*******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.**********
...WEDNESDAY JULY 8 2020 6:08 PM EDT...
See area of interest sections below for the disturbance on the Carolina coast that has a high chance of tropical cyclone formation. Elsewhere...warm southerly flow on the east side of the disturbance will amplifying upper ridging in the northwestern Atlatnic...which will cause the shortwave upper trough currently over central North America to amplify into a cut-off upper vortex as it moves into the open central Atlantic. This will cause the formation of a surface frontal low offshore of Atlantic Canada in a couple of days...with the frontal low possibly acquring tropical characteristics in 4 to 5 days while it settles over central Atlantic waters of 23 deg C and a cold enough cut-off upper vortex to de-stabilize the atmosphere at these water temperatuers (measuring in the low 1200s in dekameters in height at 200 mb in the latest GFS model run). If these model trends continue into tomorrow...I will be declaring another area of interest for tropical development.
AREA OF INTEREST #1...The broad surface low pressure over the southeastern United States has lost its original more inland tight circulation and has emerged onto the Carolina coast. This system remains supported by the eastern divergence zone of upper vorticity over the eastern United States...with this upper vorticity also keeping the heaviest thunderstorm bands on the east side of the low pressure and offshore. The thunderstorm bands are also supported by outflow of an upper ridge that extends to Florida from the Caribbean Sea. Visible satellite suggests a tightening circulation appears to be forming on the west side of the thunderstorms bands just offshore of Cape Fear and Cape Lookout...therefore given that the GFS...NAVGEM...and ECMWF show a possible tropical cyclone centered just east of the northern Outer Banks of North Carolina...I give a 95% chance of tropical cyclone formation in the next 24 hours while assuming the Atlantic surface subtropical ridge steers the tightening center north-northeastward across Cape Hatteras and into a position just east of the northern Outer Banks. The evolving upper wind pattern also support tropical cyclone formation in the next 24 hours...with the eastern United States upper vorticity to merge with the south fracture of the central North American shortwave upper trough to the west...and the remainder of the central North American upper trough passing by to the northeast...with this disturbance potentially finding a spot of lower shear in between the upper trough fragments and possibly getting an enhanced outflow channel into the upper trough fragment to pass to the northeast. As this system approaches the northeatern United States coast in 48 hours...it will move over cooler waters and likely transition into a less tropical system supported by the eastern divergence zone of a more amplified upper trough to approach from western Canada. This upper trough will also drive the frontal boundary over the north-central United States eastward into this system...another factor that will reduce tropical characteristics. Therefore I drop odds of tropical cyclone development to 0% by that timeframe.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jul 9)...95% chance of tropical cyclone formation (just offshore of northern Outer Banks of North Carolina near 36N-75.5W)
IOH 48 Hr Outlook (1800Z Jul 10)...0% chance of tropical cyclone formation (just southeast of New Jersey near 38.5N-74W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...For area of interest #1...moves north-northeast to New Jersey coast in 66 hours...loses its identity shortly after that time within frontal system currently approaching from the north-central United States. Elsewhere...frontal low becomes defined just east of Nova Scotia in 42 hours...becomes cut-off from the mid-latitude westerlies in 96 hours while located near 39N-40W...dissipates into a surface trough located within the Atlantic subtropical ridge near 40W longitude by 120 hours.
1200Z ECMWF Model Run...For area of interest #1...suggests strengthening as a possible tropical cyclone centered just east of the Virginia coast in 48 hours...centered just offshore of New Jersey in 72 hours...loses its identity over Maine within frontal system currently approaching from the north-central United States by 96 hours. Elsewhere...frontal low becomes defined just south of Newfoundland in 48 hours...becomes cut-off from the mid-latitude westerlies in 96 hours while located near 39N-42W...dissipates into a surface trough located within the Atlantic subtropical ridge near 41W longitude by 120 hours.
1200Z GFS Model Run...For area of interest #1...suggests strengthening as a possible tropical cyclone centered just offshore of the northern North Carolina Outer Banks in 30 hours...reaches New Jersey coast in 54 hours...loses its identity over the Vermont/New Hampshire/Canada border withing the currently approaching from the north-central United States by 78 hours. Elsewhere...frontal low becomes defined just east of Nova Scotia in 42 hours...becomes cut-off from the mid-latitude westerlies in 78 hours while located near 40N-47W...evolves into possible subtropical cyclone near 38.5N-45W in 96 to 120 hours.
1200Z NAVGEM Model Run...For area of interest #1...suggests strengthening as a possible tropical cyclone centered just offshore of the northern North Carolina Outer Banks in 42 hours...reaches New Jersey coast in 66 hours...transitions into frontal low over eastern Canada by 120 hours as front currently approaching from the north-central United States overruns the circulation. Elsewhere...frontal low becomes defined just southeast of Newfoundland in 54 hours...becomes cut-off from the mid-latitude westerlies in 102 hours while located near 41N-40W...dissipates into a surface trough located within the Atlantic subtropical ridge near 41W longitude by 138 hours.