BMS Tropical Update 6/20/2017 12 PM CDT

By: - June 20th, 2017

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

 

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

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

 

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

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

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

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

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

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

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