Thur Afternoon: 99L Struggling

99L is more disorganized now than it has been over the last several days. As discussed this morning, west to southwest wind shear will continue to impede development through the short term. Given the extreme lack of disorganization being exhibited on satellite imagery, there is some question as to whether 99L will have enough remaining low level vorticity to take advantage of any favorable conditions that may arise in the future. To compound matters, early afternoon model guidance is now in nearly unanimous agreement that the favorable environment progged several days ago may never materialize. For instance the GFS, CMC, and UKMET are all signaling that multiple mid-level atmospheric perturbations (and in some cases upper lows) will continue to retrograde southwest and west, underneath ridging over the Southeast US, across Florida and the Gulf of Mexico. This will leave little to no room for any favorable upper level anticyclones that would enhance development potential. Even the ECMWF, which had shown intensification into a major hurricane in the Gulf for several runs, now shows nothing more than a minimal tropical storm making landfall near Florida’s Big Bend region.

Given 99L’s structure and model trends over the last 48 hours, it is becoming clear that max intensity may never rise above depression or named storm status. There is also an increasing likelihood that 99L remains an open wave axis through the period. If the latter were to occur, the aforementioned weakness in mid-level steering over Florida that was discussed in other posts would become irrelevant. The low level steering layer would remain dominant, and allow the wave to maintain a west to west-northwest heading into the central and possibly even western Gulf of Mexico.

In summary, the outlook for south Florida and the Gulf Coast is more optimistic today. A track near, or immediately south of Miami and the Florida Keys is anticipated. Intensity will be vastly lower than what several models have been indicating over the past week. Primary impacts along southern Florida will be in the form of squally rain bands, isolated street flooding, and blustery winds. Interests from the Florida panhandle westward, much like those in south Florida and Cuba, are still advised to monitor the progress of 99L. Even a minimal tropical system including a wave axis can still generate hazardous conditions such as the threat of isolated flooding.