As expected from last week, two areas of tropical trouble are trying to form in the Atlantic Basin. If both of these tropical systems manage to get named this week, it would be fairly rare as only three Atlantic hurricane seasons on record have had two concurrent named storms in June. Those years were 1909, 1959 and 1968, all of which turned out to be average to slightly above average hurricane seasons with a higher than average landfall rate across the U.S. This is in line with the general thinking of what could occur this Atlantic hurricane season.
Since last week, the National Hurricane Center (NHC) has been watching these two disturbances. One of these has been centered north of the Yucatan Peninsula and has been labeled Invest 93L. The other disturbance is labeled Invest 92L and is currently located 325 miles ESE of Trinidad, moving rapidly toward the southern Windward Islands. In fact, for the first time ever for a tropical system, the NHC has begun issuing advisories for 92L before it is a depression or named storm and has also labeled the system “Potential Tropical Cyclone Two.” I talked about this possibility in my New Hurricane Products for 2017 Season blog post. The NHC is doing this because there is an immediate threat of tropical storm force winds to land, which, in this case, would be in the southern Windward Islands where the watches and warnings are in effect.
What is the forecast and worry for insurance industry this week?
“Potential Tropical Cyclone Two”
Potential Tropical Cyclone Two has a 90% chance of tropical development over the next two days. Early visible satellite imagery suggests the system is still an open wave and does not have a closed center of circulation, which is part of the criteria for storm naming by the NHC. My guess is that the NHC will wait to name the storm (Bret is the next storm name) until this afternoon when an Air Force reserve hurricane hunter aircraft is scheduled to investigate the potential tropical cyclone. Depending on what the aircraft finds, it could get a name. Regardless of whether the potential tropical cyclone gets a name, stormy conditions will be experienced in the southern Windward Islands. The forecast models are suggesting that after today the system will struggle to maintain itself as interaction with South America and increased wind shear will likely hamper any development in the second half of this week. This means the overall impact to the U.S. insurance industry is minimal at this time, and even if named, it would be a short lived tropical system.
Invest 93L also has a high chance of tropical development over the next two days with an 80% chance of development. The reason why the NHC has not issued advisories for this system is they currently feel the threat of tropical storm conditions is less severe and it could take a few days to produce strong winds over land. So overall, the difference between these two systems in terms of advisories is the immediate threat of tropical storm conditions to land is greater for Potential Tropical Cyclone Two. However, in the longer term Invest 93L has the higher likelihood to impact the insurance industry. This morning’s satellite imagery suggests that the low level center is decoupled from the deep tropical convection on the right (east) side of the storm.
There is a chance it’ll never actually develop into a tropical cyclone as the wind shear over the next few days could hamper development.
However, later in the week this wind shear is likely to abate and formation of a named storm becomes more likely.
As always there is uncertainty in the development and final track of tropical systems. The GFS (American model) takes this system on a more northerly track towards Louisiana and even on some early weekend runs into the Florida panhandle. However, as I highlighted in my New Hurricane Products for 2017 Season blog post, the new GFS model this year is not the model to watch. The more reliable ECMWF (European model) takes 93L into southern Texas as indicated last week, so the model has been fairly consistent with the ideas Texas will see worse of the impacts in terms of tropical storm force winds if they develop.
At this time, almost all forecast models for 93L remain below hurricane strength. Regardless, deep tropical moisture will have far reaching effects along the Gulf Coast states, so heavy rainfall and flooding are currently the biggest threats to the insurance industry to areas that don’t handle a lot of rain well like New Orleans and Houston. Depending on the track, 5 inches of rain could easily fall as a sort of atmospheric river seems to be setting up along the Central Gulf Coast.