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 #73

Updated: Jul 28

*******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 27 2020 4:26 PM EDT...

See remnants of Hanna section below for final statement on this storm system as it has weakened to a remnant low pressure area while moving west-southwest into central Mexico. See area of interest sections below for areas being monitored for tropical cyclone formation. Elsewhere...another vigorous tropical wave in the eastern tropical Atlantic with thunderstorm activity 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 ingest. Therefore not adding it as an area of interest for tropical development at this time.


REMNANTS OF HANNA...While continuing west-southwestward toward a surface monsoonal low pressure field over Mexico...what was Tropical Storm Hanna has continued west-southwest into central Mexico...resulting it in weakening further into a remnant tropical low pressure area. Colorized infrared satellite pictures suggest widespread thunderstorm clouds have mostly dissipated...therefore the heavy rainfall potential with this system has ended. This is my final statement on Hanna as it is no longer a tropical cyclone.


AREA OF INTEREST #1...The rather large tropical wave of low pressure moving across the central tropical Atlantic has continued to produce multiple thunderstorm bands...but the center of low pressure continues to lack thunderstorms due to ingestion of dry saharan air. As a result I have slightly lowered my peak 5-day odds of tropical cyclone formation to 70%...still high as most of the models indicate this system could become a tropical depression or tropical storm eventually...but it appears the chances for this system to become a hurricane in the 5-day forecast window have lessened. I also only gradually raise odds of development to the 70% over the next five days to give time for the large circulation to consolidate and also mix out the dry saharan air. During the forecast period...the tropical wave will remain in favorable low shear and upper outflow beneath a broad tropical upper ridge in the region and over warm waters...therefore continuing to watch for thunderstorm activity to flare up and persist from these factors to consolidate the large low pressure spin and mix out the dry air. I curve the track increasingly north by 72 and 96 hours as this system may still become a strong/sufficienty tall system to be dragged by the southeasterly upper flow on the southeast side of an axis of upper vorticity to persist from the central to western Atlantic...but I have lessened the northward angle to reflect a weaker system. By 120 hours...a northward angle in track is supported even for a weaker/shallower system as the large frontal system approaching from the central United States moves offshore and creates a break in the surface Atlantic subtropical ridge. Interests in the Lesser Antilles...Virgin Islands...Puerto Rico...the eastern Bahamas...the Dominican Republic...and Haiti are urged to continue to monitor the progress of this tropical wave over the next few days.

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

IOH 24 Hr Outlook (1800Z Jul 28)...40% chance of tropical cyclone formation (tropical Atlanic near 12.5N-51W)

IOH 48 Hr Outlook (1800Z Jul 29)...50% chance of tropical cyclone formation (tropical Atlantic east of the Lesser Antilles near 13N-57W)

IOH 72 Hr Outlook (1800Z Jul 30)...55% chance of tropical cyclone formation (over the Lesser Antilles near 15.5N-62W)

IOH 96 Hr Outlook (1800Z Jul 31)...60% chance of tropical cyclone formation (just southwest of Puerto Rico and southeast of the Dominican Republic near 18N-67W)

IOH 120 Hr Outlook (1800Z Aug 1)...70% chance of tropical cyclone formation (inland near the north coast of Haiti near 20N-72W)


AREA OF INTEREST #2...A tropical disturbance characterized by a swirl of low pressure offshore of the southeastern United States coast has lost thunderstorm activity...and the swirl appears to be fading in the latest satellite pictures. The disturbance was born by upper divergence on the northeast side of western Atlatnic upper vorticity over the last few days...in a location between the Atlantic subtropical ridge to the northeast and surface ridging that was over the eastrn United States. Perhaps because of the surface ridges the surface pressures were too high in the location of the upper divergence maximum for a decent surface low pressure and thunderstorms to take hold. It now appears the weak swirl of low pressure will continue northeast in the flow ahead of the approaching central United States frontal system while dissipating...this is my final statement on this disturbance on this blog.

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

IOH 24 Hr Outlook (1800Z Jul 28)...0% chance of tropical cyclone formation (western Atlantic near 35N-72W)


...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 cyclone formation shown in 42 hours near 14.5N-55W...reaches northern Lesser Antilles as a tropical depression or tropical storm in 66 hours...crosses the Virgin Islands and Puerto Rico through 78 hours...located over the central Bahamas in 120 hours. For area of interest #2...no tropical cyclone formation shown


0000Z ECMWF Model Run...For area of interest #1...reaches the central and northern Lesser Antilles just after 48 hours as a broad tropical deprssion or weak tropical storm...weakens to a remnant tropical wave in the central Caribbean Sea by 96 hours. For area of interest #2...no tropical cyclone formation shown.


1200Z GFS Model Run...For area of interest #1...reaches the central and northern Lesser Antilles at 66 hours as a broad tropical deprssion or weak tropical storm...crosses the Virgin Islands and Puerto Rico through 84 hours...at 120 hours located just east of the Bahamas as a weak tropical low/tropical cyclone. For area of interest #2...no tropical cyclone formation shown


0600Z NAVGEM Model Run...For area of interest #1...tropical cyclone formation shown near 14N-47W in 24 hours...moves into the northern Lesser Antilles as a strong tropical cyclone in 72 hours...moves across the Virgin Islands and Puerto Rico through 90 hours while strengthening into an intense tropical cyclone...positioned over the central Bahamas as an intense tropical cyclone in 120 hours. For area of interest #2...no tropical cyclone formation shown

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