*******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.**********
...THURSDAY JULY 2 2020 5:42 PM EDT...
See area of interest section below for potential subtropical development in the northwestern Atlantic from the upper vortex moving into the region from the northeastern United States. Elsewhere...computer model runs have shifted in their presentation of another western Atlantic low pressure area to form in the wake of the area of interest...now locating it further north as a non-tropical feature supported by a shortwave upper trough that dives southeastward on the back side of the longwave upper trough over southeastern Canada. Therefore tropical development in the immediate wake of the area of interest is not expected.
And finally in a few days...the CMC and ECMWF suggest a possible subtropical or tropical disturbance emerging just offshore of the southeastern United States with the support of upper vorticity currently over the southeastern United States...possibly gaining additional support from a north fracture of the upper vorticity in the northwestern Caribbean becomes entangled with the southeastern United States upper vorticity as today's 1200Z GFS model run suggested. Curiously the GFS which had been offshore with this disturbance in previous days now keeps it over land. Upper winds could become favorable for fully tropical development as the upper ridge cell currently over the central Caribbean could expand northward to the east of the upper vorticity and over the waters offshore of the southeastern United States in the wake of the upper vortex over the northeastern United States and upper trough over southeastern Canada. However not marking another area of interest for tropical development at this time unless computer models become more consistent with this disturbance.
AREA OF INTEREST #1...The cut-off upper vortex that has been persisting over the northeastern United States is finally beginning to shift eastward into the northwestern Atlantic as an upper trough diving southward from southeastern Canada has partly eroded the central North America upper ridge that has kept it trapped. In the eastern divergence zone of the upper vortex is a band of shower and thunderstorm activity across the northwestern Atlantic and surface low pressure now frontal in nature...located southeast of Nova Scotia...that I previously had as an area of interest for tropical development. Anticipating the development of another surface low pressure area in the vincity of 40N-60W in 48 hours. Although the water temperatures at this location barely support tropical activity...the cold temperatures of the upper vortex may aid in instability such that the surface low pressure may have a short window of time to acquire tropical characteristics. However I have cut the odds of subtropical development down to 15% as the ECMWF and CMC models show the surface low forming slightly further to the northeast with an elongated presentation...an indication that the surface low pressure also has a high chance of staying non-tropical while becomign a feature along the surface front being driven southward by the southeastern Canada upper trough. I drop odds of development to 0% by 72 hours as the upper trough will have absorbed by the upper vortex by that time...guaranteeing that the surface low pressure will be a non-tropical feature along the upper trough's front.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Jul 3)...0% chance of subtropical cyclone formation (northwestern Atlantic near 38N-65W)
IOH 48 Hr Outlook (1800Z Jul 4)...15% chance of subtropical cyclone formation (northwestern Atlantic near 40N-60W)
IOH 72 Hr Outlook (1800Z Jul 5)...0% chance of subtropical cyclone formation (north Atlantic near 45N-45W)
...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...weak surface low pressure develops near 38N-64W in 12 hours...becomes better defined likely as a non-tropical frontal low pressure near 41N-55W at 54 hours and accelerates northeastward into the open north Atlantic after that time. Elsewhere...broad low pressure likely non-tropical and frontal in nature forms offshore of the eastern United States near 37.5N-71W with the support of a shortwave upper trough that dives southeast on the back side of the longwave upper trough from southeastern Canada...continues eastward then northeastward into the open north Atlantic with multiple centers in the long range. Yet another low pressure shown forming offshore of the southeastern United States by 102 hours in response to the eastern divergence zone of upper vorticity orignating from the current northwestern Caribbean and southeatern United States upper vorticity.
1200Z ECMWF Model Run...For area of interest #1...a surface non-tropical frontal low becomes better defined near 41N-57.5W in 24 hours and possibly contains the remnants of the current northwestern Atlantic frontal low...continues northeastward into the open north Atlantic after 48 hours. Elsewhere...broad low pressure likely non-tropical and frontal in nature forms offshore of the eastern United States near 37.5N-72.5W with the support of a shortwave upper trough that dives southeast on the back side of the longwave upper trough from southeastern Canada...continues eastward and reaches 39N-52.5W at 144 hours. Yet another low pressure shown forming on the coast of the Carolians by 144 hours in response to the eastern divergence zone of upper vorticity orignating from the current northwestern Caribbean and southeatern United States upper vorticity.
1200Z GFS Model Run...For area of interest #1...a surface low pressure becomes better definfed near 40N-59W in 48 hours...by 78 hours is a non-tropical frontal low pressure southeast of Newfoundland accelerating northeastward into the open north Atlantic. Elsewhere...broad low pressure likely non-tropical and frontal in nature forms offshore of the eastern United States near 37.5N-71W with the support of a shortwave upper trough that dives southeast on the back side of the longwave upper trough from southeastern Canada...continues eastward and reaches 39N-53.5W at 144 hours.
1200Z NAVGEM Model Run...For area of interest #1...a surface low pressure becomes quickly defined near 40N-60.5W in 48 hours...by 84 hours is a non-tropical frontal low pressure southeast of Newfoundland accelerating northeastward into the open north Atlantic. Elsewhere...no other defined low pressure areas develop in the wake of area of interest #1.