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 #72

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


...SUNDAY JULY 26 2020 3:59 PM EDT...

See Tropical Storm Hanna section below for the only active tropical cyclone in the Atlantic basin. See area of interest sections below for additional areas being monitored for tropical cyclone formation. Elsewhere...another vigorous tropical wave of low pressure is emerging from the west coast of Africa into the eastern tropical Atlantic with thunderstorm activity. I have not added it as an area of interest for development as their is a lack of computer model support and it is uncertain how much dry saharan air this tropical wave will ingest. However should the tropical wave become better organized...will consider adding it as yet another area of interest to monitor for tropical cyclone development.


TROPICAL STORM HANNA...While continuing west-southwestward toward a surface monsoonal low pressure field over Mexico and under the drag of upper northerly winds between a sprawling upper ridge over the United States and approaching shortwave upper trough fragment to the northeast...Hanna has continued west-southwest across far south Texas and into northeastern Mexico while weakening to a tropical storm. The weakening rate has been gradual due to boost provided by split flow upper divergence between the shortwave upper trough fragment and upper ridge. Heavy rainfall with flash flooding potential will continue today across inland south Texas...northern Tamaulipas...northern Nuevo Leon...and Coahuila provinces of Mexico. Gusty winds maybe possible over northern Nuevo Leon until Hanna weakens below tropical storm force later this afternoon.

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

IOH 24 Hr Forecast (1200Z Jul 26)...40 mph maximum sustained wind tropical storm centered over northeastern Mexico at 25.9N-100.1W

IOH 48 Hr Forecast (1200Z Jul 27)...Remnant low pressure over central Mexico centered at 25N-103W


AREA OF INTEREST #1...The south side of the large tropical wave of low pressure moving into the central tropical Atlantic has continued to produce multiple organized thunderstorm bands...and the latest National Hurricane Center TAFB surface analysis confirms a center of low pressure is in progress along the wave axis in the midst the banding. Computer models continue to pick up on this tropical wave...with the GFS...NAVGEM...ECMWF...and CMC all developing this tropical wave into a tropical cyclone over the next five days. As a result I keep my high peak 5-day odds of tropical cyclone formation at 80%...but I have not raised them to 90% like the National Hurricane Center at this time as the north side of the circulation continues to have limited thunderstorm activity from the dry saharan air layer. I also only gradually raise odds of development to the 80% 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. A more northward angle in track is shown by 96+ hours as the tropical wave will likely be a tropical cyclone by that timeframe...likely tall enough 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. Interests in the central and northern Lesser Antilles...Virgin Islands...Puerto Rico...the eastern Bahamas...and the Dominican Republic are urged to monitor the progress of this tropical wave over the next few days. On the home page of this site however...I have removed the potential for hurricane force conditions over these land areas as the CMC and ECMWF show a weaker tropical cyclone than yesterday. While the NAVGEM and GFS show an intense tropical cyclone...these models recently overplayed Gonzalo in the face of the dry saharan air layer...so at this time due to the dry air I believe strengthening will be more gradual than rapid should a tropical cyclone indeed form.

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

IOH 24 Hr Outlook (1200Z Jul 27)...40% chance of tropical cyclone formation (tropical Atlanic near 12N-43W)

IOH 48 Hr Outlook (1200Z Jul 28)...50% chance of tropical cyclone formation (tropical Atlanic near 12.5N-49W)

IOH 72 Hr Outlook (1200Z Jul 29)...60% chance of tropical cyclone formation (tropical Atlantic east of the Lesser Antilles near 13N-55W)

IOH 96 Hr Outlook (1200Z Jul 30)...70% chance of tropical cyclone formation (just east of the northern Lesser Antilles near 16N-60W)

IOH 120 Hr Outlook (1200Z Jul 31)...80% chance of tropical cyclone formation (just north of the Virign Islands and just northwest of Puerto Rico near 19N-65W)


AREA OF INTEREST #2...A tropical disturbance characterized by a surface trough of low pressure with rotating cloudiness...showers...and thunderstorms continues west-northwest in the western Atlantic waters offshore of the northwest Bahamas...now arriving to the waters offshore of the southeastern United States coast. The disturbance is showing multiple spins in the cloudiness this afternoon...but I have adjusted my forecast track northward as the main area of spin appears to be further north than I previously forecasted. The disturbance will continue north over the next 24 hours while rounding the west side of the Atlantic surface subtropical ridge...then accelerate northeastward into the open western Atlantic in strong surface flow to form between the subtropical ridge and an approaching frontal system from the central United States. This path will curve the disturbance along warm Gulf stream waters and beneath northwestern Atlantic upper ridging to amplify in the warm flow ahead of the front...which will keep wind shear low and upper outflow favorably high. I have odds of tropical cyclone formation at a low peak of 30% for the next 72 hours until computer model support comes onboard...or unless the National Hurricane Center begins to mention this disturbance in their tropical weather outlook. My 24 hour odds are only at 20% to give time for the disturbance to consolidate given that it has multiple spins. Given the more north position of the disturbance...at the home page of this site I have extended the impact potential up toward the Carolina coast and have removed mention of the northeast Florida coast.

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

IOH 24 Hr Outlook (1800Z Jul 27)...20% chance of tropical cyclone formation (offshore of Georgia and the Carolinas near 32N-77.5W)

IOH 48 Hr Outlook (1800Z Jul 28)...30% chance of tropical cyclone formation (western Atlantic near 35N-74W)

IOH 72 Hr Outlook (1800Z Jul 29)...30% chance of tropical cyclone formation (northwestern Atlantic near 39N-66W)

IOH 96 Hr Outlook (1800Z Jul 30)...0% chance of tropical cyclone formation (northwestern Atlantic near 43N-57W)


...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 Tropical Storm Hanna...continues west-southwestward inland across northeast Mexico and loses its identity in 6 hours. For area of interest #1...tropical cyclone formation shown in 54 hours near 14.5N-53W...reaches northern Lesser Antilles as a tropical depression or tropical storm in 78 hours...reaches the eastern Bahamas as a strong tropical cyclone in 120 hours. For area of interest #2...no tropical cyclone formation shown


0000Z ECMWF Model Run...For Tropical Storm Hanna...continues west-southwestward inland across northeast Mexico and loses its identity just after 24 hours...For area of interest #1...tropical cyclone formation shown near 15N-54W in 48 hours...reaches the central and northern Lesser Antilles in 96 hours as a tropical deprssion or tropical storm...located just southeast of the Dominican Republic and just southwest of Puerto Rico as a stronger tropical cyclone in 120 hours. For area of interest #2...no tropical cyclone formation shown.


1200Z GFS Model Run...For Tropical Storm Hanna...continues west-southwest into central Mexico where it loses its identity in 30 hours. For area of interest #1...tropical cyclone formation shown in 42 hours near 14.5N-45W...passes just north of the northern Lesser Antilles as an intense tropical cyclone in 96 hours...at 120 hours located just east of the Bahamas near 21.5N-68W as an intense tropical cyclone. For area of interest #2...no tropical cyclone formation shown


0600Z NAVGEM Model Run...For Tropical Storm Hanna...continues west-southwest into central Mexico where it loses its identity in 60 hours. For area of interest #1...tropical cyclone formation shown near 11.5N-39W in 24 hours...moves into the northern Lesser Antilles as a very intense tropical cyclone in 114 hours...located over the Virgin Islands as a very intense tropical cyclone in 120 hours. For area of interest #2...no tropical cyclone formation shown

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