*******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.*********
...SUNDAY NOVEMBER 10 2024 11:55 PM EDT...
The Atlantic tropics finally appear to be calming as we move toward mid-November with multiple tropical systems being cancelled in this update as follows... the primary focus is moving toward the Caribbean where an area of interest is the only remainder system being monitored for possible development in the coming days:
(1) See Rafael section below for a final statement on the Gulf of Mexico tropical cyclone that recently became sheared apart into a remnant low.
(2) See area of interest #48 section below for the northwestern Bahamas low pressure swirl that lost its tropical development potential while ingesting cooler drier air.
(3) An upper trough and surface frontal system currently over the central US will be moving into offshore Atlantic waters by 24+ hours. Models are now trending away with the tail end of the surface front developing into a subtropical disturbance southeast of Bermuda in a few days... as the models no longer show the southern base of the associated upper trough being amplified enough to support subtropical development.
(4) See area of interest #49 section below for an update on the current eastern Caribbean tropical low... which has potential to develop over the next few days while sliding into the central Caribbean.
REMNANTS OF RAFAEL... While located in the Gulf of Mexico offshore of the south-facing Louisiana coast... Tropical Storm Rafael became sheared into a remnant low pressure swirl by increasing upper westerlies delivered by the current central US upper trough. The remnant low is expected to drift southwest across the western Gulf of Mexico in the flow between a new surface ridge that builds under the western convergence zone of the exiting central US upper trough and a Caribbean gyre of low pressure approaching from the east (area of interest #49). Over the next day or so wind shear over ex-Rafael is expected to relax as the Gulf of Mexico upper ridge re-builds in the wake of the exiting central US upper trough. However in as soon as 72+ hours another wave of westerly shear occurs when the remnants of the current western Caribbean upper vortex rounds the southwest side of the Gulf of Mexico upper ridge and swings over ex-Rafael... with the upper westerlies also re-enforced by the next upper trough in the mid-latitude westerlies that swings into the north-central US. Should the remnants of Rafael try to make a comeback in the western Gulf of Mexico in the lower shear environment in the next 48 hours... will introduce it as an area of interest with probabilities of tropical cyclone formation. Otherwise this is my planned final statement on Rafael on this blog.
AREA OF INTEREST #48... The swirl of low pressure that moved into the northwestern Bahamas lost thunderstorm activity while ingesting cooler drier air behind the southward-sagging western Atlantic surface cold front driven by the southeastward-diving upper trough that recently entered the northwest Atlantic from eastern Canada. Therefore tropical development of this feature is no longer possible... especially as it merges with another surface front now approaching from the central US which will soon move offshore into the Atlantic in 24+ hours. This area of interest was removed from the NHC official tropical weather outlook earlier today... and this is my final statement on this area of interest on this blog.
AREA OF INTEREST #49... The CIMSS 850 mb vorticity product shows the low-level spin associated with the eastern Caribbean broad tropical low has moved from the waters SSW of Puerto Rico and into the waters offshore of the south coast of the Dominican Republic over the last day (https://tropic.ssec.wisc.edu/real-time/windmain.php?basin=atlantic&sat=wg8&prod=vor&zoom=&time=). The broad tropical low is a merger between the remainder southern portion of the surface trough associated with area of interest #48 that was in the vicinity of the Dominican Republic and surface tropical wave of low pressure that has been sliding west across the eastern Caribbean. The NHC TAFB surface analyses have handled this feature by simply updating the position of the westward-moving surface tropical wave as if it is the dominant feature in the merger. Noting the tropical low is positioned further north toward 17N latitude... and my updated forecast track has been adjusted accordingly. The more north position of this system has allowed it to produce squalls of heavy rain across the northern Caribbean Islands from the Dominican Republic to the Virgin Islands earlier today. Although activity over the islands has waned... based on the latest infrared satellite imagery as of this writing it appears periods of heavy rainfall are filling back in and will cover Puerto Rico... the Dominican Republic... and Haiti in the next 24 hours.
Over the next 24 hours the forecast track for the tropical low is west-northwest into 17.5N latitude as this system rounds the southwest side of the surface ridge that recently moved offshore into the western Atlantic... with some of the north angle induced by the ridge weakness associated with the current central US surface front as it moves offshore into the western Atlantic. The track then bends west from 24 to 72 hours under the influence of the strong surface ridge that builds behind the western Atlantic surface front. From 72 to 120 hours models are increasingly trending with a quasi-stationary tropical low as the next upper trough/surface frontal system that arrives into the north-central US erodes the strong surface ridge and merges with the western Atlantic upper trough/surface frontal system. Although a new surface ridge tries to develop over the central US in the wake of the re-enforced western Atlantic frontal system... the tropical low could end up being quasi-stationary while stuck in the conflicting steering between the central US surface ridge and western Atlantic frontal system. Upper-level winds are currently favorable for tropical development as a sprawling upper ridge/ anticyclone... featuring low shear and outflow... has developed over this system in the wake of the retreating and weakening western Caribbean upper vortex. However after 72 hours the north-adjusted forecast track makes this system more susceptible to westerly shear that would be imparted by the longer range upper trough that moves from the north-central US into the western Atlantic... and I trim my odds of tropical cyclone formation below the peak during this timeframe. Noting the NHC added this area of interest into their tropical weather outlook today... and have gone with low 20% odds of tropical cyclone formation. In this update cycle I have lowered my peak odds of tropical cyclone formation and come into agreement with the NHC as the models are trending away from developing this area of interest. This could be due to the potential for this area of interest in ingesting cooler drier air to be ushered in behind the surface fronts that move into the western Atlantic during the forecast period (similar to how area of interest #48 met its demise today)... and also due to the possible shear in the 72+ hour window. Nonetheless interests in Jamaica... the Cayman Islands... and Central America should be aware of this disturbance as it tracks in their direction in the days ahead... in case it does develop.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Nov 12)... 10% chance of tropical cyclone formation (just offshore of southwestern Haiti near 17.5N-74W)
IOH 48 Hr Outlook (0000Z Nov 13)... 20% chance of tropical cyclone formation (eastern tip of Jamaica near 18N-76.2W)
IOH 72 Hr Outlook (0000Z Nov 14)... 20% chance of tropical cyclone formation (just west of Jamaica near 18N-79W)
IOH 96 Hr Outlook (0000Z Nov 15)... 10% chance of tropical cyclone formation (just south of the Cayman Islands near 18N-80.2W)
IOH 120 Hr Outlook (0000Z Nov 16)... 10% chance of tropical cyclone formation (just south of the Cayman Islands near 18N-80.2W)
*****National Hurricane Center (hurricanes.gov) official outlook as of 7 PM EDT*************************
Formation chance through 48 hours... 0%
Formation chance through 7 days... 20%
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
1200Z (Nov 10) CMC Model Run...
**For area of interest #48... no development shown
**For area of interest #49... current eastern Caribbean tropical low becomes entangled with current central US surface front which moves offshore into the Atlantic to become a north-south elongated low from the southeastern Bahamas to the south-central Caribbean through 54 hours... the northeast part of the elongated low continues east into the open central Atlantic while the southwest part becomes a better-defined tropical low centered near 15N-76W by 102 hours... tropical low proceeds to move slowly west-northwest into the waters just SW of Jamaica through 168 hours.
1200Z (Nov 10) ECMWF Model Run...
**For area of interest #48... no development shown
**For area of interest #49... current eastern Caribbean tropical low continues into the central Caribbean waters south of Jamaica through 102 hours where it becomes better-defined... continues slowly west toward the Nicaragua/Honduras border through 168 hours
1800Z (Nov 10) GFS Model Run...
**For area of interest #48... no development shown
**For area of interest #49... current eastern Caribbean tropical low continues into the central Caribbean waters near 15N-80W through 90 hours where it becomes better-defined while simultaneously current central US surface frontal system moves offshore into the western Atlantic... after 90 hours a north-central US frontal system joins the offshore western Atlantic frontal system to create a large enough ridge weakness that drags this area of interest eastward... the eastward-moving tropical low becomes a tropical cyclone centered south-southeast of Jamaica by 168 hours
1800Z (Nov 10) NAVGEM Model Run...
**For area of interest #48... no development shown
**For area of interest #49... current eastern Caribbean tropical low continues into the central Caribbean waters just southwest of Jamaica through 108 hours where it becomes better-defined... through 168 hours the tropical low drifts slowly WSW into the waters between Central America and Jamaica (near 15N-80W)
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