While Bonnie had gone post-tropical earlier in the week, by Thursday morning it looked more organized thanks to warm SST’s and only moderate wind shear. Convection was firing up around a low-level center of circulation. Therefore, Bonnie was re-classified from post-tropical to tropical depression.
While the storm may go through small changes in intensity over the next couple days, it’s not expected to greatly intensify. Its track should also take it further offshore by later Thursday night and well out to sea by week’s end. Nonetheless, heavy rains will continue for the North Carolina coastline into Thursday night. The storm should once again become post-tropical by this weekend.
Meanwhile, all eyes are on the Gulf for what MAY form early next week. Models have been hinting for a few days now at a potential tropical disturbance forming off the Yucatan and moving northeast toward Florida Monday/Tuesday. The ECMWF (Euro) has been the most consistent in this model solution, but is now joined by the GFS and the GEM (Canadian). All three show some form of a tropical low developing in the southeast Gulf of Mexico and tracking toward Florida between the Big Bend and Tampa Bay. Below is the ECMWF model Tuesday morning.
Regardless of tropical development, it appears that a slug of deep tropical moisture will be headed toward Florida in the Monday/Tuesday timeframe. A common measure of moisture in the atmosphere is precipitable water, or PWAT. This gives a better idea of the potential for heavy rain/flooding. PWAT values in the state early in the week, specifically across west-central Florida, look to be running several standard deviations above normal and very nearly off the charts at about 3″. In comparison, typically this time of the year west-central Florida would see PWAT values near 1.5″.
With PWATs this high, very heavy and potentially flooding rains will be possible across the west coast of Florida Monday and Tuesday. While the GFS and ECMWF don’t necessarily agree on the exact location of the heaviest rain, they both paint a swath of 4″+ for parts of Florida.
Obviously, the heavy rain threat for this system needs to be watched closely over the next few days. Besides the heavy rain threat, there is also the chance this storm develops tropically. The National Hurricane Center places 48 hour odds of development at 0%, but 5 day odds at 30%. While the Gulf waters are sufficiently warm for tropical development, the main environmental factor working against it would be wind shear. A weakening front moving into the Gulf this weekend will create a hostile wind shear regime. Nonetheless, the storm may be just far enough east to at least become a TD or TS.
We’ll continue to watch the situation closely in the coming days. The good news is that we still have several days to keep an eye on the models and note any trends. Of course nonetheless, interests along the west coast of Florida should pay attention into the weekend.