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BMS Tropical Update 8/25/2017 12 pm CDT

There is now a plethora of information regarding Harvey’s impact but in this update I will attempt to focus on the specific impact to the insurance industry. For exact weather detail, with the most up to date information, it is always best to follow the watches, warning, bulletins and advisories from the National Hurricane Center and the local National Weather Service offices.

Harvey‘s Hazard Affecting Land
• Still very much a serious multi-day situation.
• Hurricane conditions to start later today with landfall between 12 am and 2 am local time.
• High-end Category 3 winds of 115 – 129 mph are expected.
• Current forecast suggests relatively narrow areas of maximum winds 60 miles across are expected at landfall.
• 6 to 12 feet of storm surge will be generated from Padre Island National Seashore to Sargent, TX.

Historic rainfall is expected. 7” of rain could extend into other parts of Texas and the lower Mississippi Valley. The Texas coastal area is expected to get at least 20” or rain and some places could see 35” of rain over the next 7 days.

In summary, Harvey combines the worse attributes of nasty recent Texas named storms: the storm surge from Ike in 2008, strong winds from Bret in 1999 and the record rainfall form Allison in 2001 – all in one storm.

Synopsis of Harvey’s Track and Intensity

As suggested all week Harvey would likely keep intensifying until landfall and is still expected to be a high-end major category 3 hurricane at landfall, which now can be narrowed down to a landfall area between Corpus Christi and Port O’Connor, TX.
This morning a hurricane hunter aircraft dropped a probe in front of Harvey’s path and measured the sea surface temperature at 80 degrees, not at the surface, but at 226 feet deep! Which means Harvey will continue to travel over very warm Gulf waters until landfall. Some model are still suggesting a category 4 hurricane so this can’t be ruled out before landfall, but becoming unlikely. The most recent forecasts suggest a category 3 hurricane with winds 111 mph – 129 mph. One factor to watch is if frictional land effects cause the storm to tighten before landfall due to the cyclonically curved coastline of Texas. One thing is for certain Harvey is going to be a slow-moving storm, meandering over central Texas days after landfall which will exacerbate the inland flood impacts. There are still a handful of models that take Harvey back out over the Gulf of Mexico early next week and have it making a second landfall near the Texas / Louisiana boarder as a tropical storm or even a weak hurricane. Overall, over the next few days Harvey is expected to meander northeast.

Storm Surge Impacts

This is the Advisory 20 Hurricane Harvey Storm Surge Potential. Storm surge is a very detailed hazard and these maps provide a detailed view of expected water level at a street level. http://www.nhc.noaa.gov/refresh/graphics_at4+shtml/153146.shtml?inundation#contents

Recently CoreLogic provided an estimate of Texas storm surge risk. However, it is important to note CoreLogic is not forecasting impacts direct from Harvey, rather they have calculated the total homes at risk and reconstruction cost value of key regions along the coastline. In the key landfall locations that could experience category 3 storm surge just under 40,000 risks are exposed.

Table from CoreLogic Harvey Storm Surge Report

Images from social media already show water at property level so flood losses will be very high for areas between Corpus Christi to Matagorda, TX which is expected to see as much as 12 feet of storm surge. Remember Ike and the Bolivar Peninsula?

Wind Impacts
BMS clients have access to high resolution Verisk Climate wind swaths that provide 1 min and 3-second wind speed and durations for not only the forecasted part of Harvey, but also what was experienced. Currently, a 60 mile wide swath of 110 mph to 129 mph 3-second wind gusts are forecasted, with a few pockets of 130 to 149 mph 3-second wind gusts.


It should also be noted that tornadoes can be expected inland which is often an overlooked hazard form landfalling hurricanes.
With AIR-Worldwide estimating that 80% of the residential construction is wood frame and given these very strong winds that are forecasted, it is very important to look at the building codes for Texas. According to the IBHS DisasterSaftey publication, Texas has a relatively poor building assessment compared to other coastal states, but TWIA requires policyholders to meet 2006 IRC standards, so coastal standards are likely higher because of this.


http://disastersafety.org/wp-content/uploads/2015/07/rating-the-states-2015-public.pdf

NWS expected Rainfall Amount over next 7 days

Rainfall & Flood
For several days now the forecasts have suggested several days of heavy rain as Harvey stalls out. The official National Weather Service forecast calls for at least 20” or rain over the next 7 days with isolated 35” possible in some coastal areas.Over 10” could occur stretching from San Antonio, Austin, Collage Station, and into Western Louisiana. I expect wind driven rain to be a major factor over much of the Texas coastline which will also be a factor for increased insured losses.

To get a great understanding of the areas that might be prone to inland flooding, I suggest checking out FM Global’s Flood Map which shows displays high (100-year) and moderate (500-year) hazard flood zones via a 90 meter x 90 meter grid.

FM Global inland Flood Map

Power Outage
The following is a great source for live prediction of power outages from Hurricane Harvey. I expect some coastal locations to be without power for several weeks.

https://geography.osu.edu/news/live-predictions-power-outage-be-caused-hurricane-harvey

Insured losses
It is way too early to estimate insured losses that could be caused by Harvey. However, it is safe to say this will be a multi-billion dollar event. Historical analog storms, like Carla 1961 and Celia of 1970, have losses in the range of $5bn to $20bn but neither of those storms stalled out for days producing the rain that is forecasted to fall with Harvey. This brings me to the last point. The catastrophe models likely have very few events that will match Harvey’s impact. In fact, using just one of the leading modeling company’s stochastic track sets, I could only find seven events out of over 45 thousand that even come close to having a similar track that is forecasted for Harvey, and not one of those seven have the correct event parameters as to what is expected from Harvey. So at this time there is significant uncertainty and little confidence in any early insured loss estimates.

BMS selected events from one of the Cat Models. Shows only 7 events with a similar track to what Harvey is forecated over the next 5 days. None of the events match the intensity.

 

Lastly

Nature is beautiful, but its destructive fury is not. Be safe. It’s going to be a tough few days.  Now check out this satellite loop below.

http://rammb.cira.colostate.edu/ramsdis/online/loop.asp?data_folder=goes-16/mesoscale_01_band_02_sector_05&width=1000&height=1000&number_of_images_to_display=40&loop_speed_ms=80

 

BMS Tropical Update 8/24/2017 12 PM CDT

Harvey’s Hazard Affecting Land
• This is a serious situation
• It is likely that 12 year hurricane drought will end with Harvey
• 6-10 feet of storm surge
• Up to 30” of rainfall in isolated areas
• At least category 3 but a chance at category 4 hurricane force winds up to 110 mph or greater

Synopsis of Harvey
Did you know that the longest time between hurricane landfalls for the state of Texas was eleven years? This was back in 1855-1865 but, of course, some parts of the Texas coastline were pretty sparsely populated during that time period. However, just as impressive is the current eight year drought of hurricane landfalls for Texas (2009-2016), and this is where the current landfall drought will stand as Harvey is now forecasted to be at least a category 1 hurricane when it makes landfall early Saturday morning along the Central Texas coastline.
As I mentioned in the BMS Tropical Update on Monday, I was very concerned that any systems that form in the Bay of Campeche often strengthen rapidly and continue strengthening until landfall. Given that the current sea surface temperatures are some of the warmest in the water (above 86 degrees) there is plenty of fuel for Harvey to strengthen, which it is currently doing. In fact, just this morning from 4 AM CDT to 7 AM CDT the central pressure of Harvey dropped 11 millibars which technically meets the NHC definition of a rapid deepening named storm, which is defined by a drop of 1.75 mbar/hour or 42 millibars in a day.

Track & Intensity
Harvey’s landfall track has been fairly stable over the last 48 hours with a landfall location estimated between Corpus Christi and Freeport, TX. The main uncertainty is what will happen after Harvey moves inland: how much will it weaken and will it stall or will it move more south or north or even back out over the warm Gulf of Mexico. All of these are options that are produced by the weather models at this point as overall the steering currents will collapse and Harvey will meander. The most logical scenario would be a move northeast back over the Gulf of Mexico early next week.


As mentioned, there is nothing holding back Harvey from intensifying until landfall. The only constraint I see is time and with another full day over very warm waters there is no doubt Harvey will be a hurricane. The question is will it become a major hurricane before landfall? Some models are suggesting this, but often there is a lack of confidence in such forecasts because they often over estimate these intensity ramps. However, I think this time it’s different. The statistical SHIP model suggests an increase of 45 kts (50 mph) within the next 36 hours which would make Harvey a 100 kt (115 mph) storm or a major hurricane at landfall. However, at this time there is good possibility that Harvey could be a Category 3 at landfall, but some of the newest model are even suggesting a Category 4.

In meteorology they always teach that the trend is your friend when forecasting, but in this case the trend in intensity forecasts below over the last 24 hours is not our friend  with a much  stronger system expected now then event 24 hours ago.

This is the current BMS Verisk Climate Maximum 3-sec wind gust in mph.  Clients can use this type of data layer to get an ideas of what risks are exposed to the strongest winds.

Predicted power outages from UMICH/OHIOState/TEXASA&M Source: @JohnHonore

Because Harvey is expected to be a major hurricane at landfall it will likely be the strongest hurricane to hit the area since Celia of 1970 which in today’s dollars would cause an estimated of $8B USD. Beulah 1967 ($6B), Allen 1980 ($2.5B), and Brett 1999 ($110M) can also be used as analog hurricanes at this early stage to get an idea of potential impact.

Flooding
One factor that is difficult to estimate is the flood related losses from a landfalling storm and as mentioned in the last update the flooding rains that will result from Harvey look to be historic as Harvey is forecasted to stall out. Rainfall estimates keep increasing: the National Weather Service is forecasting up to 20 – 25” for rain for parts of coastal Texas with rainfall over 10” stretching from San Antonio, Austin , Collage Station, and into Western Louisiana.  I expect wind driven rain to be a major factor over much of the Texas coastline.

To put this into prospective below is some work by Ryan Maue at Weatherbell who has use the PRISM data from 1981 – 2015 to show what the maximum rainfall is over a three day period. Keep in mind the rainfall totals forecasted for Harvey are over the next 7 days.  Needless to say I expect some 3 day rainfall records to be broken from Harvey.

Below is the estimated percent of homes that have flood insurance through the NFIP.  As Bryan Wood who works for Assurant suggest the overall percentages if homes inland with flood insurance are uncomfortably and on or off flood plain homes are at risk from Harvey heavy rainfall forecast.

This is the current NHC storm surge forecast. Up to-date forecasts can be found here. http://www.nhc.noaa.gov/refresh/graphics_at4+shtml/152721.shtml?wsurge#contents

BMS Tropical Update – Mid-August

It has been 45 days since I last provided a tropical update, mostly because there has been little to write about in term of U.S threats. However, with the peak of the season approaching, I would like to provide an assessment of the seasonal outlook that was outlined at the start of .the season. I will also provide some initial thoughts on a threat to the Texas coastline with remnants of Harvey expecting to come back to life over the next 24 hours.

Harvey’s Return

My general philosophy for posting tropical updates on specific tropical systems is to not post anything until there is a real concern of a U.S. landfall and subsequent impact to the insurance industry. I think we have now reached that threshold with the system formerly known as tropical storm Harvey, which is now located over the Yucatan Peninsula. It is expected that this system will be reclassified as a tropical storm Harvey as strengthening is expected during the next couple days, and it could even reach hurricane status as it approaches the U.S coastline by the end of this week. I expect the NHC to start issuing watches and warnings for the Texas coastline within the next 24 hours.

Harvey is currently forecast to make landfall somewhere between the Texas / Mexico border and central Louisiana, so there is obvious uncertainty with the forecast track guidance until Harvey moves back into the Bay of Campeche and reconnaissance flights get a better idea of where the exact center of the system is. The computer models don’t have the best read on this weak system at this time.

Current Track Ensemble Guidance for Harvey

Currently most of the model intensity guidance keeps Harvey as a strong tropical storm until it approaches the Texas coastline. However, systems that enter the southern Gulf of Mexico can strengthen rapidly and likely will do so until they make landfall. The water temperatures in the southern Gulf of Mexico are some of the warmest in the world and this means there is plenty of fuel for Harvey to strengthen rapidly and become a hurricane at landfall, which cannot be ruled out at this point. The further north the storm tracks up the Texas coastline, the longer the opportunity for the storm to stay over warm water and become stronger. This needs to be watched carefully.

The tropical cyclone heat potential, is a measure of the integrated vertical temperature between the sea surface temperature and the estimate of the depth of the 26°C isotherm. These regions have been associated with the sudden intensification of tropical cyclones.

Regardless of Harvery’s ultimate strength and track, it almost certainly looks like Harvey will have a slow forward motion and dump as much as 8” – 12″  of rain along the Texas coastline over the next week and if it stalls out like some models forecast the amount of rain could be even higher.  This will likely cause areas of flooding and past rainfall of this amount in the Houston area have not been good.

Current NWS Accumulated Rainfall over the next 7 days.

Peak of the Season Approaching
Several tropical systems have been monitored for formation by the NHC since my last update, of which five of them have been officially tracked. As I stated in my last update, tropical systems moving off the coast of Africa in the Main Development Region (MDR) will struggle to develop, but the overall environment becomes much better for development once those system get closer to the U.S. mainland. So far this season we have seen very little development in the MDR. This is mostly due to dry dusty air that has been a common deterrent the last few seasons. It’s not impossible for a named storm to develop off the coast of Africa, but the environmental conditions are limiting the opportunities this season.

The development that we have seen has come in waves this season, and without the major influence of an El Niño or La Niña as mentioned in the July 7 update, the MJO would likely influence these waves of named storm activity. I mentioned “The next phase of the MJO which could possibly enhance Atlantic named storm activity would occur near the end of July or first part of the August.” Five systems have been tracked by the NHC during this period, with Gert actually reaching category 2 hurricane status as it moved away from the east coast of the U.S. However, most of this year’s tropical systems have been weak and short lived with no major hurricane yet in the Atlantic basin. The Accumulated Cyclone Energy (ACE) is running about 84% of normal for the year, with almost half coming from Hurricane Gert. However, we have already reached the letter H in regards to named storms. This typically wouldn’t occur until around September 24, so we are far ahead of normal in regards to named storm count, which is in line with many of the seasonal forecasts.

 

Typically the Atlantic basin would be coming alive with activity with the peak of the season approaching on September 10, but the MJO’s expected move into a negative phase over the Atlantic Basin should suppress tropical convection and make it more difficult for named storm development during the peak of this season. Although named storm formation could still occur over this period, environmental factors such as dust and the MJO are pointing to less activity than normal for the month of September.

Currently the Red Area is Suppressed. This means less activity. The Pink and Blue is Active Phase of the MJO which can enhance convection and named storm activity. The three week forecast suggest this suppressed phase will move over the Atlantic during the peak of the Atlantic Season.

With the understanding that the North American weather pattern could change over the next month or so, we have seen two distinct tracks take shape this tropical season. One of these tracks is for tropical waves to take a southern route across the Southern Caribbean and influence the Yucatan, similar to Franklin and the current path of Harvey. The other path is for storms to track north of the Leeward Islands and influence Florida and the east coast. We have seen a few tropical waves influence south Florida (currently Invest 92L being watched by the NHC) and of course Gret strengthened along the east coast. This follows the general thinking for the season that as tropical waves move off Africa, they won’t strengthen into named storms until they are close to the U.S.

Without a major North American pattern change and implementing the ideas of clustering which is built into catastrophic risk models, it appears likely that we will see tropical waves take similar paths yet this year. However, as we approach the end of September and into October, which is when the next positive phase of the MJO would likely move back over the Atlantic, the current North American weather pattern will likely change.

Although our named storm count is high, overall ACE for the season so far is below normal. However, on the 25th Anniversary of Hurricane Andrew’s formation, it may be worth the reminder that it only takes one storm to have a major insured impact.

July Tropical Update

With the formation of Tropical Depression Four (TD4) on July 5th, I wanted to remind the insurance industry of what to expect this hurricane season. TD4 is now located 690 miles to the east of the Lesser Antilles and is not currently a threat to the insurance industry due to expected weakening in the coming 24 hours. However, keep an eye on the location of it’s left over moisture plume later next week as it could be a sign of future storm tracks towards the heart of the 2017 hurricane season.
In my May 15th tropical update, I went into detail discussing how many early Atlantic Basin seasonal hurricane forecasts were putting a lot of weight into the formation of an El Niño event during the 2017 Atlantic hurricane season, but spring El Niño forecasts can be notoriously misleading. In fact, the seasonal climate models continue to back off the idea that an El Niño will develop, and currently there is only a 40% chance of an El Niño with neutral condition developing during the heart of the hurricane season.

I also mentioned in the May 15th update that many of the early season forecasts would likely be adjusted upward to a “more active or normal season,” and this is what has happened. In fact, on July 5th, Phil Klotzbach and the team of seasonal forecasters at Colorado State University revised their forecast and now call for an above average hurricane season with 15 named storms, including 8 hurricanes and 3 major hurricanes during the 2017 Atlantic hurricane season.

A great collection of 18 different seasonal hurricane forecasts can be found here:

http://www.bsc.es/ESS/seasonalhurricanepredictions/
As indicated in my May 15th update, although sea surface temperatures are conducive for tropical development in the Main Development Region (MDR), a large negative influence on named storm activity over the last few years has been the Saharan Air Layer (SAL). This is a factor this year and is likely the reason why TD4 has struggled as it tracks across the MDR.

Dusty dry air to its east of TD4

The SAL will likely continue to be an influence on named storm development in the MDR for the remainder of the season, but there will be windows of less dust which will provide opportunities for named storm development.

12z NASA-GEOS5 dust forecast for next 5-days shows series of typical Saharan air layers heading west across tropical Atlantic from Africa.

These opportunities for storm development could arise with the passing of the lesser known phenomenon of the Madden Julian Oscillation (MJO). The MJO is long known to influence tropical convection as it traverses the planet’s tropic regions every 30 to 60 days. During times when El Niño neutral, like it is forecasted to be this year, this oscillation brings more positive atmospheric upward motion and can help us determine when the Atlantic Ocean might have more named storm activity. During the first passage of the MJO this year, the Atlantic saw the formation of tropical storms Cindy and Bret. Although TD4 is likely struggling because of the SAL, the Atlantic basin is also now in the suppressive phase of the MJO which limits large scale tropical development due to a large scale atmospheric sinking motion. The next phase of the MJO which could possibly enhance Atlantic named storm activity would occur near the end of July or first part of the August, followed by a suppressive phase in the middle to end of August. If the pattern holds, it could be followed by an active phase of the MJO again in mid-September which could enhance named storm activity at that time.

With the understanding that there could be pulses of activity in the Atlantic Basin associated with the MJO, where might these storms track? As highlighted in the May 15th update, the more important concept to grasp is where named storms may make landfall and not necessarily the total number of named storms that will develop. The climate forces this season are much more conducive to named storm development closer to the U.S. coastline. This, combined with the current placement of the Bermuda – Azores high pressure and the high pressure that has been dominating the central high plains states, would allow for storms to track toward the east coast of the U.S., putting the coastline at higher risk of landfall if storms were to develop there. Add in the fact that the sea surface temperatures off the east coast are warmer then average, and this has the potential to create interesting conditions for named storm activity later this season.

 

Long range models continue to develop tropical waves over western Africa into named storm. Could these thunderstorm over central Africa be the next system of interest?

With that being said, the long range forecast modeling always seems to try to spin up a named storm in the long range, with most of these scenarios often failing to come to fruition. In looking at the extreme long range forecast (next 46 days), the Atlantic basin looks to remain quiet with only a few hints at Cape Verde storm development through mid August.

Not much activity for the next 45 days as indicated by the ECMWF MEPS Cyclone Tracks by WeatherBell. However, a few Cape Verde storm development so need to keep as we get into the heart of the season.

This is interesting because globally named storm tropical activity in terms of Accumulated Cyclone Energy (ACE) is at record low levels. In fact, the North Pacific has had 0 typhoons so far in 2017, and this is only the seventh time since 1950 that this has happened through July 7th of a season. This also follows the quietest season on record for the southern hemisphere, which recently just ended. It should be noted that years with an ACE under 200 in the southern hemisphere have also managed to be below normal in the Atlantic, with a few exceptions like 1995. Based on the seasonal forecasts, this year looks like it could also potentially be an exception due to a higher risk of named storm activity near the east coast of the U.S., as storms struggle in the MDR.

BMS Tropical Update 6/22/2017 12 PM CDT

Cindy made landfall around 4:00 a.m. CDT this morning near the Texas and Louisiana border as a weak tropical storm with maximum sustained winds of 40 mph. I have been scouring social media and NOAA local storm reports and have not seen any significant damage. The biggest impact has been flooding, as previously forecasted, but it appears at this time that a repeat of the August 2016 Louisiana flood is unlikely. The highest rainfall amount that I have seen so far is 8.5 inches in Wiggins, Mississippi. The Gulfport-Biloxi Airport in Mississippi picked up 8.43 inches, and in Florida, the 8.25 inches in Navarre is the top total that I have seen. It should again be noted that these locations are over 300 miles from where Cindy made landfall. The BMS iVision Verisk Climate total rainfall layer suggests that some isolated coastal areas have seen upwards of 6 – 9” of rain over since Monday.

BMS iVision Verisk Climate total rainfall layer for Cindy up until 1 AM EDT 6/22/2017. BMS clients can run exposure reports against these rainfall amounts.

A surprising fact for some may be the level of storm surge that has occurred along parts of the central Gulf Coast. The largest storm surge level that I have been able to find was reported in Shell Beach, AL with an observed storm surge of 6 feet above the Mean Higher High Water (MHHW). This location is roughly 250 miles from the center, suggesting that Cindy had a large circulation which allowed a lot of water to pile up along parts of the central Gulf Coast over the last several days.

Observed Water Level At Shell Beach, LA

Example of road closures and flooding in Mobile Bay, AL that is currently common along coastal areas of the central Gulf Coast.

As mentioned, the winds from Cindy have been in the 45 – 55 mph range, which is well below the international residential design minimum of 90 mph. With only a handful of damage reports in to the NOAA, all of which are reports of trees or power lines being knocked down, the wind damage should be fairly minimal.

iVision Verisk Climate maximum gust in mph. BMS cleints can run exposure reports to understand the risk to high wind speeds from Tropical Storm Cindy.

At this time PCS has not issued a catastrophe bulletin, suggesting that the insurance industry loss could remain under $25 million.

Looking ahead over the longer term, the tropics should remain quiet for the next two weeks as the active phase of the Madden Julian Oscillation moves away from the Atlantic basin and other climate forcers such as the SAL layer and high wind shear hinder tropical development.

BMS Tropical Update 6/21/2017 12 PM CDT

Just after the tropical update yesterday, the National Hurricane Center (NHC) proceeded to upgrade Potential Tropical Cyclone Three to Tropical Storm Cindy. Currently Cindy is located 170 miles SSW of Morgan City, LA and may be the ugliest organized named storm that meteorologists have seen in the Gulf of Mexico in quite some time. It’s even questionable if it meets the true definition of a named tropical storm. In their 4 a.m. tropical discussion, even the NHC suggests that the cyclone is more characteristic of a subtropical cyclone and that the current categorization is generous.

Cindy is still expected to make landfall late tonight near the Texas/Louisiana border as a tropical storm. This landfall location is no stranger to named tropical storms, with 25 other tropical storms having tracked within 55 miles of the expected landfall location, based on historical records. However, as highlighted in the past few updates, the majority of insured impacts are being felt far away from the center of Cindy across eastern Louisiana and the panhandle of Florida. Heavy rainfall and flooding still appear to be the main threats across these areas. The BMS iVision Verisk Climate total rainfall layer suggests that isolated coastal areas have seen upwards of 4 – 6” of rain over the last 24 hours.

BMS iVision Verisk Climate total rainfall layer. BMS Clients can run exposure reports against these rainfall amounts.

New Orleans recorded record rainfall yesterday of 1.62” and more is expected today as an atmospheric river of moisture is pulled north from the deep tropics over the same area, creating a storm total that may be close to 14” in some areas.


Although there have been many tornado warnings issued over the last 24 hours for the central Gulf Coast, only 2 confirmed tornados, both weak with minimal damage, have been reported. As of this morning, no wind damage reports have been logged with the National Weather Service.

Based on the iVision Verisk Climate maximum gust data layer, most coastal areas will only experience winds of 40 – 69 mph, which in most cases is below the damage threshold for many structures.

iVision Verisk Climate maximum gust in mph. BMS cleints can run exposure reports to understand the risk to high wind speeds from Tropical Storm Cindy

As history would suggest, it is difficult to estimate insured losses from weak tropical storms. Let’s look at three historical tropical storms (Chris 1982, Debra 1978, TS#2 1987) that took a similar track inland as to what Cindy is forecasted to take. The insured losses from these storms range from $2 million to $12 million. However, given the large threat of flooding from Cindy, it should be noted that the major Louisiana flood event that occurred from August 11, 2016 to August 15, 2016 reached $1 billion in insured losses.  Estimating insured losses of tropical storms can be difficult.

As expected, Tropical Storm Bret has dissipated in the southern Caribbean. Looking ahead over the longer term, the tropics should remain quiet for the next two weeks as the active phase of the Madden Julian Oscillation moves away from the Atlantic basin and other climate forcers such as the SAL layer and high wind shear hinder tropical development.

BMS Tropical Update 6/20/2017 12 PM CDT

Update:  12:39 PM CDT  the NHC will be upgrading PTC3 to Cindy.  The most recent ECMWF 12z landfalls TS Cindy into Houston.  Has some strong winds with a landfall pressure of 990 mb which is a minor hurricane pressure.

 

Yesterday afternoon the National Hurricane Center (NHC) found enough evidence from the Air Force reserve hurricane hunter aircraft to upgrade Potential Tropical Cyclone Two to the second named storm of the 2017 Atlantic hurricane season. As mentioned in yesterday’s post, Bret still does not pose a significant threat to the insurance industry and will likely weaken later this week as it transverses the South American coastline in the southern Caribbean Sea.
The bigger threat to the insurance industry remains Invest 93L which, as of yesterday afternoon, was labeled Potential Tropical Cyclone Three (PTC3). Again, the idea of issuing advisories before a tropical depression or named storm forms is to highlight the threats of a developing storm earlier in its life cycle, and PTC3 is a classic example of the reason why there has been a change in policy. In fact, tropical storm warnings and watches are now in place along the Gulf Coast as PTC3 is still expected to develop into the next named storm (Cindy) before its low center makes landfall near High Island, Texas, in the late evening hours Wednesday, but tropical storm force winds could occur as early as before sunrise  on Wednesday.

This morning, it appears that PTC3 is gradually becoming better organized as it approaches the southern Gulf Coast. There is still a great deal of wind shear impacting the convection on the western side of the low center, which is likely the primary reason that the NHC has not yet upgraded PTC3 to a tropical depression or named storm.

 

This is the GFS model depiction of winds shear impacting the west side of PTC3

Forecast models still expect gradual strengthening of PTC3 until the low center moves inland later tomorrow afternoon. Historically, developing storms in the Gulf of Mexico are notorious for rapidly straightening towards the coast, but given the broad circulation along with the large radius of maximum winds, this becomes more difficult with PTC3. Regardless of how strong PTC3 becomes over the next 36 hours, given the nature of the circulation, the wind and rain hazards extend well north and east of the center which makes PTC3 a great example of the far reaching impacts a tropical storm can have away from the main track. In this case, the NHC cone is far outside of where the very heavy rains are forecasted for the Mississippi and Alabama coastlines.

NOAA QPF forecast suggesting over 10″ of rain far away from the NHC track of the low center. Heavy rainfall will be from Houston, TX to Pensacola FL

It is this rainfall which will continue to likely be the largest loss for the insurance industry, and the rainfall is already starting to reach the coastline. This rainfall will come from training of individual thunderstorms which are already creating areas of severe weather across the Gulf Coast States. Tornado warnings are being issued and individual thunderstorms are producing localized severe weather along the Gulf Coast which could also cause insured loss far outside the  forecated path. As indicated above, the NOAA Weather Prediction Center is now forecasting for as much as 10” of rain to fall over southern Mississippi and Louisiana, with as much as 7” over eastern Texas.  There could be locally even higher amounts.

Making things worse is the soil moisture is already saturated from the recent heavy rainfall that has occurred over the last 30 days. Therefore, most of the rain that falls will run off and exacerbate the flooding threat. This saturated soil could increase tree fall from higher winds as wet soil weakens the hold on a tree’s root system.

Given the broad and large circulation, storm surge risk is higher than what it might typically be with a developing named storm. Currently, it appears that inundation levels in the tropical storm warning area could be as high as 3 feet along the coastline.

BMS Tropical Update 6/19/2017 12 PM CDT

As expected from last week, two areas of tropical trouble are trying to form in the Atlantic Basin. If both of these tropical systems manage to get named this week, it would be fairly rare as only three Atlantic hurricane seasons on record have had two concurrent named storms in June. Those years were 1909, 1959 and 1968, all of which turned out to be average to slightly above average hurricane seasons with a higher than average landfall rate across the U.S. This is in line with the general thinking of what could occur this Atlantic hurricane season.

Since last week, the National Hurricane Center  (NHC) has been watching these two disturbances. One of these has been centered north of the Yucatan Peninsula and has been labeled Invest 93L. The other disturbance is labeled Invest 92L and is currently located 325 miles ESE of Trinidad, moving rapidly toward the southern Windward Islands. In fact, for the first time ever for a tropical system, the NHC has begun issuing advisories for 92L before it is a depression or named storm and has also labeled the system “Potential Tropical Cyclone Two.” I talked about this possibility in my New Hurricane Products for 2017 Season blog post. The NHC is doing this because there is an immediate threat of tropical storm force winds to land, which, in this case, would be in the southern Windward Islands where the watches and warnings are in effect.

What is the forecast and worry for insurance industry this week?
“Potential Tropical Cyclone Two”
Potential Tropical Cyclone Two has a 90% chance of tropical development over the next two days. Early visible satellite imagery suggests the system is still an open wave and does not have a closed center of circulation, which is part of the criteria for storm naming by the NHC. My guess is that the NHC will wait to name the storm (Bret is the next storm name) until this afternoon when an Air Force reserve hurricane hunter aircraft is scheduled to investigate the potential tropical cyclone. Depending on what the aircraft finds, it could get a name. Regardless of whether the potential tropical cyclone gets a name, stormy conditions will be experienced in the southern Windward Islands. The forecast models are suggesting that after today the system will struggle to maintain itself as interaction with South America and increased wind shear will likely hamper any development in the second half of this week. This means the overall impact to the U.S. insurance industry is minimal at this time, and even if named, it would be a short lived tropical system.

Last Night ECMWF Ensemble Breakdown of disturbance two tracks and intensity

Invest 93L
Invest 93L also has a high chance of tropical development over the next two days with an 80% chance of development. The reason why the NHC has not issued advisories for this system is they currently feel the threat of tropical storm conditions is less severe and it could take a few days to produce strong winds over land. So overall, the difference between these two systems in terms of advisories is the immediate threat of tropical storm conditions to land is greater for Potential Tropical Cyclone Two. However, in the longer term Invest 93L has the higher likelihood to impact the insurance industry. This morning’s satellite imagery suggests that the low level center is decoupled from the deep tropical convection on the right (east) side of the storm.

Visible Satellite shows low level center is decoupled from the deep tropical convection on the right (east) side of the storm.

There is a chance it’ll never actually develop into a tropical cyclone as the wind shear over the next few days could hamper development.

ECMWF forecasted strong southwesterly wind shear associated with a trough aloft blowing t-storms away from surface center of Invest 93L inhibiting development. Also shown is the shear that could impact disturbance two.

However, later in the week this wind shear is likely to abate and formation of a named storm becomes more likely.

As always there is uncertainty in the development and final track of tropical systems. The GFS (American model) takes this system on a more northerly track towards Louisiana and even on some early weekend runs into the Florida panhandle. However, as I highlighted in my New Hurricane Products for 2017 Season blog post, the new GFS model this year is not the model to watch. The more reliable ECMWF (European model) takes 93L into southern Texas as indicated last week, so the model has been fairly consistent with the ideas Texas will see worse of the impacts in terms of tropical storm force winds if they develop.

At this time, almost all forecast models for 93L remain below hurricane strength. Regardless, deep tropical moisture will have far reaching effects along the Gulf Coast states, so heavy rainfall and flooding are currently the biggest threats to the insurance industry to areas that don’t handle a lot of rain well like New Orleans and Houston. Depending on the track,  5 inches of rain could easily fall as a sort of atmospheric river seems to be setting up along the Central Gulf Coast.

NOAA Weather Prediction Center showing much of the central gulf coast is expected to get 2 – 5″ of rain which is conservative in my opinion based on the sort of atmospheric river that seems to be setting up into the Central Gulf Coast with a possible poorly organized tropical disturbance.

 

 

New Hurricane Products for 2017 Season

Every year there are new tools and products that can help the insurance industry understand named storm risks.  In this write-up, I highlight some of these new tools and products for the 2017 hurricane season, which starts today.   For ideas on the type of activity that is expected this season please see my previous update here:  May Tropical Update issued May 15th.

Advisories Will Be Issued Before a Storm Is Named

The National Hurricane Center (NHC), which decides when a named storm gets a name, will issue advisories for tropical systems before the tropical system has a name. In these cases, these tropical systems will pose a threat of bringing tropical storm-force or hurricane-force winds to land areas within 48 hours. For decades these tropical disturbances have been called ‘Invests’, or areas of investigation, and for the last few years the NHC has been giving Invests forecasts related to the chance of formation within the next five days.

Currently some re/insurance contract language is directly related to named storm activity. However, the advisories for these tropical systems that will likely impact land could now lead to earlier activity in re/insurance contracts where coverage is triggered by storm warnings or watches, as the NHC would previously wait for a storm to be named before issuing such warnings or watches. In most cases, these types of named systems would be in a developing stage just off the U.S. coastline and would highlight not only the likelihood of genesis of a named storm, but the possible strength of winds along the coastline.

Hurricane Humberto in 2007 is a classic example of where the NHC would have likely issued watches and warnings before Humberto was named if it took place in 2017. Humberto strengthened into a hurricane in a 24 hour period. Source: AccuWeather Inc. & NOAA

Storm Surge Watches and Warnings Are Coming 

For the last several years, the NHC has made large improvements to storm surge forecasts from named storms.  In fact, the detailed Potential Storm Surge Flooding Maps now rival the high resolution flood model simulations that are becoming common in the insurance industry by various Cat Modeling vendors.  However, another tool that might help the insurance industry is that the NHC plans to release storm surge watch and warning graphics to provide further guidance on where the greatest threat to life and property from a named storm might be.   The insurance industry is all too familiar with the hazards and damaging storm surge that occur with a threatening named storm and this guidance can help pin point areas likely to be most impacted by storm surge.

New storm surge watch and warning product for 2017 hurricane season. Source: NHC

Earliest Reasonable Arrival of Tropical Storm-Force Winds Will Be Forecast

The NHC has always provided guidance as to the position and timing of the center of a named storm; however, to provide more added value, the NHC will now be directly forecasting when tropical storm-force winds will begin to affect land. This will allow the insurance industry to better understand when winds greater than 39 mph are expected, which should aid in allowing more time for an insured to apply preventative measures to mitigate risk from damaging storms. Above 39 mph, winds can make it difficult and even dangerous to be outside continuing preparations for a tropical storm or hurricane.

The IBHS has some helpful hints to reduce hurricane damage to homes and businesses.


The Cone of Uncertainty Will Be Smaller

Every year the NHC reviews the accuracy of their previous five seasons of hurricane forecasts.  This review suggests the forecasts are getting better, and with that, the average error in the NHC forecasts that make up that famous cone of uncertainty will result in a smaller cone and just maybe more certain hurricane forecasts for the 2017 season.  Track errors have gone down over the last 10 years and forecasts have gotten better.  In fact, since 2007, the size of the cone of uncertainty at 120 hours (or five days) has shrunk by more than 35%.  Since last year, the size of the cone at 120 hours has shrunk by more than 10%.

The shrinking cone of uncertainty. Source Brian McNoldy Univ. of Miami

Hurricane Model Wars

As long as I have been studying meteorology there have been wars among the various forecast models as to which model is the most accurate at forecasting named storm activity.  This war was brought into the public limelight after Hurricane Sandy in 2012, when the American Model [Global Forecast System (GFS)] falsely forecasted Sandy to track offshore, and the European ECMWF model correctly predicted Sandy to make landfall in New Jersey.  Just like the various hurricane products described above, the weather models themselves are under ongoing improvements.  One item to watch this hurricane season is the upgrade to the GFS model on July 12th.  As part of these upgrades, the NOAA asks forecasting divisions like the NHC to run performance tests.   Although the tests might suggest better temperature forecasts or precipitation forecasts for different areas of the globe, one area where the upgraded GFS shows deficient skill is with hurricane forecasting.   The report I have seen from the NHC suggests for the 2014-2016 retrospective runs, in comparison to the 2016 GFS model, the 2017 GFS showed a 9-10% degradation in track forecast skill at 48-72h in the Atlantic Basin.  In terms of intensity forecasting, the 2017 GFS showed degradations in intensity forecast skill at nearly every forecast interval out to 120 hours in the Atlantic Basin.  The new GFS model also indicated less run-to-run consistency.  It likewise showed little overall improvements in TC genesis forecasts for the Atlantic Basin.

Evaluation of the proposed 2017 GFS implementation done by the NHC in February 2017

Another troubling factor is that the GFS model will likely have other fallouts with the regional models, such as the HWRF and GFDL, and the statistical models such as the GFEX.

Here is the quote from the NHC about the upgrade to the GFS model:

“The loss of short- to medium-range TC track and intensity forecast skill for the Atlantic basin in the proposed 2017 GFS is unacceptable to the National Hurricane Center.  We are also concerned about the lack of testing of the downstream impact of the 2017 GFS on the regional hurricane models.  Therefore, we oppose this implementation.”

As the insurance industry watches all of the various hurricane forecast model runs to determine where a hurricane might track, it might be good to put a bit more weight in the ECMWF model this season.  However, the ECMWF will also be upgraded on July 11th and very few people know what these upgrades will do to its hurricane forecasting.

Detail of this model upgrade can be found here:

http://www.emc.ncep.noaa.gov/gmb/noor/GFS2017/GFS2017.htm

May Tropical Update

Seasonal Hurricane Forecast Skill

Seasonal hurricane forecasts, with varying lead times, have been produced in the Atlantic basin since 1984 by the late Dr. Gray from Colorado State University (CSU).  Partly as a result of the early success of those forecasts, seasonal named storm forecasts are now a dime a dozen with many different research and operational groups making seasonal hurricane forecasts for tropical basins around the world.  Although there are some very brilliant minds making these forecasts, some might argue there has been little skill improvement over the last several years. The insurance industry is accustomed to using climatology to understand the risk of a U.S. landfalling hurricane.  This climatology also suggests, on average, the more active the overall Atlantic basin hurricane season is, the greater the probability of U.S. hurricane landfall which can be useful guidance to the insurance industry heading into the hurricane season. However, when it comes to seasonal landfall forecasts, really no skill has been demonstrated; this is ultimately what matters for the insurance industry.  In fact, there isn’t a forecast group that has skillfully predicted the current drought in major hurricane strikes over the last 11 years.

CSU Atlantic Basin wide hurricane forecasted and observed hurricanes with missed forecasted number shown.

CSU provides easy access to historical forecasts which allows for simple validation of there seasonal forecasts.  In a simple analysis, the CSU forecast has done fairly well with their April predictions when compared to using historic climatology (6.5 hurricanes per year) .  Fourteen CSU forecasts since 1995 have come within three hurricanes of the seasonal hurricane total in the Atlantic Basin.  On seven occasions, they have only missed the cumulative number by one.  They hit the mark in 2008.  Of course, CSU have posted a few wayward forecasts as well: 2005 (undershot the total by eight hurricanes) and 2012 (fell short by six hurricanes).

CSU Atlantic Basin wide major hurricane forecasted and observed hurricanes with missed forecasted number shown.

Regarding the major hurricane forecasts, CSU has made seven forecasts that failed to fall within two storms of the final tally. This should not obscure the fact that they’ve also posted four perfect forecasts of major hurricane occurrence and 13 others that approximated the seasonal total within one storm.
It is very easy for one to sit back and grade objective season hurricane forecasts like CSU, and there is no doubt a lot of work goes into the refinement of these forecasts each year. I am a firm believer that seasonal forecasts and even landfall forecasts will improve over time. Currently, many of these seasonal forecasts are statistical schemes which will inherently fail some years. There is some promise that a hybrid of statistical and dynamical forecast could be the future of seasonal hurricane forecasting.

https://www.gfdl.noaa.gov/hyhufs/

The Real Value – Landfall Forecasts

As mentioned, the real value to the insurance industry is in getting an accurate picture of potential landfalling storm activity. CSU issues probabilities for landfalling hurricanes across various regions of the U.S. This year, they are forecasting a 75% probability of a hurricane landfall. The probability of landfall for any one location along the coast is very low and reflects the fact that, in any one season, most U.S. coastal areas will not feel the effects of a hurricane no matter how active the individual season is. And, given the variation of exposure along the coast, providing accurate estimated insured loss ahead of season is very difficult if not impossible.
However, given the current state of the science of seasonal forecasting it is possible to provide guidance to which area of the coastline will see a higher than normal probability of landfall. This year, landfall forecasts may prove to be one of the more challenging years. This is due to the large amount of uncertainty of many of the climate forcers used to predict Atlantic named storm activity. One of the most common climate forcers used is El Niño Southern Oscillation (ENSO) and, this year, many forecasts are uncertain if an El Niño event will take hold during the summer, which historically suppresses hurricane activity. CSU thinks an El Niño will be weak or moderate by the peak of the Atlantic hurricane season based on their April forecast. However, as mentioned a few weeks ago, spring El Niño forecasts can be notoriously misleading, and result in difficult forecasts. (This phenomenon is so familiar that it has its own name – the “spring predictability barrier”.) Over the last few months many of the monthly climate models have backed off of the idea of a strong El Niño during the peak of the Atlantic hurricane season and now have a weak to neutral ENSO condition. If the El Niño is weak, it could result in increased landfall chances, and El Niño historically has little to do with any activity in the Western Caribbean / Gulf of Mexico and any activity in this region increases the chances of U.S. landfall.

Official Climate Prediction Center ENSO probability forecast for Mid-April (Top) and Early May (Bottom) Showing in just a half of month the probability of a El Niño during the hurricane season (Gray Box) went form 70% to below 50%. There is an increasing signal that ENSO will be neutral during the hurricane seasons.

The other challenge this year is that earlier this spring, water in the far North Atlantic and water off the coast of Africa had a relatively cold signal which is potentially indicative of a negative phase of the Atlantic Multi-Decadal Oscillation (AMO).  However, over the last month or so, the Atlantic water has warmed substantially.  This continues the debate as to whether the AMO has switched to a negative phase.  The U.S. government suggests the Atlantic is still in a positive state, whereas the CSU data suggests the AMO has trended negatively over the past few years.  If water continues to warm over the main development region, like it has over the last month, it could allow more storm formation in the heart of the hurricane season.

NOAA SST anomaly (degree C) for 4/10 (left) and 5/11 (right) showing a warming of SST off the west coast of Africa off the East Coast of the US. The cold SST in the North Atlantic have expanded and SST after months of above normal in the Gulf Of Mexico have recently turned colder than normal which should be short lived.

Another factor that has had a large influence on named storm activity over the last few years has been the Saharan Air Layer (SAL).  Named storms interact with the SAL in several ways.  Some named storms get embedded in the SAL their entire life-cycle and often struggle to intensify beyond strong tropical storm strength.  Other named storms can be overrun by the faster moving SAL and are quickly weakened.  The SAL in general can hamper convection, making it hard for named storms to develop.  This year could be similar to the last couple of years which would hamper development of named storm activity in the main development region but, as tropical waves get closer to the U.S. and Caribbean, the SAL decreases, and conditions become more favorable for development outside of the SAL.

SST anomaly for 5/11 showing warmer than normal SST around Hawaii.

Not to forget about Hawaii, which is also a target for named storm activity and, like the U.S. mainland, has gone a long time without a major hurricane impact.   This year, the insurance industry should also keep an eye on this 50th state as, just like the warm sea surface temperature (SST) off the East Coast of the U.S., the SSTs are above normal near Hawaii, and any tropical activity that might come close to the islands could be enhanced by these warmer than normal SSTs.

Summary
Forecasting of Atlantic named storm activity is not easy, and CSU has demonstrated variability in skill year over year, with no real improvement in the April seasonal forecasts over the last several years, but overall there is skill improvement over using basic climatology. Although some forecasts are currently calling for below normal activity in the Atlantic basin, climate forcers are pointing toward the ideas that these forecasts will be adjusted upward as we approach June 1 to a more active or normal season. The major climate forcers suggest there could be less development in the main development region of the Atlantic but, as tropical waves move closer to the U.S., they could have a better chance at developing, due to lack of wind shear and lower SAL environment. SSTs near the U.S. coastline are also expected to be warmer than normal which would add fuel to any disturbances that develop. Therefore, parts of the U.S. coastline have a higher probability of a landfalling named storm this season, with the Mid-Atlantic and Northeast seeing the highest chance.
Resources:
Barcelona Supercomputing Center has a nice summary of the various Atlantic Hurricane Forecasts
http://www.bsc.es/ESS/seasonalhurricanepredictions/
NOAA Climatology Products – Avg Start Dates, Return Periods, Develop Origin by Date, Strike Density
http://www.nhc.noaa.gov/climo/
CSU U.S. Landfalling Hurricane Probability Project
http://www.e-transit.org/hurricane/welcome.html