9/8/05 FCST: Tropical Storm Nate

[Sam Sagnella]

QuikSCAT data indicates a well defined surface low over the open waters of the atlantic and this is confirmed by the fact that advisories will be initiated at 21z on a newly formed tropical depression located at 27.8N 67.5W. The developing cyclone is currently over warm waters of the western Atlantic(>29C), however the warm waters are not overly deep and the TCHP is less than 75 kJ cm-2. Vertical shear is relatively light (on the order of 10-15kts), and upper level divergence has been increasing over the past 12-24hrs.

This system should be steered in the general direction of Bermuda over the next few days and the SHIPS brings the system to just shy of hurricane strength in 4 days.

 

[Jeff Snyder]

Re: 9/5/05 FCST: Tropical Depression Fifteen

Based on the Floater 2 Visible Loop, a circulation appears to be developing over the NWrn Bahamas and a C-MAN station located near Grand Bahama Island is reporting 29kt winds from 50deg. This is confirmed by the fact that advisories will be initiated at 21z on a newly formed tropical depression located at 27.8N 67.5W. The developing cyclone is currently over VERY warm waters of the Gulf Stream (>30C), however the waters are not overly deep and the TCHP is less than 75 kJ cm-2. Vertical shear is relatively light (on the order of 5-10kts), low level convergence has become more concentrated over the Nrn Bahamas, and upper level divergence has been increasing over the past 12-24hrs.

What I don't understand is why most, if not all, of the forecast models indicate that the system should meander around the FL Atlantic coast region for the next couple days considering steering currents support movement to the W or even SW (barring any SIGNIFICANT deepening).

Sam,

TD15 isn't the activity off the FL coast, it's the activity sw of Bermuda. TD15 is located about 750 miles east of the FL coast. I don't really have the time to look at forecast guidance, but I just wanted to note that that TD15 isn't the activity along the eastern FL coast.

 

[Sam Sagnella]

Ya whoops. I obviously am stupid enough to forget that there are numerous disturbances in the atlantic basin right now and didn't think about the fact that the listed coordinates are NOT off the florida coast. Sigh...I've edited my post so that it is pertinent to the real TD15.

 

[HAltschule]

I'm fairly certain that the advisories will be initiated within 24 hours on the system near Florida also. I am already seeing a closed circulation on Doppler radar (KAMX) and satellite looks impressive. It is over the Gulf Stream but the waters may be churned up enough by upwelling from Katrina that development/strengthening will be slow to occur. Since we don't know enough about tropical systems yet...this small perturbation may not even be a factor. But we shall see.

 

[Sam Sagnella]

TD15 has officially become Nate, the 14th named storm of the season, as of the 03z advisory. Without a Floater on the storm it is difficult to discern any banding features, however it is obvious there is a large blob of DEEP convection over/just to the north of the center of circulation. Nate is beginning to get its act together and with wind shear remaining very light (~5kts) and with warm SSTs (>29C) I expect the system to gradually increase in organization overnight. The one thing working against Nate right now is its slow forward speed; upwelling will become an issue sooner rather than later and with a relatively low TCHP, intensification will probably not occur rapidly. Steering currents remain weak, so the current lack of movement should continue at least through the short term. Bermudans and mariners (and maybe the ern seaboard?) will need to keep an eye on this storm as the SHIPS model brings it to 71kts in three days.