*******Note that forecasts and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.********** ...SATURDAY MAY 16 2020 9:55 PM EDT...
Surface low pressure system from the Florida Straits has moved northeastward through the northwest Bahamas and has become Tropical Depression One just north of the islands and east of Florida. See Tropical Depression One section below for details on this developing situation. Elsewhere...longer-range model runs continue to have a more east position of a potent upper trough expected to arrive into the Great Lakes region of North America in 2 to 3 days. This positions the associated surface low pressure system to be further east along the United States east coast...which will not allow for another subtropical development in the wake of tropical depression one. Therefore not declaring another area of interest at this time. TROPICAL DEPRESSION ONE...The surface low pressure that formed in the Florida Straits under the supportive upper divergence regime on the east side of an amplified shortwave upper trough in the Gulf of Mexico has moved northeastward across the northwestern Bahamas this morning and is now tropical depression one at a location north of the islands and east of the Florida peninsula. Warm air advection ahead of a fast-moving frontal low pressure system that has moved into the northwest Atlantic from the Great Lakes appears to have shifted upper ridging directly over the tropical depression...which has allowed for low enough shear and upper anticyclonic outflow to allow this system to strengthen as a fully tropical system. The cool upper trough from the Gulf of Mexico is expected to play even less of a role with tropical depression one as it dissipates due to significant warm air advection to occurs ahead of a vigrous frontal cyclone and upper trough to enter the Great Lakes region in 2 to 3 days. This means the clump of thunderstorms biased to the northeast of the center from light shear induced by the upper trough should become more directly stacked with the center...which should allow for strengthening into a tropical storm sooner or later. However I stay below hurricane strength in my forecast as the Gulf stream water temps at the 24 and 48 hour forecast points are only running 26 deg C...remember it is not hurricane season just yet. In fact...my intensity forecast is a touch lower due to the current strength of the depression compared to the previous forecast. During the first 48 hours...this system is expected to track more north and less east across the western Bahamas and close to the United States east coast as the surface ridge currently in the western Atlantic blocks progress out to sea. In fact this system is likely to clip the Outer Banks of North Carolina by Monday where a tropical storm watch is in effect...therefore interests here should make preparations for tropical storm conditions. The early part of my forecast is adjusted slightly eastward due to the current eastward angle of the track despite being slightly west of the previous forecast at 1800Z...and is also slightly north of the previous while the depression was also north of the previous forecast at 1800Z. By 72+ hours...an upper trough is currently expected to eject southeastward from the current energy over Hudson Bay Canada and arrive into southeastern Canada...with divergence out ahead of this upper trough creating a weakness in the western Atlantic surface ridge that has potential to draw this system eastward away from the United States east coast. However convergence on the back side of the upper trough will create another surface ridge to the north...which combined with the western Atlantic surface ridge will make the weakness fairly narrow. The NAVGEM...CMC...and Euro models accelerate this system eastward through the weakness while the GFS still suggests the weakness would not be enough to pull this system out to sea...instead showing this system stall offshore of the northeastern United States coast and then getting absorbed by the vigorous weather system to come from the Great Lakes. Given that three of the four models show an out to sea solution...I continue to show an out to sea solution in the long range. But I compromise between the GFS and the other models by showing a slower eastward track than the NAVGEM...CMC...and Euro...followed by a southwestward drift at 120 hours as the ridge weakness closes. Upper westerly winds ahead of the upper trough expected over southeastern Canada at 72 to 96 hours will likely shear this system...so I show a slightly lower forecast intensity during this timeframe. I still expect a tropical system through 96 hours as the forecast track through that time keeps this system perfectly following the warm Gulf stream waters. I then show dissipation to a remnant low by 120 hours as the southwestward turn would move this system out of the Gulf stream into cooler waters. ******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast*********** 0 Hr Position (1800Z May 16)...35 mph maximum sustained wind tropical depression centered north of the northwest Bahamas and east of Florida at 28.4N-78.6W IOH 24 Hr Forecast (1800Z May 17)...50 mph maximum sustained wind tropical storm centered offshore of the southeastern United States at 30.5N-77.5W IOH 48 Hr Forecast (1800Z May 18)...60 mph maximum sustained wind tropical storm centered just east of Cape Hatteras North Carolina at 35N-75W IOH 72 Hr Forecast (1800Z May 19)...45 mph maximum sustained wind sheared tropical storm centered at 36.5N-70W IOH 96 Hr Forecast (1800Z May 20)...45 mph maximum sustained wind sheared tropical storm centered at 36.5N-65W IOH 120 Hr Forecast (1800Z May 21)...Remnant low pressure centered at 35N-68W