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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 2024 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #108

Writer's picture: NCHurricane2009NCHurricane2009

Updated: Oct 29, 2024

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


...UPDATE...MONDAY OCTOBER 28 2024 3:41 PM EDT...

The surface and upper air charts valid for October 27 have been added below.


...SUNDAY OCTOBER 27 2024 11:59 PM EDT...

For the Caribbean Sea... continuing to watch for possible tropical development in the days ahead... see area of interest #44 section below for details.


In the mid-latitudes of the central Atlantic… the surface trough of low pressure that was near 27.5N-40W on Friday has been absorbed by the surface front driven into the region by ex-Oscar. The usually more reliable GFS and ECMWF suggest a large portion of the current eastern North America upper trough will become a cut-off upper vortex that heads east-southeast toward the surface front. If so… the eastern divergence zone of the upper vortex would trigger a surface cyclone along the front with possible tropical character… due to the focused divergence zone of the vortex helping to make a well-defined surface center plus the cold de-stabilizing temps of the upper vortex which would help with thunderstorm generation. If these model trends continue… will add an area of interest for possible tropical development for the mid-latitudes of the central Atlantic in my next update.


AREA OF INTEREST #44... The surface tropical wave of low pressure that was in the central Caribbean over the weekend moves across Central America… helping to spread the thunderstorms that were over the south-central Caribbean northwestward across Central America. Thunderstorms are also re-building in the south-central Caribbean as the tropical wave that was crossing the Lesser Antilles on Friday is now crossing the central Caribbean. A well-defined low-level spin has not developed so far in the Caribbean as seen in the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=)… and at this point it is not likely that the aforementioned pair of surface tropical waves will contribute to the formation of one while simply continuing west through and then away from the region. Up next… watching for the possible development of a southwest-northeast tilted surface trough spanning much of the Caribbean… to be initialized in the central Caribbean (just offshore of Central America) by the ongoing outflow of the western Caribbean upper anticyclone… then expanding northeastward with time toward the northeastern Caribbean Islands due to split flow upper divergence between the anticyclone and west side of the upper vorticity that arrives from its current central US position and into the northern Caribbean Islands by day 5. The northeast end of such a surface trough… to be directly over the northeastern Caribbean Islands… would be supported by the eastern divergence zone of the upper vorticity. Over the weekend… the NHC TAFB added a surface tropical wave that has recently crossed the Lesser Antilles and into the eastern Caribbean… probably a wave of African origin that was not previously well-defined. Another similar wave is currently in the eastern tropical Atlantic. Over the next five days expecting both waves to merge with the Caribbean surface trough. Noting that upstream upper ridging that amplifies over North America will help the upper vorticity in being amplified… which will also keep westerly wind shear levels low over the northeastern Caribbean Islands… therefore cannot rule out tropical development for that portion of the surface trough. For now my outlook below suggests the most likely location for tropical development of the surface trough within the next five days is further southwest toward Jamaica… where the aforementioned split flow upper divergence would be. In this update I have lowered peak odds of tropical development to 10% for the 5-day window as there is no well-defined low-level low pressure center within this area of interest as noted above… therefore time for tropical development before wind shear associated with the incoming upper vorticity increases has ran out. The above-zero odds are reserved for day 5 when northerly wind shear in the vicinity of Jamaica… imparted by the upper vorticity… relaxes as the upper vorticity shifts east and away into the northeastern Caribbean Islands.


Given the current outlook... expect additional periods of heavy rain across Central America over the next couple of days. Interests in Jamaica should continue to monitor the progress of this area of interest in the days ahead.

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

IOH 24 Hr Outlook (1800Z Oct 28)… 0% chance of tropical cyclone formation (just offshore of the Nicaragua/Honduras border near 15N-83W)

IOH 48 Hr Outlook (1800Z Oct 29)… 0% chance of tropical cyclone formation (just offshore of the Nicaragua/Honduras border near 15N-83W)

IOH 72 Hr Outlook (1800Z Oct 30)… 0% chance of tropical cyclone formation (between Central America and Jamaica near 15.5N-81W)

IOH 96 Hr Outlook (1800Z Oct 31)… 0% chance of tropical cyclone formation (south-southwest of Jamaica near 15.5N-78.5W)

IOH 120 Hr Outlook (1800Z Nov 1)… 10% chance of tropical cyclone formation (south-southeast of Jamaica near 15.5N-78.5W)

*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************

Formation chance through 48 hours… 0%

Formation chance through 7 days… 40%


...COMPUTER MODEL SUMMARY...

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


0000Z (Oct 27) CMC Model Run...

**For area of interest #44... broad tropical low develops in the south-central Caribbean near 12.5N-80W by 132 hours… within east side of the broad low tropical cyclone formation occurs near 13.5N-77W at 156 hours… while slowly intensifying through 168 hours is quasi-stationary

**Tropical wave currently in the eastern tropical Atlantic becomes a tropical low near 8.5N-34W at 18 hours… tropical low then continue west-northwest to northwest and reaches 20N-52.5W by 168 hours while weakening to a trough.


0000Z (Oct 27) ECMWF Model Run...

**For area of interest #44... through 168 hours a SW/NE tilted surface trough develops from the south-central Caribbean to the waters east of the SE Bahamas

**Large portion of the current eastern North America upper trough becomes cut-off upper vorticity that moves toward current central Atlantic surface front… the divergence zone of the vorticity develops a rapidly-forming surface frontal cyclone near 40.5N-44W by 114 hours… while cyclonically orbiting in the flow associated with the upper vorticity the surface cyclone moves SE to 38.5N-40W by 126 hours where it becomes a possible tropical cyclone with the aid of the de-stabilizing cold upper air temps… the possible tropical cyclone then completes one cyclonic loop at a location west-northwest of the Azores through 168 hours


0600Z (Oct 27) GFS Model Run...

**For area of interest #44… broad tropical low forms offshore of Nicaragua/Costa Rica border by 102 hours… while quasi-stationary the southwest part of the tropical low becomes a compact tropical cyclone at 120 hours… through 168 hours the tropical cyclone makes a slow cyclonic loop while orbiting the remainder northeast part of the tropical low and becomes increasingly larger and stronger as it absorbs the remainder northeast part… at 168 hours hurricane-strength tropical cyclone shown centered at 13.5N-78W

**Tropical wave currently in eastern tropical Atlantic moves into the eastern Caribbean Sea through 129 hours… during this time north apex of the wave evolves into a tropical low over the NE Caribbean Islands while interacting with divergence zone of upper vorticity that descends SE from its current central US position to the waters just north of the northern Caribbean Islands… while whirling beneath the core of the upper vorticity at a position just north of Puerto Rico evolves into a possible subtropical cyclone through 168 hours

**Large portion of the current eastern North America upper trough becomes cut-off upper vorticity that moves toward current central Atlantic surface front… the divergence zone of the vorticity develops a rapidly-forming surface frontal cyclone near 39.5N-43W by 102 hours… while drifting east toward 40N-40W through 120 hours it becomes a possible tropical cyclone with the aid of the de-stabilizing cold upper air temps… the possible tropical cyclone then completes one cyclonic loop at a location west-northwest of the Azores through 168 hours while weakening

**Current upper vortex just offshore of western Canada proceeds across North America as an upper trough… the southwest tail of the upper trough later becomes cut-off from the rest of the trough when entering the Atlantic at 144 hours… through 168 hours the divergence zone of the cut-off upper vorticity produced a frontal cyclone with possible tropical characteristics near 38.5N-53.8W (tropical character possible with de-stabilizing cold upper air temps associated with the upper vorticity)


0600Z (Oct 27) NAVGEM Model Run…

**For area of interest #44... rather road surface low pressure field materializes across the central Caribbean through 126 hours... the lowest surface pressures become concentrated in the east side of this system and moves north into eastern Jamaica through 168 hours

**Tropical wave currently in the eastern tropical Atlantic becomes a tropical low near 10N-38.8W at 48 hours… tropical low then continue west-northwest and reaches 16.5N-52.5W by 168 hours while weakening to a trough.

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