Invest 91L has changed little in organization since yesterday.
Analysis
Looking at satellite imagery, convective (shower and thunderstorm) activity has increased this morning. However, it has been waning in intensity and coverage with the diurnal cycle for the past several days.
850 mb (low-level) vorticity has also continued to increase. But there is no evidence of a well-defined center of circulation.
Model guidance
The ECMWF is now the only model predicting development as of the 00z model cycle.
The ECMWF now predicts development of a tropical depression by tomorrow morning, with strengthening to a low-end tropical storm tomorrow afternoon.
In regard to track, the ECMWF is predicting a track just along the northeast Gulf Coast of Mexico tomorrow night; a turn northeast, with a track just offshore of the Texas Gulf Coast Wednesday to Thursday; landfall in southwest Louisiana late Thursday.
Looking at the latest ensemble guidance, there is still support for development from the EPS, and the the GEFS and GEPS.
Additionally, many EPS members and GEPS favor a track similar to that of the ECMWF. The UKMET also shows a track similar to that of the ECMWF, albeit farther east, but remains consistent in predicting no development of 91L.
Development potential
Despite lack of organization thus far, Invest 91L still has a chance to develop today and tomorrow, as wind shear will remain in the 5 – 10 kt range.
In their 8 AM EDT Tropical Weather Outlook, the National Hurricane Center (NHC) kept the chances of development at 60% over both the next 2 and 5 days, respectively.
The hurricane hunter mission yesterday was cancelled, likely because of lack of organization. There is another mission scheduled for this afternoon. Although, it could very well be canceled too.
If 91L fails to develop by the end of the day tomorrow, the chance of development will go down, as wind shear will begin to increase.
Track and intensity
Track: Based on the latest model guidance, it seems the most likely outcome is going to be a northwest to north-northwest track through tomorrow.
A turn to the north and then northeast will be likely late tomorrow/early Wednesday as an upper-level low approaches. But beyond tomorrow night/early Wednesday, the details get murky.
There are currently two scenarios on the table as per the latest model guidance:
1) Landfall in northeast Mexico, followed by a track just inland of the Texas Gulf Coast and into Louisiana Wednesday – Thursday.
2) A track just offshore, skirting the coast of northeast Mexico late tomorrow/early Wednesday, before making landfall in Texas or Louisiana either later Wednesday or Thursday.
Intensity: Should Invest 91L develop, we will be looking at a tropical storm at most. It should also be noted that that 91L might not even be tropical by the time it gets to Texas/Louisiana.
Impacts
Direct impacts for Texas and Louisiana are looking more probable at this point given that a turn to the north/northeast is now likely mid to late week.
The main impact will be rain. Currently, the Weather Prediction Center is calling for a general 2 – 3 inches. Locally higher amounts will be a possibility.
Obviously this raises flood concerns given the very, very wet start to May.
