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 #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 JUNE 7 2021 11:30 AM EDT...

See area of interest #1 section below regarding the potential tropical development between Bermuda and the northern Caribbean Islands over the next five days. See area of interest #2 section below regarding the potential for tropical development in the southern Gulf of Mexico and Caribbean waters adjacent to Central America and southeastern Mexico over the next week.


AREA OF INTEREST #1...Warm upper ridging has amplified across eastern North America due to surface warm southerly flow on the west side of the Atlantic surface ridge and east side of the current central Canada frontal low. This upper ridging is cutting off the south end of the current northwest Atlantic upper trough into a southeastward-diving vortex...well-defined as a faint cloud swirl on visible and water vapor imagery near 30N-70W. The vortex is expected to shift southeast into the waters between Bermuda and the northern Caribbean Islands...and the GFS model continues to forecast the formation of a well-defined surface subtropical or tropical feature in 3 to 5 days...triggered by the eastern divergence zone of the vortex. My forecast track after day 3 is adjusted eastward in accordance with the latest runs of the GFS. A northward track is likely to begin by day 5 as a North Atlantic upper trough is forecast to amplify southward and gradually erode the west extent of the Atlantic surface ridge...while driving a frontal cyclone to exit from Atlantic Canada by days 3...and by day 5 while driving a surface front to eject from the northeast US. Beyond day 5...conditions for tropical development will be less favorable as the north track will take this system to waters below 26 deg C. The potential for this system to bring coastal sea swells to Bermuda remains very low with the latest east shift in the long-range forecast track. I have also lowered peak odds of tropical cyclone development to 15% as the GFS is trending with a southwest-to-northeast elongation of the upper vortex...which would increase wind shear over the potential tropical disturbance which would be located under the eastern divergence zone of the vortex.

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

IOH 24 Hr Outlook (1200Z Jun 8)...0% chance of tropical cyclone formation (western Atlantic near 27.5N-68W)

IOH 48 Hr Outlook (1200Z Jun 9)...0% chance of tropical cyclone formation (western Atlantic near 25N-65W)

IOH 72 Hr Outlook (1200Z Jun 10)...10% chance of tropical cyclone formation (western Atlantic near 25N-62.5W)

IOH 96 Hr Outlook (1200Z Jun 10)...15% chance of tropical cyclone formation (western Atlantic near 25N-61W)

IOH 120 Hr Outlook (1200Z Jun 11)...15% chance of tropical cyclone formation (western Atlantic near 27.5N-59W)


AREA OF INTEREST #2...Computer models remain in agreement on the eventual dissipation of the current Caribbean cold core upper vorticity as it remains cut-off from mid-latitude cold air. The vorticity is forecast to be replaced by the warm core upper ridging currently over the Gulf of Mexico. The low shear and outflow of the upper ridging will make conditions more conducive for the lowering of surface pressures and tropical development across Central America and the Caribbean. Per the latest suite of model runs...the CMC and NAVGEM suggest the development of a broad surface low pressure over southeastern Mexico and northwestern Central America by day 6...supported by the forecast upper outflow. The GFS is more bullish while forecasting a surface low pressure to form in the southern Caribbean in as soon as 3 to 5 days...albeit in the long range it parks the broad surface low over southeastern Mexico and northwestern Central America similar to the NAVGEM and CMC. Meanwhile the ECMWF is out to lunch while not showing any development.


The National Hurricane Center has introduced the southern Caribbean as an area of interest for tropical development in their 5-day tropical weather outlook...probably in response to the GFS solution. The surface tropical wave of low pressure currently at 55W longitude...east of the southern Lesser Antilles...will arrive to the southern Caribbean Sea by days 4 and 5 in a region of forecast split flow upper divergence between the south sides of the upper vortex mentioned in area of interest #1 and the forecast upper ridging. The depiction of this split flow upper divergence may be why the GFS forecasts the formation of the surface low pressure sooner relative to other models and in the southern Caribbean Sea. I forecast low 10% odds of tropical cyclone formation by day 5...lower than the NHC 5-day outlook...as the GFS is the only model showing any development within the next 5 days...and even the GFS solution only shows the formation of a surface low and not a tropical cyclone. In the long range...any broad low pressure that develops in the southern Caribbean is likely to progress across northwestern Central America and toward southeastern Mexico per the latest GFS-CMC-NAVGEM consensus...and it is hard to say if a tropical cyclone would ultimately consolidate over the adjacent eastern Pacific waters...or over the adjacent western Caribbean and southern Gulf of Mexico waters...or perhaps over both basins (i.e. an eastern Pacific tropical cyclone that develops in the long range...which then crosses over to the southern Gulf of Mexico...or alternatively a pair of twin tropical cyclones...one over the eastern Pacific...and another over the western Caribbean or southern Gulf of Mexico).

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

IOH 24 Hr Outlook (1200Z Jun 8)...0% chance of tropical cyclone formation (Trinidad and the southern Lesser Antilles near 10N-60W)

IOH 48 Hr Outlook (1200Z Jun 9)...0% chance of tropical cyclone formation (north coast of Venezuela near 10N-65W)

IOH 72 Hr Outlook (1200Z Jun 10)...0% chance of tropical cyclone formation (northwest coat of Venezuela near 11N-70W)

IOH 96 Hr Outlook (1200Z Jun 10)...0% chance of tropical cyclone formation (southern Caribbean Sea near 11.5N-75W)

IOH 120 Hr Outlook (1200Z Jun 11)...10% chance of tropical cyclone formation (southern Caribbean Sea near 12.5N-80W)


...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...no tropical cyclone formation shown. For area of interest #2...broad surface low pressure consolidates over southeastern Mexico and northwestern Central America by 138 hours.


0000Z ECMWF Model Run...For areas of interest #1 and #2...no tropical cyclone formation shown.


0600Z GFS Model Run...For area of interest #1...weak surface low forms near 25N-59.5W at 102 hours...drifts northward to 27N-59W by 129 hours. For area of interest #2...broad surface low pressure forms in the southern Caribbean Sea near 13.5N-80W at 96 hours...drifts west-northwest across Central America and into southeastern Mexico in the long range.


0600Z NAVGEM Model Run...For area of interest #1...no tropical cyclone formation shown. For area of interest #2...broad surface low pressure consolidates over southeastern Mexico and northwestern Central America by 144 hours.

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