MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #87
Updated: Aug 12
*******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 AUGUST 10 2020 11:12 AM EDT...
See area of interest section below for the eastern Atlantic tropical wave of low pressure being monitored for development.
A tropical wave of low pressure moving into Nicaragua from the central Caribbean Sea continues to produce a significant amount of thunderstorms this morning while experiencing upper outflow beneath an upper ridge cell...with further enhancement induced by an outflow channel streaming northward into upper vorticity currently in the western Atlantic. Although tropical cyclone formation is not expected as the wave makes landfall across Nicaragua...heavy rainfall with flash flooding potential is possible across Honduras and Nicaragua this morning through this early afternoon.
The GFS and ECMWF models have recently suggested the cold front currently over the central United States will become stretched southwest-to-northeast across the norhwestern Atlantic in about 5 days while its supporting upper vortex likewise becomes streteched by a warm upper ridge to build over Canada...with the front possibly becoming a focal point for tropical or subtropical cyclone formation. One possibility is the tail end of the front becomes embedded below upper ridging associated with warm air ahead of the front...with upper outflow and low shear beneath the ridging triggering tropical cyclone formation offshore of North Carolina or north of Bermuda next week. Another possiblity is the streteched upper vortex becomes concentrated south of Newfoundland and triggers a vigorous frontal cyclone along the north edge of the warm Gulf stream waters next week...in which case the frontal cyclone could acquire tropical characteristics and transition to a subtropical cyclone. If these model trends continue in the coming days...will consider adding this front as another area of interest to monitor for development.
AREA OF INTEREST #1...The tropical wave of low pressure in the eastern Atlantic continues maintaining organized thunderstorm bands that suggest rotation. Currently the rotation appears to be centered at 10N-33W. The thunderstorm activity remains supported by divergence and upper outflow on the south side of a broad tropical upper ridge in the region. Overall I have not raised odds of tropical cyclone formation above 40% as the system has not become better organized despite thunderstorm bands once again becoming more symmetric about the rotation...because the bands are generally producing weaker thunderstorm acivity. The GFS model has been consistent with the position of cut-off upper vorticity that lies to the north of this tropical wave...soon to be pushed southward toward the tropics in the vicinity of 40W longitude by the current central Atlantic upper ridge. Based on the consistency of the GFS model...I believe the upper vorticity will be far north enough to not disrupt this system. Even though this system will also be firmly beneath a cell of favorable tropical upper ridging after slipping by the upper vorticity by the end of the forecast period...the computer models (with the exception of the CMC) curiosly weaken this system after it crosses 40W to 45W longitude. Therefore I am inclined to keep longer range odds pegged at 40% instead of raise them despite the favorable upper wind outlook...and at this time I am also witholding mention of possible impacts to the Lesser Antilles on the home page of this site in case the majority model consensus is correct in that this system will in fact weaken in the long range.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (1200Z Aug 11)...40% chance of tropical cyclone formation (tropical Atlantic near 10.5N-38W)
IOH 48 Hr Outlook (1200Z Aug 12)...40% chance of tropical cyclone formation (tropical Atlantic near 11N-43W)
IOH 72 Hr Outlook (1200Z Aug 13)...40% chance of tropical cyclone formation (tropical Atlantic near 11N-48W)
IOH 96 Hr Outlook (1200Z Aug 14)...40% chance of tropical cyclone formation (tropical Atlantic near 11.5N-53W)
IOH 120 Hr Outlook (1200Z Aug 15)...40% chance of tropical cyclone formation (just east of the Lesser Antilles near 12N-58W)
...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...tropical low pressure spin becomes better defined while crossing 12N-45W in 78 hours...passes northeast of the Lesser Antilles at 20N-59W in 138 hours.
0000Z ECMWF Model Run...For area of interest #1...tropical low pressure spin becomes better defined near 11N-35W in 24 hours...opens back into a tropical wave near 45W longitude in 72 hours. Elsewhere...current central United States surface front becomes stretched across the northwestern Atlantic and North Carolina by 120 hours...possible tropical cyclone formation along the front at a location just east of North Carolina in 144 hours...also a possible subtropical cyclone formation just south of Newfoundland in the vicinity of 42.5N-53W in 144 to 168 hours.
0600Z GFS Model Run...For area of interest #1...current tropical low pressure spin opens into a tropical wave near 40W longitude in 48 hours. Elsewhere...current central United States surface front becomes stretched across the northwestern Atlantic and North Carolina by 120 hours...possible tropical cyclone formation along the front at a location north of Bermuda near 37N-65W in 150 hours...also a possible subtropical cyclone formation just south of Newfoundland in the vicinity of 41.5N-54W in 186 hours.
0600Z NAVGEM Model Run...For area of interest #1...current tropical low pressure spin opens into a tropical wave near 41W longitude in 78 hours.