BMS Tropical Update 8/30/2017 12 PM

Harvey Help
Over the week I have shared resources that can help the insurance industry understand the impact from Hurricane Harvey. Now that Harvey is moving slowly inland, with smaller creeks receding and damage assessments beginning, I would like to summarize and share more resources that will help the insurance industry understand Harvey’s impact.

As previously mentioned, BMS clients and prospects have access to several tools that may help understand the various impacts of Hurricane Harvey via the BMS iVision Geospatial Mapping Solution. These products are available across various geographic regions, including the Gulf Coast, with storm attributes that include hurricane and severe weather perils that often accompany a hurricane. Users can intersect these attributes with policies at risk to get an idea of exposure and apply damage ratios as a first guess at potential losses.

STORM ATTRIBUTES FOUND IN IVISION (CREDIT: VERISK CLIMATE DATA):
• Hurricane past and forecasted track, sustained winds and wind gusts
• Hail size, probability and duration
• Severe Thunderstorm winds, radar max and rainfall

BMS iVision Verisk Climate Total Rainfall Map from between 8/23/2017 – 8/29/2017

 

BMS iVision Verisk Climate Hurricane 3-sec Wind Gust Swath

 

BMS iVision Verisk Climate Hurricane 1-min Sustained Wind Swath

 

BMS iVision Verisk Climate Wind Gust Duration (hr) of 50+ mph

Of course it is possible to add other data attributes to iVision as needed and that has been done for specific users. Outside of BMS iVision, there are several great sources that have appeared to help understand Harvey’s impacts.

Harvey Wind Damage Resources
The NOAA Remote Sensing Division has provided high resolution airborne imagery to support NOAA national security and emergency response requirements. These images have been combined into a larger mosaic and tiled for distribution. The approximate ground sample distance (GSD) for each pixel is 50 cm / zoom level 18.
https://storms.ngs.noaa.gov/storms/harvey/index.html

ESRI Harvey Disaster Response Mapping with various resources with Social Media Layers in which your login for these would be required.
http://disasterresponse.maps.arcgis.com/apps/PublicInformation/index.html?appid=542e7fa7eadd49deb780648daf487e76

Harvey Flood Resources
Detailed FEMA Flood Zone Mapping of the Houston Area
http://water.weather.gov/ahps2/inundation/index.php?gage=pptt2

U-Flood is a crowd sourced effort to map inundated roads in Houston. Flooded (or cleared) streets may be reported by zooming into the map and clicking/tapping them.
https://map.u-flood.com/houston/#14/29.8000/-95.4000

The interactive map of evacuation zones for the Brazos and San Bernard Rivers is below.
http://fbcgis.maps.arcgis.com/home/webmap/viewer.html?webmap=97aa8889f54545d5a9c3accd4fa8cb6a

Addicks and Barker Potential Flood Maps

http://www.swg.usace.army.mil/Media/News-Stories/Article/1294384/addicks-and-barker-potential-flood-maps/

FM Global Flood Mapping
https://www.fmglobal.com/research-and-resources/global-flood-map/flood-map

Houston Harvey maps from the New York Times
https://www.nytimes.com/interactive/2017/08/28/us/houston-maps-hurricane-harvey.html
https://www.nytimes.com/interactive/2017/08/24/us/hurricane-harvey-texas.html

Background of urban development in the Houston Area with some flood maps
https://projects.propublica.org/houston-cypress/

Other Tropical Troubles
As I mentioned in Monday’s post, a new tropical wave has been named (Irma) in the Main Development Region of the Atlantic and will track toward the U.S. coastline. Irma is still 10 days away, but given the pattern so far, the chances of a U.S. tropical threat late next week are high, but there is still a lot of uncertainty in the pattern as a major cool down for the east coast next week will likely play a role in Irma’s future track. I will provide new updates on this threat as it develops.

BMS Tropical Update 8/28/2017 12 PM

Harvey the Good and Bad News

If there is a bit of good news, it might be that Harvey is pulling in dry air which is giving some reprieve to the heavy rainfall near the center of Harvey.  The bad news is that Harvey as forecasted to moving out over the warm water of the Gulf of Mexico which could further enhance convection and increasing the flow of moisture once again over the next few days.

Harvey Current Status and the End Game

Harvey is currently a tropical storm near Port O’Connor, which is about 50 miles from where Harvey initially made landfall on Friday evening as a Category 4 hurricane. Harvey, which is only moving at 3 mph, will slowly head back over the warm Gulf of Mexico. It is at this point that it will likely slowly start its northeastward movement towards a second landfall area between Houston and the Texas / Louisiana border.  During this time Harvey will continue to tap moisture from the Gulf of Mexico, but at this point there is very little model support for Harvey to regain hurricane strength.  As it moves to the northeast the extensive rain shield will also move to the northeast into Louisiana, which will increase the flood potential for much of the state over the next few days.  By Friday this week Harvey will be extra tropical system over Arkansas and the named Harvey will be retired into the history books only to be referenced back to much like Andrew, Katrina and Sandy are today.

 

Flood

The flood situation continues to unfold.  I honestly can’t keep track of all the records that have been broken, there are so many. So far as far as I can tell the 48″ rainfall record has not been broken yet, but 35″ rainfall totals have been reported which verify the forecasts made early last week.   Some of the most important records are the forecasted river crest in and around the Houston area.  For example, Buffalo Bayou that flows into downtown Houston, has already seen record flooding, in some places by 10 ft.  The gauge at Point Village suggest it will be at record flood stage for at least five days which is likely due to the  Army Crop releasing water from the giant flood retention areas of George Bush Park (Barker Reservoir) and Addicks reservoir and dam just north of the Katy Freeway (1-10).  Both of which are Army Corps project to protect Buffalo Bayou and downtown Houston from flooding.

The Army Corp has told some residents their homes could be flooded for up to two months.

 

Insured losses

It is still too early to get a complete view of what the insured impacts will be from Harvey as the flood situation continues to develop. With the wind and surge loss estimates ranging from $1 to $3 Billion in insured losses the flood losses will highly depend on what the commercial and energy sectors sustain from the flooding.  There could likely be high content and BI losses within these sectors. The general view is personal line home owner risk is largely not covered and falls on the NFIP. However, if past events are used severe flooding can take its toll on to the auto segment of the industry.  A bit unknown is some private-sector insurers have started to sell stand-alone flood coverage to homeowners, but it is unclear what the market penetration is at this point.

Economically Harvey will likely be one of the largest natural disasters in U.S History. There is talk that it could rival Katrina and given that Houston is the 4th largest city in the U.S. there is clearly more economic potential to be damaged.

Maybe the best initial conservative estimate of Harvey on economic loss might be from disaster economist Kevin M. Simmons, Austin Collage. 

Other Tropical Troubles

Currently Potential Tropical Cyclone #10 is off the Georgia/South Carolina border and has a 90% chance of becoming a tropical depression or named storm Irma over the next 48 hours.  The overall impact to the insurance industry should be minimal as the Outer Banks would be the only area to experience tropical storm force conditions as it races out over the north Atlantic this week.

The next area of tropical trouble is off Africa this weekend and is currently south of the Cape Verde Islands.  This system is looking healthy and unlike many of the other African waves the dry dusty air currently is not a factor.   I expect that a depression could form later this week.

The long-range models take this system across the Atlantic over the next 10 days. The general consensus is that it would follow a track similar to Garet and approach the East Coast of the U.S.  However, as stated many times this season as tropical systems get closer to the U.S. overall conditions get better for strengthening.

Hurricane Risk from now until September 11th. Again after this tropical wave I think the overall activity shuts down for most of September.

 

BMS Tropical Update 8/27/2017 12 PM

Bad Situation Getting Worse

Another day that I am overwhelmed with data and the impacts from Harvey and unfortunately today the data is suggesting the rainfall amounts are likely higher than what was predicted to fall over the seven-day period starting this past Thursday.  I will once again try to focus on insurance industry impacts from Harvey which has now turned to major flooding in the Houston area and will likely be one of the costliest flood events in U.S History.

Harvey Position and Forecast

Harvey, now a tropical storm with winds of 40 mph, is currently centered near Yorktown, TX or about 70 miles east southeast of San Antonio, TX and moving at 1 mph to the southeast.  Harvey is still not forecasted to move out of Texas until later next week, therefore days of rain are still expected on top of what has already fallen.  The general consensus is that Harvey will weaken to a tropical depression and move slowly back towards the coastline and work its way up the Texas coastline toward the Texas Louisiana border.  Some models suggest Harvey could move back over the Gulf of Mexico where it could regain some strength as it moves toward the border, but the wind damage threat is mostly over for Harvey and any wind damage would come from tornadoes or isolated thunderstorm.

Because Harvey will continue to draw in warm Gulf of Mexico moisture, its rain shield will continue move to the northeast along its track.  The heaviest rain will move into Louisiana as Harvey moves to the Northeast over the next several days.

Radar Image showing that moisture trail feeding heavy rainfall into the Houston area.

Tornadoes

I only briefly touched on the tornado threat leading up to Harvey’s landfall.  So far Harvey has spawned 20 confirmed tornadoes and some of these tornadoes have cause insured loss and more tornadoes can be expected as Harvey continues to impact the area over the next few days.

Areas of Tornado Yesterday are represented by Tornado Warnings issued by the NWS

Flood & Rain

Since Monday the forecast have called for over 20” of rain to fall from Harvey as it stalls out along the Texas coastline.  These forecasts continue to show that another 26” of rain could still fall over the area over the next 7 days.   This means that Harvey will likely go down as one of the heaviest rainfall events form a Named Storm in history as total rainfall reaches over 50”. This is very impressive considering Texas is no stranger to very heavy rainfall events. Just last year the Tax Day flooding event in Houston area caused widespread flooding, dumping as much as 23.5″ in 14.5 hours in Pattison, TX and causing insured losses of $584 million dollars according to PCS.

Tropical Storm Amelia in 1978 still holds the record for most rainfall over the state from a named storm as it dumped 48” over a five-day period and Harvey could just surpass this event before the end of the week.

Tropical storm Claudette 1979 still remains the twenty-four-hour rainfall record for any location in the United States with 42” of rain falling.     

More recently Allison 2001 caused massive flooding in the Houston area.

The rain continues to fall from Harvey, below is the most recent rainfall totals as viewed in BMS iVision in its severe weather module which has rainfall maps over the last seven days.

 

 

Radar estimated storm total for Harvey so far and the areas of major river flooding.  Basically any body of water is likely to see record flooding.Below is a Free Flood mapping tool created by FM Global that can help determine areas of flood hazard. This is not a flood map for Harvey, but it’s a safe bet any areas shown as flood areas are or will be flooded from Harvey

Insured Loss

It is now easy to understand that Harvey will easily reach well over $10 billion USD in economic loss.  The winds and surge losses are still being assessed and given the footprint of affected areas, it is going to take weeks until full assessments are gathered to understand the totality of the damage.   However, from what we know now the general consensus seem the wind related losses will likely be in excess of $2 Billion in insured loss with a much higher economic loss. If you combine this with what historical flood events have done just to the Houston area in the past (Allison 2001 $3.4B adjusted – $10B economic) insured losses are likely in excess of $5 billion dollars.   In fact, for more perspective the catastrophic flooding that occurred in Louisiana last year (August 11 – 15) caused $1 Billion in insured loss according to PCS.   That flooding occurred over an area with about 850K people.  Houston has 7 times more population being the fourth largest city in the U.S. and the rainfall totals will be higher than what occurred in Louisiana last year.

In all the figures above I have not even accounted for NIFP losses which will just add to the expected losses.  As indicated earlier in the week flood coverage is highest along the Texas coastline, however, according to NIFP many areas along the coastline still fall below 20%  coverage.


Clearly this could likely be one of the largest NFIP flood payout in recorded history which will require a major relief bill.  It will likely have major impacts to the flood reform that will be discussed in Washington over the next several months.

Storm off the East Coast

I expect the storm off the Southeast Coast Invest 92L  to develop into a named storm (Irma) but this will not be a threat to the U.S. Coastline.

There is a medium chance of more storm development off the coast of Africa later this week.

 

BMS Tropical Update 8/26/2017 12 pm CDT

What a Week

What a week meteorologically that shows the opposite ends of how great and devastating nature can be.  The week started with a rare eclipse that crossed the U.S. and ended with a tropical system that went from a depression to a Category 4 in 48 hours.

With daylight we are starting to see the initial impacts from a major hurricane landfall that made landfall at 10 pm CDT last night .  Given that this is the first major hurricane in the information mobile age there is just a wealth of information to take in that is almost overwhelming.  In fact, since this is the first major category 4 to make landfall since Hurricane Charley in 2004 it will likely provide very valuable data to the insurance industry, which has a lack of datasets for such events.  From mobile weather stations and surge devices being deployed ahead of landfall to mobile radar and drone aircraft, this will no doubt be one of the best documented major hurricane landfalls that has ever occurred.

However, I can’t stress enough that the event is not over. It is just starting, and as forecasted, the storm has slowed and is still expected to stall out over the next week and is expected to dump feet of rain along the Texas Coastline.

Harvey Landfall Details

Hurricane Harvey is now only the sixth Category 4+ landfall in Texas weather history (since 1851), and the 2nd in the last 100 years.  Below are the top ten strongest hurricanes at landfall and Harvey is the strongest since Charley in 2004, but likely won’t make it into the top ten in terms of wind and will be 14th in terms of pressure.

List of the strongest hurricane by wind speed to make landfall in U.S. Harvey will not make this top ten list.

In fact, what is more remarkable is from 1926-1969 (44 years) 14 Category 4 U.S. landfalls occurred, but since 1970-2017 (46+ years) only 4 Cat 4+ landfalls have occurred.  This is a decrease greater than 70%.  Statistically the 12 years without a major hurricane landfall will be very hard to replicate, but let’s hope this does not start a trend in the opposite direction.

As pointed out the building standards in Texas are not as good as other states, but the fact is even the best built homes are not designed to withstand category 4 winds. The heaviest wind damage from Harvey appears to be in Rockport, Fulton  area.  Thankfully Harvey’s highest winds likely occurred over Matagorda Island State Park and Aransas National Wildlife Refuge, where there are very few structures or population. This will no doubt limit wind damage form Harvey.

Area of landfall that shows overall luck played a roll in limited damage as a state park likely took on the strongest winds. Any other island like this along the U.S. coastline would be full of homes.

 

If Harvey would have tracked just 20 miles further south it would be a completely different story in Corpus Christi, which has sustained damage to buildings, but not like the Rockport area.

It would be rare for a surface observation to verify Harvey category 4 winds, but category 3 winds have been verified.  In fact, at 8:48pm CDT, the C-MAN station at Port Aransas, TX sustained 10 meters winds of 114mph with gusts to 131mph. Some other notable wind speed gusts were 110 mph at Copano Bay, 108 mph in Rockport and 102 mph in Aransas Wildlife Refuge, but as mobile station data is collected and communication is restored, more data will be collected providing even more high wind readings.  Another interesting observation is that the pressure gradient was very steep, with an air pressure of 994mb in Sinton, TX and 943mb or so in Rockport, TX  which is a difference of 51mb over 30 miles. This is why the winds were so strong but also indicates that the radius of maximum winds was quite narrow which will also limit damage over a large area.  However, it is known there are many high value homes in the area as lots of folks from Austin and San Antonio like going to the beach on weekends.

 

BMS iVision Max Wind Gust over the last 24 hours.

BMS iVision Max 1 Min Sustained Wind Speed showing the swath of Harvey and track. Notice the limited inland impacts from high winds.

The exact central pressure has yet to be verified as there are several storm chasers that recorded a pressure of 938 mb.  One notable chaser “icyclone” who likely holds the world record for a human to experience so many hurricanes worldwide said on twitter that this was “one of the worst I’ve been in”.  His calibrated pressure reading was 940.8 mb at 10:31 pm.  This could be very important as once again these readings could influence payout in the Cat Bond market, in particular the newly revised  IBRD / FONDEN 2017  Mexico’s Fund for Natural Disasters Bond that was revised to cover points in North Texas this go around, however, at this early stage it is unclear if the center crossed the box needed with a pressure of 930 mb.

Insured Loss

As mentioned above there are several cat bonds at risk of payout.  However, it is still too early to determine what the exact insured loss will be as the event is still unfolding with days of heavy rain yet to occur.  And with heavy rain still to fall in Harris County this will likely determine the overall event impact with a high percentages of flood-prone properties there.  It has been suggested that the LiveCat market was predicting a payout attachement point of $10B U.S. dollars, however Harvey strengthened right up until landfall and will stall out making modeling of this event very difficult.  The modeling that was provided yesterday will likely better account for the strengthening at landfall and new loss estimate will likely be revised upwards because of this.

Storm Surge

At this point in time the storm surge has not been as high as predicted as Harvey just did not have the overall size to cause devastating surge similar to Hurricane Ike, this will also limit some insured losses.

http://surge.srcc.lsu.edu/harvey_2017.html

https://tidesandcurrents.noaa.gov/quicklook/view.html?name=HARVEY

Various Storm Surge Readings from the landfall area.

Flooding Rains

As mentioned all week, flooding rain will be a major problem with Harvey stalling out.   The latest storm summary from the national weather service suggests rainfall totals are already approaching 15″ with several other spots closing in on 10″.

 

This is the latest 7 day forecast rainfall total.

Forecast

There is no change in Harvey’s forecast.   Harvey will slowly spin in the same spot for the next several days.   The option of a second landfall later next week are slowly dwindling off the table, but it can’t be ruled out at this moment as pointed out by the ECMWF model below

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.