SPECIAL UPDATE…SEP. 10, 2013…ISSUED 2:20 P.M. EDT…PALM HARBOR FORECAST CENTER:
A special advisory issued by the NHC at 1:30 p.m. indicates 2 ASCAT passes have shown Gabrielle is a little stronger than previously thought. Her maximum sustained winds are now at 50 MPH and some further strengthening is forecast over the next 24 hours. NHC now forecasts a 60 MPH Tropical Storm.
Information from the Navy ATCF site and ATCF/FTP site indicate the area of disturbed weather in the NW Caribbean has been designated INVEST 93L. Satellite imagery indicates this disturbance has become slightly better organized since this mornings analysis. Subsequently, the NHC has increased the chances of this slightly, of becoming a Tropical Cyclone during the next 48 hours to LOW (20%), and HIGH (70%), up from 10% and 60% from this morning.
In light of this, I will be posting a full update later this evening.
Good day all!
INVEST 92L / GABRIELLE became better organized overnight, and has been reclassified Tropical Storm Gabrielle.
The following information from the NHC 11:00 a.m. EDT advisory is posted on the Global Tracks map:
Satellite loop imagery indicates convection continues to build over the center of Gabrielle at this time. Upper level winds are currently conducive for further strengthening today, and should remain favorable through this afternoon. thereafter, more moderate shear takes over. However, given that shear will be moving almost in line with the storm, and with Gabrielle remaining over warm water, she should maintain her strength as forecast by the NHC. Based on these factors, I concur with the NHC intensity forecast, and based on the forecast steering maps, I concur with the NHC forecast track and 12Z Dynamic Model Guidance tracks which are pretty well clustered. The island of Bermuda is under a Tropical Storm warning, and residents should make the appropriate preparations.
Tropical Storm Humberto continues to become better organized, and current winds are at 65 mph. Upper level winds are very conducive for further strengthening, and should remain conducive during the next 36 hours to 48 hours, before shear increases, and the environment becomes drier. Recent information in the NHC forecast discussion from 11:00 a.m indicates Humberto has ceased strengthening for the time being. Humberto is expected to attain hurricane status later today, however I agree at the moment with the NHC in lowering forecast intensity, at least for the next 36 hours. Based on the current steering layer mean, the turn to the right this morning may have been just a jog, as MIMIC animations show a tug back to the left in the very last frames. Based on this, I may expect a slight delay in the more NW motion.
Based on the forecast steering maps, I do however, agree with the NHC overall track guidance, which concurs with the 12Z Dynamic Model Guidance.
I will continue to monitor Humberto over the next 96-120 hours for any significant changes.
The area of disturbed weather I’ve been monitoring in the NW Caribbean has become somewhat organized this morning. Based on current steering layer mean, this should be moving very slowly to the WNW. This area of disturbed weather is forecast to move over the Yucatan peninsula, and eventually into the BOC. Upper level winds are marginal at the moment, however the GFS wind shear forecast for the past 48 hours has been consistent with upper level winds becoming more favorable in about 36 hours from 06Z this morning, or around early tomorrow afternoon. Once this enters the BOC, the wind shear forecast indicates an upper level anticyclone will develop over the BOC. Based on this, I believe we will see this develop into a Tropical Storm within the next 5 days. The NHC has designated a LOW (10%) chance of this becoming a Tropical Cyclone during the next 48 hours, and a HIGH (60%) chance over the next 5 days.
Based on forecast steering maps, this disturbed weather is in a weak steering regime at the moment, and indications at this time are, that this may move slowly in the BOC, so it may have time to get very organized. Right now, based on forecast steering, if this area move a little quicker than forecast, the central Mexico coast may again be the area affected. However, should this move slowly, or even stall, the chances become greater for it to feel the effect of the U.S. ridge weakening somewhat within the next 7 days, and could be drawn further up the western GOMEX coast. This scenario is supported right now by the GFS and to some extent, the CMC model, and the central Mexico scenario is supported by the FIM model. Based on this uncertainty, I recommend residents from S. Padre Island / Brownsville TX, southward, monitor this disturbance closely during the next 7 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)