UPDATE…2:00 P.M. EDT JUNE 30, 2014:
SPECIAL TROPICAL DISTURBANCE STATEMENT…ISSUED 2:00 P.M. EDT…JUNE 30, 2014…WEST CENTRAL FLORIDA HURRICANE AND SEVERE WEATHER FORECAST CENTER.
THE LATEST TROPICAL WEATHER OUTLOOK UPDATE FROM THE NHC IN MIAMI INDICATES TROPICAL DISTURBANCE INVEST 91L THUNDERSTORM ACTIVITY HAS INCREASED WITH THE SYSTEM, AND THE PROBABILITY OF DEVELOPMENT OF A TROPICAL CYCLONE DEVELOPING DURING THE NEXT 48 HOURS HAS INCREASED TO 80%, AND A SLIGHT INCREASE IN ORGANIZATION WOULD RESULT IN FORMATION OF A TROPICAL DEPRESSION. SHOULD THIS OCCUR, A TROPICAL STORM WATCH COULD BE ISSUED FOR PORTIONS OF THE CENTRAL or NORTHERN ATLANTIC COAST OF FLORIDA.
THIS OFFICE RECOMMENDS RESIDENTS ALONG THE EASTERN SEABOARD UP TO CAPE HATTERAS MONITOR THIS SYSTEM CLOSELY FOR ANY SIGNIFICANT CHANGES IN ENVIRONMENTAL CONDITIONS SHOULD THEY OCCUR, AND MONITOR THE SITUATION IN THE EVENT TROPICAL STORM WATCHES OR WARNINGS, IF ISSUED, EXTEND NORTHWARD.
ALL forecasts from this Forecast Center are based on my analysis and knowledge of various forecast tools, including information contained in NHC products. These forecasts are my product based on this, and are not copies from any other entity.
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Good day everyone!
As of the 12Z ATCF FTP data, the following was available on INVEST 91L:
MOVEMENT: EAST DRIFT
MAX SUSTAINED WIND: 30 MPH
CENTRAL PRESSURE: 1011 mb / 29.85 in.
Satellite loop imagery this morning indicates Tropical Disturbance INVEST 91L has become recently poorly structured. The LLC can be seen exposed to the north of the thunderstorm activity, and is located approximately near 28.4N…78.7W. In the last couple of frames in the loop imagery, it appears INVEST 91L may be now beginning its turn toward the west, which is in line with my previous forecasts. Steering currents are still somewhat weak, however based on my analysis of the current forecast steering layers modeling, I expect this new motion to continue throughout the day, and the turn toward the north beginning either late Tuesday, or early Wednesday. Based on comparison in analysis of the forecast steering maps, and Global Model solutions on this system, it should track either on the coast of the SEUS coast, or with the center of circulation just offshore, up through the Cape Hatteras area. Based on this, I prefer a blend in the track guidance of the TVCN / TVCC and the track just left of these two models in the 12Z run of the Dynamic Model Guidance package.
The appearance of 91L at the moment indicates not only a slightly sheared system, which is indicated by a tilt in vorticity from North to SE, but also a system being affected by dry air, which is noted to the North of the system.
Based on analysis of the solutions provided by the Global Models ECMWF and GFS…and regional NAM model, conditions as of the latest run of these models are forecast to improve with increasing humidity levels up through the 500 mb level of at least 70% RH. One item I find a little strange however, that TPW (Total Precipitable Water) values are at some pretty decent levels given the fact dry air is being a hindrance right now.
I did mention shear, and INVEST 91L has temporarily lost the upper level anticyclone that was over it for the past 48 hours or so. However if you recall, this was forecast to occur. Based on analysis of the current run of the GFS Wind Shear product, upper level winds are forecast to become more conducive for further slow development in about the next 36 – 48 hours. Even though there could be an improvement, the pattern may not be optimal for any significant development, unless the COC can remain over the Gulfstream, with the upper level anticyclone directly above the center of the system. Based on this one uncertainty, albeit the slim possibility cannot be ruled out, I cannot lend credence to the ECMWF solution of a minimal hurricane at this particular time, albeit a couple of the more accurate intensity forecast models suggest this. Based on all of the parameters in my analysis this morning, I am opting to go with a moderate to possibly high end Tropical Storm in about 72 – 96 hours, should development continue. Residents along the Eastern Seaboard from SC to Cape Hatteras should monitor the progress of this system during the next 48-72 hours for any significant changes.
I am going to try and have an evening update.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST / SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
OFFICIAL SKYWARN SPOTTER (ADVANCED)