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 #127

*******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 SEPTEMBER 21 2020 12:28 PM EDT...

See Hurricane Teddy...Tropical Storm Beta...and remnants of Wilfred sections below for all three currently named tropical systems in the Atlantic basin. See area of interest sections below for two disturbances being monitored for tropical or subtropical cyclone formation...one of which is the remnant circulation of Hurricane Paulette currently located in the open eastern Atlantic Ocean.


HURRICANE TEDDY...While moving northward just to the southeast of Bermuda...Teddy has slightly weakend further to 100 mph maximum sustained winds...most probably due to slightly cooler 27 deg C waters upwelled by Hurricane Paulette several days ago as the incoming upper trough from eastern North America has yet to disrupt Teddy as the hurricane's cloud shield remains symmetric about the center this morning. However the southerly flow ahead of the upper trough has made Teddy turn northward on schedule such that the center will pass east of Bermuda later today...with the western rain bands of Teddy potentially brining tropical storm conditions to the island. In the next 24 hours...the northerly surface flow on the west side of Teddy will amplify the incoming cold core upper trough by pushing cold air southward...with increasing divergence on the east side of the amplifying upper trough in turn helping Teddy...thus the weakening rate for Teddy as the upper trough begins to disrupt the west side of the storm will be slow. This mechanism will also make Teddy increasingly less tropical...but with the forecast amplification of the upper trough there will likely be a tremendous amount of upper divergence on the east side of the upper trough such that we are faced with Teddy transitioning into a powerful non-tropical frontal cyclone at strong tropical storm force by 48 hours. With Teddy initially being a strong hurricane roaming the western Atlantic...and then becoming a large powerful non-tropical cyclone with winds becoming further widespread by a pressure gradient between Teddy and a strengthening surface ridge to be supported by the western convergence zone of the amplifying upper trough...expect sea swells and rip currents to continue reaching the northeastern Caribbean Islands...the Bahamas...United States east coast...and Atlantic Canada coast over the next couple of days. The track by 48 hours will be influenced by another upper trough currently pivoting across North America...which in today’s model guidance remains less amplified...and so when it phases with the amplified upper trough to be interacting with Teddy...it won’t cause Teddy’s trough to be as amplified. Therefore I still prefer a landfall point toward eastern Nova Scotia as the slightly less amplified upper trough will not pull Teddy as far to the west...and all of today's model runs agree with this idea. I recommend interests in eastern Maine...New Brunswick...Nova Scotia...Prince Edward Island...and Newfoundland to continue preparing for impacts from what will be the non-tropical remnant cyclone of Teddy...which will include damaging wind arriving by late Tuesday and Wednesday....the worst of which would be over Nova Scotia and Prince Edward Island if the current track forecast holds. Southerly and easterly onshore push of water on the east and north side of Teddy will cause coastal storm surge problems for parts of Nova Scotia...Prince Edward Island...Quebec...New Brunswick...and Newfoundland.

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

0 Hr Position (1200Z Sep 21)...100 mph maximum sustained wind hurricane centered just southeast of Bermuda at 30.5N-63W

IOH 24 Hr Forecast (1200Z Sep 22)...85 mph maximum sustained wind hurricane centered in the northwestern Atlantic at 37.5N-61.5W

IOH 48 Hr Forecast (1200Z Sep 23)...70 mph maximum sustained wind non-tropical remnant gale centered over eastern Nova Scotia at 45N-61.5W


TROPICAL STORM BETA...Beta’s slow westward track has accelerated enough to bring the center of circulation just offshore of Texas near the Matagorday Bay region...with the center likely coming ashore later today just east of the bay. After landfall...Beta will be strong/tall enough to be turned slowly northeastward by an upper trough to pivot into the southwestern United States...jamming Beta against the central and eastern United States surface ridge...resulting in a slow motion along the Texas coast and toward the southwest Louisiana coast after landfall. Given the current position of Beta which is nearly on par with my previous assessment...my updated track is the same as before and has the slow post-landfall northeastward motion commencing just inland from the coastline. The tropical storm has weakened since yesterday while trying to mix out the dry air that was created earlier over southern Texas in the western convergence zone of the eastern North American upper trough that has since left the area...and time is running out for Beta to strengthen as its center is near the coast. The forecast track not only increases land interaction in the next 24 hours...but also places Beta more into the shearing upper westerlies from the upper trough to pivot into the southwestern US...so I have lowered the intensity forecast due to Beta's current strength and forecast it to become a remnant low pressure by 24 hours.


Interests along the Texas and southwest Louisiana coast should have finished preparations by now for tropcial storm conditions (damaging winds...coastal storm surge...and heavy rainfall with flooding potential). Albeit the chances for damaging winds have gone down as Beta is on the weaker side of tropical storm force...and coastal storm surge will slowly wind down as Beta weakens further. Don't let the current lack of thunderstorm intenisty in Beta's circulation fool you...there is still a severe rainfall flooding threat for southeast Texas and southern Louisiana in the coming days...especially if Beta's thunderstorms intensify in the divergence zone of the upper trough to approach from the southwestern US.

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

0 Hr Position (1200Z Sep 21)...50 mph maximum sustained wind tropical storm centered just offshore of Texas at 27.9N-95.7W

IOH 24 Hr Forecast (1200Z Sep 22)...40 mph maximum sustained wind tropical storm centered just inland from the eastern Texas coast at 29N-96W

IOH 48 Hr Forecast (1200Z Sep 23)...Remnant low pressure centered just inland and along the Texas/Louisiana border at 30.5N-94W


REMNANTS OF WILFRED...Tropical depression Wilfred has weakened to a remnant surface trough of low pressure while attacked by wind shear induced by upper vorticity in the central tropcial Atlantic. Just as we saw with Vicky’s remnant low pressure...I expect Wilfred’s remnant low pressure to also dissipate beneath the western convergence zone of the upper vorticity which will tend to keep surface pressures higher. This is my final statement on Wilfred on this blog as it is no longer a tropical cyclone.


AREA OF INTEREST #1 (REMNANTS OF PAULETTE)...What was Hurricane Paulette remains a post mature non tropical low pressure centered in the eastern Atlantic at 34N-30W slowly weakening beneath its parent upper vorticity...as evidenced by the central surface pressure of the circulation now rising to 1012 mb per the 0600Z NHC TAFB surface analysis. As the upper ridge axis to the west expands while re-enforced by Hurricane Teddy’s latent heat release...followed by warm air advection on the east side of Teddy when it becomes a remnant frontal cyclone...this will cause the upper vorticity and Paulette to shift eastward toward the general direction of the Canary Islands. The north fracture of the upper trough exiting eastern North America will also pass around the upper ridge axis and try to drive Paulette and its upper vorticity eastward. Water temperatures at Paulette's current location have cooled to below 26 deg C over the last few days...and reaching this water temperature is critical for Paulette to re-acquire tropical characteristics as the overhead upper vorticity is not cold enough to de-stablizie the atmosphere. Because Paulette has yet to become a subtropical cyclone...my odds of subtropical cyclone formation are now lowered to 40% for the next 24 hours as Paulette's circulation is continuing to weaken as noted above. This is however slightly higher than my previous outlook for September 22 which was at 30% as Paulette is producing some bands of shower activity in its north side despite the current thermodynamic picture. Odds are lowered to 0% by 48 hours as Paulette reaches even cooler waters in the vicnity of the Canary Islands. For the Canary Islands...coastal sea swells are possible if Paulette retains or regains strength by re-acquiring tropical characteristics and developing a warm core upper outflow that sustains it low surface pressure...or alternatively if Paulette is able to engage with the eastern divergence zone of the upper vorticity and hold strength by non-tropical means. And if this occurs...gusty winds and heavy rain is possible by late Tuesday or Wednesday for Madeira as the circulation is more likely to track here rather than toward the southern Canary Islands.

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

IOH 24 Hr Outlook (1200Z Sep 22)...40% chance of subtropical cyclone formation (eastern Atlantic near 32.5N-27.5W)

IOH 48 Hr Outlook (1200Z Sep 23)...0% chance of subtropical cyclone formation (just south of Madeira Island and north of the southern Canary Islands near 32N-17W)


AREA OF INTEREST #2....A swirl of low pressure over south Florida...and along the tail end of the western Atlantic cold front associated with the upper trough exiting eastern North America has lost its identity just offshore of southwestern Florida overnight. However the National Hurricane Center is still monitoring the tail end of the front as it will shift southward into Cuba over the next couple of days due to the strength of the surface ridge over the central and easstern United States. As Beta transitions into a less tropical system in the vicinity of southern Louisiana in the coming days...it will push the warmest air in the Gulf of Mexico southeastward toward Cuba...resulting in a warm upper ridge directy over the decaying front over Cuba such that the decaying front might evolve into a tropical disturbance with thunderstorms aided by the outflow and low shear of the upper ridge. After 48 hours...whatever disturbance develops over Cuba would shift northwestward across the eastern Gulf of Mexico around the southwest side of the eastern United States surface ridge. For the next five days...I have peak odds of development only at a very low 10% due to lack of computer model suport and as there is no organized or concentrated thunderstorm activity along the front at this time. I have lower odds of 5% by 96+ hours as the tropical disturbance...if it develops at all...would enter shearing upper southwesterly winds on the northwest side of the Cuba upper ridge.

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

IOH 24 Hr Outlook (1200Z Sep 22)...0% chance of tropical cyclone formation (just north of Cuba near 23.5N-79.5W)

IOH 48 Hr Outlook (1200Z Sep 23)...5% chance of tropical cyclone formation (over Cuba near 22.5N-80W)

IOH 72 Hr Outlook (1200Z Sep 24)...10% chance of tropical cyclone formation (southeastern Gulf of Mexico offshore of western Cuba near 24N-84W)

IOH 96 Hr Outlook (1200Z Sep 25)...5% chance of tropical cyclone formation (eastern Gulf of Mexico near 26.5N-86W)

IOH 120 Hr Oulook (1200Z Sep 26)...5% chance of tropical cyclone formation (offshore of southeastern Louisiana near 28N-87.5W)


...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 Teddy...makes landfall over eastern Nova Scotia in 66 hours. For Tropical Storm Beta...makes landfall at Matagorda Bay Texas in 24 hours...drifts slowly eastward back over the northwestern Gulf of Mexico and southern Louisiana as a broadening low pressure that loses its identity between 96 and 120 hours. For area of interest #1 (remnants of Paulette)...dissipates just north of the Canary Islands in 72 hours. For area of interest #2...no tropical cyclone formation shown.


0000Z ECMWF Model Run....For Hurricane Teddy...makes landfall over eastern Nova Scotia just before 72 hours. For Tropical Storm Beta...makes landfall at Matagorda Bay Texas in 24 hours...while stationary at landfall point weakens to a remnant low by 48 hours...remnant low drifts slowly eastward back over the northwestern Gulf of Mexico and southern Louisiana as a broadening low pressure that loses its identity just after 96 hours. For area of interest #1 (remnants of Paulette)...dissipates just north of the Canary Islands just after 72 hours. For area of interest #2...no tropical cyclone formation shown.


0600Z GFS Model Run...For Hurricane Teddy...makes landfall over eastern Nova Scotia in 60 hours. For Tropical Storm Beta...makes landfall at Matagorda Bay Texas in 12 hours...drifts slowly eastward back over the northwestern Gulf of Mexico and southern Louisiana as a broadening low pressure that loses its identity at 96 hours. For area of interest #1 (remnants of Paulette)...dissipates just northeast of the Canary Islands at 96 hours. For area of interest #2...no tropical cyclone formation shown.


0600Z NAVGEM Model Run...For Hurricane Teddy...makes landfall over eastern Nova Scotia in 60 hours. For Tropical Storm Beta...makes landfall just norhteast of Matagorda Bay Texas in 24 hours...remnant low pressure gradually accelerates northeastward into the Ohio Valley region by 120 hours where it loses its identity. For area of interest #1 (remnants of Paulette)...weakens to a surface trough well west of the Canary Islands near 30N-27.5W at 60 hours...remnant surface trough shifts westward around the northeast Atlanic surface ridge and arrives to 28.5N-36.5W at 120 hours. For area of interest #2...no tropical cyclone formation shown.

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