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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 #124

*******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 17 2023 12:32 AM EDT...

The central Caribbean surface low pressure area is expected to continue northeastward across the northern Caribbean islands... southeastern Bahamas... and then toward Bermuda over the next three days while bringing heavy rainfall. This system continues to be monitored for signs of tropical cyclone formation... see area of interest #53 section below for more information.


A new frontal low has developed near the northwestern Bahamas and southeastern Florida... however this feature has not developed tropical characteristics thus far and is not expected to do so going forward. See area of interest #54 section below for more information.


Elsewhere... the tail end of the surface cold front and upper trough of area of interest #54 is forecast to settle into the open central Atlantic over the next five days. Some global model runs suggest enough upstream upper ridging to the west could develop to cut-off the upper trough and surface front from the mid-latitude westerlies... resulting in the surface front and upper trough evolving into an erratically moving deep-layer low pressure system with possible tropical characteristics in approximately one week from today. As such may need to declare yet another tropical area of interest for the open central Atlantic in future updates... particularly if global models converge on this scenario.


AREA OF INTEREST #53 (POTENTIAL TROPICAL CYCLONE TWENTY-TWO)... The surface trough of low pressure lifting northeastward across the central Caribbean Sea has evolved further into a broad tropical low pressure spin. The northeastward track is due to deep-layer steering flow ahead of the new frontal low near southeastern Florida and associated southern stream upper trough (more information on the southern stream upper trough and frontal low is in the area of interest #54 section below). The thunderstorm activity that was in the south-central Caribbean and southeast side of the broad tropical low... generated by the outflow of the regional tropical upper ridge... has spent much of this Thursday wrapping into the central area of rotation while becoming better organized. The National Hurricane Center has since increased odds of tropical cyclone formation and upgraded this system to potential tropical cyclone twenty-two... in order to issue tropical storm advisories across Jamaica... eastern Cuba... Haiti... and the southeastern Bahamas. I have also increased odds of tropical cyclone formation... however I have kept odds just below the 50% mark for the following reasons:

(1) Thunderstorm activity in the circulation has decreased tonight

(2) The CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) shows this system is still elongated rather than circular... a circular structure with single center needed for focused surface convergence and resultant thunderstorms is typically needed for tropical cyclone formation.

(3) Going forward... the approaching southern stream upper trough should overspread this system with an elongated upper divergence zone... in particular as it merges with a higher-latitude upper trough currently over central Canada... which will likely keep this system elongated. Southwesterly shear will also be increasing as the upper trough overspreads this system. I drop odds of tropical cyclone formation to 0% by 48 hours due to the progressively worsening conditions caused by the incoming upper trough.


Regardless of tropical cyclone formation or not... periods of heavy rainfall with possible flash flooding are expected across Jamaica... eastern Cuba... the southeastern Bahamas... Haiti... and the Dominican Republic through this weekend. With the current forecast... the corridor of heavy rainfall shifts into Bermuda by Sunday.

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

IOH 12 Hr Outlook (1200Z Nov 17)... 40% chance of tropical cyclone formation (western Jamaica near 18N-78W)

IOH 24 Hr Outlook (0000Z Nov 18)... 20% chance of tropical cyclone formation (northeast coast of Cuba near 21N-76W)

IOH 48 Hr Outlook (0000Z Nov 19)... 0% channce of tropical cyclone (western Atlantic near 25N-70W)

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

Formation chance through 48 hours... 70%

Formation chance through 7 days... 70%

*****National Hurricane Center (hurricanes.gov) official forecast as of 4 PM EDT***************************

Peak Strength (1800Z Nov 18)... 50 mph maximum sustained wind tropical storm centered over the southeastern Bahamas at 21.9N-73.3W

Loss of Tropical Cyclone Status (1800Z Nov 19)... 50 mph maximum sustained wind remnant frontal cyclone centered south of Bermuda at 29.4N-64.5W


AREA OF INTEREST #54... The eastern divergence zone of the southern stream upper trough that has been sliding eastward across the southeastern United States and eastern Gulf of Mexico has produced a new frontal low between southeastern Florida and the northwestern Bahamas. Meanwhile the previous frontal low generated by the upper trough has been diving southward across the Gulf of Mexico in deep-layer northwesterly flow on the back western side of the upper trough and new frontal low... with the previous frontal low decaying due to a lack of divergence on the back side of the upper trough. The new frontal low has not developed concentrated thunderstorms near its center thus far... and the global models now agree that the upper trough will not become amplified enough to develop an upper divergence maximum to support a concentrated core of thunderstorms near the center. Therefore tropical cyclone formation of this feature is no longer possible... and this will be my final statement on this area of interest on this blog.


Going forward the southern stream upper trough will be merging with the upper trough currently positioned over central Canada... with the combined lengthy upper trough accelerating the new frontal low near southeast Florida northeastward parallel to the United States east coast and into Atlantic Canada. The frontal low is expected to strengthen into a frontal cyclone supported by the divergence zone of the combined upper trough. The pressure gradient between the strengthening system and surface ridge to the north will be inducing gusty winds and surf for the coastal regions of the southeastern United States over the next 24 hours. By Saturday the surf then transfers north across the mid-Atlantic and northeastern US shoreline with the track of this system... gusty winds for this part of the coastline cannot be ruled out should the cyclone track a little closer to shore. Gusty winds and coastal surf will then transfer northeastward across Atlatnic Canada by Sunday.

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

IOH 24 Hr Outlook (0000Z Nov 18)... 0% chance of tropical cyclone formation (offshore of the southeastern United States near 30N-75W)

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

Formation chance through 48 hours... 0%

Formation chance through 7 days... 0%


...COMPUTER MODEL SUMMARY...

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


1200Z (Nov 16) CMC Model Run...

**For area of interest #53... broad tropical low moves east-northeast and passes just south of Jamaica through 60 hours... subsequently stalls just south of southwestern Haiti at 102 hours while missing the ridge weakness associated with western Atlantic cold front... under influence of surface ridge that builds behind the front the tropical low turns west-northwest into Jamaica and eastern Cuba through 168 hours while weakening to a trough.

**For area of interest #54... frontal low currenlty just offshore of southeastern Florida moves northeast and becomes an SW/NE elongated feature offshore of the Carolinas by 36 hours... subsequently strengthens into a frontal cyclone that moves into western Nova Scotia by 60 hours... frontal cyclone continues northeast across the Gulf of St Lawerence... southeastern Quebec... and Labrador through 78 hours... continues into southwestern Greenland through 120 hours

**Tail end of cold front driven by area of interest #54 arrives into the open central Atlantic through 120 hours... the tail end of the front and associated upper trough evolve into a cut-off deep-layer subtropical low that moves south-southwest to 28.5N-45W through 168 hours


1200Z (Nov 16) ECMWF Model Run...

**For area of interest #53... broad tropical low moves northeast across Jamaica and eastern Cuba through 36 hours and then the southeastern Bahamas by 48 hours... loses identity along cold front driven by area of interest #54 shortly thereafter

**For area of interest #54... frontal low currenlty just offshore of southeastern Florida moves northeast and becomes an SW/NE elongated feature offshore of the Carolinas by 42 hours... northeast end of frontal low intensifies into a frontal cyclone that moves into western Nova Scotia by 60 hours... frontal cyclone continues northeast across the Gulf of St Lawerence... southeastern Quebec... and Labrador through 84 hours... continues into southwestern Greenland through 120 hours

**Tail end of cold front driven by area of interest #54 arrives into the open central Atlantic through 120 hours... the tail end of the front and associated upper trough evolve into a cut-off deep-layer subtropical low that moves south-southwest to 28.8N-50W through 144 hours... surface layer of subtropical low then cyclonically orbits southward beneath the west side of the upper layer (upper vortex)... arriving to 24.8N-48W


1800Z (Nov 16) GFS Model Run...

**For area of interest #53... broad tropical low degenerates into two centers... one just west-southwest of Jamaica and one on the southeast coast of Cuba... through 27 hours... both centers dissipate shortly thereafter

**For area of interest #54... frontal low currently just offshore of southeastern Florida moves northeast and becomes an SW/NE elongated feature offshore of the Carolinas by 36 hours... northeast end of frontal low intensifies into a frontal cyclone that moves into western Nova Scotia by 54 hours... frontal cyclone continues northeast across the Gulf of St Lawerence... southeastern Quebec... and Labrador through 72 hours... continues into southwestern Greenland through 102 hours


1800Z (Nov 16) NAVGEM Model Run...

**For area of interest #53... broad tropical low moves northeast into Jamaica through 48 hours... while weakening to a trough through 84 hours reaches far southeastern Cuba... far southeastern Bahamas... and northwestern Haiti... trough dissipates shortly thereafter

**For area of interest #54... frontal low currently just offshore of southeastern Florida moves northeast and becomes an SW/NE elongated feature offshore of the Carolinas by 36 hours... northeast end of frontal low intensifies into a frontal cyclone that moves into eastern Nova Scotia by 60 hours... frontal cyclone continues northeast across Newfoundland and Labrador through 72 hours... continues northeast into southwestern Greenland through 114 hours

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