BMS Tropical Update 8/25/2017 12 pm CDT

By: - August 25th, 2017

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

 

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