The tropical wave we have been tracking for the past several days has been designated Invest 91L by the National Hurricane Center (NHC), and is likely to develop between now and Wednesday.
Satellite imagery reveals that 91L has a decent amount of convection and increasing vorticity (see figure 1). Wind shear is only 15 – 20 kts in the vicinity of 91L, and continues to decrease. The increase in vorticity and the convective activity signal that 91L is gradually becoming more organized.
91L is currently moving slowly to the west-northwest, and will track into the Southeast Gulf by tomorrow afternoon. As 91L tracks through the Gulf, upper level winds (shear) will become more conducive for development. By late Tuesday/early Wednesday, Invest 91L will be approaching the Northern Gulf Coast.
All of the reliable model guidance used for predicting tropical cyclone (TC) genesis (ECMWF, GFS, and UKMET) developed 91L over the Gulf in their 00z runs. The majority of the ECMWF ensembles (EPS) and GFS ensembles (GEFS) also developed 91l in their 00z runs.
In their 8 AM EST tropical weather outlook, the NHC gave 91L a medium chance (50%) of developing over the next 2 days and a high chance (80%) chance of developing over the next 5 days.
It is still too early to get into specifics (such as overall impacts, strength, and track). However, one thing that can be said with confidence at this time is that 91L will bring heavy rain to the Northern Gulf Coast this week (see figure 3) and potentially some coastal flooding.
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