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BIRDSEYE VIEW POSTS

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 IOHurricanes@outlook.com 

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MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #119

*******Note that forecast 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 NOVEMBER 10 2023 10:12 AM EDT...

Over the next few days a tropical disturbance with development potential could emerge in the central Caribbean Sea and later move toward the northwestern Caribbean through day 5... see area of interest #53 section below for more information. Elsewhere... no other tropical areas of interest are expected to emerge in the Atlantic basin.


AREA OF INTEREST #53... Over the next few days models are increasingly onboard with the following upper air pattern causing the development of a new tropical disturbance in the central Caribbean Sea:

(1) A large upper trough that has recently moved into the central Atlantic from the western Atlantic has left behind a string of upper vorticity in the vicinity of the northern Caribbean islands due to upstream upper ridging over the Florida peninsula and vicinity. The outflow of upper ridging ahead of (south of) the upper vorticity is leading to Caribbean showers and thunderstorms further west and just offshore of Central America... however over the next 48 hours the southeastern divergence zone of the upper vorticity may produce additional activity further east and in between Colombia and Jamaica. For the next 48 hours I have shifted my initial position of this area of interest further west... in between the aforementioned western and eastern activity zones. Excess westerly shear across the south side of the upper vorticity should prevent short-term tropical development.

(2) After 48 hours... the upper vorticity is forecast to decay and dissipate due to prolonged isolation from high-latitude cold air. This will allow for the expansion of southern Caribbean upper ridging in its wake. Per the latest upper wind forecasts... the western activity zone just offshore of Central America is likely to become the dominant and evolve into a tropical disturbance due to split flow upper divergence between westerlies on the north side of the expanding southern Caribbean upper ridge and easterlies on the south side of the upstream upper ridging approaching from Florida. Any further east pocket of surface low pressure that does develop from the possible eastern activity zone is likely to drift westward and merge with the western activity zone offshore of Central America by 72 hours while pushed by a strong surface ridge to the north that develops under the convergence zone of the current central North America upper trough... followed by the convergence zone of a second upper trough that quickly follows behind. This second upper trough is forecast to undergo a southern and northern split in the long range as well... with the southern split to approach from the Gulf of Mexico by days 4 and 5. The divergence zone of the southern split upper trough produces a Gulf of Mexico frontal low whose surface ridge weakness should help coax the track of the tropical disturbance northwestward in the 4 to 5 day range. Less favorable westerly shear generated by the southern split upper trough is forecast to overspread the disturbance beginning on day 5... with the disturbance likely reversing to a north-northeastward track away from central America and toward eastern Cuba... the Cayman Islands... and Jamaica beyond day 5 while transitioning into a broadening system supported by the large divergence zone of the southern split upper trough.


Regarding odds of tropical cyclone formation... other global models have been joining the GFS in showing the development of a Caribbean tropical disturbance and I have pulled up my peak odds of development to 20%... matching the latest available NHC tropical weather outlook. I do not have odds above 20% at this time as the GFS which previously showed more rapid development is joining the other models in showing slower development... and by 5+ days the disturbance has a decent chance of instead becoming disorganized under increasing westerly shear while it also potentially broadens into a system with competing multiple centers instead of a singular center needed for tropical cyclone formation.


Regardless of tropical cyclone formation or not... expect periods of increasing rainfall for eastern Nicaragua and Honduras by Tuesday and Wednesday... with increasing westerly shear by Wednesday likely preventing rainfall further west. By late in the week a large area of heavy rainfall overspreading Jamaica... eastern Cuba... and the Cayman Islands appears the most likely scenario.

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

IOH 24 Hr Outlook (1200Z Nov 11)... 0% chance of tropical cyclone formation (south-central Caribbean near 14N-77.5W)

IOH 48 Hr Outlook (1200Z Nov 12)... 0% chance of tropical cyclone formation (south-central Caribbean near 14N-77.5W)

IOH 72 Hr Outlook (1200Z Nov 13)... 0% chance of tropical cyclone formation (south-central Caribbean near 14N-79W)

IOH 96 Hr Outlook (1200Z Nov 14)... 10% chance of tropical cyclone formation (offshore of northeastern Nicaragua near 14.5N-81.5W)

IOH 120 Hr Outlook (1200Z Nov 15)... 20% chance of tropical cyclone formation (just offshore of northeastern Honduras near 15.5N-83.8W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 7 AM EDT***************************

Formation chance through 48 hours... 0%

Formation chance through 7 days... 20%


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields(http://moe.met.fsu.edu/tcgengifs/).


0000Z (Nov 10) CMC Model Run...

**For area of interest #53... becomes a better-defined surface trough in the central Caribbean near 80W longitude by 168 hours


0000Z (Nov 10) ECMWF Model Run...

**For area of interest #53... becomes a better-defined surface trough in the central Caribbean near 80W longitude by 168 hours


0600Z (Nov 10) GFS Model Run...

**For area of interest #53... broad surface low with multiple centers develops just offshore of northeastern Nicaragua through 126 hours... becomes a north-south elongated tropical-storm force tropical low with multiple centers through 168 hours while moving into Jamaica


0600Z (Nov 10) NAVGEM Model Run...

**For area of interest #53... broad tropical low develops in the south-central Caribbean near 11.5N-79W at 114 hours... moves north-northwest in the vicinity of 80W longitude and becomes a large tropical cyclone just southwest of Jamaica by 150 hours... center of tropical cyclone then drifts northeast into the southwest coast of Jamaica by 168 hours.

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