MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #121

*******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.*********

...MONDAY NOVEMBER 13 2023 2:20 PM EDT...

Showers and thunderstorms have increased across the south-central Caribbean... spreading onshore into eastern Nicaragua and eastern Honduras. A tropical disturbance is likely to develop here... and is expected to move northeastward across the north-central Caribbean islands (eastern Cuba... Jamaica... as well as Haiti and the Dominican Republic) and southeastern Bahamas over the next five days. 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... Cold core upper vorticity currently parked over the northeastern Caribbean islands is in the process of dissipating due to prolonged isolation from high-latitude cold air... and over the next 24 hours will become replaced by the warm core upper ridge now over the western Caribbean. Although thunderstorm activity across the south-central Caribbean waned for much of Sunday... it has notably increased today and has spread onshore into eastern Nicaragua and eastern Honduras with the support of split flow upper divergence between the aforementioned upper vorticity and upper ridge... and a disturbance is likely to materialize in this location in the short-term. Noting the model guidance has shifted east with the formation and northeastward acceleration of the forecast disturbance since my previous update... however my updated outlook below has a similar track as before due to the current location of the thunderstorm activity and split flow upper divergence where I assess the surface pressures are most likely to fall. Thus my current forecast track is west of the latest global model guidance envelope... calling for an initial west drift drift of the disturbance toward Central America in the next 24 hours under the influence of the strong surface ridge currently over North America... and then a north drift through 48 hours toward the surface ridge weakness of the developing Gulf of Mexico frontal low. After that time the frontal low and its supporting southern stream upper trough move toward this disturbance and accelerates the disturbance northeastward. I have raised my peak odds of tropical cyclone formation in this update cycle due to the recently increased thunderstorm activity of the developing disturbance... but only to 25% as this disturbance is at risk of becoming an elongated tropical low with multiple centers... instead of a single center needed for tropical cyclone formation... due to the large size and elongated nature of the incoming upper trough’s divergence zone... in particular as it merges with a higher-latitude upper trough that moves across North America late in the 5-day forecast period. Wind shear imparted by the incoming upper trough will also be a negative factor going against tropical development. I have also extended the 0% short-term odds of development to a longer period of time as the developing disturbance still has not developed a well-defined surface low pressure spin and hence is less likely to develop in the short-term as it interacts with the landmass of Central America.

Regardless of tropical cyclone formation or not... the following impacts to land areas are anticipated:

(1) In the short-term... through Wednesday... expect increasing periods of heavy rainfall with possible flash flooding for Nicaragua as well as eastern and central Honuduras.

(2) By later this week and into the weekend... expect a large area of heavy rainfall to develop with possible flooding concerns. The rainfall is most likely to overspread Jamaica... eastern Cuba... Haiti and the Dominican Republic... and the southeastern Bahamas. Periods of heavy rainfall cannot be ruled out of the Cayman Islands... particularly toward Little Cayman and Cayman Brac... however rainfall accumulations here are likely to be less as shear imparted by the incoming upper trough keeps the strongest thunderstorm activity off to the east.

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

IOH 24 Hr Outlook (1800Z Nov 14)... 0% chance of tropical cyclone formation (southeast coast of Nicaragua near 12N-84W)

IOH 48 Hr Outlook (1800Z Nov 15)... 0% chance of tropical cyclone formation (northeastern Nicaragua near 14N-84W)

IOH 72 Hr Outlook (1800Z Nov 16)... 10% chance of tropical cyclone formation (offshore and east-northeast of Honduras near 15.5N-82W)

IOH 96 Hr Outlook (1800Z Nov 17)... 25% chance of tropical cyclone formation (just northwest of Jamaica near 19N-78.8W)

IOH 120 Hr Outlook (1800Z Nov 18)... 25% chance of tropical cyclone formation (just north of the southeastern Bahamas near 23N-72.5W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 1 PM EDT***************************

Formation chance through 48 hours... 0%

Formation chance through 7 days... 70%

...COMPUTER MODEL SUMMARY...

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

0000Z (Nov 13) CMC Model Run...

**For area of interest #53... becomes a better-defined but north-south elongated tropical low in the central Caribbean near 15N-79.5W at 120 hours... tropical low moves northeast and makes landfall acrss Haiti at 156 hours... tropical low continues northeast and passes just east of the eastern Bahamas through 168 hours

0000Z (Nov 13) ECMWF Model Run...

**For area of interest #53... becomes a better-defined tropical low in the south-central Caribbean Sea near 12.5N-80.5W at 72 hours... tropical low moves northeast and makes landfall acrss Haiti at 138 hours and passes just east of the eastern Bahamas by 150 hours... transitions into a strengthening non-tropical frontal cyclone that continues northeast into the waters southeast of Bermuda near 29.8N-61.5W through 168 hours

1200Z (Nov 13) GFS Model Run...

**For area of interest #53... becomes a better-defined tropical low in the south-central Caribbean Sea near 12.5N-80W at 66 hours... the strengthening tropical low continues northeast with multiple centers but finally consolidates into a tropical cyclone with a single center while located just south-southeast of Jamaica at 105 hours... tropical cyclone continues northeast into northwestern Haiti through 120 hours and then across the southeastern Bahamas through 126 hours... tropical cyclone begins to transition into a non-tropical frontal cyclone while passing just east of Bermuda through 150 hours... remnant frontal cyclone located southeast of Newfoundland by 168 hours

0600Z (Nov 13) NAVGEM Model Run...

**For area of interest #53... becomes a better-defined tropical low centered just southeast of Jamaica at 84 hours... moves northeast across far eastern Cuba and southeastern Bahamas through 114 hours shortly after which time it loses its identity to developing frontal cyclone to the north