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 #170

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


...WEDNESDAY NOVEMBER 4 2020 12:45 PM EDT...

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


TROPICAL STORM ETA...While continuing westward across northern Nicaragua since last evening and through this morning...Eta has weakened from a hurricane to an inland tropical storm (60 mph maximum sustained winds as of 7 AM EDT...and 50 mph by 10 AM EDT). The center of circulation is now reaching the border with Honduras...and should continue into southern Honduras while remaining pushed around the southeastern United States surface ridge. My short-term track forecast points are shifted west due to the current position of Eta which is further west given that Eta has moved a little faster to the west once it made landfall yesterday.


Models for the most part agree that Eta's westward track inland will remain slow...and then reverse on a northeast track back over western Caribbean water. This is due to a cut-off upper trough over the southeastern United States left behind by the upper trough now moving into the northwest Atlantic...to be re-enforced by the current upper vorticity over the southwestern US as that vorticity later slides eastward. This cut-off upper trough’s eastern divergence zone is lowering surface pressures to the southeast of the southeast US surface ridge and to the northeast of Eta...with this low pressure field expected to draw Eta back northeastward instead of allowing Eta to continue west around the surface ridge. Therefore my forecast remains extended thru 5 days to track what will be the remnant low of Eta...in preparation for issuing probability outlooks on the remnants of Eta once Eta weakens to a remnant low after landfall. I forecast a slow westward drift of Eta's remnant low thru 24 to 36 hours as Eta rounds the south side of the southeastern US surface ridge while the surface low pressure field to the northeast slows its progress around the ridge. After that time my forecast turns Eta northeastward into the western Caribbean Sea...as this is when the cut-off upper trough and resulting surface low pressure field intensifies due to the arrival of the energy from the southwestern US. My updated forecast continues to show the remnant low of Eta bending more sharply eastward in track around the south side of the strengthening suface low pressure field which could very well become its own tropical/subtropical disturbance to the north of Eta. This is also why I held off on explicitly showing tropical cyclone reformation in my forecast unlike the NHC does...in case we end up in a scenario where Eta's remnant and seperate subtropical/tropical disturbance to the north end up competing with each other for low-level inflow/upper outflow. The 0600Z GFS model run from this morning showed dueling surface centers in the western Caribbean and southeastern Gulf of Mexico...which echoes this idea. The ECMWF and CMC runs which turn Eta northward earlier than my forecast have Eta becoming the dominant feature while lining up with the divergence maximum of the cut-off upper trough...but I see no reason for an early northward turn as the cut-off upper trough will not strengthen until the arrival of the energy from the southwestern US.


The heaviest rainfall has shifted to offshore bands well northeast of the center...and also bands to the northwest of the center that have potential to spread onshore into Honduras...El Salvador...Guatemala...Belize...and the Yucatan peninsula of southeastern Mexico where flash flooding is possible over the next couple of days as Eta continues to move slowly. A later round of heavy rainfall is likely across the Cayman Islands...Cuba...the Bahamas...and Florida peninsula as Eta's remnants become entangled with the forecast strengthening cut-off upper trough...and intersts here should monitor this situation carefully as Eta could regenerate into a tropical cyclone in this interaction...or alternatively a second subtropical/tropical system could emerge to the north of Eta if Eta does not line up with the divergence maximum of the cut-off upper trough.

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

0 Hr Position (1200Z Nov 4)...50 mph maximum sustained wind tropical storm centered over northern Nicaragua and just south of the Honduras border at 13.9N-85.2W

IOH 24 Hr Forecast (1200Z Nov 5)...Remnant low pressure centered over southern Honduras at 13.9N-87.5W

IOH 48 Hr Forecast (1200Z Nov 6)...Remnant low pressure centered over the Honduras/El Salvador/Guatemala border at 14.5N-89.5W

IOH 72 Hr Forecast (1200Z Nov 7)...Remnant low pressure centered over southern Belize 16N-89W

IOH 96 Hr Forecast (1200Z Nov 8)...Remnant low pressure centered over the western Caribbean Sea at 18N-84W

IOH 120 Hr Forecast (1200Z Nov 9)...Remnant low pressure centered just east of the Cayman Islands and just west of southern Cuba at 20N-79W


...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 Tropical Storm Eta...weakens to an inland remnant low while crossing the central Nicaragua/Honduras border at 18 hours...regenerates into a tropical storm centered at 17.5N-86.5W at 72 hours...passes just north of the Cayman Islands at 96 hours...tropical storm makes landfall across central Cuba at 102 hours...tropical storm curves northward toward southern Florida peninsula by 126 hours.


0000Z ECMWF Model Run...For Tropical Storm Eta...weakens to a remnant low over Honduras between by 24 hours...remnant low lifts northward from Honduras and into the western Caribbean Sea by 72 hours...accelerates northeastward and re-strengthens quickly into a tropical cyclone at a location just south of western Cuba at 96 hours...after passing over western Cuba intensifies into a strong tropical cyclone between Cuba and Florida at 120 hours.


0600Z GFS Model Run...For Tropical Storm Eta...weakens to an inland remnant low while reaching eastern Pacific coast of El Salvador at 18 hours...remnant low lifts northward into western Caribbean Sea from Honduras by 54 hours...remnant low broadens into two centers (one offshore of Honduras and another over the Cayman Islands) by 72 hours...two centers merge into one broad center over the Cayman Islands at 96 hours...broad low pressure elongates into two centers (one over eastern Cuba and another over the southeastern Gulf of Mexico) by 114 hours.


0600Z NAVGEM Model Run...For Tropical Storm Eta...weakens to an inland remnant low reaching Pacific coast of El Salvador at 18 hours. Elsewhere...surface trough of low pressure extending northeast of Eta's remnant low develops into a tropical cyclone near 17.5N-86.5W at 60 hours...strengthening tropical cyclone accelerates northeas and passes just north of the Cayman Islands by 90 hours...passes over central Cuba by 102 hours..quickly intensifies into a strong hurricane while passing over the western Bahamas at 120 hours.

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