Since 2012 on the now retired Weather Underground blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at 

  • NCHurricane2009


*******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 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 dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********

...THURSDAY OCTOBER 10 2019 3:53 PM EDT...

See area of interest sections below for areas being monitored for tropical and subtropical cyclone formation. Elsewhere...showers and thunderstorms in the southern Caribbean Sea remain supported by a surface tropical wave interacting with split flow upper divergence between an upper trough extending southwest from a large central Atlantic upper vortex and south side of the upper ridge axis currently extending from the northwestern Caribbean to western Atlantic. This upper trough is expected to become a cut-off small upper vortex off to the east...and the southern part of the upper trough currently over the eastern US is forecast to cut-off into another cut-off upper vortex to the west...with the latent heat release of the southern Caribbean thunderstorms potentially bolstering an upper ridge cell whose outflow is further enhanced by the two upper vortices. Although satellite animation and an ASCAT pass show that a surface low pressure spin is already forming at a location east of model support for this feature developing has dropped as the rotation will soon be making landfall in Nicaragua...thus tropical cyclone formation is unlikely. model support has decreased for the central African active tropical wave headed into western Africa despite the presence of favorable tropical upper ridging expected over the next few days. Perhaps this is because the models appear to show the maximum surface rotation of the wave being far north enough to ingest dry saharan air...only the Euro (ECMWF) model shows the tropical wave circulation staying further south and developing. And finally...the north end of a tropical wave in the central Atlantic is interacting with divergence on the east side of the large central Atalntic upper vortex and north side of the eastern tropical Atlantic upper ridging...with satellite animation and ASCAT passes suggesting a broad surface rotation in the vicinity of 22.5N-42.5W. None of the computer models show this system developing as any surface low pressure that develops here is expected to accelerate northwestward between the Atalntic subtropical ridge and northwest Atlantic frontal cyclone (area of interest #2) into less divergent upper winds beneath the upper vortex.

AREA OF INTEREST #1...The surface and upper-level circulations of the cut-off deep-layered low pressure in the central Atlantic have seperated...with the surface circulation continuing westward toward the low-level ridge weakness of the non-tropical frontal cyclone mentioned in area of interest #2. Meanwhile warm air advection ahead of the frontal cyclone has built upper ridging that has kept the upper-level circulation (cut-off upper vortex) off to the east. The result is that the surface circulation is weakening and lacks thunderstorms while moving beneath suppressive upper convergence on the northwest quadrant of the upper circulation. While the surface circulation turns northwest toward the frontal is likely to lose its identity to the vast low pressure field of the frontal cyclone. So even though the circulation will move into favorable upper winds directly below the aforementioned upper ridging...the massive low pressure field of the frontal cyclone will likely prevent the surface circulation from staying fully closed and developing tropically. Therefore this system is no longer expected to become a subtropical or tropical cyclone...and this is my final statement on this feature on this blog.

****** outlook. Visit (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Oct 11)...0% chance of tropical cyclone formation (central Atlantic near 31.5N-58W)

AREA OF INTEREST #2...The non-tropical frontal cyclone south-southeast of Massachusetts has strengthened further over the last 24 hours while remaining under the influence of increasing divergence on the east side of a sharpening upper trough approaching from the eastern US. The cyclone has turned westward and now recently southward under the influence of blocking deep-layered ridging to the north and west and the tropical low pressure to the southeast that it has been absorbing. Coastal interests in Bermuda and eastern US shore should take precautions from sea swells and rip currents if venturing through these areas in the next 48 hours. The worst of the ocean effects will be along the northeastern US coast where a large wind field between the deep-layered ridging and frontal cyclone is blowing towards the shoreline. National Weather Service observations indicate strong to damaging gusty winds are occuring over coastal Massachusetts including well as Rhode Island...Connecticut...and eastern Long Island of New York. Due to the current south motion of the cyclone it appears the coastline further west (western Long Island...New Jersey...and Delaware) will be spared the worst of the gusty winds. Heavy rainfall is currently spreading onshore across Massachusetts...Connecticut...Rhode Island...Delaware...and Long Island of New out for possible flash flooding in these areas. Due to the current southward motion toward warmer waters...I am continuing a subtropical cyclone formation forecast for this cyclone. In the next 24 hours..the frontal cyclone's west side will pull cold air southward with its west side...thus allowing the incoming upper trough from the eastern US to amplify or nearly amplify into an overhead cut-off upper vortex. My forecast points are shifted eastward because of the current position of the frontal cyclone. I expect this system to reach its peak strength shortly...then begin weakening after 24 hours as the forecast formation of an upper vortex near the surface cyclone will produce an area of unfavorable upper convergence in the vicnity of the surface cyclone...with the additional weakening by 48+ hours occurring as the vortex opens into a fast-moving upper trough such that the cyclone is likely to be trapped in the western convergence zone of the upper trough while trying to keep up with its fast northeastward acceleration. The cyclone currently lacks thunderstorms near the I have delayed forecast subtropiacl cyclone formation for 24 more hours to give time for this system to develop sustained thunderstorms at the core. Cooler water temperatures at the 72 hour forecast position makes it likely that this system will have lost any acquired subtropical characteristics by that timeframe.

****** forecast. Visit (hurricanes dot gov) for official outlook***********

0 Hr Position (1800Z Oct 10)...Frontal cyclone centered south-southeast of Cape Cod Massachusetts at 38N-69W

IOH 24 Hr Forecast (1800Z Oct 11)...Frontal cyclone centered south-southeast of Cape Cod Massachusetts at 36.5N-69W

IOH 48 Hr Forecast (1800Z Oct 12)...50 mph maximum sustained wind subtropical storm centered at 38N-66W

IOH 72 Hr Forecast (1800Z Oct 13)...40 mph maximum sustained wind non-tropical remnant gale centered south of Newfoundland at 43N-55W

AREA OF INTEREST #3...Despite being under a favorable eastern Atalntic tropical upper ridge (with low shear and upper outflow)...the tropcial wave with rotating cloudiness has lost thunderstorm activity while passing over and south of the Republic of Cabo Verde Islands. This is due to ingestion of dry saharan air...which is very visible in GOES-16 high resolution satellite imagery as a beige tint of air from Africa is seen swirling into the tropical wave. Therefore tropical cyclone formation here is no longer expected...this is my final statement on this feature on this blog.

****** outlook. Visit (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Oct 11)...0% chance of tropical cyclone formation (tropical Atlantic near 28W)

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