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 #157

*******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 22 2020 3:00 PM EDT...

See Hurricane Epsilon section below for the only active tropical cyclone in the Atlantic basin. See area of interest sections below for areas in the Atlantic being monitored for tropical cyclone formation.


HURRICANE EPSILON...Throughout the morning...Epsilon has weakened from a category 3 to a strong category 1. This could be from the hurricane moving into 26 deg C waters which is just at the threshold for tropical development...dry air just to the west generated by the western convergence zone of the western Atlantic upper vortex the hurricane has been interacting with...and perhaps from the western outflow of the hurricane being constricted by residual upper vorticity to the west being left behind by the upper vortex. In addition the upper atmosphere is not cold enough to support instability needed for thunderstorms as Epsilon moves toward cooler water...with the 200 mb layer of the upper atmosphere being at 1230 dekameters in height (would like to see heights towards 1200 dekameters for tropical development at these water temperatures). The 0600Z GFS model run suggests the latent heat release of Epsilon's thunderstorms will weaken the residual upper vorticity to the west while causing it to tilt into a northwest-to-southeast axis...a configuration that would reduce the amount of westerly wind shear it would impart and increase the supportive upper divergence to the east of the axis and over the hurricane. Therefore I agree with the 11 AM EDT NHC intensity forecast of keeping Epsilon at its current strength for the next 48 hours.


The hurricane has recently turned more northward in track on satellite animation...thus my short-term track forecast is adjusted eastward. However I still forecast a west bend in the track to occur in the next 24 hours as a surface ridge will be building to the north under the convergence zone of an upper trough fragment soon to eject eastward from the current central North America upper trough. A turn to the northeast is shown after 48 hours from a surface ridge weakness to be induced under the eastern divergence zone of the central North America upper trough once the trough shifts east. By 72 hours the hurricane should transition to a non-tropical remnant frontal cyclone due to the combination of cooler waters which should weaken the thunderstorms and warm core and the supportive divergence zone of the central North America upper trough overspreading Epsilon. Therefore weakening after 48 hours when Epsilon moves into waters below 26 deg C will be slow from the upper divergence zone.


Although the east shift in the short-term track keeps Epsilon's center further away from Bermuda...the outer circulation of the hurricane is large enough to still reach Bermuda with some gusty winds...so some isolated power outages cannot be ruled out in addition to coastal sea swells. Coastal sea swells are also likely for Newfoundland this weekend as Epsilon transitions into a strong non-tropical cyclone located not far offshore.

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

0 Hr Position (1200Z Oct 22)...90 mph maximum sustained wind hurricane centered east-southeast of Bermuda at 30.9N-61.2W

IOH 24 Hr Forecast (1200Z Oct 23)...90 mph maximum sustained wind hurricane centered northeast of Bermuda at 34N-62.5W

IOH 48 Hr Forecast (1200Z Oct 24)...90 mph maximum sustained wind hurricane centered in the northwest Atlantic at 36.5N-62.5W

IOH 72 Hr Forecast (1200Z Oct 25)...Non-tropical remnant frontal cyclone centered south-southeast of Newfoundland at 43N-55W


AREA OF INTEREST #1...Showers and thunderstorms have become a little more concentrated and better organized on the east side of the large and broad surface low pressure field in the western Caribbean Sea. Based on the organization shown in the lastest satellite imagery...I estimate that the lowest pressure of the disturbance is now southwest of Jamaica near 17.5N-79W...pivoting slowly northward around the remainder of the broad low pressure field which continues to be centered over the Yucatan peninsula in the NHC TAFB surface analysis. It appears possible that the dominating center to move northward near Jamaica...the Cayman Islands...and eventually Cuba and the western Bahamas could be energized further in 72 hours by the divergence zone of a current southwest US shortwave upper trough to arrive...but this shortwave may also disrupt the organization by introducing wind shear. However given the aforementioned increase in the thunderstorm activity...I have raised my short-term odds of tropical cyclone formation to as high as 30% by 72 hours. With the shortwave upper trough forecast to move into the western Atlantic after 72 hours...there is some longer term uncertainty if the disturbance will relocate to the northeast over open water while remaining tied to the eastern divergence zone of the shortwave trough...or simply further organize over the western Bahamas in the wake of the shortwave and under the low shear/outflow of the western Caribbean upper ridge. For now my vote is for the latter scenario...and I increase odds of development further to 40% by 120 hours given the potential of more favorable upper winds in the wake of the shortwave. A northward drift of this disturbance is expected to continue in the long term due to the approach of a frontal system and more substantial upper trough to approach from the western and central US.

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

IOH 24 Hr Outlook (1200Z Oct 23)...5% chance of tropical cyclone formation (between Jamaica and the Cayman Islands at 18.5N-79W)

IOH 48 Hr Outlook (1200Z Oct 24)...15% chance of tropical cyclone formation (over the eastern Cayman Islands near 19.5N-79W)

IOH 72 Hr Outlook (1200Z Oct 25)...30% chance of tropical cyclone formation (just south of central Cuba near 21N-79W)

IOH 96 Hr Outlook (1200Z Oct 26)...30% chance of tropical cyclone formation (north coast of central Cuba near 22.5N-79W)

IOH 120 Hr Outlook (1200Z Oct 27)...40% chance of tropical cyclone formation (just west of Andros Island in the western Bahamas at 23.8N-79W)


AREA OF INTEREST #2...The vigorous tropical wave of low pressure from the eastern tropical Atlantic has moved briskly westward into the central tropical Atlantic under the influence of the strong surface ridge to the north...and within its thunderstorm activity there appears to be a spin on satellite animation that passed 7.5N-40W as of 1200Z earlier today. Because of this and its fast movement away from the westerly shear induced by the northeastern Atlantic upper vorticity...I have introduced this tropical wave as an area of interest for tropical development on this blog. Over the next 48 hours upper-level winds over the tropical wave may become increasingly conducive for some development as an expanding area of upper outflow develops in the wake of the weakening western Atlantic cut-off upper vortex (this weakening is expected as the cold core upper vortex remains cut-off from high latitude colder air). However by 72 hours...the upper vortex is forecast to be pushed southward toward the tropical wave as the warm western Caribbean upper ridge expands from the thunderstorm latent heat release tied to the disturbance in area of interest #1...thus I drop odds of development back to 0% by that time. The forecast position of the upper vortex by that time should shield the southern Lesser Antilles and northeast coast of Venezuela from any heavy weather tied to this tropical wave by pushing the thunderstorms to the east of the wave axis...thus I do not mention these land areas in relation to this wave on the home page bulletins of this site.

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

IOH 24 Hr Outlook (1200Z Oct 23)...10% chance of tropical cyclone formation (central tropical Atlantic near 8N-48W)

IOH 48 Hr Outlook (1200Z Oct 24)...20% chance of tropical cyclone formation (central tropical Atlantic near 9N-56W)

IOH 72 Hr Outlook (1200Z Oct 25)...0% chance of tropical cyclone formation (northeast coast of Venezuela near 10N-61W)


...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 Hurricane Epsilon...passes east of Bermuda at 24 hours...accelerates rapidly into the open North Atlantic and reaches 58N-34W by 126 hours as a very intense and large remnant frontal cyclone. For area of interest #1...northeastern lobe of broad low pressure consolidates at a location between Florida and the western Bahamas at 84 hours....possible weak tropical cyclone formation suggested by 120 hours as consolidated circulation reaches 29N-73.5W. For area of interest #2...organizes into a low pressure spin at 9.5N-51W at 48 hours...weakens back to a tropical wave near 57.5W longitude by 66 hours.


0000Z ECMWF Model Run...For Hurricane Epsilon...passes east of Bermuda at 24 hours...accelerates rapidly into the open North Atlantic and merges with another frontal cyclone by 120 hours. For area of interest #1...northeastern lobe of broad low pressure consolidates as a sharp surface trough of low pressure over the southeast Florida coast at 96 hours....however no tropical cyclone formation suggested in the long range. For area of interest #2...no tropical cyclone formation shown.


0600Z GFS Model Run... For Hurricane Epsilon...passes east of Bermuda at 18 hours...accelerates rapidly into the open North Atlantic and merges with another frontal cyclone by 102 hours. For area of interest #1...northeastern lobe of broad low pressure consolidates as a surface trough of low pressure spanning from south Florida to the western Atlantic by 84 hours...east end of surface trough develops into a compact tropical cyclone southwest of Bermuda near 30N-67.5W at 102 hours...tropical cyclone shown drifting northward to 31N-67W by 126 hours. For area of interest #2...no tropical cyclone formation shown.


0600Z NAVGEM Model Run...For Hurricane Epsilon...passes east of Bermuda at 24 hours...accelerates rapidly into the open North Atlantic and merges with another frontal cyclone by 108 hours. For area of interest #1...broad low pressure consolidates just south of western Cuba at 66 hours...the consolidated circulation elongates into a surface trough that spans from western Cuba to the western Atlantic by 108 hours...no tropical cyclone formation shown along the surface trough in the long range. For area of interest #2...no tropical cyclone formation shown.

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