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 #167

*******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.**********  

...SUNDAY NOVEMBER 1 2020 4:00 PM EDT...

See Tropical Storm Eta section below for the only active tropical cyclone in the Atlantic basin.


TROPICAL STORM ETA...Since last night...tropical depression twenty-nine in the central Caribbean Sea became Tropical Storm Eta...making the 2020 Atlantic Hurricane Season tie with 2005 for having the most number of subtropical and tropical storms on record (although 2005 did not reach the name Eta...it also had 28 storms as one of them was not declared operationally...but instead during a post-season analysis). The tropical storm through the morning hours did not intensify beyond 40 mph maximum sustained winds while it lacked a core of strong thunderstorms...but this has changed as of this afternoon with such a core becoming established...with outer bands of activity also strengthening...and with max sustained winds increasing to 50 mph as of 1800Z (1 PM EDT). Additional strengthening to a hurricane before landfall in northeastern Nicaragua is expected as the western Atlantic string of upper vorticity that sheared Eta’s precursor disturbance days ago has broken up into one string off to the east in the eastern Atlantic...and another string in the north-central Caribbean in the vicinity of Cuba...with an expanding anticyclone with low shear and upper outflow favoring Eta overhead. Forecast track points below have been adjusted to the south and west due to the current position of Eta. The tropical storm is expected to slow down and turn west-southwest in response to the strong central US surface ridge to the northwest building beneath the current eastern North America upper trough’s western convergence zone. Regarding intensity...given that Eta is compact...rapid intensity fluctuations will be possible as not as much surface pressure falls need to occur to bring winds up given the tight pressure gradient between the center and outside of small systems...and also as the thunderstorm latent heat release and resulting warm core upper outflow needed for surface pressure falls will be concentrated instead of spread out as we see in larger sprawling systems that take time to strengthen in their early stages. As a result...I forecast brisk strengthening till this system makes landfall in northeastern Nicaragua just after 24 hours. I currently anticipate a high chance of Eta becoming a category 2 hurricane just after 24 hours and just before landfall.


There has been some indications in multiple model runs over the last few days that Eta will slow down to a stall as it or after it makes landfall...and then reverse on a north or northeast track back over water and reform or hang on as a tropical cyclone. It appears this could happen as the current eastern North America upper trough leaves behind a cut-off trough in the vicinity of Florida in a couple of days or so...to be re-enforced by the current upper vorticity offshore of California as that vorticity later slides eastward into the southeast US. This cut-off upper trough’s eastern divergence zone is forecast to lower surface pressures to the southeast of the blocking central US surface ridge and to the northeast of Eta...with this low pressure field potentially drawing Eta or its remnants back northeastward instead of allowing Eta to continue southwest around the surface ridge. Given that Eta’s track is trending southwest of previous forecasts...I prefer the ECMWF idea of burying Eta southwest well inland as a remnant low pressure...so for now my forecast ends at day 3 with possible plans to initiate a new western Caribbean area of interest in future updates should the ECMWF and my current forecast verify...with the area of interest likely to be triggered by the eastern divergence zone of the forecast cut-off upper trough.


Interests in eastern Nicaragua and eastern Honduras should be finishing preparations for potentially severe damaging winds and coastal storm surge to arrive late tomorrow. Severe rainfall flooding is a possibility across all of Nicaragua and Honduras with the potential slow down in the track after landfall as discussed in the previous paragraph.


Update as of 4 PM EDT...Eta strengthens further to 65 mph max sustained winds with a 992 mb central pressure...on its way to becoming a hurricane in the next few hours.

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

0 Hr Position (1800Z Nov 1)...50 mph maximum sustained wind tropical storm centered well south of Jamaica at 14.9N-78.1W

IOH 24 Hr Forecast (1800Z Nov 2)...95 mph maximum sustained wind hurricane centered just offshore of northern Nicaragua at 14.2N-82.5W

IOH 48 Hr Forecast (1800Z Nov 3)...35 mph maximum sustained wind tropical depression centered over north-central Nicaragua at 13N-85W

IOH 72 Hr Forecast (1800Z Nov 4)...Remnant low pressure centered over western Nicaragua at 12.5N-86W


...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 Tropical Storm Eta...while intensifying makes landfall on north coast of Nicaragua at 48 hours...weakens to a remnant low over eastern Honduras at 78 hours...remnant low moves west-northwest inland and reaches Guatemala/Mexico border by 120 hours...in long range remnant low lifts northward into Gulf of Mexico with possible reformation into a tropical cyclone.


0000Z ECMWF Model Run...For Tropical Storm Eta...while intensifying makes landfall on north coast of Nicaragua between 48 and 72 hours...weakens to a remnant low over eastern Honduras at 78 hours...weakens to a remnant low over the western Nicaragua/Honduras border by 96 hours. Elsewhere...northeast part of Eta’s remnant low pressure field regenerates into a northeast moving tropical cyclone in the western Caribbean Sea after 144 hours.


1200Z GFS Model Run...For Tropical Storm Eta...while intensifying as a strong hurricane makes landfall on north coast of Nicaragua at 48 hours...while stationary near the coast weakens to a tropical storm thru 72 hours...weakens further to a remnant low while moving inland across eastern Honduras and reaches north Honduras coast at 96 hours...in long range remnant low lifts northeastward into western Caribbean Sea where regeneration into a tropical cyclone is suggested.


0600Z NAVGEM Model Run...For Tropical Storm Eta...while intensifying into an intense hurricane makes landfall on northeast coast of  Honduras at 66 hours...drifts westward while weakening to a tropical storm along the north Honduras coast...by 120 hours re-strengthens while lifting northwest across the western Caribbean Sea and toward a second landfall at the Belize/Mexico border.

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