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 #182

Updated: Nov 17

*******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 NOVEMBER 16 2020 6:35 PM EDT...

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


MAJOR HURRICANE IOTA...Iota has moved into the west side of the Caribbean upper ridge cell whose upper outflow helped in the hurricane's explosive intensification to category 5 over the last 12 hours. Rather than the hurricane experiencing symmetrical outflow like it had yesterday and early today beneath the center of the upper ridge cell...the outflow has become restricted to the southeast and enhanced to the northwest due to the anticyclonic flow of the upper ridge cell...apparently resulting in an end to Iota's intensification with the central pressure no longer falling and instead rising from 917 mb as of 10 AM EDT to 919 mb as of 4 PM EDT. Even if the hurricane weakens to a top end category 4 over the next few hours before landfall...that kind of a hurricane is still catastrophic. My forecast track points for Iota are shifted westward as the hurricane has moved faster to the west around the south side of the steering southern US surface ridge. Apparently the ridge is not far south enough to slow the steering and bend the track as far southward as previously thought...so my updated forecast shows a faster westward track and a reduced southward angle.


Interests in Nicaragua and Honduras should have finished preparations for Iota as weather conditions in northeastern Nicaragua and eastern Honduras are already deteriorating. Catastrophic wind damage and coastal storm surge are imminent near the landfall area...with wind damage extending inland into north-central Nicaragua and central Honduras as Iota will take some time to weaken from its very high intensity after landfall. Even though Iota is moving a little faster as mentioned in the previous paragraph...the mudslide and flooding potential from heavy rain remains high as the forecast track has not sped up enough to drastically shortern the forecast heavy rainfall periods...and extends to El Salvador. Because the hurricane will not track as far to the south after making landfall...the heavy rainfall threat to Costa Rica has greatly reduced.

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

0 Hr Position (1800Z Nov 16)...160 mph maximum sustained wind major hurricane centered offshore of northeastern Nicaragua at 13.6N-82.7W

IOH 24 Hr Forecast (1800Z Nov 17)..60 mph maximum sustained wind tropical storm centered over northern Nicaragua just south of the Honduras border at 13.2N-85W

IOH 48 Hr Forecast (1800Z Nov 18)...Remnant low pressure centered just inland from the eastern Pacific coast along Nicaragua/Honduras border at 13N-87.5W


AREA OF INTEREST #1...The eastern divergence zone of the cut-off upper vortex northeast of the Lesser Antilles continues producing showers and thunderstorms...but the associated surface trough of low pressure has become less defined over the last 24 hours. The outlook below assumes a surface trough of low pressure to emerge from this activity will soon begin to track northwest around the north side of the upper vortex and toward a surface ridge weakness from the frontal cyclone to exit eastern North America. A southwest track is likely from 72 to 96 hours as the surface ridge weakness closes and a strong surface ridge over the southern US approaches. Tropical cyclone formation is unlikely for much of the next 5 days as this disturbance will likely be exposed to some southwesterly shear to be generated by the upper trough tied to the frontal cyclone that will exit eastern North America. The shear is expected to persist through 96 hours due to upper vorticity to be left behind by the upper trough. By 120 hours...the GFS...NAVGEM...and ECMWF models indicate that the upper vorticity is likely to amplify into a cut-off upper vortex in the vicinity of the western Bahamas (due to an adjacent amplified warm eastern US upper ridge ahead of a mid-latitude front)...which would increase the upper divergence and reduce the shear over this disturbance. Those models show a defined surface low pressure forming in the long range in response...and we could be dealing with an organizing subtropical or tropical disturbance just east or northeast of the Bahamas just after 5 days. I raise the odds of development to a very low 5% by 120 hours as models agree on a defined surface low pressure after 5 days.

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

IOH 24 Hr Outlook (1800Z Nov 17)...0% chance of tropical cyclone formation (central Atlantic near 22.5N-60W)

IOH 48 Hr Outlook (1800Z Nov 18)...0% chance of tropical cyclone formation (western Atlantic near 23.5N-65W)

IOH 72 Hr Outlook (1800Z Nov 19)...0% chance of tropical cyclone formation (western Atlantic near 22N-67.5W)

IOH 96 Hr Outlook (1800Z Nov 20)...0% chance of tropical cyclone formation (just east of the eastern Bahamas near 21N-70W)

IOH 120 Hr Outlook (1800Z Nov 21)...5% chance of tropical cyclone formation (just east of the eastern Bahamas near 22N-70W)


AREA OF INTEREST #2...The GFS model has continues to forecast development from the tropical wave of low pressure currently crossing 67.5W longitude in the eastern Caribbean Sea as of 1800Z...as the wave later enters the central Caribbean Sea in the wake of Iota and potentially taps into favorable upper winds in a Caribbean upper ridge cell to persist. I forecast 0% odds of development in the next 24 hours as the tropical wave has been void of thunderstorms due to exposure to upper convergence on the southwest side of the upper vortex tied to area of interest #1. I continue with low longer term odds of development at 20% as the GFS model has been the sole model championing development. The westward track of the tropical wave has slowed down due to the surface ridge weakness induced by the current eastern North America frontal cyclone. Some increase in forward speed and south angle is expected with the track by 48+ hours as the strong surface ridge over the southern US approaches. This forecast track brings this tropical wave close to Nicaragua by day 4...but since the wave is currently inactive thunderstorm-wise and since there is low computer model support for development at the present time it is hard to gage how much significant impact could occur if any. Therefore have not included this tropical 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 (1800Z Nov 17)...0% chance of tropical cyclone formation (central Caribbean Sea near 15N-70W)

IOH 48 Hr Outlook (1800Z Nov 18)...10% chance of tropical cyclone formation (central Caribbean Sea near 15N-74W)

IOH 72 Hr Outlook (1800Z Nov 19)...15% chance of tropical cyclone formation (central Caribbean Sea near 14N-78W)

IOH 96 Hr Outlook (1800Z Nov 20)...20% chance of tropical cyclone formation (just offshore of northeast Nicaragua near 13.5N-82W)

IOH 120 Hr Outlook (1800Z Nov 21)...0% chance of tropical cyclone formation (western Nicaragua near 13N-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 Major Hurricane Iota...makes landfall just south of the Nicaragua/Honduras border at 18 hours...weakens to a remnant low over central Honduras at 42 hours. For area of interest #1...no tropical cyclone formation shown. For area of interest #2...no tropical cyclone formation.


1200Z ECMWF Model Run...For Major Hurricane Iota...makes landfall just south of the Nicargua/Honduras border between 12 and 24 hours...weakens to a remnant low over western Honduras by 48 hours. For area of interest #1...evolves into an elongated western Atlantic suface low pressure in the western Atlantic near 28N-72.5W by 168 hours. For area of interest #2...tropical wave evolves into a weak low pressure area in the central Caribbean Sea near 12.5N-80W at 144 hours...but no tropical cyclone formation suggested in the long range.


1200Z GFS Model Run...For Major Hurricane Iota...makes landfall just south of the Nicargua/Honduras border at 18 hours...weakens to a remnant low over central Honduras at 36 hours. For area of interest #1...evolves into a weak low pressure in the western Atlantic at 28N-73.5W by 162 hours. For area of interest #2...tropical wave organizes into a central Caribbean tropical low pressure at 12.5N-80W at 72 hours...compact tropical cyclone formation suggested at 11.5N-81.5W at 96 hours...compact tropical cyclone crosses northern Costa Rica by 114 hours...tropical cyclone reaches the eastern Pacific and re-strengthens in the long range.


1200Z NAVGEM Model Run...For Major Hurricane Iota...makes landfall just south of the Nicaragua/Honduras border at 12 hours...weakens to a remnant low over southwestern Honduras by 36 hours. For area of interest #1...surface low pressure consolidates over the western Bahamas by 156 hours. For area of interest #2...no tropical cyclone formation.

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