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 #150

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


...THURSDAY OCTOBER 15 2020 8:38 PM EDT...

Satellite Image from 0100Z (red indicates tropical cyclone or remnants of tropical cyclone...with D marking Delta. Green indicates an area of interest in the National Hurricane Center Tropical Weather Outlook. Yellow indicates an area of interest not in the National Hurricane Center Tropical Weather Outlook.):


NHC TAFB Surface Analysis 1800Z:


GFS Model Upper Level Winds 1800Z:



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


Elsewhere...the current northeast Atlantic upper trough is expected to amplify into an impressive and large upper vortex...with the amplification of the upper trough to be kicked off by the amplification of north Atlantic upper ridging in the warm sector of mutliple frontal systems/upper troughs pivoting around the central North America upper vortex. While the forecast northeastern Atlantic upper vortex will be cold enough to support thunderstorms over mild water temps...the latest model runs suggest the upper vortex will be elongated such that the surface frontal cyclone to be supported by the vortex will be elongated without a singular center needed for subtropical development. Therefore not adding another area of interest in the northeast Atlantic.


AREA OF INTEREST #1...The tropical wave of low pressure in the eastern tropical Atlanic continues to have a broad spin that passes near near 12.5N-26W as of 1800Z...but the bands showers and thunderstorms on its north and west sides that have defined the spin have weakened over the last 24 hours. Given these observations and the fact that the broad spin of the tropical wave has not shown signs of consolidation...I have lowered my peak 5-day odds of tropical cyclone formation to 5%. For now the tropical wave remains protected from wind shear and has supportive upper outflow while under the eastern tropical Atlantic upper ridge axis. However over the next few days...wind shear is expected to increase once the upper ridge axis shifts southward due to the forecast amplification of the current northeast Atlantic upper trough into a cut-off upper vortex...as well as the push provided by the current central Atlantic upper trough as well as the west Atlantic upper trough associated with area of interest #2 as they both shift eastward with time. In response to the forecast increase in shear...odds are dropped back down to 0% by day 3.

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

IOH 24 Hr Outlook (1800Z Oct 16)...0% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-31W)

IOH 48 Hr Outlook (1800Z Oct 17)...5% chance of tropical cyclone formation (eastern tropical Atlantic near 13N-36W)

IOH 72 Hr Outlook (1800Z Oct 18)...0% chance of tropical cyclone formation (central tropical Atlantic near 13.5N-41W)


AREA OF INTEREST #2...An upper trough that has recently exited eastern North America is now in the western Atlantic triggering the formation of a central Atlantic broad surface low pressure with its eastern divergence zone. This upper trough is expected to amplify due to adjacent amplification of the current western Atlantic upper ridge and expected formation of north Atlantic upper ridging in the warm sector of frontal systems to be supported by upper troughs pivoting around the central North America upper vortex. The GFS...ECMWF...and NAVGEM are joining the CMC in showing a more amplified upper trough...especially as they show a fragment of the current northeast Atlantic upper trough retrograde southwestward into this upper trough which will re-enforce it. A more amplified upper trough will mean a more defined surface low pressure...thus it makes sense to add this area as a potential interest for subtropical cyclone formation in the coming days...and the NHC has already done so in their tropical weather outlook.


Most of the model suite indicates that the developing surface low pressure will drift southwestward as the current north Atlantic surface ridge intensifies under the convergence zone of the expected north Atlantic upper ridging...and from surface ridges over eastern North America that will be supported by the western convergence zones of the other upper troughs to pivot northeastward around the central North America upper vortex. However the ECMWF shows a more east-weighted surface low in response to the chunk of energy to arrive from the northeast Atlantic upper trough...thus in my track forecast I am not as far west as the GFS-NAVGEM-CMC camp. I also have lower odds of development than the NHC...at 10%...as the introduction of the energy from the northeast Atlantic upper trough could keep the upper trough large and broad...resulting in an equally broad surface low pressure without a tightly defined center which is needed for tropical development.

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

IOH 24 Hr Outlook (1800Z Oct 16)...0% chance of subtropical cyclone formation (central Atlantic near 30N-55W)

IOH 48 Hr Outlook (1800Z Oct 17)...10% chance of subtropical cyclone formation (central Atlantic near 30N-55W)

IOH 72 Hr Outlook (1800Z Oct 18)...10% chance of subtropical cyclone formation (central tropical Atlantic near 28N-56W)

IOH 96 Hr Outlook (1800Z Oct 19)...10% chance of subtropical cyclone formation (central tropical Atlantic near 26N-57W)

IOH 120 Hr Outlook (1800Z Oct 20)...10% chance of subtropical cyclone formation (central tropical Atlantic near 25N-58W)


AREA OF INTEREST #3...The current area of showers and thunderstorms in the western Caribbean Sea to the east of Nicaragua is supported by the divergence zone of a small upper vortex that has over the last couple of days broken away from the central Atlantic upper trough...thanks to the strength of the current western Atlantic to Gulf of Mexico upper ridge. This thunderstorm activity is expected to increase over the next few days once the small upper vortex dissipates...and as a part of the aforementioned upper ridge shifts southward into the western Caribbean Sea in response to the series of strong upper troughs to pivot around the central North America upper vortex...increasing the upper outflow needed for thunderstorms and low surface pressure. This could result in the formation of a tropical cyclone in the western Caribbean region in the long range...and because the western Caribbean had been added as an area of interest in the NHC outlook it is likewise tagged as an area of interest here. I only have low 10% odds of tropical cyclone formation and at day 5 as the models that do show development are unanimous in not showing a defined surface low pressure until day 5....with development shown after that time.

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

IOH 24 Hr Outlook (1800Z Oct 16)...0% chance of tropical cyclone formation (western Caribbean Sea near 13N-80W)

IOH 48 Hr Outlook (1800Z Oct 17)...0% chance of tropical cyclone formation (western Caribbean Sea near 13N-80W)

IOH 72 Hr Outlook (1800Z Oct 18)... 0% chance of tropical cyclone formation (western Caribbean Sea near 13N-80W)

IOH 96 Hr Outlook (1800Z Oct 19)...0% chance of tropical cyclone formation (western Caribbean Sea near 13N-80W)

IOH 120 Hr Outlook (1800Z Oct 20)...10% chance of tropical cyclone formation (western Caribbean Sea near 13N-80W)


...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...weak broad surface low forms near 30N-55W at 24 hours...drifts southwestward to 24N-61.5W by 120 hours while undergoing some strengthening. For area of interest #3...weak surface low forms in the western Caribbean Sea near 13.5N-80W by 120 hours...possible tropical cyclone formation suggested in long range. Elsewhere...tropical wave organizes into a tropical low pressure near 10N-36.5W at 150 hours...tropical cyclone formation suggested in the long range.


1200Z ECMWF Model Run...For area of interest #1...no tropical cyclone formation shown. For area of interest #2...weak broad surface low forms near 30N-54W at 24 hours...drifts southwest and then southeast while undergoing some strengthening...reaching 26.5N-53W by 120 hours. For area of interest #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...weak broad surface low forms near 30N-54W at 24 hours...drifts southwest while undergoing some strengthening...reaching 23N-62W by 120 hours. For area of interest #3...weak surface low forms in the western Caribbean Sea near 13N-80W by 120 hours...possible tropical cyclone formation suggested in long range. Elsewhere...portion of current northeast Atlantic upper trough cuts off and triggers formation of small low pressure near 31N-44W at 120 hours...possible subtropical cyclone formation in long range.


1200Z NAVGEM Model Run... For area of interest #1...no tropical cyclone formation shown. For area of interest #2...weak broad surface low forms near 30N-55W at 24 hours...drifts southwest while undergoing some strengthening...reaching 24N-65W by 120 hours. For area of interest #3...weak surface low forms in the western Caribbean Sea near 13N-80W by 120 hours...however no tropical cyclone formation suggested in long range.

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