10 September 2014

Two weak disturbances to watch

Tropical tidbit 1: The last time there was not a named storm in the Atlantic on September 10 was in 2000! And even then, a subtropical depression formed (not named).  So, the last time there was not any tropical or subtropical cyclone at all on this date was 1992.

Tropical tidbit 2: You may recall a previous bit of trivia I shared: the last time the A, B, and C storms all became hurricanes was also in 1992.  AND, the A storms in 1992 and 2014 both made landfall on the U.S. as hurricanes.

As I mentioned in my update yesterday, there are two areas of interest right now: one over the Bahamas and one just west of the Cape Verde islands.  Neither are very impressive, but are worth watching over the coming days.

First, the system over the Bahamas... it's actually being generous to even consider it for discussion, but because of its proximity to Florida, I'll give some highlights.  It's not from an easterly wave, but rather an upper-level Low that interacted with a weak surface trough over the past few days.  It occasionally spawns some widespread thunderstorms, but this morning isn't one of those times, as you can see in the benign-looking satellite image here:

However, global models do show the disturbance persisting (not developing) and heading west into Florida.  It should result in nothing more than some welcome rain for the area in the coming 1-3 days.

Total rainfall forecast in south Florida valid from today through Monday. (NOAA/WPC) 
The second system of interest is an easterly wave that exited the African coast this past Saturday.  It is now centered about 450 miles west of the Cape Verde islands, or about 1900 miles east of the Windward islands, and is extremely disorganized.

As has been the story for the entire season so far in the deep tropics, a copious amount of low-mid level dry air is choking it off and limiting any development... the SST and wind shear are both favorable for development. Global and regional models alike forecast it to continue moving WNW and eventually get better organized once it escapes the Saharan Air Layer. According to a consensus of leading models, getting a hurricane out of this one is actually not out of the question by Sunday-Monday.

Infrared satellite image (grayscale background) with a depiction of the Saharan Air Layer overlaid (yellow-red).  The center of the disturbance is marked with a red I. (CIMSS)

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