*******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.*********
...WEDNESDAY OCTOBER 30 2024 10:18 PM EDT...
See area of interest #44 section below for more information on possible Caribbean tropical development in the days ahead.
In the open central Atlantic… now watching a pair of areas of interest for possible tropical development… see areas of interest #45 and #46 sections below for details. And over the next week… the current central North America upper trough moves into the north-central Atlantic… and another warm core upper ridge develops over eastern North America (not to be confused with the current eastern North America upper ridge). Model runs suggest the long-term eastern North America upper ridge could be strong enough to separate some of the upper vorticity on the southwest side of the north-central Atlantic upper trough from the rest of the trough. If the cut-off upper vorticity becomes amplified enough to produce a pocket of low shear and focused upper divergence on its east side… it could trigger yet another central Atlantic tropical disturbance at a location northeast of the Caribbean Islands in approximately one week from today.
AREA OF INTEREST #44... Shower and thunderstorm activity that was over Central America has begun to shift east into the central Caribbean due to a developing supporting area of split flow upper divergence between the east side of the western Caribbean upper anticyclone/ ridge and southwest side of upper vorticity diving southeast from the Bahamas. Convergence provided by multiple surface tropical waves of low pressure passing west through the region has also been supporting the activity. 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=)... however in the next 24 hours there is an increasing chance that one develops in the central Caribbean (SSW of Jamaica) due to the aforementioned split flow upper divergence. Continuing to hold a 0% chance of tropical cyclone formation through November 2 due to northerly shear to be induced by the aforementioned upper vorticity while it settles over the northern Caribbean Islands as an upper vortex. The latest models have the upper vortex slipping more east than previously shown through 48 hours which may lower the shear in the central Caribbean. However in the longer range the upper vortex reverses to a westward turn under the influence of another upper ridge that builds over eastern North America in the wake of the current central North America upper trough/ surface frontal system… once that system later moves into the North Atlantic... therefore northerly shear quickly re-increases in as soon as 72 hours which re-enforces keeping development odds at 0% through November 2. The track forecast after 24 hours in my outlook below is a cyclonic orbit around the south side of the west pivoting upper vortex… as the area of split flow upper divergence is shown in the models to cyclonically move around the south side of the upper vortex… then by 4+ days momentum for possible tropical development will be in the eastern divergence zone of the west moving upper vortex… especially as the vortex moves west enough to begin dropping shear levels around that time. Note the updated track forecast is nudged east due to the latest forecast positions of the influencing upper vortex. I have a low 20% peak odds of tropical cyclone formation for days 4 and 5 as not all models agree on developing this area of interest during that timeframe (for instance in the model mix in the model summary section below… only the CMC and GFS showed development by day 5). Final note… from now through day 5 tropical development could occur sooner and further northeast over the northern Caribbean Islands (Hispaniola to northern Lesser Antilles) in a pocket of low shear and upper divergence on the east side of the upper vortex... if so may have to shift the outlook forecast points notably northeast in future updates.
Given the current outlook... interests across Jamaica… Hispaniola (Haiti and the Dominican Republic)… Puerto Rico… Virgin Islands… and northern Lesser Antilles should be on alert for possible periods of prolonged heavy rainfall with flood potential and possible tropical cyclone formation in the days ahead.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 31)... 0% chance of tropical cyclone formation (south-southwest of Jamaica near 15N-79W)
IOH 48 Hr Outlook (1800Z Nov 1)... 0% chance of tropical cyclone formation (south-southwest of Jamaica near 15N-78.5W)
IOH 72 Hr Outlook (1800Z Nov 2)... 0% chance of tropical cyclone formation (south-central Caribbean near 13.5N-77W)
IOH 96 Hr Outlook (1800Z Nov 3)... 10% chance of tropical cyclone formation (central Caribbean near 14N-74.5W)
IOH 120 Hr Outlook (1800Z Nov 4)... 20% chance of tropical cyclone formation (just southeast of Jamaica near 16.5N-76W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Formation chance through 48 hours… 0%
Formation chance through 7 days… 40%
AREA OF INTEREST #45… Due to the strength of the current eastern North America upper ridge… for the next 24 hours model runs have come into agreement that a large portion of the current northwest Atlantic upper trough will become a cut-off upper vortex that heads east-southeast toward the surface front in the open central Atlantic. The focused eastern divergence zone of the vortex is expected to trigger a surface cyclone along the front in the next 24 hours… with the surface cyclone potentially gaining tropical characteristics afterwards even though water temps in the region are in the low-20s of deg C… due to the cold de-stabilizing temps of the upper vortex (200 mb heights well below 1200 dekameters) which would help with thunderstorm generation. Just after 24 hours the surface cyclone will be whirling into the core of the upper vortex where it then reaches peak strength and begins to weaken due to the lack of divergence beneath the upper vortex core. Beyond that time the current central North America surface frontal system and upper trough break through the current eastern North America upper ridge and moves toward this system… lifting this system (surface cyclone and upper vortex) increasingly east then northeast into the open northeast Atlantic. By 96 hours this system becomes absorbed by the incoming surface frontal system and upper trough. My peak odds of subtropical development are shown at 48 hours when the surface cyclone is at peak strength… with decaying odds shown thereafter as the surface cyclone loses development potential with time as it weakens should it continue to fail to acquire tropical characteristics. Noting that if it does acquire fully tropical character by firing sustained thunderstorms that generate a latent heat release driven warm core outflow layer just below the upper vortex… the outflow layer would help the surface cyclone in holding peak strength for longer. In this update I have increased subtropical development odds as the models have converged on an upper vortex and associated organized surface cyclone forming (as opposed to an upper trough whose elongated divergence zone would trigger a less organized multi-center surface system). However I only slightly increased the odds as the model consensus has also shifted north… increasing the potential of this system running into even cooler waters below 20 deg C sooner. Regardless of tropical development or not… this system will bring coastal surf to the Azores by Saturday while passing just north of the islands.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 31)… 0% chance of subtropical cyclone formation (central Atlantic near 39.5N-40.5W)
IOH 48 Hr Outlook (1800Z Nov 1)… 50% chance of subtropical cyclone formation (west-northwest of the Azores near 41N-37.5W)
IOH 72 Hr Outlook (1800Z Nov 2)… 25% chance of subtropical cyclone formation (northwest of the Azores near 42.5N-32.5W)
IOH 96 Hr Outlook (1800Z Nov 3)… 0% chance of subtropical cyclone formation (northeast Atlantic near 47.5N-29W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Not in the official outlook
AREA OF INTEREST #46… A review of the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=)… satellite imagery (https://www.nhc.noaa.gov/tafb_latest/gehov1latest.gif)… and surface analyses (https://ocean.weather.gov/unified_analysis.php) show the current small tropical low pressure swirl near 12.5N-42W is a feature that was left behind by the recent surface tropical wave of low pressure that has been tracking across the eastern and central Atlantic and currently at 54W. The small tropical low has recently tracked more north while moving toward the surface ridge weakness associated with area of interest #45… however by 48 hours will track increasingly west while coming under the influence of the surface ridge that recently entered the western Atlantic from the eastern US. In the upper-levels some of the warm core upper ridging that was over the Caribbean is shifting east toward this area of interest while pushed by the developing upper vortex associated with area of interest #45 and upper vorticity currently moving toward the northern Caribbean Islands from the Bahamas. Thunderstorms are currently pushed east of the swirl center by northwesterly shear induced by the east side of the approaching upper ridging… and by 24 hours the forecast track allows this system to just miss the lowest shear beneath the core of the upper ridging. However the shear may still be low enough at that time to allow for tropical cyclone formation. I have assigned a low 10% chance of development as the models do not develop this system… and the shear will not be zero at 24 hours. By 48 hours I pull the development odds back to 0% and end the outlook at that time as the forecast track places this system more firmly in stronger westerly shear on the north side of the upper ridging.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1800Z Oct 31)… 10% chance of tropical cyclone formation (central tropical Atlantic near 15N-44W)
IOH 48 Hr Outlook (1800Z Nov 1)… 0% chance of tropical cyclone formation (central tropical Atlantic near 16N-47.5W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 8 PM EDT*************************
Not in the official outlook
…COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
1200Z (Oct 30) CMC Model Run...
**For area of interest #44... tropical low develops in the south-central Caribbean near 12N-80W by 54 hours... through 96 hours the tropical low becomes larger/broader and shifts northeast while merging with surface trough that develops over northern Caribbean Islands... south part of broad tropical low becomes a tropical cyclone near 15N-75W at 114 hours... while strengthening into a hurricane the tropical cyclone whirls northwest into the waters just offshore of the southwest coast of Jamaica through 150 hours... becomes a potentially intense hurricane while moving west-northwest into Grand Cayman Island through 168 hours
**For area of interest #45...Large portion of the current NW Atlantic 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 38.5N-42W by 24 hours... while cyclonically orbiting in the flow associated with the upper vorticity the surface cyclone moves ESE to 38N-39.5W at 36 hours where it becomes a possible tropical cyclone with the aid of the de-stabilizing cold upper air temps... the possible tropical cyclone then moves slowly northeast into the waters NW of the Azores through 78 hours while weakening... while shifting east into the waters N of the Azores through 108 hours the weakening system loses identity to frontal system that leaves North America and crosses the North Atlantic late in the forecast period
**For area of interest #46... no development shown
0000Z (Oct 30) ECMWF Model Run...
**For area of interest #44... tropical low develops in the south-central Caribbean near 12.5N-79W by 72 hours... through 132 hours the tropical low becomes larger/broader and shifts slowly northeast while merging with surface trough that develops over northern Caribbean Islands... the broad tropical low proceeds west-northwest into the western Caribbean through 168 hours
**For area of interest #45... Large portion of the current NW Atlantic 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-39.5W by 42 hours... while moving northeast to 42.5N-35W through 60 hours becomes a possible tropical cyclone with the aid of the de-stabilizing cold upper air temps... the possible tropical cyclone then continues northeast to 45N-32.5W through 96 hours while weakening... while accelerating north across the open northeast Atlantic through 138 hours the weakening system loses identity to frontal system that leaves North America and crosses the North Atlantic late in the forecast period
**For area of interest #46... no development shown
1200Z (Oct 30) GFS Model Run...
**For area of interest #44... tropical low develops in south-central Caribbean near 12.5N-80W by 54 hours... through 90 hours the tropical low becomes larger/broader and shifts slowly northeast while merging with surface trough/low that develops over northern Caribbean Islands... rapid and very compact tropical cyclone formation occurs in east side of the broad system and near 12.5N-74.5W at 93 hours... through 132 the compact tropical cyclone lifts north into the southern peninsula of Haiti while orbiting the remainder of the broad system... the compact system emerges into the waters between Haiti and Cuba at 147 hours as a remnant low... the compact remnant low regains tropical cyclone status while turning west into the waters between east Cuba and Jamaica through 168 hours
**For area of interest #45... Large portion of the current NW Atlantic 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-41W by 24 hours... while cyclonically orbiting in the flow associated with the upper vorticity the surface cyclone moves east to 39.5N-38W at 42 hours where it becomes a possible tropical cyclone with the aid of the de-stabilizing cold upper air temps... the possible tropical cyclone then moves slowly ENE into the waters NW of the Azores through 87 hours while weakening... while shifting east into the waters NE of the Azores through 111 hours the weakening system loses identity to frontal system that leaves North America and crosses the North Atlantic late in the forecast period
**For area of interest #46... no development shown
1200Z (Oct 30) NAVGEM Model Run…
**For area of interest #44... Rather large/broad tropical low develops over the central Caribbean through 72 hours... the broad system then shifts west toward the western Caribbean through 126 hours while a better-defined center develops in the east side of this system and just west of Jamaica... the better-defined center crosses Grand Cayman Island at 138 hours and proceeds to become a tropical cyclone while entering the southeastern Gulf of Mexico from the Yucatan channel (between west tip of Cuba and northeastern Yucatan peninsula) through 168 hours
**For area of interest #45... Large portion of the current NW Atlantic 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-39W by 36 hours... while continuing east in the direction of the Azores and along 40N latitude becomes a potential subtropical cyclone through 54 hours... passes just north of the Azores while still moving along 40N latitude through 84 hours... subsequently turns northeast into the open northeastern Atlantic and at 114 hours becomes absorbed by frontal system that leaves North America and crosses the North Atlantic late in the forecast period
**For area of interest #46... no development shown
**Surface frontal system and upper trough that absorbs area of interest #45 leaves behind upper vorticity that shifts east across the mid-latitudes of the central Atlantic... eastern divergence zone of the upper vorticity triggers a surface low with possible tropical character near 27.8N-35.5W at 168 hours
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