BIRDSEYE VIEW POSTS

Since 2012 on the Weather Underground (www.wunderground.com) blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments via Disqus on Weather Underground at www.wunderground.com/cat6. You can see my Disqus feed at this link for my latest comments. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
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MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #106

*******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.**********


...SATURDAY AUGUST 29 2020 11:45 PM EDT...

Satellite image (as of 0310Z) showing all areas of interest being monitored for development in yellow circles...and the remnant low pressure of Laura circled in red and marked with an L:

NHC TAFB Surface Analysis from 1800Z:

GFS Model Upper Level Winds from 0000Z:

See area of interest sections below for all areas of interest being monitored for tropical cyclone formation over the next few days.


AREA OF INTEREST #1...The central Atlantic tropical wave of low pressure has not merged with or been dragged by the tropical wave fragment that ejected from the eastern Atlantic and currently at 42.5W...thus it has maintained a brisk westward track and is already closing in on the Lesser Antilles while producing thunderstorm bands in the vicinity of 15N-57.5W. My updated forecast track is adjusted westward accordingly. As this system crosses the Caribbean Sea...I slightly bend the track of this system northward while it reaches the weaker western extent of the Atlantic surface subtropical ridge...to be kept generally weaker by a pair of frontal cyclones (the current one over eastern North America absorbing Laura’s remnants...the second one to develop later and over Canada). My peak 5 day odds of development are at a low 25% and toward 120 hours as only the CMC model developed this system during the 1200Z cycle...but this is slightly higher than my previous outlook due to the appearance of the thunderstorm bands. Regarding upper-level winds...the streteched upper vorticity from the Caribbean Sea to central and northeast Atlantic is expected to consolidate into two lobes of upper vorticity that retrograde westward around high-latitude upper ridging to be induced by the warm sectors of the aforementioned frontal cyclones...with this tropical wave forecast to be in a favorable low shear and upper outflow environment between both lobes of upper vorticity. Therefore this tropical wave bears watching even with the current lackluster computer model support.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Aug 30)...5% chance of tropical cyclone formation (eastern Caribbean Sea near 15N-62.5W)

IOH 48 Hr Outlook (1800Z Aug 31)...10% chance of tropical cyclone formation (central Caribbean Sea near 15.5N-67.5W)

IOH 72 Hr Outlook (1800Z Sep 1)...15% chance of tropical cyclone formation (central Caribbean Sea south of Haiti near 16N-72.5W)

IOH 96 Hr Outlook (1800Z Sep 2)...20% chance of tropical cyclone formation (central Caribbean Sea south of Jamaica near 16.5N-77.5W)

IOH 120 Hr Outlook (1800Z Sep 3)...25% chance of tropical cyclone formation (western Caribbean Sea south of the Cayman Islands near 17.5N-82.5W)

AREA OF INTEREST #2...The eastern Atlantic tropical wave of low pressure has split into two halves...a northwest half presenting itself as an inconsequential broad cloud swirl buried in dry Saharan air at 42.5W and flowing westward around the Atlantic subtropical ridge...and a southeast half near 25W to 26W to the southwest of the Republic of Cabo Verde Islands and gravitated toward the latest tropical wave that just exited the west African coast. The CMC and ECMWF continue to suggest the wave fragment near 26W and the wave that just exited Western Africa will merge and potentially develop...while the GFS and NAVGEM have dropped showing development of the merged wave. My updated forecast track is adjusted eastward as the two waves have yet to start merging...and will be slow to move westward till they merge. My peak 120-hour odds of development remain at 30% due to less model support...but this is still higher than my odds for area of interest #1 as the model support remains higher for this disturbance.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Aug 30)...0% chance of tropical cyclone formation (southwest of the Republic of Cabo Verde Islands near 12.5N-26W)

IOH 48 Hr Outlook (1800Z Aug 31)...0% chance of tropical cyclone formation (southwest of the Republic of Cabo Verde Islands near 12.5N-28W)

IOH 72 Hr Oulook (1800Z Sep 1)...10% chance of tropical cyclone formation (tropical Atlantic near 12.5N-31W)

IOH 96 Hr Outlook (1800Z Sep 2)...20% chance of tropical cyclone formation (tropical Atlantic near 12.5N-35W)

IOH 120 Hr Outlook (1800Z Sep 3)...30% chance of tropical cyclone formation (tropical Atlantic near 12.5N-40W)

AREA OF INTEREST #3...Computer models have come into agreement that the cold front currently absorbing the remnants of Laura over the eastern United States will develop a pocket of low pressure when the front moves into the western Atlantic capable of tropical cyclone formation...therefore the National Hurricane Center has added the front as an area of interest for tropical development in their 5 day tropical weather outlook. The potential enablers for tropical development will be warm Gulf Stream waters and warm upper ridging (with low shear and upper outflow) expanding from the Gulf of Mexico and into the northwest Atlantic thanks to the warm sector of a frontal cyclone to develop over Canada during the forecast period. The eastern divergence zone of a shortwave upper trough to separate from the Canadian frontal cyclone’s longwave upper trough appears to be what will trigger the pocket of low pressure along the tail end of the front once it moves into the Atlantic from the Carolinas. The shortwave trough is forecast to continuously amplify into a small upper vortex as the warm northwest Atlantic upper ridging amplifies around it...so this may keep shear from the shortwave trough feature low enough to allow for tropical development. It could be argued that by 96 and 120 hours any development could be more subtropical in nature if the eastern divergence zone of the upper vortex becomes the primary driver for the forecast pocket of low surface pressure.

I give low 30% odds of tropical cyclone formation at this time as the models vary on how strong or how tropical this system will be...with the 1200Z GFS being the most aggressive in suggesting tropical characteristics. I plan to raise odds of development if more models show a tropical system or if the thunderstorm activity of the pocket of low pressure shows organization once it forms in about 24 to 48 hours.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Aug 30)...0% chance of tropical cyclone formation (over the Carolinas near 34N-80W)

IOH 48 Hr Outlook (1800Z Aug 31)...0% chance of tropical cyclone formation (just offshore of the Carolinas near 34N-75W)

IOH 72 Hr Oulook (1800Z Sep 1)...30% chance of tropical cyclone formation (western Atlantic near 36N-69.5W)

IOH 96 Hr Outlook (1800Z Sep 2)...30% chance of tropical cyclone formation (western Atlantic near 38N-59W)

IOH 120 Hr Outlook (1800Z Sep 3)...30% chance of tropical cyclone formation (northern Atlantic near 38N-55W)

...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)

1200Z CMC Model Run...For area of interest #1...tropical cyclone formation suggested south of Jamaica in 84 hours...passes just north of the Honduras coast in 120 hours. For area of interest #2...tropical cyclone formation suggested near 14N-30W in 96 hours...located near 12.5N-32.5W in 120 hours. For area of interest #3...front emerges from US East coast in 18 hours...surface low forms in tail end of front and just offshore of North Carolina in 60 hours...located at 40N-63W in 120 hours (low pressure mostly shown to be elongated...indicating low pressure most likely non-tropical and frontal in nature).

1200Z ECMWF Model Run...For area of interest #1...no tropical cyclone formation shown. For area of interest #2...organizes into a tropical low pressure near 11N-35W in 120 hours. For area of interest #3...front emerges from US East coast in 24 hours...surface low forms in tail end of front and near 35N-72.5W in 72 hours...located at 39.5N-55W in 120 hours as a large and strong low pressure.

1200Z GFS Model Run...For area of interest #1...no tropical cyclone formation shown. For area of interest #2...no tropical cyclone formation shown. For area of interest #3...front emerges from US east coast in 18 hours...tropical cyclone formation along front shown near 34N-73W in 60 hours...strong compact tropical cyclone shown near 37N-68.5W in 78 hours...transitions into elongated nontropical frontal low near 39N-62.5W in 102 hours. Elsewhere...tropical wave shown to emerge from west Africa in 96 hours and develops into a tropical cyclone near 13.5N-20W in 120 hours.

1200Z NAVGEM Model Run... For areas of interest #1 and #2...no tropical cyclone formation shown. . For area of interest #3...front emerges from US East coast in 18 hours...weak surface low forms in tail end of front and near 35N-66W in 72 hours...located at 39N-56W in 120 hours,

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