose is in the process of finishing its dance in the Bermuda Triangle and will slowly track northwest over the next several days.

The risk of Jose’s impact on the U.S. had been relatively low (less than 20%) until the last 24 hours. With better long-range modelling, however, we can now get a clearer picture of what the end game might entail for Jose. In fact, currently the official National Hurricane Center (NHC) track puts a good chunk of the coastal Northeast just inside the “cone of uncertainty,” which means there is now a chance that Jose will directly impact areas from the NC Outer Banks to points north, including Cape Cod, later next week.

This is the American GFS Model Forecated Trend heights at the middle of the Atmosphere. Showing a trend of higher heights which means more blocking to the north of Jose’s track.

The key to the forecast is going to be just how strong and how far west the Atlantic ridge of high pressure is as Jose begins to turn north this weekend. Also, with the ridge of high pressure trending stronger north of New England next week, the general idea that Jose will escape out to sea is becoming more uncertain, given this large-scale atmospheric pattern. This could allow for Jose to track into New England versus turning east. So, once again, there is some long-range forecast drama to watch next week. My general feeling is the high pressure to the north looks to be stronger, which means the probability of landfall is now as high as 70% for parts of New England on Thursday of next week.

In terms of intensity, although the NHC is not forecasting Jose to become a major hurricane on its current path towards the East Coast of the U.S., I think there is a decent chance that Jose could become a solid Category 3 again before encountering cooler waters north of North Carolina.

As Jose tracks northward west it will first run into warmer than normal water before it tracks over cooler than normal waters.

These cooler waters will be a critical factor in how intense Jose becomes after Wednesday of next week.  Currently these sea surface temperatures of 23 C / 73 F are not very supportive of a hurricane.

Current surface water temperatures off the east coast of the U.S

This will likely result in a much weaker storm,  but it depends on how strong Jose can get earlier next week.  Right now a Category 1 hurricane impacting the East Coast next week can’t be ruled out, but it is unlikely.  There is a better likelihood of Jose becoming extra tropical at this point and could even slow and become a bigger rain maker late next week.

Next week I can provide more details about the possible impact once the track becomes more stable, but, at this time, big swells will be increasing along the East Coast which will cause beach erosion. As Jose tracks closer to the East Coast, the most likely scenario is that it will track just off shore, which would mean that the strongest winds on the right side of the storm would stay off shore, but coastal flooding could be an issue, as the winds possibly push water down Long Island Sound and against the New Jersey coastline later next week.

Main Development Troubles

Meanwhile, last night the NHC upgraded a tropical wave coming off of Africa to Tropical Depression (TD) 14. It will likely develop into Tropical Storm (TS) Lee later today and should eventually turn north to the open Atlantic. However, this should be watched more closely, as the general steering flow this year has indicated that these tropical systems are tracking closer to the U.S. because of the Bermuda High. To the west of TD 14 is an invest area labelled 96L which could become TD 15 or TS Maria at some point as it cruises west toward the Windward Islands later next week. Currently the NHC has a 50% chance of cyclone formation over the next two days, but a 90% chance of formation over the next 5 days.  It should be noted both Invest 96L and TD 14 will run into higher wind shear which could weaken the systems as they track westward this weekend. If the storms do last until early next week, expect Invest 96L to be close to the Windward Islands and TD 14 to be tracking northeast toward the Leeward Islands.  I am most concerned with Invest 96L at this time, because as it gets closer to the U.S Caribbean, we have seen this season that conditions are more conducive for East Coast impacts.

General ideas of track of current tropical systems into next week.

Regardless, this is simply a busy season, the likes of which we have not seen since 2012. It is important with all of the other news and distractions going on around the world and locally that we remain focused on hurricane preparedness and these future storm threats.