BMS Tropical Update 4/20/2016 4 PM CDT

You might have noticed that the first named storm (Arlene) of the 2017 Atlantic Hurricane season has formed in the middle of the North Atlantic Ocean – 815 miles west of the Azores Islands.   The biggest impact from this storm will be the discussion in the meteorology community as to whether this system should even be monitored by the National Hurricane Center.  Currently Arlene is over relatively cold ocean water (66 F (19 C)) for a tropical system, and according to satellite data, it is questionable if the system has a warm core.

IR Satellite image show the system is over 19C water.

Typically a tropical cyclone is characterized by lack of warm/cold fronts attached, a “warm core” (air is warmer in center of the cyclone than elsewhere), and persistent deep convection wrapped close to the center; these attributes are commonly referred to as “tropical characteristics” of a cyclone.

It would appear that the decision to track Arlene is very subjective: there have likely been dozens of similar systems over the last 100 years (systems that develop in water warmer than 66 F and with a marginally warm core) that have gone unclassified, including systems that have impacted the U.S. (Sept 2008 SC coast, Sept 2009 NJ).

All this matters to the insurance industry because our hurricane catalogs in the catastrophe models are tuned to the historical data, and after decades there is still no objective guidance as to what type of system gets tracked by the NHC. In some cases like Sandy, questionably categorized storms can have large impacts on landfall definitions as well.

Regardless, Arlene is now in our record books as a storm in the North Atlantic, but it will not be around for long as a strong mid-latitude trough will merge with this system later this weekend and make it unrecognizable. These early-season tropical systems should be no surprise (this will be the sixth early-season storm in the past six years). In fact, history suggests that tropical/subtropical systems in April are uncommon, but not necessarily rare. There have been a few, but they are typically short-lived and innocuous.

Historical Storms that have occurred in April

I am currently tracking the various early season forecasts for the 2017 Atlantic basin season.  I should have my views formulated in a couple of weeks.  What I can tell you right now there is no correlation for April storms and the rest of the season, partly because of a small sample size.

Another New Hurricane Landfall Study

Three weeks ago, James Kossin published a major study in the scientific journal Nature: “Hurricane intensification along United States coast suppressed during active hurricane periods” (http://www.nature.com/nature/journal/v541/n7637/full/nature20783.html). This paper has gotten a bit of press in various insurer publications as over the last decade near term hurricane risk has dramatically influenced the insurance industry in hurricane-prone states. In short, Kossin’s paper provides valuable insight into rapid hurricane intensification during active and inactive periods of hurricane activity in the Atlantic basin (known as the warm and cold phase of the Atlantic Multi-Decadal Oscillation [AMO]). The findings suggest that approaching hurricanes are more likely to intensify before landfall during colder phases of the AMO and are more likely to weaken before landfall during warmer phases. Suggesting that during times when the sea surface temperatures are anomalously warm in the main development region, regions along the U.S. coast experience higher then normal vertical wind shear. Furthermore, the local sea surface temperatures are substantially cooler than the main development region which tend to inhibit intensification and form a “protective barrier” along the United States coastline during this period.

 

My very first thought as I read about this “protective barrier” was, finally, someone has scientifically proven the existence of HAARP and electromagnetic capabilities of the ionosphere that conspiracy theories suggest can also be used in weather modification and more. (i.e., a “protective barrier” created to control the weather (hurricane landfall))! (If you’re unfamiliar with the HAARP conspiracy theories that abound, then you won’t get this reference, but it’s one of the top questions meteorologists get asked, and you can learn more at http://www.nbcnews.com/science/weird-science/conspiracy-theories-abound-u-s-military-closes-haarp-n112576.)

How the Science has Changed

In all seriousness, to truly understand the impact of Kossin’s paper, it’s important to review how our understanding of active and inactive phases of the Atlantic Ocean has evolved and influenced the insurance industry. Since the 1960’s, the late Dr. Gray showed distinctly differing environmental conditions for tropical cyclone development. But not until the marked increase beginning in 1995 did insurers begin to notice what drives this activity. After the costly 2004 and 2005 hurricane seasons, a dozen and half papers highlighted a link to increased hurricane activity due to a warming world and/or the current phase of the AMO. About the same time, catastrophe modeling companies were being pressured to adjust for this increased frequency and severity that had impacted the insurance industry since 1995. Modeling companies incorporated a range of statistical analyses, and in some cases expert elicitation, to make assessment on future hurricane landfalling risk.

Mother Nature, however, does not always follow weather trends; and since 2005, the U.S. has entered what some have called a “U.S. landfall hurricane drought.” While overall named storm activity remains elevated across the Atlantic basin with some very active years since 2005 (2010, for example), many hurricanes have not made landfall as expected, which is actually influencing the long term landfall rates across the U.S. A few recent research papers suggest that scientists never settled on the exact impact the warmer phase of the AMO might have had on U.S. landfalls. Some of these papers suggest that in a warmer world, African dust and/or North Atlantic sea surface temperatures could actually encourage hurricanes to form further east or recurve before impacting North America, resulting in a lower U.S. hurricane landfall rate.

But Kossin’s paper provides new evidence that the science is not settled, and there is a lot to learn about hurricanes and the rate at which they make landfall. In general, the correlation between the number of hurricanes that develop in the Atlantic basin and number of hurricanes that make landfall is weak. This new study in Nature could explain part of this relationship as it highlights that elevated wind shear (changing wind speeds with height) and cooler sea-surface temperatures along the U.S. coast during the warm active phase of the AMO create conditions that tend to weaken hurricanes as they approach the U.S. coast. Conversely, the cool phase of the AMO makes approaching hurricanes more likely to intensify. This might conflict with ideas that some scientists suggested prior to 2004 and 2005, that the warmer phase of the AMO was correlated to more landfalls and possibly stronger landfalling storms (and fewer landfalls during the cooler phase of the AMO).

The Hurricane “Drought” can be Explained

Kossin suggests in his paper’s closing that this new research could possibly explain the recent “drought” of major hurricane landfalls. However, in late 2015 another research paper funded by Risk Prediction Initiative (“The Arbitrary Definition of the current Atlantic Major Hurricane Landfall Drought”) suggested the major hurricane drought is more a function of the definition of a major hurricane (defined as a Category 3 or higher on the Saffir-Simpson Scale) and the uncertainty in wind estimates. As an example, Ike (2008) made landfall as a high-end Category 2, but could just as easily have been classified as a low-end Category 3 at landfall. For contrast, consider a storm like Sandy (2012), which was not even classified as a hurricane at landfall, but still resulted in large wind and storm surge insurance losses.

Image created by Roger Pielke Jr. who has been keeping track of the days between major hurricane landfalls.

It’s important to remember that only 78 major hurricanes have made landfall since 1900 (117 years), which results in a particularly small sample size, and that there are likely many other factors that affect intensification before landfall. Hurricanes can experience higher levels of disruptive wind shear while turning north, which could be due to a large scale trough of low pressure or drawing in dry air from landmasses. Hurricanes can also send large waves and surge ahead of the storm causing warm water to mix with cooler water and deplete important energy from the storm as it approaches land. These vacillating factors highlight the complex interactions hurricanes may experience during a life cycle. These factors could also explain why many hurricanes have not intensified prior to U.S. landfall (with the exception of Charley [2004] and Humberto [2007]).

Future Hurricane Landfall Rate Models

As always, new research will continue to become available and catastrophe modeling companies will continue to judge how the science best fits into catastrophe models. This new research should not discredit near term view modeling work. Hindsight is 20/20, and as Hall, T.M., and K. Hereid, 2015: The frequency and duration of U.S. hurricane droughts paper suggests several observations point to the current drought being more a case of good luck than any shift in hurricane climate. Therefore this luck could have swayed higher then normal insured losses in a completely different direction over the last 10 years. These facts highlight why it is important to continuously evaluate new science. Modeling companies need to ensure they avoid knee-jerk reactions to industry demands or speculative science. Seasonal hurricane forecasts are improving, and with time, multidecadal sea surface patterns and other variables could help clarify the cause of reduced landfall rates, not just in the Atlantic basin, but in other basins near high exposure. El Niño/Southern Oscillation (“ENSO”) and other variables could also be worked into the landfall rate catalogs produced by model vendors.

As pointed out in this blog, the science might not be settled on hurricane landfall rates and what drives these rates during particular climatic conditions. Although it is short by climate standards, the U.S. landfall hurricane record is one of the best natural catastrophe databases insurers have to understand frequency and severity. There is a reason why catastrophe model companies calibrate their models to the longest period of record available.

There is plenty of room for debate about near term hurricane landfall rate models, the drivers of this risk, and what position an insurer should take regarding rate models. Are they a good idea or a bad idea? Should a blended approach be used? Those are interesting questions and a worthy topic, which is why I will be moderating the session, “Is Near Term vs. Long Term View of Hurricane Risk Over?” at the February RAA Cat Management Conference. We hope this subject generates lively discussion and hope to see you there!

2016 – The Good News

As 2016 natural catastrophe headlines funnel in from various media outlets and insurance publications, a theme of negative highlights quickly emerges. Few headlines point out the positives that occurred. In this post, I want to highlight a few of the 2016 insurance industry positives that might otherwise be lost in the sea of negative news as it relates to natural catastrophes.

Severe Weather
When the calendar flipped to 2017, a switch seemed to turned on for US severe weather season: severe weather impacted the Gulf Coast states with 31 tornadoes on January 2 (PCS 1711). Just two weeks into the year, 2017 already has 4.4 times more than the normal number of tornadoes. However, the great news is that 2016 ended with lower reported tornado numbers, and the preliminary numbers suggest that 2016 ended up as a year with the fewest tornadoes since 1954 (when records started).

2016InflationAdjustedTornado

NOAA plot of the annual running total of tornado reports compared to inflation adjusted values.

This might not seem remarkable given the US has experienced five years a row of below near term normal tornado reports (2005 – present year) since the near record high year of 2011. So the good news is the US continues to see lower tornado counts for several years in a row now and is currently in what some scientist call a “tornado drought.” The other good news is that, as a matter of luck, the tornadoes that did occur did not result in large insured loss events. There were many close calls like this major tornado that occurred just 3 miles south of Dodge City, Kansas.

Twin tornadoes are seen near Dodge City, Kansas, with Dodge City Raceway Park in the foreground on Tuesday, May 24, 2016. (Instagram/bradguay)

Twin tornadoes are seen near Dodge City, Kansas, with Dodge City Raceway Park in the foreground on Tuesday, May 24, 2016. (Instagram/bradguay)

Various reports point out that 2016 produced the highest severe weather-related losses since 2011, but along with the lower tornado count, 2016 also produced hail reports below the 11-year average. As a matter of a different kind of luck however, these hail events targeted several populated regions across the state of Texas which produced most of the 2016 severe weather-related loss. The overall good news is that hail events across the other states were at or below average.
2016SvWxLossWithTxLossPercent
Flood
It is easy to highlight devastating 2016 U.S. flood events, but given the current flood take-up rates, these events were mostly uninsured. But the good news is the federal government and uninsured homeowners and business are taking steps to protect themselves from future flood events. And there’s more positive 2016 flood news: Since 1965, 60% of U.S. measured locations have seen a decrease in flood magnitudes according to the newest EPA study. Finally, no significant trend in major flood events seems to be emerging when looking at historical major flood events as defined by FEMA.

FEMA_MajorFloodEvents
Named Tropical Storms
On average, 87 named tropical storms occur worldwide in any given year. 2016 saw 79 tropical storms, and just 42 were hurricanes (which is again below the average of 48). It should also be noted that so far for the 2016/2017 Southern Hemisphere named storm season (starts July 1), only 2 named storms and 0 hurricanes have formed to date (an average of eight named storms and four hurricanes occur at this point in the season), which equates one of the slowest starts to that basin in history.
However, what the insurance industry cares most about is landfalls, and in 2016 global landfalls were spot-on average: 14 hurricane-force storms made landfall, and five of them were major. Two of those 14 hurricane-force storms impacted the U.S. coastline: Hermine and Matthew both produced isolated impacts that could have resulted in much worse impacts for the insurance industry (considering that one cat modelling company estimates the average annual loss for U.S. hurricane is $15B). The modelling company’s average annual loss number might seem high due to the lucky streak the US has experienced in recent decades: a continued record period without a major hurricane making US landfall.

Image created by Roger Pielke Jr. who has been keeping track of the days between major hurricane landfalls.

Image created by Roger Pielke Jr. who has been keeping track of the days between major hurricane landfalls.

Undoubtedly there will always be major catastrophes in any given year, and the media will focus on these events. Undoubtedly some insurance and reinsurance companies suffered in 2016. But all in all, 2016 was a great year and could have been much worse for many more organizations within the insurance industry if the trends mentioned above were reversed. 2017 could likely change the trend of these natural perils which is why it’s best to understand exposures to all natural catastrophes.

For other great news in 2016, check out this tweet string by astronaut Chris Hadfield:

 

 

Tis the season for severe weather across the south, but it’s been extremely quiet so far?

Tornado and hurricane drought?
It’s no surprise that the recent lack of hurricane landfalls has drawn the attention of the insurance industry. The long-standing Florida hurricane drought ended with hurricane Hermine’s landfall on September 2, and of course, Matthew threatened to end the major U.S. hurricane drought as well. However, there is another drought quietly confounding the insurance industry. After 2011 and reports of a “new normal” for severe weather, several years have now passed with lower than normal tornado activity.
So far the 2016 U.S. tornado count is among the lowest of the last 11 years. As of Nov 27, 981 tornadoes touched down in the U.S., which is 303 less than the 17-year average for that time period.

Tornado counts are below the 17-year average in eight of 10 months so far this year. Most recently, tornadoes in September and October were well below average. This is despite hurricane Hermine, which spawned eight confirmed tornadoes and hurricane Matthew which spawned two confirmed tornadoes. Hurricanes can produce a significant number of tornadoes, but neither Hermine or Matthew produced very many.

torgraph-big

U.S. Inflation Adjusted Tornado Count from 1950. It shows that this year could take the record for the lowest inflation adjusted tornado count since 1950.

This year’s unusually dry tornado spell started in June, which produced only 86, the fewest in that month since 1988. The 17-year average number of tornadoes for June is 216. February, March and August are the only months that featured above-average tornado activity this year.

Had it not been for a concentrated outbreak of 35 tornadoes in Indiana and Ohio on August 24, August would have finished below its 20-year average as well. Though the tornado pace has been slow for the year as a whole, February was an exception. With 138 confirmed tornadoes during the month, it was the second most tornadic February since 1950. Only 2008 produced more February tornadoes: 146 total tornadoes, including the record “Super Tuesday” outbreak of 84 tornadoes.

avgnovtornado

 

2016tornadoreports

2016 Tornado touch down locations and daily total count which shows the lack of tornadoes since the end of September.

Through last Monday, November 21, zero tornadoes had been reported this month, which is highly unusual. With an average November tornado tally of 58 (1991-2010), we are in near-record low territory again this month. Only four other years since the 1950’s have witnessed comparably low tornado activity in November (according to NOAA Storm Prediction Center Data): zero tornadoes in 1976, two tornadoes in 1954, and three tornadoes each in 1980 and 2009.

Severe Weather Insured Losses

As one might expect, insured losses from severe weather are often a matter of luck, and although there were some powerful tornados this year, very few impacted large populated areas. Yet despite scant tornado activity, 2016 is already the second costliest severe weather year in recent years, totaling $16.6B in insured loss. This total is far behind the $28B of insured loss experienced in 2011 as a result of several deadly and damaging tornadoes across the southeast U.S. Large insured loss losses this year were likely driven by wind and hail events. In fact, over 80% of U.S. insured loss results from hail and wind events, but luck is an ever-present factor. This year, bad luck settled over the state of Texas. Several hail storms impacted large metropolitan area such as Dallas-Fort Worth, San Antonio and El Paso, and these storms have driven the large losses experienced in the U.S this year. In fact, almost half of the total loss of $7.9B so far this year occurred in Texas.

Louisiana was also hit hard by severe weather and flooding, and that bad luck could continue today with a new severe weather threat.

This week’s severe weather threat

Tornadoes happen all year, but climatologically two seasons exhibit peak activity. Spring is prime time for tornado activity. That’s when warm Gulf of Mexico air clashes with winter’s remnant cold as dry air masses spill over the Rockies. Another peak arrives in October and November, but tends to be more erratic throughout fall. In something of a reverse of the spring air migration, jet streams again traverse and target specific parts of the country as the calendar changes from summer to winter.
It’s been over seven weeks since the U.S. has had a day with over 50 severe weather reports, and today this trend may snap due to expected severe weather across the south-central U.S. The HRRR model is forecasting the formation of prefrontal super-cells by mid-day Monday across central and northern Louisiana.

hrrr_ref_louisiana_7

Today HRRR Forecasted Radar for 2 CST over the South Central U.S.

This severe weather threat will continue to move across the southeast U.S. over the next weeks, which in some cases will be welcome given the ongoing drought conditions that triggered recent wildfires.

So although it has been quiet and the U.S is at near near-record low tornado fatalities and low tornadoes counts, we shouldn’t forget what occurred in December of 2015. That December began with a record-low of 10 tornado deaths. Then waves of tornadoes struck the South and the yearly toll jumped to 36. With a more energetic weather pattern ahead, we should stay tuned and remember that droughts won’t last forever.

BMS Tropical Update 10/10/2016 12 PM CDT

Now that Matthew’s story is complete, immediate attention will turn to Nicole, a tropical storm currently 450 miles south of Bermuda. The models generally agree that Nicole will slowly strengthen back into a hurricane and that there is a good chance that Matthew will become a strong category 1 or weak category 2 hurricane as it tracks close to Bermuda this Thursday.
So with no tropical troubles threatening the U.S. coastline in the immediate future, this is the time of year that the insurance industry often wonders if there is any other tropical trouble forecasted for the remainder of the year.

Climatologically over the next two weeks we tend to see stable named storm activity, but after October 18th, the activity in the Atlantic Basin drastically trails off.

Season

This is also roughly the time of year that the West African – Cape Verde type hurricane season trails off due to the equator-ward shift of the African Monsoon. This past weekend the overall tropical rainfall seemed to shift below 10 degrees north latitude, which is the benchmark for tropical waves coming off Africa to obtain enough spin to become named storms.

1010_bmstropicalupdate_monsoon

Here is a look at the tropical rainfall totals since mid July. It shows the height of the African Waves during middle of August with a trailing off over since this period. The axis to the left is latitude showing a trend towards the equator.

This is also the time of year that colder Canadian troughs of low pressure air start to invade the U.S. Often these weather systems leave trailing cold fronts that sometimes extend into the southern Gulf of Mexico or Caribbean. Low pressure can form at the tail end of these fronts, and if the water is warm enough in the Gulf or Caribbean, it can encourage tropical convection which could then become organized. These typical developments are consistent with some of the models’ long-range weather forecasts for later next week.

1010_bmstropicalupdate_72hr

Forecasts for Thursday morning show an area of low pressure moving across the upper Great Lakes, which could provide the first freeze of the year for the upper Midwest. This forecast also shows Nicole moving toward Bermuda.

This low pressure moves across the north Atlantic late next week, and it leaves a trailing cold front with an area of low pressure off the east coast of Mexico in the western Caribbean. This is the area that needs to be watched for tropical trouble later next week as the water in this area is plenty warm enough to support tropical convection.

1010_bmstropicalupdate_216hr

The long range forecast from Oct 17  – Oct 24th  total precipitation plot below show a decent amount of rain which could be  from  convection thunderstorms.

1010_bmstropicalupdate_rainfall

 

The graphic below illustrates the climatological pattern that is typical of tropical storms that originate in October so the Western Caribbean is the place to watch over the next three week.

october_tctracks

BMS Tropical Update 10/9/2016 10 AM CDT

 

Mathew End Game

Matthew is now classified as a post tropical storm as the majority of its energy has merged with a mid-latitude frontal system.   As a result Matthew will once again defy the long range forecast models that had suggested Matthew’s energy would travel southward towards the Bahamas.  Now Matthew will go out to sea just like the majority of tropical systems and Matthew’s long story will end.

1009_matthew_nhcforecast1

Matthew Forecast issued at 8 am EDT Saturday Morning. Showed Matthew likely taking a southern track in the long term

1009_matthew_nhcforecast2

Almost a complete 180 degree change in the direction Matthew is expected to take in today’s 8 AM NHC official forecast. Now Matthew is expected to track north of Bermuda.

Flooding

However, the damage is done and it is becoming apparent that water related damages could add up to more than the wind related damages.   In fact’ the water damages will continue to add up as many major rivers in Carolinas are expected to hit record flood levels.  In some cases there have been dam breaks which is reminiscent of the incredible rain event just over a year ago from tropical moisture from Hurricane Joaquin.  So with major rivers still rising, the flood situation is still unfolding, particularly in North Carolina which will lead to more losses in the next few days. However, it is assumed the majority of the inland flooding / river/ storm surge losses are either uninsured or are being assigned to flood policies by the NFIP.   As shown yesterday, the National Flood Insurance Program take-up rate by counties which are heavily coastal in nature across northern Florida through the Carolinas decreases for inland counties.  Therefore the majority of insured losses should be driven by wind related claims.

1009_matthew_goldsboro

Record flooding forecasted at Goldsboro, NC

 

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Record Flooding forecated for Kinston, NC

This record river flooding is a result of heavy rainfall which in some places has totaled more than 12”

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Past 7 Days of Rainfall observed. It should be noted BMS iVision also has a rainfall layer users can use to understand risk impacts to flooding.

As highlighted in yesterday’s update storm surge has also done a lot of damage along the entire coast from Flroida up to North Carolina.

  • Mayport, FL 3.28 feet:  Previous record of 2.47’, during Hurricane Jeanne on September 27, 2004 (records since 1928.)
  • Fort Pulaski, Georgia 5.06 feet:  Previous record of 3.40’ during the October 15, 1947 hurricane (records since 1935.)
  • Wilmington, NC 8.21 feet:  Previous record of 8.15 feet during Hurricane Hazel in October 1954.

 

Notice in the image above however that one of the areas hardest hit by winds in Florida right along the coastline. Most of the homes are relatively undamaged from this view.   Other damage from University Florida Damage Assessment group find minor roof and exterior damage along parts of the Florida coastline with surge leading to most of the damage observed.

Wind damage

As pointed out several days ago, treefall would be enhanced due to the saturated soil conditions in the Carolinas. With this combined with wind gusts and the lack of any significant large scale wind event over the region in several years, wind related tree damage could increase insured losses.

Since wind related damages will likely drive the insured loss, users of BMS iVision can now get a full picture of Matthew’s wind swath by looking at the 1 minute wind speed and 3 sec gust wind speed.   In the coming days   users will find wind duration information.

1009_matthew_ivision

BMS iVision Verisk Climate 3 sec wind gust swath for Matthew

Industry Loss

The only public report of insurance industry loss numbers was in a report issued Saturday afternoon by, CoreLogic, which estimates Matthew’s insured losses to range between $4B to $8B with 90% of loss being driven by wind claims, 10% by storm surge.  These estimates are well below the industry loss estimates projected by the major catastrophe modeling firms late last week.  However, they are somewhat inline with the other industry loss numbers from other modeling firms (not yet released publicly).

While Matthew was within 20 miles of bringing much larger insured property losses, Phil Klotzbach of Colorado State has compiled the historic statistics on Hurricane Matthew.

Hurricane Matthew Records/Notable Facts Recap (through October 8)

Intensity

  • 80 mph intensification in 24 hours – the 3rd strongest rapid intensification in the Atlantic on record (trailing Wilma-2005 & Felix-2007).
  • 31st Atlantic Category 5 hurricane on record and the 1st since Hurricane Felix (2007)
  • Lowest latitude Atlantic Category 5 hurricane on record
  • 6th lowest MSLP for any Atlantic October on record at 934 mb (trailing Joan, Opal, Mitch, Wilma & Joaquin). Consistent MLSP records date back to 1979.

Longevity

  • Longest-lived Category 4-5 hurricane in the eastern Caribbean (<=20°N, 90- 60°W) on record.
  • Generated the most Accumulated Cyclone Energy on record for any hurricane in the eastern Caribbean
  • Maintained Category 4-5 hurricane strength for 102 hours in October – the longest that a hurricane has maintained Category 4-5 strength on record during October in the Atlantic
  • Maintained major hurricane strength for 7.25 days – the longest-lived major hurricane forming after September 25 on record and longest lasting at any time of year since Ivan (2004). Tied with Fabian (2003) for 5th longest major hurricane in satellite era (since 1966)
  • Currently ranked 8th for Accumulated Cyclone Energy by an Atlantic hurricane in the satellite era

Landfall

  • 1st Category 4 hurricane to make landfall in Haiti since Cleo (1964) – 1st Category 4 hurricane to make landfall in Cuba since Ike (2008)
  • 1st time on record that a major hurricane has made landfall in Haiti, Cuba and the Bahamas
  • 2nd time that a Category 4 hurricane has made landfall in the Bahamas since 1866 (Joaquin-2015 was the other)
  • 1st hurricane to make landfall in South Carolina since Gaston (2004)
  • 1st hurricane to make landfall north of Georgia in October since Hazel (1954)

Note: While Atlantic hurricane records go back to 1851, there are likely underestimates in storm intensity prior to the satellite era (since 1966) and especially prior to aircraft reconnaissance (since 1944).

 

BMS Tropical Update 10/8/2016 10 AM CDT

Matthew Weakening

Matthew has weakened from a category 3 hurricane yesterday afternoon down to a category 1 hurricane overnight.  Matthew has officially made landfall near Mcclellanville, SC as a category 1 hurricane.   Matthew has weakened due to a shallower continental shelf and lower ocean heat content. Also as Matthew has tracked further north it has been able to wrap in some cooler, drier air into the center of its circulation allowing some weakening.

Over the next day Matthew will continue to weaken as it moves along the South Carolina coastline before it moves out into the Atlantic near Wilmington, NC where it will start to track southeastward. The biggest impacts over the next 24 hours will be inland flooding as the rain shield from Matthew extends across the Carolinas and into the southern  Mid-Atlantic states as the warm moist air from Matthew rides up and over a frontal boundary across the eastern United States.  Just one year after hurricane Joaquin, enhanced rainfall parts of the Carolina’s could see 5 – 14 inches of rain again.

 

1008_matthew_7dayrainfall

Total radar observed rainfall over the last 7 days

 

1008_matthew_nfip

Percent of homes that have flood policy thru National Flood Insurance Program (NFIP). Very low take-up rate inland.

Overnight Impacts

Storm surge has been the biggest impact overnight. Savannah, GA  has seen record flooding breaking the previous record which was created during hurricane David in 1979.  Other hard hit areas by high storm surge were Tybee Island, GA, Hilton Head Island, SC and Charleston, SC.   However, it would appear the overall height of storm surge was 2 feet below what was forecasted for many of these areas.

1008_matthew_savannahflood

Tide Gage at Fort Pulaski near Savannah, GA

It has been a long time since a hurricane of this strength has impacted the Georgia, South Carolina coastline.  In fact a few years ago I took a trip to Hilton Head Island, SC and I could not believe the over growth of foliage on the island, which was likely due to the fact this area has not recently been hit by a hurricane.  Hurricanes are nature’s way of cleaning out some of that foliage.  I expect this could lead to some higher than normal insured loss from tree fall right along the coastline.   The maximum wind gust record at Hilton Head, SC was 87 mph and Tybee Island, GA was 96 mph.

1008_matthew_windgust

treehiltonhead

 

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BMS iVision shows the historical 3 sec Max Wind Gust and now the forecasted wind gust. This allows clients to get a complete picture of possible wind damage.

 

Matthew Extended Forecast    

Later next week Matthew will be a tropical storm or depression off the southeastern U.S.   It would now appear that Matthew’s energy will reach the Bahamas and even track south into the southern Gulf of Mexico later next week, however, not as a named system.   Hurricane Ivan in 2004 made a similar large loop and reformed in the Gulf of Mexico.  No models at this time forecast Matthew reforming in the southern Gulf of Mexico, but this is something to watch out for. In the next three weeks this would be the area to watch for new tropical development.     There is still a chance that Matthew will get caught up with hurricane Nicole in the Atlantic and move out into the open ocean later next week as well.

 

1008_matthew_00zecmwf

ECMWF ensemble forecast showing many of the 51 members tracking the remnants of Matthew south of the Florida keys next week.

BMS Tropical Update 10/7/2016 10 AM CDT

Summary

  • 4,001days: that is how long it has been since a major hurricane (Wilma) made landfall in south Florida. And today, Matthew, the violent end to the U.S major hurricane drought, rages into day two.
  • Many of the hurricane models that forecasted a central Florida landfall were clearly wrong, as Matthew is currently 35 miles off the coast of Cape Canaveral as a 120-mph category 3 hurricane. Even the trusted ECMWF model predicted a central Florida impact yesterday. But there are some model winners. The BMS iVision Verisk Climate wind model never predicted a landfalling outcome. And yet again, we see that there is continued room for improving hurricane track and intensity forecasting.
  • As I suggested on October 5, hurricane track will drive outcomes. I also mentioned that the storm size would make a difference, and Matthew’s hurricane force winds never really expanded.
  • Matthew is now expected to parallel the Florida coastline and slowly weaken, so insured loss should be confined to near-coastal areas close to its current location and up to the southern North Carolina coastline.
  • Matthew is forecasted to stall or loop near the southeast coast of the U.S.

Landfall and Wind Impacts

“Landfall” is defined as the center of low pressure that intersects with the coast. This has not occurred with Matthew. For several days, weather models suggested that Matthew’s ultimate landfall (or lack thereof) would be determined by just a matter of miles. What might be more interesting than whether or not Matthew makes landfall is the fact that the last two largest U.S. insured losses from a hurricane will ultimately be caused by storms that failed to make landfall. Sandy (2012) was never officially classified as a hurricane and thus didn’t make landfall. Matthew may never make landfall, but will still likely cause significant insured loss; most likely the highest insured loss since Sandy.

Matthew never grew in size as expected, and for the most part, always maintained a very small area of hurricane force winds. This area grew only nominally as it moved north as illustrated in the NHC wind history plot below.

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Past extent of the hurricane force winds and tropical storm force winds

Matthew has maintained its track parallel to the Florida coastline overnight, as it never got pulled landward, and the hurricane-force wind around its small center of circulation have primarily stayed off shore.
This will likely mean that insured losses will be limited, so in some cases insurers will ultimately retain a greater portion of their losses (versus collecting on higher attaching reinsurance programs designed to respond to major natural catastrophes). These retentions could add up, especially since it has been 35 days since hurricane Hermine impacted the state and caused minimal insured loss primarily retained by insurers. Still, the full extent of insured losses will continue to develop as Matthew continues to track up the north-Florida, Georgia, and South Carolina coast.
Wind Reports

I have yet to identify a hurricane-force wind speed recorded at an official weather station. The highest wind gust I have seen so far is 74 mph, recorded at Vero Beach, Florida. This would not translate into a hurricane-force wind, which must be measured at 1 minute resolution. There have been other reports of high wind, especially on the high tower near the Cape Canaveral coastline. Keep in mind, however, that many of these towers are hundreds of feet tall, and much higher than the official 30-foot measuring height.  Other higher windspeed gusts could occur yet today as Matthew tracks very close to the Florida coastline.

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Strongest wind guest from observations last nights

Although structures will likely sustain damage given the observed wind speeds, ultimate damage should be minimal. To illustrate, see the damage plot below for a pre-2002 home that experienced category2 wind speeds. The outcome shows 35% probability of at least roof sheathing damage. Probability drops to a 5% for a category 1, and even less for a tropical storm force wind.

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General  probability of at least roof sheathing damage vs wind speed

Rainfall
As one would expect, and as my blog previously suggested, flooding can be expected in Georgia and the Carolinas as Matthew tracks northward.

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NOAA rainfall forecast showing 13 inches rainfall for areas of the coastline

Surge
Storm surge has not been as bad as forecasted. Areas with 9-foot surge forecasts ultimately experienced only 6-foot surges. However, high storm surge values are still forecasted for coastal Georgia and South Carolina as Matthew works it way northward. Currently some of the highest surge forecast values are found along the North Georgia.

 

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Water value observed near Trident Pier, FL showing the build up storm surge at this station in this area and the fall of that water as the storm passed and the water gets pulled away from the shoreline.

Matthew Just Won’t Go Away
The burning questions seem to be, “Is Matthew really going to do a loop off the southeast coastline? Is this possible?” Yes, it is very possible, but also unusual.
Gordan (1994), Felix (1995), Ivan (2004) and Jeanne (2004) are all examples of looping storms. However, as indicated in the plot below, south or even southeast hurricane movement is rare, as most trajectories for Atlantic hurricanes track northeast.

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Hurricane Gordon 1994 did a nice loop off the southeast coast

Another burning question is, “Will Matthew loop back and impact the Bahamas and Florida again?” It is possible and still a possible outcome on many of the long-range ensemble forecasts. My bet is that Matthew will loop northeast of the Bahamas, but then be kicked back out to sea toward Bermuda around Thursday next week.

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ECMWF track model showing the chances of the Matthew getting back to Florida or Bahamas

BMS Tropical Update 10/6/2016 10 AM CDT

Summary

  • Matthew is a weak category-4 hurricane and will likely slowly strengthen today as passes over Nassau, Bahamas.
  • Matthew will likely make landfall between Jupiter, Florida, and West Palm Beach, Florida, as a category-4 hurricane. Landfall should weaken Matthew to a category 2 by the time it reaches Daytona Beach, Florida, and then travels up the coastline. I don’t anticipate that the center will track more than 10-20 miles inland.
  • There is a very small chance that Matthew will become a category 5 hurricane before it reaches the Florida coastline, as it will likely strengthen until its inner core starts to interact with the Florida coastline.
  • Estimating the maximum storm surge is a bit complicated as these forecasts depend on Matthew’s track and strength as it travels up the Florida coast. If Matthew weakens due to land interaction, surge will be less severe; but if Matthew stays off shore, more water may move onto the coast, and this surge could be further complicated by multiple tide cycles that are expected during Matthew’s move up the coastline.
  • Given the large amount of exposure along the coast and expected wind gusts of 144 mph, this will no doubt be a significant insured loss event. For specific impacts, each National Weather Service (NWS) office is offering detailed forecasts for Matthew.
  • In the longer-range forecast, Matthew will likely loop over or the stall off the southeast coast this weekend or early next week. This will limit insured losses in locations that are north of South Carolina.

Forecasted Landfall Location and Specifics
As I have mentioned, Matthew is tracking over very warm water in the Bahamas. This warm water will continue to fuel Matthew until it starts to interact with the Florida coastline tomorrow morning. Keep in mind that hurricane-intensity forecasting is typically more predictable than hurricane-track forecasting. Matthew already surprised us this past weekend with rapid intensification to a category-5 hurricane in the southern Caribbean. It should be noted that, currently, no model guidance is forecasting further rapid intensification.  The intensity guidance below show most models are in the camp that Matthew will be category 4 hurricane at landfall or along the Florida coastline.

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With Florida land interaction expected in the 36 hours. The intensity of Matthew should weaken considerable especially if it tracks inland a bit vs staying over open water.

For the last week, meteorologists have used the long-range hurricane models to predict Matthew’s track. We are now within what is considered the short-term forecast window where higher-resolution weather models become a bit more useful for providing specific hurricane forecasting.
HRRR (High Resolution Rapid Refresh) is a high-resolution (3K grid resolution) model which shows the details of a hurricane and its impacts. This model is updated hourly and forecasts the next 18 hours. Here is the latest hourly forecasts.

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My general expectation is that Matthew will make landfall and track inland 10-20 miles along interstate highway 95. This counters some high-resolution models that suggest Matthew will track along the Florida coastline. Three of these models are the HWRF, GFDL and Verisk Climate model (which is the basis for BMS iVision).

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HWRF Forecasted Wind Swath. This is not surface wind speeds These are winds at 900 mb which close to the surface.

 

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GFDL Forecasted Wind Swath. This is not surface wind speeds These are winds at 900 mb which close to the surface.

 

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This is the National Weather Service (NWS) Forecated wind swath

 

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BMS iVision Verisk Climate wind swath which is a version of the WRF model. Users of iVision can use this product to get an ideas of risks impacted by wind speed.

One important point I want to make is no numerical weather prediction model is at a high enough resolution to resolve the details of surface roughness. It is this surface roughness that would likely weaken the winds inland. So many of the modeled forecast plots above are likely overestimating the wind speed. This is particularly apparent in the National Weather Service forecasted wind swath.

At this time, much can be gleaned from the various NWS forecast products because they offer great detail on potential impacts. These details include likely power outages, specific areas that are prone to flooding, tornado threats, etc. Many of these NWS offices offer public video briefings as well. In some cases the wording is quite strong, and for good reason, as Matthew is a dangerous, life-threating storm.

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Estimating the maximum storm surge is a bit complicated as these forecasts depend on Matthew’s track and strength as it travels up the Florida coast. If Matthew weakens due to land interaction, surge will be less severe; but if Matthew stays off shore, more water may move onto the coast, and this surge could be further complicated by multiple tide cycles that are expected during Matthew’s move up the coastline.  Please utilize the new NHC storm surge forecast guidance. This guidance will change with the NHC track forecast. Right now the worse storm surge will occur in north Florida where the continental shelf extends out into the Atlantic and water will have more time to pile up.  Surge values in this general area could be greater than 9 feet in isolated locations.

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Storm Surge Forecast For Jupiter, FL

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Storm Surge Forecast For St. Augustine

 

Another issue that is not being talked about much is the possible flooding of Lake Okeechobee. The lake level is very high right now at 15.78 feet.  A  risk of flooding starts to occur if this lake reaches 17″. If the lake level goes up to 20″ this could be a major concern as this is a known dike that is dire need of upgrades and if given to much stress it could break if water levels get too high. Matthew will no doubt raise this lake level.   The Weather Channel has a good summary  of the risk.

Long Range Forecast

As we have seen for over the last week, Matthew’s long-range forecast remains uncertain. But the chance of significant insured loss at locations north of South Carolina is declining. Many global models suggest Matthew will loop off the southeast coast. Some of these model solutions even take Matthew back into the Bahamas or Florida, and in one extreme case, back into the Gulf of Mexico. Most likely, Matthew will sit and stall near the southeast coast and weaken while doing so. Matthew will eventually be kicked out into the Atlantic Ocean. However, as with any long-range hurricane track forecast, a lot of variables are at play, so Matthew’s long-range tracking still requires watching.

 

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The newest ECMWF forecast which has shown the best skill in the long range 3+ day range

 

 

BMS Tropical Update 10/5/2016 11 AM CDT

Summary

  • Matthew has weakened slightly due to interaction from Cuba and Haiti yesterday and is currently still a weaker Category 3 hurricane 115 miles south of Long Island Bahamas. However, it will only take 12 – 24 hours to regain strength into a stronger category 3 or 4 hurricane as it nears the Florida coastline.
  • Wouldn’t it be something if a major hurricane comes within miles of the Florida coastline and the major hurricanes drought lives on?  How about the fact than that the last two major hurricanes to impact the U.S. never made landfall?  This is still an option as some models keep Matthew from making landfall and other models have it making landfall in Florida.    I have no change in the analog storms provided in yesterday’s update as it relates to southeast impacts.
  • When a hurricane is forecast to take a track roughly parallel to a coastline, as Matthew is forecast to do from Florida through South Carolina, its impact can vary greatly depending on this final track. A small deviation of the track to the left of the NHC forecast could bring the core of a major hurricane onshore, while a small deviation to the right could keep all of the hurricane-force winds offshore.
  • Depending on location some parts of the southeast have been fairly wet over the last 30 days. This could amplify the inland flood threat and increase tree fall where the ground could be saturated.   As much as 5 to 7 inches of rain is forecasted for coastal areas of the southeast.
  • There is still uncertainty in the long range forecast. As mentioned almost a week ago there is a chance Matthew would do a loop off the southeast coast.  More and more model runs are coming around to this idea.  This decreases the threat to northeast impacts late this weekend and into next week.  However, this increases the chances that the Bahamas or even Florida could see a second landfall from Matthew.  Rising issue of hour clauses and what part of the storm caused the loss if this scenario occurs.

Expect Strengthening

As expected Matthew has weakened slightly due to interaction from Cuba and Haiti yesterday.   However, as stated almost a week ago the water along the forecasted path of Matthew is very warm and should allow for Matthew to strengthen as it moves closer to the Florida Coastline.  I was also expecting Matthew to grow in size as currently the hurricane force winds only extend out 40 miles from the center of Mathew.  Depending how far off shore Matthew stays will determine the strength of the hurricane north of the Bahamas.  If Matthew stays off shore I still see no reason why Matthew would not become larger and stronger than the current NHC forecast.

 

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Tropical Cyclone Heat Potential highlighting the water over the Bahamas is near the top of the scale. Lots of energy for hurricane growth.

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Current Hurricane Matthew Intensity Guidance

 

Tricky impact forecast

As you might imagine the overall impact of Matthew on the southeast coastline will depend ultimately where it tracks along the coast or if it makes landfall.  The NHC sums up the overall uncertainty here in its key messages.

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To illustrate the point let’s take the current NHC forecast point near West Palm Beach, Florida, and shift an illustrated impact area 10 miles on either side of that point.  As you can see the overall track of the storm makes a big difference.

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Image credit Bryan Wood

There is still a risk of storm surge potentially affecting certain coastal locations. Overall, the Atlantic side of Florida has a steep shelf offshore which tends to protect the coastline from large surge.  However, wave action could be a concern given the lack of beach area along the east coast of Florida.  As stated yesterday the direction of Matthew to the north will also mitigate the most significant of surge threats but this threat increases in northern Florida and in Georgia and the Carolinas.  Again, like wind impacts, the surge impacts are dependent on the size of the storm, the intensity, and the track.

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Latest 3 sec wind speed swath in BMS iVision

Other impacts to think about

With the understanding that it’s been a long while, over 10 years, since a major hurricane impacted Florida and in some cases a major hurricane has never impacted parts of Florida.  This means the overall foliage is likely over grown and needs a good cleaning.   It is Mother Nature’s job to do this and if it has not been done in a while this can surely increase insured loss. We can also look to see if tree fall has a higher likelihood of occurring due to wet soil conditions.     Some parts of the southeast have been fairly wet over the last 30 days. This could amplify the inland flood threat and increase tree fall where the ground could be saturated.   As much as 5 to 7 inches of rain is forecasted for coastal areas of the southeast.

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Rainfall over the last 30 days for the Southeast U.S.

 

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Departure from normal of this rainfall over the last 30 days. In some locations the rain might be a welcome sight as it has been dry.

 

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NOAA Seven Day Rainfall Forecast

 

Northeast impact or Loop?

With any hurricane forecast there uncertainty in the long range forecast.  As mentioned almost a week ago there is a chance Matthew would do a loop off the southeast coast.  More and more model runs are coming around to this idea.  This decreases the threat to northeast impacts late this weekend and into next week.   It is still too early to have complete confidence in this shift.  However if this does occur maybe we will have yet another example of a hurricane that loops.  This would also increases the chances that the Bahamas or even Florida could see a second landfall from Matthew.  Rising issue of hour clauses and what part of the storm caused the loss if this scenario occurs.

A large GIF annimation of 00z GFS 240-hr forecast at full-res 13-km showing surface wind speed.

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