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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 #123

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


...WEDNESDAY NOVEMBER 15 2023 2:55 PM EDT...

The surface trough of low pressure that was located in the vicinity of the Caribbean coast of Central America has begun to shift northeast into central Caribbean waters. This system continues to be monitored for signs of tropical cyclone formation... and is expected to continue northeastward across the northern Caribbean islands... southeastern Bahamas... and then toward Bermuda over the next four days while bringing heavy rainfall... see area of interest #53 section below for more information.


Elsewhere... a frontal low is expected to develop in the vicinity of the Florida peninsula and northwestern Bahamas over the next day or so. The supporting upper trough may be amplified enough to produce low enough wind shear and high enough upper divergence for thunderstorm activity and tropical characteristics of this feature... see area of interest #54 section below for more information.


AREA OF INTEREST #53... The surface trough of low pressure that was near the Caribbean coast of Central America has begun to lift northeast into central Caribbean waters while steered in deep-layer flow ahead of the approaching Gulf of Mexico frontal low 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). Based on satellite animation the area of maximum cyclonic turning is on track with my previous forecast... in the vicnity of 15.5N-82W. Thunderstorm activity has increased in the south-central Caribbean Sea... underneath the supportive outflow of the tropical upper ridge in the region and on the southeast side of the surface trough... therefore there is potential for a center of low pressure to develop toward that side of the trough and my updated forecast track is adjusted toward that direction. The track ends by 96 hours (day 4) when this system arrives toward cooler waters in the vicnity of Bermuda... ending its potential for tropical development. I mantain a low 10% peak odds of tropical cyclone formation for the following reasons:

(1) Southwesterly shear is expected to increase across the disturbance with the approach of the aforementioned upper trough

(2) 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 from its current western Canada position by late in the 4-day forecast period.


Regardless of tropical cyclone formation or not... a corridor of heavy rainfall is expected to develop over the next 48 hours and into the weekend... overspreading Jamaica... eastern Cuba... the southeastern Bahamas... and Haiti. With the forecast track below adjusted southeastward... the Dominican Republic is now more likely to be included in the heavy rainfall corridor. There is potential for flooding from excess rainfall. 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 24 Hr Outlook (1800Z Nov 16)... 0% chance of tropical cyclone formation (just southwest of Jamaica near 16.5N-79.5W)

IOH 48 Hr Outlook (1800Z Nov 17)... 10% chance of tropical cyclone formation (just south of the southeastern Cuba coast near 19.5N-75.5W)

IOH 72 Hr Outlook (1800Z Nov 18)... 10% chance of tropical cyclone formation (western Atlantic near 24N-70W)

IOH 96 Hr Outlook (1800Z Nov 19)... 0% chance of tropical cyclone formation (just south of Bermuda near 30N-65W)

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

Formation chance through 48 hours... 40%

Formation chance through 7 days... 50%


AREA OF INTEREST #54... The eastward progress of the surface frontal low that has been pivoting across the northern Gulf of Mexico has slowed due to the strength of a surface ridge over the United States east coast. The surface pressure gradient between the two features is producing gusty winds and coastal surf for the Gulf of Mexico coastal regions of Florida... Alabama... Mississippi... and southeastern Louisiana. Pockets of heavy rainfall as of this writing are currently in progress across Florida... southeastern Alabama... southern Georgia... southern South Carolina... now spreading into the northwestern Bahamas.


The eastward speed of the southern stream upper trough that generated the Gulf of Mexico frontal low has outpaced the frontal low... as a result the next 48 hours should see the original frontal low dissipating under a lack of divergence beneath the upper trough axis while the eastern divergence zone of the upper trough generates a replacement frontal low in western Atlantic waters near the east coast of Florida and northwestern Bahamas. This should result in an eastward shift of the heavy rainfall into offshore waters... as well as an eastward transfer of the gusty winds and coastal surf into the southeastern US coastal region and offshore Atlantic waters. The upper trough may be amplified enough during this time to have an upper divergence maximum to concentrate thunderstorm activity and surface pressure falls to make the replacement frontal low feature a well-defined instead of elongated center and tropical characteristics... with some intermittent runs of global models agreeing with this. However I assign a low 10% chance of tropical cyclone formation as at any given time the majority of global models are not in agreement with this idea. By 72+ hours the upper trough currently position over western Canada merges with the southern stream upper trough... with the combined lengthy upper trough accelerating this system northeastward into cooler waters... as such my outlook for tropical cyclone formation ends at 72 hours with 0% development odds. This system is likely to strengthen into a non-tropical frontal cyclone supported by the divergence zone of the combined upper trough by then... with the cyclone expected to produce coastal surf for the mid-Atlantic and northeastern US coastline... as well as Atlantic Canada... by this weekend. Atlantic Canada is the most likely land area to see notable gusty winds from this phase of the system... however gusty winds for the mid-Atlantic and northeastern US coast cannot be ruled out should the cyclone develop and track a little closer to shore.


Note regarding the updated forecast track below... I have shifted the track toward the south in alignment with where the most recent GFS model runs show the upper divergence maximum of the upper trough being located.

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

IOH 24 Hr Outlook (1800Z Nov 16)... 0% chance of tropical cyclone formation (offshore of the east-central Florida peninsula coast near 28N-79.8W)

IOH 48 Hr Outlook (1800Z Nov 17)... 10% chance of tropical cyclone formation (offshore of the southeastern United States near 30.5N-75.5W)

IOH 72 Hr Outlook (1800Z Nov 18)... 0% chance of tropical cyclone formation (northwestern Atlantic near 36N-68.5W)

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

Formation chance through 48 hours... 10%

Formation chance through 7 days... 10%


...COMPUTER MODEL SUMMARY...

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


0000Z (Nov 15) CMC Model Run...

**For area of interest #53... becomes a better-defined but broad tropical low in the south-central Caribbean near 12.5N-80W at 54 hours... the broad tropical low subsequently shifts northeast while the southeast side of the circulation consolidates into a tropical cyclone that makes landfall over southwestern Haiti at 114 hours... subsequently this system misses ridge weakness associated with western Atalntic cold front and meanders over southern Haiti thorugh 144 hours while coming under the influence of a strong ridge that builds behind the front (tropical cyclone weakens to a remnant low during this time)... remnant low then drifts northwest toward southeastern Cuba through 168 hours while weakening further to a trough

**For area of interest #54... through 72 hours the decaying frontal low currently in the north-central Gulf of Mexico merges with a pair of new frontal lows to the east (one just offshore of southwestern Florida and one just north of the northwestern Bahamas) to make a WSW/ENE elongated frontal low spanning the eastern Gulf of Mexico to the waters offshore of east-central Flroida... northeast part of the elongated frontal low intensifies into a frontal cyclone that reaches waters just offshore of Nova Scotia at 102 hours... center of frontal cyclone positioned over the central Gulf of St Lawrence at 108 hours... frontal cyclone continues northeast across Newfoundland and Labrador through 120 hours.


0000Z (Nov 15) ECMWF Model Run...

**For area of interest #53... becomes a better-defined but broad tropical low in the south-central Caribbean near 11.5N-80W at 30 hours... while becoming a north-south elongated feature the tropical low moves north-northeast across Jamaica and eastern Cuba through 72 hours shortly after which time it loses identity to area of interest #54 to the north.

**For area of interest #54... rapid tropical cyclone formation suggested between southeastern Florida and just northwest of the northwestern Bahamas at 54 hours... through 78 hours the tropical cyclone transitions into a more elongated and non-tropical frontal low offshore of the Carolinas... north side of elongated frontal low intensifies into a frontal cyclone just offshore of Massachusetts through 90 hours... center of frontal cyclone makes landfall at the Maine/New Brunswick border at 96 hours and reaches the northwest corner of the Gulf of St. Lawrence through 108 hours... frontal cyclone continues northeast across southeastern Quebec and Labrador through 126 hours.


0600Z (Nov 15) GFS Model Run...

**For area of interest #53... becomes a better-defined but broad tropical low in the south-central Caribbean near 12N-80W at 30 hours... continues northeast while featuring multiple centers and reaches Jamaica... eastern Cuba... Haiti... and the southeastern Bahamas by 84 hours... transitions into a frontal cyclone with multiple centers while passing just southeast of Bermuda by 111 hours... continues northeast toward the north-central Atlantic through 168 hours while losing dominance to another frontal cyclone that gradually develops just to the south.

**For area of interest #54... frontal low develops between southeast Florida... west of the northwestern Bahamas... and north-central Cuba at 33 hours... becomes an increasingly southwest-northeast elongated feature in the vicinity of 30N-74.5W through 72 hours... northeast part of elongated frontal low becomes a frontal cyclone that moves into Nova Scotia through 96 hours... center of frontal cyclone located in the central Gulf of St Lawrence at 102 hours... frontal cyclone continues northeast across southeastern Quebec and Labrador through 111 hours and then into the far north Atlantic waters just offshore of Labrador through 120 hours.


0600Z (Nov 15) NAVGEM Model Run...

**For area of interest #53... becomes a better-defined tropical low near 11.5N-79.5W at 18 hours... continues north to 15.5N-80.2W through 36 hours... tropical low then continues east-northeast into eastern Jamaica through 66 hours and then more northeastward into far eastern Cuba and southeastern Bahamas through 78 hours shortly after which time it loses identity to area of interest #54 to the north.

**For area of interest #54... frontal low develops just offshore of southwestern Florida at 30 hours... continues northeast and develops into a more circular and potentially tropical system near 30.5N-79W by 60 hours... transitions into a frontal cyclone just east of the North Carolina Outer Banks by 78 hours... frontal cyclone positioned just east of Massachusetts at 90 hours and over Nova Scotia at 96 hours... frontal cyclone continues north-northeast across southeastern Quebec and Labrador through 120 hours.

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