MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #55
Updated: Jul 21, 2021
*******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 JULY 19 2021 11:40 PM EDT...
Recent infrared satellite pictures suggest a large tropical wave of low pressure on the west coast of Africa featuring widespread low-level clouds…with one cluster of thunderstorms south of the Republic of Cabo Verde Islands and another inland thunderstorm cluster nearing the west coast of Africa. Due to the large scale nature of the wave’s circulation… it is likely to ingest dry Saharan air to the north… and none of the models forecast this wave to develop as it moves across the eastern tropical Atlantic.
Elsewhere… today’s model runs agree that a portion of the current northeast Canada upper vortex will become an eastern US-to-western Atlantic upper trough cut-off by the current upper ridge over western North America. The divergence zone of this cut-off upper trough is forecast to support a surface frontal zone (elongated surface low pressure area with air mass contrasts) across the western Atlantic in about five days. Meanwhile the warm sector of a strong frontal system moving across Canada in 4+ days is also forecast to weaken the cold core cut-off upper trough…which would reduce wind shear induced by the trough and potentially allow for tropical development at one or more areas along the front in about 5+ days. Due to the models only recently converging on such a solution…will wait to see if this solution persists before declaring an area of interest for tropical development for the forecast surface front.
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...
**Tropical wave currently over western Africa forecast to enter the eastern Atlantic at 24 hours…briefly forms a surface low near 10N-26W at 30 to 36 hours…surface low subsequently dissipates and no development shown afterwards
**Surface frontal low forms just offshore of South Carolina at 120 hours…weakens to a surface trough near 38N-64W by 168 hours.
1200Z ECMWF Model Run...
**Tropical wave currently over western Africa forecast to enter the eastern Atlantic with a low pressure spin just northeast of the Republic of Cabo Verde Islands at 24 hours…moves rapidly west-southwest and by 72 hours the wave loses its low pressure spin near 42W longitude.
**Surface frontal low forms on South Carolina coast at 120 hours…tropical cyclone formation suggested at 39N-62.5W at 168 hours.
1800Z GFS Model Run...
**Tropical wave currently over western Africa forecast to enter the eastern Atlantic at 24 hours…tropical wave continuously weakens through 48 hours while reaching 33.5W longitude.
**Tropical cyclone formation suggested along frontal zone near 39.5N-57W at 120 hours
**Additional surface low pressure formation suggested along frontal zone near 35.5N-61W at 141 hours
1800Z NAVGEM Model Run...
**Tropical wave currently over western Africa forecast to enter the eastern Atlantic with a low pressure spin just northeast of the Republic of Cabo Verde Islands at 18 hours…moves rapidly west-southwest and by 48 hours the wave loses its low pressure spin near 32W longitude.
**Current upper trough over the northeastern US produces surface frontal low near 36.5N-70W at 42 hours…tropical cyclone formation suggested near 38N-64W at 54 hours….transitions into vigorous frontal cyclone while located over cooler water southeast of Newfoundland at 45N-52W at 78 hours.