*******Note that forecast 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.*********
...TUESDAY AUGUST 13 2024 1:25 AM EDT...

See Tropical Storm Ernesto section below for information on the new tropical storm already closing in on the northeastern Caribbean Islands (Dominican Republic to northern Lesser Antilles)… the southeastern Bahamas are also likely to see coastal surf from the storm by Wednesday…. and it appears increasingly likely that Ernesto will line up for a strike on Bermuda as a hurricane this weekend.
Further east... the large tropical wave of low pressure currently in the east Atlantic has become less organized while becoming elongated east-to-west… and remains suppressed by ingestion of dry Saharan air. Satellite imagery over Africa (https://www.goes.noaa.gov/FULLDISK/GMIR.JPG) shows another similarly large wave is over western Africa... however none of the models develop it when it emerges into the eastern tropical Atlantic in a couple of days perhaps while also forecasting this wave to ingest dry Saharan air.
TROPICAL STORM ERNESTO… The continuously organizing tropical wave of low pressure in the central tropical Atlantic over the last several hours has established more solidified curved thunderstorm bands and a better-defined center on its northwest side… with the remainder southeastern part of the wave appearing to fling the better-defined center on a faster west track toward the northeastern Caribbean islands. The center has been upgraded to Tropical Storm Ernesto since 5 PM EDT based on NHC aircraft recon data. There is a notable west shift in the short-term forecast track due to Ernesto’s more west position and faster forward hearing compared to the previous forecasts… which brings the center of the storm across the northeastern Caribbean Islands a day sooner. While gradually curving Ernesto north towards a forecast western Atlantic surface ridge weakness… to be generated by the divergence zone of the current east Canada upper trough when that trough moves into the western Atlantic… my updated forecast track calls for the center to pass over the northern Lesser Antilles and just south of the Virgin Islands in the next 24 hours… then increasingly northwest across the southwest corner of Puerto Rico and near the Dominican Republic north coast through 48 hours… then on a north turn into the west Atlantic along 70W longitude through 72 hours. During the next 24 hours Ernesto has a high likelihood of becoming a stronger tropical storm while positioned beneath upper anticyclonic flow (low shear and supporting outflow)… and with land interaction being minimal as the storm passes over or nearby the smaller northeastern Caribbean Islands. Through 48 hours I stop short of forecasting hurricane strength due to potential land interaction with the Dominican Republic and possible shear while running into the decaying upper vorticity to the northwest (previously was not expecting Ernesto to catch up to the decaying upper vorticity before the vorticity dissipates… however this has changed with today’s west shifted track). By 72 hours… as the upper vorticity dissipates… as Ernesto clears away from the Dominican Republic… and as the northern outflow of Ernesto is potentially enhanced by the southwesterly flow ahead of the western Atlantic upper trough… I call for brisk strengthening into a hurricane.
For the longer range (96 and 120 hours)… the short-term west adjusted forecast track has longer-term implications. Instead of becoming aligned with the more southerly flow on the east side of the western Atlantic upper trough and simply accelerating north-northeast across Bermuda then out to sea… the more west adjusted track aligns Ernesto with the south side of the upper trough that through 96 hours drags the storm more east and less north. This allows the upper trough and associated surface ridge weakness to then leave behind Ernesto… with the storm curving more north and less east in track from 96 to 120 hours as the blocking surface ridge built by the back side of the departing west Atlantic upper trough merges with the Atlantic surface ridge… creating a solid wall that prevents Ernesto from continuing east. Noting my 120-hour position shows Ernesto turning north into Bermuda. Regarding intensity… I show Ernesto being weakened by westerly shear imparted by the south side of the passing west Atlantic upper trough between 72 and 96 hours. Then from 96 to 120 hours whatever disrupting cool core upper vorticity left behind by the upper trough and near Ernesto likely dissipates from Ernesto’s thunderstorm latent heat release… with the storm also overspread by a warm core upper ridge (low shear and outflow environment) in the warm sector of the next frontal system to approach from eastern North America. Therefore I call for Ernesto to finally reach category 2 by day 5. However my 5-day peak intensity is slightly lower than the latest NHC forecast (as of this writing) and my previous forecast due to the net effect of possible land interaction with the Dominican Republic (24 to 48 hours) and forecast burst of westerly shear (72 to 96 hours).
Regarding impact to land areas:
(1) Interests in the northern Lesser Antilles… Virgin Islands… and Puerto Rico should be rushing preparations to completion this morning for tropical storm force winds… heavy rain… and coastal surf to arrive later today.
(2) I recommend interests along the northeast coast of the Dominican Republic to prepare for possible tropical storm force winds and coastal surf to arrive by Wednesday. Interests in the southeastern Bahamas should also monitor the progress of Ernesto… the current forecast track allows for coastal surf to reach the islands on Wednesday… however any additional west shift in the forecast track would also bring tropical storm winds.
(3) Interests in Bermuda should also watch this system as by day 5 (Saturday) this system appears likely to move into the island as a potentially strong hurricane.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Aug 13)… 40 mph maximum sustained wind tropical storm centered just east of the northern Lesser Antilles at 16N-59.6W
IOH 24 Hr Forecast (0000Z Aug 14)… 60 mph maximum sustained wind tropical storm centered just south-southwest of the Virgin Islands and southeast of Puerto Rico at 17.5N-65.5W
IOH 48 Hr Forecast (0000Z Aug 15)… 65 mph maximum sustained wind tropical storm centered just offshore of the northern Dominican Republic coast at 20.2N-69.8W
IOH 72 Hr Forecast (0000Z Aug 16)… 95 mph maximum sustained wind hurricane centered in the western Atlantic at 24N-70W
IOH 96 Hr Forecast (0000Z Aug 17)… 85 mph maximum sustained wind hurricane centered south of Bermuda at 29N-65W
IOH 120 Hr Forecast (0000Z Aug 18)… 105 mph maximum sustained wind hurricane centered just south of Bermuda at 31.5N-65W
*****National Hurricane Center (hurricanes.gov) official forecast as of 11 PM EDT**************************
Landfall (1200Z Aug 13)... 45 mph maximum sustained wind tropical storm centered over the northern Lesser Antilles at 16.4N-62W
Landfall (0000Z Aug 14)... 60 mph maximum sustained wind tropical storm centered over the southern Virgin Islands at 17.7N-64.6W
5-Day Position (0000Z Aug 18)… 110 mph maximum sustained wind hurricane centered just northeast of Bermuda at 32.7N-64.2W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/).
1200Z (Aug 12) CMC Model Run...
**For Tropical Storm Ernesto… passes over the northern Lesser Antilles and just north of the Virgin Islands through 36 hours… passes just north of Puerto Rico at 42 hours… gradually turns north and strengthens into a strong hurricane with the center passing just west of Bermuda at 132 hours… hurricane then accelerates northeast to 40.5N-59.5W through 168 hours
1200Z (Aug 12) ECMWF Model Run...
**For Tropical Storm Ernesto… passes over the northern Lesser Antilles and Virgin Islands through 30 hours…passes just north of Puerto Rico at 42 hours… gradually turns north and strengthens into a strong hurricane with the center passing just west of Bermuda at 120 hours… hurricane then accelerates north-northeast to 38N-60.5W through 168 hours
**Vigorous tropical wave of low pressure emerges from western Africa at 60 hours and passes over the Republic of Cabo Verde Islands as a broad tropical low at 90 hours… gradually weakens back to a wave while moving into the central tropical Atlantic through 168 hours
1800Z (Aug 12) GFS Model Run...
**For Tropical Storm Ernesto… passes over the northern Lesser Antilles at 15 hours then strengthens into a compact strong tropical storm in the northeast corner of the Caribbean that moves into the south coast of Puerto Rico at 36 hours… after turning northwest across Puerto Rico gradually re-curves northeast while strengthening into a large and strong hurricane with the center passing just west of Bermuda at 132 hours… hurricane subsequently accelerates north toward western Nova Scotia through 168 hours
**Vigorous tropical wave of low pressure emerges from western Africa at 63 hours and slowly passes over the Republic of Cabo Verde Islands by 102 hours as a broad tropical low… shortly thereafter weakens back to a wave with no development shown in the long range
1800Z (Aug 12) NAVGEM Model Run...
**For Tropical Storm Ernesto… passes west-northwest across the northern Lesser Antilles… Virgin Islands… and Puerto Rico through 30 hours… subsequently curves north then northeast while becoming an intense hurricane with the center moving into Bermuda by 120 hours… hurricane continues accelerating northeast toward Newfoundland through 168 hours
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