Invest 90L is not going to develop over the next few days due to strong southwesterly wind shear. However, by Friday shear will decrease as 90L lifts north into the Gulf of Mexico, likely allowing development into a tropical/sub-tropical depression or storm.
As of now, all three of the reliable global models used in predicting tropical cyclone (TC) genesis (the ECMWF, GFS, and UKMET) are all predicting 90-L to organize into a TC.
The National Hurricane Center currently gives 90-L a 70% chance of developing over the next 5 days in the central or eastern Gulf of Mexico (see figure 2).
When 90L develops (assuming it does), it won’t strengthen very much; a weak, disorganized tropical storm with most of the weather to the east and north of the center is most likely.
There is still some disagreement between the ECMWF and GFS in regard to the future track of 90-L. The ECMWF is still projecting 90-L to track towards the northern Gulf Coast Sunday/Monday (see figure 1), and the GFS continues to favor a Florida landfall on Saturday/Sunday.
The ECMWF solution appears more likely. This is because the GFS appears to be having issues with convective feedback, which makes its Florida landfall prediction less credible. The GFS also lacks any other model support, while the ECMWF has support from its ensembles (EPS), the GFS ensembles (GEFS), UKMET, and CMC.
However, nothing is certain in regard to the track. Everyone from Florida to Southeast Louisiana should continue to monitor the progress of 90-L.
Impacts:
Flash flood potential: Regardless of development, very heavy rainfall and flash flooding — possibly widespread — is likely from Southeast Louisiana to Florida this weekend into at least early next week.
The latest quantitative precipitation forecast (QPF) from the Weather Prediction Center calling for accumulations of 5 – 7″ for coastal Mississippi, coastal Alabama, and the Western Florida Panhandle (see figure 3). Granted, this is subject to change as 90-L evolves.
Coastal impacts: Surf will be rough, and there will be a high risk of rip currents. Some coastal flooding is also probable.
Severe weather: Severe weather (tornadoes) will be possible.
Wind: Gusty winds are likely on the coast. Though the extent of the wind impact will depend on how strong 90-L gets.
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