*******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.*********
...MONDAY OCTOBER 21 2024 3:50 PM EDT...
See Tropical Storm Oscar section below for an update on the tropical cyclone that continues to affect the southeastern Bahamas and eastern Cuba.
In the mid-latitudes of the Atlantic... the current western Atlantic upper vorticity is forecast to shift toward the eastern Atlantic while remaining amplified enough to keep wind shear levels low on its east side... as such will watch to see if its eastern divergence zone produces a mid-latitude eastern Atlantic disturbance with tropical characteristics in the days ahead. Meanwhile the upper vorticity currently moving into the western Atlantic from the southeastern United States will be merging with an upper trough that approaches from its current western Canada position. The merger will result in a western Atlantic upper trough amplified enough to keep wind shear levels low on its east side... as such will also watch to see if its eastern divergence zone produces a mid-latitude western Atlantic disturbance with tropical characteristics in the days ahead.
For the Caribbean Sea... surface tropical waves of low pressure currently approaching from the eastern and central tropical Atlantic have potential to interact with the persisting regional upper ridge/anticyclone which will supply an environment of low shear plus upper outflow that could boost thunderstorms... potentially resulting in a new Caribbean disturbance that may need to be monitored for tropical development in the days ahead.
TROPICAL STORM OSCAR... Infrared satellite image of Hurricane Oscar making landfall on the north-facing coast of Cuba's eastern tip on Sunday October 20 as of 2050Z:
As expected... on Sunday the strong surface ridge that remains over the eastern United States deflected Hurricane Oscar west-southwest into a landfall with the north-facing coast of eastern Cuba... with the NHC calling a landfall time of 5:50 PM EDT. Up until landfall... it appeared the track moved the hurricane into an environment of reduced northwesterly shear as the area of thunderstorms tied to Oscar became a little larger... circular... and more symmetrically distributed around the center. This allowed Oscar to maintain hurricane strength through landfall time (landfall intensity was 80 mph maximum sustained winds with 986 mb minimum surface pressure)... higher than my previous intensity forecast which expected Oscar to weaken slightly to a high-end tropical storm prior to the landfall... also noting the landfall location was slightly east of my previous track forecast. Since last night and throughout today... Oscar has been drifting slowly west across the eastern tip of Cuba while the western Atlantic surface ridge weakness is expanding due to the divergence zone of the upper vorticity approaching from the southeastern United States... because the expanding weakness reducing the ability of Oscar to continue west around the eastern US surface ridge. Because Oscar is a small tropical cyclone... even the small landmass associated with the eastern tip of Cuba has substantially weakened it from a hurricane to a minimal tropical storm through today's 11 AM EDT NHC advisory. Going forward... the models have come into agreement that a turn towards the northeast is expected at any moment as Oscar gets vacuumed into the surface pressure falls associated with the expanding west Atlantic surface ridge weakness. My updated forecast track line is similar to my previous as the recent westward drift of Oscar has re-aligned it back to the previous track... the only difference is that Oscar is hitting the milestones along the track at a later time because the northeast turn has not occurred yet. Noting in the short-term my forecast track (through 24 hours) is more east and less north relative to the NHC track and model consensus... in alignment with an area of split flow upper divergence that will develop soon between the approaching upper vorticity from the southeast US and western Caribbean upper anticyclone... as I speculate that Oscar will be vacuumed toward locally stronger surface pressure falls generated by the split flow upper divergence. Regarding intensity... Oscar is currently below my previous forecast due to the combination of prolonged land interaction with the eastern tip of Cuba and the development of westerly shear associated with the approaching upper vorticity from the southeastern US which has recently caused the thunderstorms to be displaced to the eastern half of the circulation. Therefore my updated intensity forecast is lower than the previous... however keeps Oscar a minimal tropical storm through 24 hours as the aforementioned split flow upper divergence may help Oscar in keeping its current strength. By 48 hours I forecast Oscar to become an elongated remnant surface trough as the storm tracks into the forecast elongated divergence zone on the east side of the upper vorticity. Regarding impact to land areas... sheared-off moisture from Oscar has reached as far east as Haiti... expect an ongoing period of heavy rainfall with flash flooding potential for the eastern tip of Cuba... Haiti... and the southeastern Bahamas over the next day or so... coming to an end sooner for the eastern tip of Cuba and later for Haiti and the southeastern Bahamas. The same story is true for any coastal surf that the minimal tropical storm generates. Gusty winds will also be possible for the eastern tip of Cuba and the southeastern Bahamas... again coming to an end sooner for the eastern tip of Cuba and later for the southeastern Bahamas.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Oct 21)... 40 mph maximum sustained wind tropical storm centered over far eastern Cuba at 20.3N-75.4W
IOH 24 Hr Forecast (1200Z Oct 22)... 40 mph maximum sustained wind tropical storm centered between eastern Cuba and the southeastern Bahamas at 21.5N-74W
IOH 48 Hr Forecast (1200Z Oct 23)... Remnant trough located northeast of the southeastern Bahamas near 24N-71W
*****National Hurricane Center (hurricanes.gov) official outlook as of 11 AM EDT*************************
60-Hr Position (0000Z Oct 24)... 45 mph maximum sustained wind tropical storm losing identity while centered in the west Atlantic at 28.3N-68.3W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
0000Z (Oct 21) CMC Model Run...
**For Tropical Storm Oscar... turns north then northeast into the eastern/central Bahamas through 42 hours... while continiuing north-northeast toward Bermuda loses identity to rapdily developing frontal low positioned just west of Bermuda at 78 hours
0000Z (Oct 21) ECMWF Model Run...
**For Tropical Storm Oscar... turns north then northeast into the eastern/central Bahamas through 42 hours... while continuing north-northeast toward Bermuda loses identity to rapdily developing frontal low positioned just west of Bermuda at 72 hours
0600Z (Oct 21) GFS Model Run...
**For Tropical Storm Oscar... turns north then northeast into the eastern/central Bahamas through 33 hours... while continuing north-northeast toward Bermuda loses identity to rapidly developing frontal low positioned just west of Bermuda at 69 hours
**Through 102 hours frontal low just west of Bermuda that absorbs Oscar becomes increasingly elongated north-south and degenerates into a surface cold front positioned in the waters south-southeast of Newfoundland to 34N-58W... through 120 hours a fragment of the associated west Atlantic upper trough (which is a merger between the current SE US upper vorticity moving offshore and the next North America upper trough that follows behind) becomes a cut-off upper vortex whose eastern divergence zone triggers a surface low along the front at 36N-35W... as the upper vortex passes over the surface low the instability provided by its cold temps causes the surface low to transition into a subtropical or tropical cyclone near 37.5N-35W at 135 hours... the tropical or subtropical cyclone moves northeast in the flow ahead of an upper trough/surface frontal low approaching from Atlantic Canada and loses identity to the much larger frontal low by 162 hours while located near 42.5N-46W
1800Z (Oct 19) NAVGEM Model Run…
**Not available at above-mentioned source
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