*******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 NOVEMBER 11 2024 2:44 PM EDT...
The surface and upper air charts valid for November 1 have been added below.
...FRIDAY NOVEMBER 1 2024 3:55 PM EDT...
It does not feel like we have entered the final month of the Atlantic hurricane season as we are tracking four concurrent areas of interest for possible tropical development:
(1) See area of interest #44 and #47 sections below for information on a pair of disturbances covering much of the Caribbean region.
(2) See area of interest #45 and #46 sections below for information on a pair of disturbances in the open central Atlantic.
In addition yet another tropical disturbance could develop in the open central Atlantic around day 5 as follows... the current eastern Canada upper trough will soon move into the north-central Atlantic... and another warm core upper ridge is forecast to develop over the eastern US. Model runs suggest the upstream 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 five days from today.
AREA OF INTEREST #44... We finally have a tropical low pressure rotation in the south-central Caribbean Sea as seen on CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) and in the curvature of thunderstorm squalls in the region. In the upper-levels upper vorticity from the northwestern Gulf of Mexico has shifted southeast toward the northwestern Caribbean and the upper vorticity that was over the Bahamas is over the northeastern Caribbean Islands and western Atlantic... with both lobes of upper vorticity being pushed by the upper ridge now entering the western Atlantic from the eastern US. The western lobe of upper vorticity (nearing the northwestern Caribbean) displaced the western Caribbean upper ridge/ anticyclone into the south-central Caribbean... the upper outflow of which likely contributed to developing the south-central Caribbean tropical low... especially as the northeastern outflow is enhanced by the flow curving into the eastern lobe of upper vorticity (toward the northeastern Caribbean Islands). At the surface... a tropical wave of low pressure that approached from the southeastern Caribbean also likely contributed to the formation of the south-central Caribbean tropical low. The eastern lobe of upper vorticity is contributing to a subtropical disturbance over the northeastern Caribbean Islands (area of interest #47)... and in the next 48 hours the south-central Caribbean tropical low is likely to shift east toward the waters offshore of Colombia while cyclonically orbiting the subtropical disturbance. There is only a low chance of tropical cyclone formation during this time as westerly shear increases while the western lobe of upper vorticity continues shifting southeast toward this area of interest. After that time another warm core upper ridge develops over the eastern US which will help amplify the western lobe of upper vorticity into an upper vortex... with the vortex also retrograding westward and away with time under the influence of the new upper ridge. This will allow wind shear to drop... and the models now agree on developing this area of interest at some point in its life cycle. Therefore I agree on increasing odds of tropical cyclone formation to above 50% in this update cycle... but reserve the high odds for days 4 to 5 as the models disagree on how fast tropical cyclone formation occurs... with the GFS being the fastest and showing tropical cyclone formation by day 3 and the ECMWF being the slowest by showing tropical cyclone formation after day 5. For the long-range track... expecting a northward lift from 48 to 72 hours due to the combination of the surface ridge weakness associated with the northeastern Caribbean Islands subtropical disturbance and the steering provided by the retrograding upper vortex to the west. The track deflects to a more west and less north angle after 72 hours once this system bumps into a sprawling surface ridge developing to the north under the convergence zone of the current eastern Canada upper trough... generally taking this system in the environment of Jamaica... the Cayman Islands... and Cuba. Note after day 5 the models are split on the long-range track... some have the next North American upper trough in the mid-latitude westerlies create a weakness in the sprawling surface ridge that allows for a track toward Florida or the eastern Gulf of Mexico... and others have this upper trough stay far north enough to instead allow its western convergence zone to extend the sprawling surface ridge westward such that the extended ridge steers this system into the south-central Gulf of Mexico.
Given the current outlook... interests across Jamaica... Haiti... Cuba... the Cayman Islands... and south Florida including the Keys should be aware of possible tropical cyclone formation during the first half of this upcoming week and the potentially hazardous impacts that comes with such a situation (heavy rainfall with flash flooding potential... gusty winds... and coastal surf).
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Nov 2)... 10% chance of tropical cyclone formation (south-central Caribbean near 12.5N-79W
IOH 48 Hr Outlook (1200Z Nov 3)... 15% chance of tropical cyclone formation (offshore of Colombia near 13N-75W)
IOH 72 Hr Outlook (1200Z Nov 4)... 50% chance of tropical cyclone formation (south of southwestern Haiti near 16N-74W)
IOH 96 Hr Outlook (1200Z Nov 5)... 60% chance of tropical cyclone formation (northeast coast of Jamaica near 18N-76.5W)
IOH 120 Hr Outlook (1200Z Nov 6)...70% chance of tropical cyclone formation (just south of central Cuba near 21.2N-80W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Formation chance through 48 hours… 30%
Formation chance through 7 days… 70%
AREA OF INTEREST #45... Satellite sequence showing the rapid development of a surface cyclone in the open central Atlantic on October 31... location of the forming surface cyclone in each frame pointed to with yellow arrow:
Due to the strength of the upper ridge which has recently moved into the western Atlantic from the eastern US... the much of the previous northwest Atlantic upper trough evolved into a cut-off upper vortex in the open central Atlantic. The amount of upper divergence on the east side of the materializing upper vortex contributed to the rapid formation of a surface cyclone along a surface front that was previously in the region... and the surface frontal cyclone has already whirled into the core of the upper vortex where upper divergence is lacking... therefore the surface cyclone is at peak strength and will likely decay going forward unless tropical development occurs. Despite water temps in the region and along the forecast track being at 20 deg C... tropical development is becoming more likely as the upper vortex is cold enough for instability and resultant pockets of showers and thunderstorms now occurring at the core of the surface cyclone... and the GFS and ECMWF are now explicitly calling for subtropical or tropical cyclone formation.
As a result... I have increased odds of subtropical cyclone formation to above 50%. Regarding the track... the currently approaching eastern Canada surface frontal system and upper trough will shove this system (upper vortex and surface cyclone) east over the next 72 hours... with the upper vortex becoming pushed against the southwest side of the deep-layer ridge over the British Isles. Previous model runs suggested some chance the surface flow of the incoming surface frontal system would help bend the track of the surface cyclone more north early. However the updated forecast track now calls for the surface cyclone to continue east very close to or over the Azores while moreso caught in the flow associated with the upper vortex. After 72 hours though... the surface cyclone and upper vorticity should finally deflect more north in track due to the influence of the British Isles deep-layer ridge. I begin trimming down subtropical development odds from the peak at 72 hours as this system enters cooler waters below 20 deg C... and quickly drop the odds to 0% by 96 hours when this system will be over sharply cooler waters offshore of northwestern Spain where it will have shed any remainder thunderstorms and associated latent heat release driven supporting upper outflow... and combined with the ongoing lack of divergence beneath the core of the upper vorticity the fading surface cyclone should weaken fast.
The Azores have seen heavy rainfall associated with the surface cold front of the surface cyclone through early this morning. As the core of the surface cyclone nears tomorrow on the updated forecast track... periods of heavy rainfall... gusty winds... and coastal surf are likely.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Nov 2)... 60% chance of subtropical cyclone formation (vicinity of northwestern Azores near 40N-32.5W)
IOH 48 Hr Outlook (1200Z Nov 3)... 60% chance of subtropical cyclone formation (just north of the eastern Azores near 40N-26.5W)
IOH 72 Hr Outlook (1200Z Nov 4)... 50% chance of subtropical cyclone formation (northeastern Atlantic near 40N-19W)
IOH 96 Hr Outlook (1200Z Nov 5)... 0% chance of subtropical cyclone formation (just offshore of northwestern Spain near 44N-10W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 PM EDT*************************
Formation chance through 48 hours… 40%
Formation chance through 7 days… 40%
AREA OF INTEREST #46... The small tropical low pressure swirl in the central Atlantic has reached a further northwest location at 15N-45W as expected while gravitated toward the surface ridge weakness associated with area of interest #45. This further north location has placed it deeper in shearing upper westerly winds... and tropical cyclone formation of this feature is no longer possible. The weakening tropical low is forecast to bend increasingly west in track while under the influence of the current western Atlantic surface ridge until it dissipates. This is my final statement on this area of interest on this blog.
AREA OF INTEREST #47... The divergence zone of upper vorticity that has moved into the western Atlantic and northeastern Caribbean Islands from the Bahamas has been producing inclement weather across Puerto Rico... the Virgin Islands... and the northern Lesser Antilles through yesterday and today. Was initially tying the area of disturbed weather to area of interest #44... however the NHC since yesterday afternoon declared the disturbed weather as its own area of interest. Therefore this marks the forth-seventh such area of interest tracked on this site this year. Due to the amplified upper ridge that is now shifting into the western Atlantic from the eastern US... the upper vorticity is amplified enough to produce a focused eastern upper divergence zone allowing for at least a mid-level low pressure spin in the vicinity of Puerto Rico per the CIMSS 850 mb vorticity product (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=) while at the same time allowing for decreasing westerly shear levels more favorable for tropical development... especially as the upper vorticity amplifies further into a upper vortex parked over Puerto Rico in the next 24 hours. During this time I forecast the mid-level low to become a subtropical surface low that whirls into the north side of the steering Puerto Rico upper vortex... the subtropical designation meaning that the divergence along the periphery of the upper vortex helping this system develop via non-tropical means while at the same time warm core outflow generated by the thunderstorm latent heat release... which would occur north of the upper vortex in this case... also helps this system develop via tropical means. Beyond 24 hours the surface low will already be encountering a more hostile environment for subtropical development as a sprawling surface ridge that develops to the north... to be supported by the convergence zone of the eastern Canada upper trough... helps push this system into the northwestern quadrant of the upper vortex where suppressive upper convergence will be in place. The northwest quadrant of the upper vortex also has potential to lean the west track more southward into the north coast of the Dominican Republic... increasing land interaction. Due to the short window of conditions favoring subtropical development... I agree with low odds of subtropical cyclone formation through 24 hours... then end the outlook by 48 hours with 0% odds. Beyond that time I currently forecast the inland Dominican Republic remnants of this area of interest to be absorbed by area of interest #44.
Heavy rainfall over the northeastern Caribbean Islands is likely to decrease in the next 24 hours as the aforementioned upper vortex settles over Puerto Rico... due to a lack of divergence beneath the upper vortex core. Coastal surf will be possible for the north shore of Puerto Rico and Dominican Republic... with gusty winds possible for the Dominican Republic depending on how strong the forecast surface subtropical low gets.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Nov 2)... 20% chance of subtropical cyclone formation (just north-northwest of Puerto Rico near 20N-67W)
IOH 48 Hr Outlook (1200Z Nov 3)... 0% chance of subtropical cyclone formation (north coast of the Dominican Republic near 19.8N-70.5W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 2 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 1) CMC Model Run...
**For area of interest #44... through 54 hours tropical low pressure field in south-central Caribbean Sea becomes larger/broader and shifts northeast while absorbing area of interest #47... east part of the broad system develops a better-defined center just south of Jamaica at 72 hours... while orbiting with remainder western part of the broad system the better-defined center whirls northwest into the waters just south of the Cayman Islands and becomes a large tropical storm by 102 hours while absorbing the remainder low pressure field... the center of the gradually strengthening large tropical storm moves west-northwest into the Yucatan channel (between west tip of Cuba and northeast corner of the Yucatan peninsula) by 138 hours... while not strengthening further the large tropical storm then turns north across the eastern Gulf of Mexico through 168 hours
**For area of interest #45... surface cyclone moves east to east-southeast into the waters just south of the Azores through 54 hours while gradually weakening... subsequently continues east-northeast while weakening further to a surface trough offshore of Portugal through 102 hours where it then dissipates by 132 hours while turning on a northward drift
**For area of interest #46... no development shown
**For area of interest #47... westward-moving surface trough becomes increasingly defined over the southeastern Bahamas and vicinity through 54 hours and becomes absorbed by area of interest #44 shortly thereafter
0000Z (Nov 1) ECMWF Model Run...
**For area of interest #44... through 96 hours tropical low pressure field in south-central Caribbean Sea becomes larger/broader and shifts northeast while absorbing area of interest #47... the broad tropical low continues across the western Caribbean while its north side develops a better-defined center in the Yucatan channel (between west tip of Cuba and northeastern Yucatan peninsula) by 156 hours... tropical cyclone formation suggested through 168 hours as the better-defined center swings west into the waters just offshore of the northern Yucatan peninsula
**For area of interest #45... surface cyclone moves east to east-southeast into the waters just south of the Azores through 54 hours while very slowly weakening due to acquisition of tropical characteristics... the slowly weakening system then continues east-northeast into the waters just offshore of the Portugal/Spain border through 108 hours... dissipates just offshore of the northwest corner of Spain at 132 hours
**For area of interest #46... no development shown
**For area of interest #47... westward-moving surface trough becomes increasingly defined over the southeastern Bahamas and vicinity through 72 hours and becomes absorbed by area of interest #44 shortly thereafter
**Southwest side of surface frontal system and upper trough currently over eastern Canada 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 24.5N-40W at 126 hours... after initially moving east the surface low later comes under the influence of a surface ridge to the northwest that builds behind the upper vorticity which causes it to turn west-southwest... while weakening to a surface trough late in the forecast period it reaches 22.5N-41.5W by 168 hours
0600Z (Nov 1) GFS Model Run...
**For area of interest #44... broad surface low pressure field in the south-central Caribbean initially drifts northeast toward area of interest #47... by 60 hours a compact tropical cyclone forms within the east side of the broad low pressure field and near 13N-75W... the remainder western low pressure field absorbs area of interest #47 and swings the strengthening compact tropical cyclone northward into the waters between Jamaica and Haiti through 84 hours... while cyclonically orbiting the remainder western broad low pressure field the compact tropical cyclone turns northwest into the north side of the broad low pressure field and into eastern Cuba by 102 hours... the compact tropical cyclone then continues west-northwest across central and western Cuba through 135 hours which causes it to weaken... continues west-northwest across the south-central Gulf of Mexico through 168 hours where the tropical cyclone intensifies into a hurricane.
**For area of interest #45... surface cyclone moves east to east-southeast into the Azores through 45 hours while very slowly weakening due to acquisition of tropical characteristics... the slowly weakening system then continues east-northeast into the waters offshore of the Portugal/Spain border through 93 hours while finally decaying to a surface trough... the trough dissipates offshore of the northwestern corner of Spain by 108 hours
**For area of interest #46... no development shown
**For area of interest #47... westward-moving surface low becomes increasingly defined over the southeastern Bahamas and vicinity through 57 hours... the surface low then swings west across eastern Cuba through 84 hours while becoming absorbed by area of interest #44.
**Through 117 hours the southwest side of upper trough/surface frontal system over eastern Canada deposits upper vorticity that re-enforces current western Atlantic upper vorticity extending from the northeastern Caribbean Islands... during this time the elongated divergence zone of the SW/NE upper vorticity axis produces an equally surface trough axis in the open central Atlantic featuring multiple surface lows... the southwest side of upper vorticity evolves into a cut-off upper vortex near the northern Lesser Antilles by 132 hours due to the strength of long-range eastern North America upper ridge that begins to shift offshore with the eastern divergence zone of the upper vortex triggering a surface subtropical low along the surface trough and near 20N-57.5W... the subtropical disturbance (surface low and upper vortex) begin to retrograde westward around the aforementioned upper ridging with the surface low becoming a tropical storm then hurricane while passing just north of Puerto Rico through 168 hours
0600Z (Nov 1) NAVGEM Model Run...
**For area of interest #44... while cyclonically orbiting area of interest #47 zooming west across the northern Caribbean Islands the broad surface low pressure field in the south-central Caribbean drifts northeast into the waters just south of Jamaica through 90 hours... tropical cyclone formation suggested over the eastern Cayman Islands by 108 hours... the tropical cyclone continues northwest into western Cuba by 126 hours while absorbing area of interest #47 located just to the west... the tropical cyclone continues north-northwest across the eastern Gulf of Mexico through 168 hours while only gradually strengthening.
**For area of interest #45... surface cyclone moves east to east-southeast into the waters just south of the Azores through 48 hours while gradually weakening... subsequently continues east-northeast while weakening further to a surface trough offshore of the Portugal/Spain border through 96 hours where it then dissipates by 114 hours while turning on a northward drift
**For area of interest #46... no development shown
**For area of interest #47... westward-moving surface low becomes increasingly defined over the southeastern Bahamas and vicinity through 57 hours... the surface low then swings west across Cuba through 108 hours and becomes absorbed by area of interest #44 incoming from the southeast shortly thereafter
**Southwest side of surface frontal system and upper trough currently over eastern Canada leaves behind upper vorticity that dives south toward waters just northeast of the Lesser Antilles... divergence ahead of the upper vorticity produces a tropical low near 11.5N-54W by 108 hours... tropical low proceeds west-northwest into the central Lesser Antilles through 168 hours
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