*******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.**********
...SUNDAY MAY 24 2020 1:40 AM EDT...
Even though the Atlantic hurricane season does not start until June 1...resuming daily birdseye view posts on the Atlantic tropics as two potential areas of tropical development appear to be emerging...see pair of area of interest sections below for additional details. Elsewhere...a cut-off upper vortex that has been parked over the eastern United States is finally shifting eastward into the western Atlantic...as it does so its eastern upper divergence is supporting a surface frontal low pressure just offshore of the northeastern United States featuring somewhat organized thunderstorm activity. Eastern convergence of a longwave upper ridge building over eastern North America is producing surface ridging to the east blocking this surface low pressure from moving eastward out to sea...and yet the supporting upper vortex will continue shifting quickly southeastward away from the surface low pressure as it swings around the much larger upper vortex currently present in the north Atlantic. Therefore the surface low pressure will soon encounter upper winds unfavorable for tropical development in the wake of the upper vortex...specifically shearing upper northwesterly winds and upper convergence on the east side of the longwave upper ridge. Thus no tropical development is expected here.
AREA OF INTEREST #1...A cluster of thunderstorms has developed in the western Caribbean Sea as a surface tropical wave interacts with the eastern divergence zone of an upper trough that has arrived into the Gulf of Mexico and western Caribbean Sea. A larger scale pattern is expected to persist as the jet stream becomes stuck during the forecast period...specifically an upper trough over western North America and an upper ridge over the eastern North America extending into the western edge of the Atlantic. The Gulf-to-Caribbean upper trough will more or less merge with the stuck western North America upper trough while drifting north on the west side of the upper ridge axis. This pattern will favor the formation of a surface trough of low pressure and thunderstorms that shift northward from the tropical wave...supported by the eastern divergence zone of the northward shifting upper trough. The disturbance would also track northward from the surface flow between western Atlantic surface ridging expected to persist beneath the convergence on the east side of the upper ridge axis and a broad area of surface low pressure over the central United States to be supported by divergence on the east side of of the western North America upper trough. Because such a surface trough disturbance will be largely also tucked beneath the highly amplified upper ridge axis which would favor low shear and upper ouflow for additional support of thunderstorm activity...will be on the lookout for possible tropical cyclone development from this northward shifting disturbance. I have kept odds of development on the low side due to land interaction along the forecast track and no computer models explicity showing tropical cyclone formation at the present time.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z May 24)...0% chance of tropical cyclone formation (south of western Cuba near 21N-82.5W)
IOH 48 Hr Outlook (1800Z May 25)...5% chance of tropical cyclone formation (Florida Keys near 25N-83W)
IOH 72 Hr Outlook (1800Z May 26)...10% chance of tropical cyclone formation (northeastern Florida coast near 29N-81W)
IOH 96 Hr Outlook (1800Z May 27)...10% chance of tropical cyclone formation (South Carolina coast near 32N-80W)
IOH 120 Hr Outlook (1800Z May 28)...0% chance of tropical cyclone formation (Inland over the Carolinas near 35N-79.5W)
AREA OF INTEREST #2...A shortwave upper trough supporting a surface frontal low pressure is ejecting east-northeastward across the north-central United States this evening from a large scale longwave upper trough over the western North America. Over the next few days computer models have been and continue to be in agreement that this shortwave upper trough will shift eastward across the north side of the longwave upper ridge expected to persist across eastern North America...followed by a southeastward dive across the western Atlantic on the east side of the longwave upper ridge. On its southeastward dive the shortwave upper trough has long been forecast by models to amplify into a cut-off upper vortex...producing another frontal low pressure system southeast of Bermuda where water temperatures are currently running at 24 to 26 deg C...at or just below the threshold for tropical development. However the forecast cut-off upper vortex is expected to be cold enough where it can help boost thunderstorm activity...therefore the forecast frontal low pressure system could acquire tropical characteristics and become a subtropical cyclone. I have kept odds of subtropical development at 0% through 96 hours and begin rising odds above 0% at 120 hours as the model consensus shows development of a surface forntal low pressure system just after 120 hours.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z May 24)...0% chance of subtropical cyclone formation (Michigan near 45.5N-83W)
IOH 48 Hr Outlook (1800Z May 25)...0% chance of subtropical cyclone formation (east of Cape Cod Massachusetts near 41N-68W)
IOH 72 Hr Outlook (1800Z May 26)...0% chance of subtropical cyclone formation (northeast of Bermuda near 33N-65W)
IOH 96 Hr Outlook (1800Z May 27)...0% chance of subtropical cyclone formation (western Atlantic near 28N-60W)
IOH 120 Hr Outlook (1800Z May 28)...5% chance of subtropical cyclone formation (western Atlantic near 28N-62W)