93L a possible threat to the Azores

A large tropical wave (Invest 93L) is located in the Central Atlantic about 1000 miles southeast of Bermuda. Satellite loops this morning show a surface circulation attempting to form, and heavy thunderstorm activity has increased markedly since Monday. Wind shear is light, and ocean temperatures are warm, near 27.5°C. The latest Saharan Air Layer Analysis from the University of Wisconsin shows that 93L has moistened its environment considerably, but dry air is still a significant impediment to development. The 8 am EDT run of the SHIPS model predicts that mid-levels of the atmosphere will remain very dry through Wednesday, then moisten considerably. The storm is expected to move west-northwest and then north, recurving well to the east of Bermuda. By Saturday, as 93L is headed northeastwards towards the Azores Islands, the GFS and NOGPAS models predict development into a tropical depression. Residents of the Azores Islands should keep an eye on 93L, which could pass close to the islands as early as Sunday night. In their 8 am Tropical Weather Outlook, NHC gave 93L a 30% chance of becoming a tropical depression by Thursday morning. Given the recent increase in 93L's organization, I put these odds at 50%.


Figure 1. Morning satellite image of 93L over the Central Atlantic.

Ex-TD-7 not a threat to develop
The remains of Tropical Depression Seven are headed westward at 20 mph across the Western Caribbean, and will bring heavy rain to Honduras and Nicaragua today. These heavy rains will spread to northern Guatemala, Belize, and Mexico's Yucatan Peninsula tonight. Although wind shear is low and ocean temperatures high, there is not going to be enough time for ex-TD 7 to develop before it moves inland over the Yucatan Peninsula. None of the reliable models forecasts that ex-TD 7 will regenerate, and in their 8 am Tropical Weather Outlook, NHC gave ex-TD 7 a 20% chance of becoming a tropical depression by Thursday morning.

Watch the Gulf of Mexico this weekend
Another area to watch this weekend will be the Gulf of Mexico, where a fall-like cold front is expected to stall out. Wind shear is predicted to be low to moderate this weekend, and cold fronts stalled out over the Gulf of Mexico often serve as the seed for tropical storms. The GFS model has been showing some development may occur in the waters close to shore near the Texas/Mexico border early next week.

I'll have a new post early this afternoon. What are the chances that a hurricane will force a mass evacuation of Tampa during the Republican National Convention, August 27 - 30?

Jeff Masters