MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #74
Updated: Jul 29
*******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.**********
...TUESDAY JULY 28 2020 2:30 PM EDT...
See area of interest section below for an update on the large and organizing tropical wave of low pressure in the central tropical Atlantic approaching the Lesser Antilles and northeastern Caribbean islands. Elsewhere...another vigorous tropical wave in the eastern tropical Atlantic with thunderstorm activity...currently passing 22.5W longitude...has not shown signs of organization...continues to lack computer model support...and there is uncertainty as to how much dry saharan air it will ingesgt. Therefore not adding it as an area of interest for tropical development at this time.
AREA OF INTEREST #1 (POTENTIAL TROPICAL CYCLONE NINE)...The rather large tropical wave of low pressure moving across the central tropical Atlantic has now produced sustained thunderstorm bands...in particular on its west side...that have allowed for the circulation to strengthen to tropical storm force. But because the surface circulation is large without a tightly defined center...it does not yet qualify to be a tropical storm...but regardless tropical storm force conditions are likely across the central and northern Lesser Antilles...the Virgin Islands...Puerto Rico...and the Dominican Republic within the next three days...sooner toward the northern Lesser Antilles...and later toward the Dominican Republic. Therefore the National Hurricane Center has upgraded this disturbance to potential tropical cyclone nine...to allow for the issuance of tropical storm warnings and watches across the aforementioned land areas.
Regarding my forecast track...I have adjusted my forecast points to the north and west due to the current position of potential tropical cyclone nine...albeit this position may change if a tighter circualtion forms elsewhere. I have leaned to a more southern solution that takes this system's center just south of Puerto Rico and into the Dominican Republic in the middle of the forecast period as my vote is that the circulation will consolidate toward the large-scale thunderstorm bands on the west side of the circluation as opposed to the smaller clump of activity to the northeast. An axis of upper vorticity spanning the central and western Atlantic is likely to pull this system on a northward angle as this system strengthens/gets taller...thus a northward angle in track is shown throughout the forecast period. The northward angle in track may increase by 120 hours as the frontal system across the eastern United States creates a break in the Atlantic surface subtropical ridge.
Regarding intensity...due to the large size and resulting time needed for consolidation I think that gradual (instead of rapid) stregnthening will occur beneath the favorable low shear and upper outflow supplied by broad tropical upper ridging in the area...and possibly from an outflow channel extending north into the axis of upper vorticity mentioned in the previous paragraph. However I also think this system could make a run toward category 1 hurricane strength in between 48 and 72 hours...just before it moves across the Dominican Republic. For the later part of the forecast...I only slightly drop the intensity due to land interaction with the Dominican Republic and then possible southwesterly shear as a portion of the upper vorticity merges with the upper trough currently moving into the western United States (to be over the eastern United States by the end of the forecast). The reason only for the slight drop amid these unfavorable factors is I am uncertain if the thunderstorm latent heat release of this currently large circulation will be widespread or strong enough to fracture the upper vorticity and keep an upper anticyclone with less shear over this system.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (1200Z Jul 28)...40 mph maximum sustained wind potential tropical cyclone centered at 13.8N-53.7W
IOH 24 Hr Forecast (1200Z Jul 29)...50 mph maximum sustained wind tropical storm centered just east of the Lesser Antilles at 14.5N-59W
IOH 48 Hr Forecast (1200Z Jul 30)...65 mph maximum sustained wind tropical storm centered just south of the Virgin Islands at 17.5N-64.5W
IOH 72 Hr Forecast (1200Z Jul 31)...65 mph maximum sustained wind tropical storm centered over the Dominican Republic at 19N-70W
IOH 96 Hr Forecast (1200Z Aug 1)...65 mph maximum sustained wind tropical storm centered between Cuba and the Bahamas at 22N-75W
IOH 120 Hr Forecast (1200Z Aug 2)...60 mph maximum sustained wind tropical storm centered between the western Bahamas and south Florida at 26.5N-79.5W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
0000Z CMC Model Run...For area of interest #1 (potential tropical cyclone nine)...tropical cyclone formation shown in 24 hours east of the northern Lesser Antilles near 16.5N-57W...reaches northern Lesser Antilles as a tropical storm in 42 hours...crosses the Virgin Islands and Puerto Rico through 54 hours...moves near or along the north coast of the Dominican Republic by 66 hours...crosses the entire Bahamas island chain from 78 to 120 hours while beginning to strengthen further.
0000Z ECMWF Model Run...For area of interest #1 (potential tropical cyclone nine)...tropical cyclone formation shown by 24 hours at a location just east of the Lesser Antilles near 15N-59W...reaches the central and northern Lesser Antilles just after 24 hours as a broad weak tropical storm...passes just south of Puerto Rico by 48 hours...moves across Haiti and the Dominican Republic by 72 hours...after dirsuption from land reorganizes as a small tropical storm between Cuba and the Bahamas in 96 hours...reaches the southern tip of the Florida peninsula as a small tropical storm by 120 hours.
0600Z GFS Model Run...For area of interest #1 (potential tropical cyclone nine)...tropical cyclone formation shown by 30 hours at a location just east of the Lesser Antilles near 16N-59W...reaches the central and northern Lesser Antilles at 36 hours as a broad weak tropical storm...crosses the Virgin Islands and Puerto Rico through 60 hours...moves into eastern Bahamas as a more compact and strengthening tropical storm in 78 hours...moves across the Bahamas island chain while weakening and reaches the western Bahamas in 120 hours.
0600Z NAVGEM Model Run...For area of interest #1 (potential tropical cyclone nine)...tropical cyclone formation shown near 14N-55W in 12 hours...moves into the northern Lesser Antilles as a strengthening tropical storm in 30 hours...moves across the Virgin Islands and Puerto Rico through 48 hours while continuing to gradually strengthen...passes over or just north of the Dominican Republic coast at 60 hours...moves into the eastern Bahamas as a strong tropical cyclone in 72 hours...moves across the Bahamas island chain and reaches the western Bahamas in 102 hours as an intense tropical cyclone...curves northward while staying just east of the Florida coast in 120 hours.