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 #147

Updated: Oct 13

*******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 OCTOBER 12 2020 4:40 PM EDT...

See area of interest sections below for areas being monitored for tropical development.


AREA OF INTEREST #1...The vigorous tropical wave of low pressure in the central tropical Atlantic has continued to develop an increasingly defined spin...and as of 1800Z the spin was passing near 13N-51.5W using satellite animation. However the thunderstorm activity has become lopsided to the east of the spin due to increasing westerly wind shear as it approaches a central Atlantic upper trough that has coalesced from upper trough fragments that recently ejected from eastern North America. It could be argued that the thunderstorms are now supported by the eastern divergence zone of the upper trough...instead of the outflow of the eastern tropical Atlantic upper ridge as was the case over the previous days. This system should continue tracking west-northwest toward a surface ridge weakness induced by a decaying central Atlantic front and also a northwestern Atlantic front moving into the region...a path that will take the tropical wave toward the axis of the upper trough by 24 hours where there is less upper divergence to support thunderstorms...and even after passing through the upper trough axis the wave may have to deal with a zone of suppressive upper convergence between the west side of the upper trough and southeast side of the western Atlantic upper ridge. Thus I forecast a 0% chance of development by 24 hours. However given the NHC outlook still has 30% odds of development...I have included a special 12 hour forecast point showing odds above 0% in case some last minute development occurs before the upper-level wind conditions become more hostile. Not mentioning the Lesser Antilles in regards to this tropical wave on the home page bulletins of this site as the upper trough axis where there is a lack of divergence needed for thunderstorms will be settling over the islands.

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

IOH 12 Hr Outlook (0600Z Oct 13)...15% chance of tropical cyclone formation (central tropical Atlantic near 14N-53.5W)

IOH 24 Hr Outlook (1800Z Oct 13)...0% chance of tropical cyclone formation (central tropical Atlantic east of the Lesser Antilles near 15N-56W)


AREA OF INTEREST #2...Based on the latest satellite imagery...a tropical wave of low pressure over interior western Africa is near 12.5N-9W...featuring a recent increase in curved thunderstorm bands on its west side. This tropical wave of low pressure will soon be emerging into the eastern tropical Atlantic....where a tropical upper ridge with low shear and upper outflow will persist and may potentially aid in developing this wave. However I retain low 20% odds of tropical cyclone formation and day 4 as the development signal from the CMC...GFS...and NAVGEM models remains weak...showing the development of a broad low pressure area instead of explicitly showing tropical cyclone formation. By days 4 and 5 less favorable wind shear over this tropical wave will likely increase as the central Atlantic upper trough currenly affecting area of interest #1 shifts eastward toward this tropical wave while pushed by an upper trough fragment to eject from the current western North America upper trough. Therefore odds by day 5 are tapered downward from the 20% peak. Forecast points are adjusted northwestward due to the current positon of the tropical wave...close enough to the Republic of Cabo Verde Islands for me to begin statements on this wave in regards to those islands on the home page bulletins of this site.

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

IOH 24 Hr Outlook (1800Z Oct 13)...0% chance of tropical cyclone formation (western Africa near 12.5N-14W)

IOH 48 Hr Outlook (1800Z Oct 14)...5% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-19W)

IOH 72 Hr Outlook (1800Z Oct 15)...10% chance of tropical cyclone formation (just south of the Republic of Cabo Verde Islands near 13.5N-24W)

IOH 96 Hr Outlook (1800Z Oct 16)...20% chance of tropical cyclone formation (eastern tropical Atlantic near 14N-29W)

IOH 120 Hr Outlook (1800Z Oct 17)...15% chance of tropical cyclone formation (eastern tropical Atlantic near 14.5N-34W)


AREA OF INTEREST #3...The area of disturbed weather southeast of area of interest #1...possibly another tropical wave that has not been previously well-defined...has become considerably less organized over the last 24 hours. This is likely from northwesterly shear induced by the outflow of the thunderstorms from area of interest #1. Therefore I have lowered odds of tropical cyclone formation to 0%...especially as this disturbance will soon move into shearing upper southwesterly winds induced by the central Atlantic upper trough as it also moves west-northwest toward the same surface ridge weakness that area of interest #1 is tracking towards. 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 Oct 13)...0% chance of tropical cyclone formation (central tropical Atlantic near 8.5N-42.5W)


...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 wave amplifies into a surface low pressure while arriving into the northern Lesser Antilles at 60 hours...tropical wave weakens while crossing northern Caribbean Islands through 120 hours. For area of interest #2...tropical wave with broad low pressure spin emerges from western Africa at 36 hours...after crossing Republic of Cabo Verde Islands at 60 hours the low pressure opens back to a wave at 35W at 126 hours. For area of interest #3...no tropical cyclone formation shown.


1200Z ECMWF Model Run....For areas of interest #1 to #3...no tropical cyclone formation shown.


1200Z GFS Model Run...For area of interest #1...no tropical cyclone formation shown. For area of interest #2...tropical wave with broad low pressure spin emerges from western Africa at 36 hours...broad low pressure reaches 14N-39W at 120 hours. For area of interest #3...no tropical cyclone formation shown.


1200Z NAVGEM Model Run... For area of interest #1...organizes into a tropical low pressure east of the Lesser Antilles at 14N-56.5W at 48 hours...weakens back to a tropical wave while passing over the northern Lesser Antilles at 84 hours. For area of interest #2...tropical wave organizes into a broad low pressure spin just east of the Republic of Cabo Verde Islands at 84 hours...while crossing the islands shortly thereafter weakens back to a tropical wave. For area of interest #3...no tropical cyclone formation shown.

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