91L Update: Still Fighting [UPDATED]

UPDATE (10:54 PM EDT): About a couple of minutes after clicking “post”, I found out that the NHC has declared the disturbance the first tropical depression of the season. TD 1 is moving southwest at 2 knots. It has max sustained winds of 30 knots and a minimum central pressure of 1009 mb. I will post more sometime tomorrow (Tuesday).


Since this morning’s update, the low off Florida’s east coast had some good signs of development earlier in the afternoon but hasn’t shown much progress. The low is being inhibited by dry air to the north and, therefore, hasn’t become better organized.

The Hurricane Hunters found the lowest pressure of 1009 mb and a max wind of 29 knots (33.4 mph) near 27.68N 78.91W at 4:36 PM EDT. Another recon flight could be sent out again tomorrow (if needed), based on the latest “plan of the day” for tomorrow (Tuesday). 

For most of the day, the invest had thunderstorm development on the southern half of the system. At one point, the system started getting some thunderstorms developing and wrapping around the eastern side. But the development soon went away and it’s now back just to the southern half of the system.

Water vapor imagery (see below) shows drier air on the northern side of the system. As long as this dry air is there aloft, it will have a hard time developing.

(Source: NHC/NOAA)
(Source: NHC/NOAA)

On the synoptic (large) scale, a trough is over the open Atlantic waters and over the upper Midwest (though not as amplified) (see water vapor image with drawing of trough below). Upper air maps show an upper ridge centered over northern Florida and southern Georgia. Winds aloft (at Jacksonville, for instance) are pretty light aloft per the latest sounding. The lack of shear is a good indicator that environmental conditions will likely be favorable for continued development. But now it has to pull a Rocky and fight the dry air to the north of the center.

(Source: NHC/NOAA)
(Source: NHC/NOAA)

In the meantime, the disturbance will likely bring what it has for the last few days across southern and portions of central Florida: Rain. In fact, metro southeast Florida has had reports of flooding. Miami International Airport has received almost two inches of rain today. Additional heavy rain in places where they don’t need it could be a problem in the next few days.

There could be a few strong gusts associated with the disturbance, but it’s nothing to go bonkers over. I believe the greatest threat is the rain.

I’ll post more updates when needed. Keep an eye on my Twitter feed, too.