BIRDSEYE VIEW POSTS

Since 2012 on the now retired Weather Underground 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 at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at IOHurricanes@outlook.com 

 
 
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MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #69

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


...WEDNESDAY AUGUST 4 2021 12:27 AM EDT...

See the area of interest sections below for multiple areas being monitored for tropical development in the Atlantic…which include:

(1) area of interest #1…surface trough of low pressure currently passing north through Republic of Cabo Verde Islands

(2) area of interest #2…surface low pressure area along a frontal boundary offshore of the southeastern United States.

(3) area of interest #3…tropical wave of low pressure currently over central Africa which has model support showing development when it enters the eastern tropical Atlantic in a few days.


AREA OF INTEREST #1…Over the last several hours…the east end of a surface trough of low pressure in the eastern tropical Atlantic developed a small swirl with thunderstorm bursts just northwest of center. As the surface trough continues to shift northwest while steered by the east side of the large scale parent tropical wave near 30W longitude…this has resulted in the swirl moving into the southeastern islands of the Republic of Cabo Verde near 15N-22.5W. However the swirl has lost its definition and thunderstorms as of late while moving into dry Saharan air which blankets the islands and areas north. Therefore as the surface trough turns more west in track while running into the south end of the Atlantic surface ridge...I forecast 0% odds of tropical cyclone formation going forward. I plan this to be my final statement on this area of interest on this blog unless it continues to be mentioned in the NHC tropical weather outlook by my next update.

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

IOH 24 Hr Outlook (0000Z Aug 5)…0% chance of tropical cyclone formation (west of the Republic of Cabo Verde Islands near 17N-26W)


AREA OF INTEREST #2…More recent satellite image of the surface low pressure offshore of the southeastern United States…taken at 0211Z…with an estimated center of lowest pressure at the red plus:


Based on the satellite imagery…the surface low pressure area offshore of the southeastern US and along the tail end of a cold front appears to have become a little better organized near 31.2N-79W…albeit as of late the thunderstorm activity near this center appears to have waned. Models agree that this surface low pressure will strengthen and become more defined with the support of the eastern divergence zone of the cold front’s upper trough and also the outflow on the west side of the western Atlantic upper ridge. The outflow and low shear of the upper ridge could allow for tropical development as the surface low slides along or just offshore of the US east coast over the next day or so due to the deep-layer southerly flow between the upper trough and upper ridge and west side of the Atlantic surface ridge whose strength will keep the surface low pressure close to shore. The NAVGEM still explicitly shows tropical development…while its a close call on the GFS which shows an initially elongated low that becomes more circular. With some model support ongoing and slightly better organized structure on tonight’s infrared satellite pictures…I have nudged my odds of development upward to 25%. I drop odds of development to 0% by 48 hours as the surface low moves into cooler waters and sheds whatever tropical characteristics it may obtain.


I have adjusted the track forecast points further south and a little more offshore due to the current position of the surface low. From now through Friday expect:

**Heavy rainfall with flash flooding potential from coastal North Carolina all the way up the US east coast to Maine regardless of tropical development. As of this writing…a flash flood watch is in effect for parts of this region.

**The potential for gusty winds and coastal

surf from the coastal North Carolina to coastal Maine…at first from possible tropical development in the short-term and then possible support from the upper trough by non-tropical means after this system moves into cooler water. With the more offshore forecast track shown below…the potential for gusty winds appears greater for coastal North Carolina and Cape Cod Massachusetts.

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

IOH 24 Hr Outlook (0000Z Aug 5)…25% chance of tropical cyclone formation (offshore of the North Carolina/Virginia border near 36.2N-74.5W)

IOH 48 Hr Outlook (0000Z Aug 6)…0% chance of tropical cyclone formation (Cape Cod Massachusetts near 41.5N-70W)


AREA OF INTEREST #3…More recent satellite image of the current Central Africa tropical wave of low pressure…taken at 0000Z…with an estimated center of lowest pressure at the red plus (near 9N-5E):


The GFS and ECMWF models continue to insist that the current tropical wave of low pressure currently over central Africa will emerge into the eastern tropical Atlantic by Thursday or Friday and possibly develop further with the support of low shear and upper outflow beneath the eastern tropical Atlantic upper ridge forecast to persist over the next several days. As a result the tropical wave is now an area of interest in the NHC tropical weather outlook. Given that thunderstorm activity has greatly increased on the west side of the wave in the latest infrared satellite pictures and ongoing GFS and ECMWF model support…I forecast slightly higher odds of development than the NHC’s outlook as of this writing…putting my odds at 25% by day 5. I have not chosen higher odds as it is uncertain how the wave’s exact structure and position will be when it exits the west coast of Africa…a more north position and/or larger structure could cause it to ingest dry Saharan air to the north…and the opposite is true for a more south position and/or compact structure. Forecast track in the outlook below is based on the initial position in the above 0000Z satellite picture…with a slightly faster track than the typical 5W longitude per day track of tropical waves in order to keep up with the forecast positions shown in the GFS and ECMWF.

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

IOH 24 Hr Outlook (0000Z Aug 5)…0% chance of tropical cyclone formation (western Africa near 9N-0W)

IOH 48 Hr Outlook (0000Z Aug 6)…0% chance of tropical cyclone formation (western Africa near 9N-6W)

IOH 72 Hr Outlook (0000Z Aug 7)…0% chance of tropical cyclone formation (near west coast

of Africa in vicinity of 9N-13W)

IOH 96 Hr Outlook (0000Z Aug 8)…15% chance of tropical cyclone formation (eastern tropical Atlantic near 10.5N-20W)

IOH 120 Hr Outlook (0000Z Aug 9)…25% chance of tropical cyclone formation (eastern tropical Atlantic near 11.5N-27W)


...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…no tropical cyclone formation shown

**For area of interest #2…elongated frontal low consolidates over the Outer Banks of North Carolina at 30 hours…frontal low moves across Cape Cod Massachusetts at 48 hours…remnant low makes landfall over Maine at 54 hours while weakening to a surface trough.

**For area of interest #3…tropical wave of interest emerges from Africa and into the eastern tropical Atlantic at 66 hours…while featuring a broad low pressure the wave passes south of the Republic of Cabo Verde Islands at 96 hours…broad low pressure center located at 11.5N-30W at 126 hours.


1200Z ECMWF Model Run…

**For area of interest #1…no tropical cyclone formation shown

**For area of interest #2…elongated frontal low consolidates over the Outer Banks of North Carolina at 24 hours…frontal low moves across Massachusetts at 48 hours…between 48 and 72 hours weakens to a surface trough while making landfall across Maine.

**For area of interest #3…tropical wave of interest emerges from Africa and into the eastern tropical Atlantic by 72 hours…develops low pressure spin near 11N-25.5W at 96 hours…broad tropical depression suggested near 12N-30W at 120 hours.


1200Z GFS Model Run...

**For area of interest #1…no tropical cyclone formation shown

**For area of interest #2…elongated frontal low consolidates over the Outer Banks of North Carolina at 24 hours…consolidates further into a compact circular circulation offshore of Maryland near 38N-74W at 33 hours…becomes elongated and less tropical while moving across Massachusetts at 48 hours…remnant low makes landfall over Maine at 60 hours while weakening to a surface trough.

**For area of interest #3…tropical wave of interest emerges from Africa and into the eastern tropical Atlantic by 48 hours…develops a compact low pressure center near 11.2N-20.5W at 60 hours…tropical cyclone formation shown near 10.8N-21.2W at 69 hours…moves northwest and gradually weakens while moving into the southwestern islands of the Republic of Cabo Verde at 102 hours…weakened tropical cyclone turns west and reaches 15.5N-27.5W at 120 hours.

1200Z NAVGEM Model Run...

**For area of interest #1…low pressure becomes defined just east of the Republic of Cabo Verde Islands at 18 hours…weakens to a surface trough just west of the islands by 54 hours.

**For area of interest #2…tropical cyclone formation suggested just offshore of Cape Hatteras North Carolina at 24 hours…cyclone center moves across Massachusetts at 54 hours…makes landfall in Maine by 60 hours while weakening to a remnant low

**For area of interest #3…no tropical cyclone formation shown

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