*******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.**********
...FRIDAY OCTOBER 11 2019 8:57 AM EDT...
The cyclone south-southeast of Massachusetts has developed a thunderstorm core this morning...and as of 8:30 AM EDT the National Hurricane Center issued a special tropical weather outlook that advisories on a subtropical storm could be issued later today. Therefore I am issuing this special update to update my forecast to show subtropical storm formation by 1800Z today...with initial intensity of 60 mph based on 50-knot (60 mph) vectors on the north side of the circulation and just south of Massachusetts as seen in recent ASCAT passes. I have also nudged my track forecast points west given the current position of the surface cyclone. Although the cyclone has not moved southward toward warmer water...the instability to produce thunderstorms appears to have been induced by the increasingly cold temperatures of the amplifying upper trough approaching from the eastern US...with the amplification of the upper trough being induced by the southward cold air transport on the west side of the cyclone and also due to the amplification of deep-layered ridging to the north and west. Gradual weakening is shown with the eastward acceleration in forecast track...as the upper trough is expected to accelerate quickly northeastward this weekend...leaving the surface cyclone to be caught underneath the unfavorable western convergent side of the upper trough while struggling to keep up with the accelerating trough. Even cooler water temperatures at the 54 hour forecast position makes it likely that this system will have lost any acquired subtropical characteristics by that timeframe.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
0 Hr Position (1200Z Oct 11)...Cyclone with thunderstorm developing at the core...centered south of Cape Cod Massachusetts at 38.5N-69.8W
IOH 6 Hr Forecast (1800Z Oct 11)...60 mph maximum sustained wind subtropical storm centered south of Cape Cod Massachusetts at 38.2N-69.8W
IOH 30 Hr Forecast (1800Z Oct 12)...50 mph maximum sustained wind subtropical storm centered at 38N-67W
IOH 54 Hr Forecast (1800Z Oct 13)...40 mph maximum sustained wind non-tropical remnant gale centered south of Newfoundland at 43N-56W