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 #125

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


...SATURDAY SEPTEMBER 19 2020 7:45 PM EDT...

Satellite Image from 2300Z (red indicates tropical cyclone or remnants of tropical cyclone...with V marking Vicky...T marking Teddy...W marking Wilfred..B marking Beta. Green indicates an area of interest in the National Hurricane Center Tropical Weather Outlook. Yellow indicates an area of interest not in the National Hurricane Center Tropical Weather Outlook.):

See Hurricane Teddy...Tropical Storm Beta...and Tropical Storm Wilfred...sections below for all three currently active tropical cyclones in the Atlantic basin. See area of interest sections below for multiple disturbances being monitored for tropical or subtropical cyclone formation...one of which is the remnant circulation of Hurricane Paulette currently located just southwest of the Azores.

Note that the forecasts for Teddy and Beta were completed earlier in the day and have a 1200Z timestamp...while the forecasts for the other systems were completed recently with 1800Z timestamps.

MAJOR HURRICANE TEDDY...In the last day Teddy has weakened further to a still dangerous category 3 hurricane due to an eye wall replacement cycle. The hurricane has been moving northwestward while steered by cut-off upper vorticity in the western Atlantic located north of the Caribbean islands. As of 11 AM EDT the National Hurricane Center stated that the eye wall replacement is nearing completion...and as of this afternoon there is evidence of a new large eye popping open on satellite...so I forecast Teddy to re-strengthen into a lower end category 4 hurricane in the next 24 hours.

The biggest concern with Teddy is how it will affect Bermuda not long after Paulette already struck the island. As a powerful hurricane coupled to upper-level steering...at some point Teddy will be recurved northward in track due to the approach of the large upper trough currently over eastern North America. My forecast track is nudged northeastward due to Teddy’s current position....so if there is any good news Teddy will be a little further away from Bermuda as it turns northward. However the updated forecast is only a small change....so Bermuda will still see coastal storm surge along with some potentially damaging tropical storm force winds caused by the western rain bands of Teddy by Monday....I recommend interests here to continue preparing for these impacts. I forecast weakening to a minimal category 3 by 48 hours due to cooler waters that were upwelled by Paulette that Teddy would be passing over and increasing westerly shear as the large upper trough from the west approaches. Between 48 and 72 hours...the northerly surface flow on the west side of Teddy will amplify the 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. This mechanism will 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 category 1 hurricane force by 96 hours. With Teddy initially being a powerful 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 also reach the northeastern Caribbean Islands...the Bahamas...United States east coast...and Atlantic Canada coast over the next few days. The track by 96 hours will be influenced by another upper trough to pivot across North America...which in today’s 0600Z GFS model guidance is 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 my updated longer range track is shifted eastward as the slightly less amplified upper trough does not pull Teddy as far to the west. I recommend interests in eastern Maine...New Brunswick...Nova Scotia...Prince Edward Island...and Newfoundland to start 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 19)...120 mph maximum sustained wind major hurricane centered at 26N-59W

IOH 24 Hr Forecast (1200Z Sep 20)...130 mph maximum sustained wind major hurricane centered southeast of Bermuda at 29.5N-62.5W

IOH 48 Hr Forecast (1200Z Sep 21)...115 mph maximum sustained wind major hurricane centered just east of Bermuda at 31.5N-62.5W

IOH 72 Hr Forecast (1200Z Sep 22)...95 mph maximum sustained wind hurricane centered in the northwestern Atlantic at 38N-61W

IOH 96 Hr Forecast (1200Z Sep 23)...75 mph maximum sustained wind non-tropical remnant gale centered over eastern Nova Scotia at 45.5N-61W

TROPICAL STORM BETA...Beta has begun to turn westward under the influence of the central United States surface ridge building under the western convergence zone of the large upper trough over eastern North America. However the west motion is expected to be slow as the western convergence zone of the southwestern lobe of the upper trough will extend the central United States surface ridge southwestward in the next 24 hours...with the southwestern lobe of the ridge blocking west progress. Also Beta is strong and hence tall enough to be slowed by the upper southwesterly flow ahead of the upper trough. I have returned to showing a slower motion relative to special update #124A from early this morning as Beta’s strong thunderstorm activity has dwindled to only smaller circular flares near the center...thus there is less thunderstorm latent heat release output and it will take longer for Beta to weaken the south part of the cold upper trough and its blocking effects. As the south part of the upper trough dissipates after 24 hours upon which time its blocking effects fade away...I forecast a slightly faster west track into the southern Texas coast by 48 hours. A second upper trough to pass over North America will be too far north to play a role with Beta...which leaves the question of how Beta interacts with a third upper trough to move into the southwestern US. Because Beta will take longer to reach the coast...it won’t weaken as much from land interaction before this third upper trough hits it in my new forecast track...so now my updated forecast track agrees with the idea Beta will be strong/tall enough to be turned slowly northeastward by the third trough and jammed against the central Unites States surface ridge...resulting in a slow motion along the Texas and toward the southwest Louisiana coast from 48 to 120 hours.

Given that Beta is still expected to weaken the south side of the current upper trough in the region as noted in the previous paragraph....wind shear will lessen and thus I still forecast intensification to category 2 hurricane strength before landfall at 48 hours. A shortwave orbiting around the main body of the upper trough to move into the southwest US should induce a burst of shear by 72 hours...so I forecast Beta to be knocked down to weak tropical storm status by then despite the center being on the coast. Once the shortwave passes...I slow the weakening rate as the shear relaxes (but does not disappear). Also Beta could become supported by the eastern divergence zone of the upper trough’s main body...especially as it nears by 120 hours and tries to push Beta a little faster...another reason I show a slower weakening rate. Interests along the Texas coast should be preparing for tropical storm and possible hurricane force conditions (damaging winds...coastal storm surge...and heavy rainfall with flooding potential)...and when shopping during preparation to also frequently hand sanitize and wear a mask to reduce your risk of contracting the COVID-19 virus amid the outbreak in the region. Although there is some uncertainty in the exact track of this system...weather conditions could deteriorate as early as Sunday night. Think of a hotel or family/friend residence if you live along a vulnerable section of coastline...as you may have to relocate for example if storm surge becomes severe...as a public storm shelter may not be as ideal to controlling your exposure to COVID-19. Interests further north along the southwest Louisiana coast are under tropical storm advisories and should also be preparing as it appears more likely Beta will take a slow and erratic track into the area. The slow track will become a problem for severe rainfall flooding along the Texas and southwest Louisiana coasts and areas inland....especially if Beta develops strong thunderstorm complexes supported by the divergence zone of the upper trough to approach from the southwestern US. The wind and storm surge threat at this time appears greater for the southern Texas coast as wind shear will likely keep Beta weaker as it moves further north.

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

0 Hr Position (1200Z Sep 19)...60 mph maximum sustained wind tropical storm centered in the western Gulf of Mexico at 26.6N-92.6W

IOH 24 Hr Forecast (1200Z Sep 20)...75 mph maximum sustained wind hurricane centered in the western Gulf of Mexico at 26.8N-94W

IOH 48 Hr Forecast (1200Z Sep 21)...100 mph maximum sustained wind hurricane centered just offshore of the southern Texas coast at 26.8N-97W

IOH 72 Hr Forecast (1200Z Sep 22)...50 mph maximum sustained wind tropical storm centered over the eastern Texas coast at 28N-96W

IOH 96 Hr Forecast (1200Z Sep 23)...45 mph maximum sustained wind tropical storm centered over the eastern Texas coast at 28.2N-95.8W

IOH 120 Hr Forecast (1200Z Sep 23)...40 mph maximum sustained wind tropical storm centered just west of the Texas/Louisiana border at 29.5N-94.8W

TROPICAL STORM WILFRED...Not much to change with the forecast for this weak tropical storm. Wilfred will weaken from shear induced by cut-off upper vorticity that lies just to the northwest...which will get pushed southward into Wilfred by expanding warm upper ridging in the central and north Atlantic re-enforced by Teddy's thunderstorm latent heat release and also later on by the warm southerly flow on the east side of Teddy after Teddy transitions to non-tropical. This warm upper ridging will also push a chunk of the upper vortex associated with Paulette's remnant cyclone southward which will re-enforce the shearing upper vorticity. Weakening is shown after 24 hours as Wilfred moves closer to the shearing upper vorticity. A northward angle in the westward track is underway as Wilfred is strong/tall enough to be dragged by the upper vortex. Even though Wilfred will become more shallow as it weakens later on...there will be a surface ridge weakness to the northwest courtesy of Hurricane Teddy for Wilfred to continue its northwest direction. On a final note...my updated track forecast is once again nudged northward from my previous as Wilfred's center fix is slightly north of my previous forecast.

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

0 Hr Position (1800Z Sep 19)...40 mph maximum sustained wind tropical storm centered in the tropical Atlantic at 14N-39.2W

IOH 24 Hr Forecast (1800Z Sep 20)...40 mph maximum sustained wind tropical storm centered in the tropical Atlantic at 16N-42.5W

IOH 72 Hr Forecast (1800Z Sep 21)...Remnant low pressure centered in the tropical Atlantic at 18N-45.5W

AREA OF INTEREST #1 (REMNANTS OF PAULETTE)...What was Hurricane Paulette remains a post mature non tropical low pressure slowly weakening beneath its parent upper vortex. Paulette and upper vortex are moving southward away from the western Azores islands in the northerly flow setting up on the east side of amplifying upper ridging to the west. The upper vortex by in the middle of the forecast period is forecast to become stretched southwest-to-northeast by the strength of the upstream upper ridging to be 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 leaves Paulette to stall beneath the stretched upper vorticity axis. The currently forecast stall location is in warm 26 deg C sea surface temperatures...and so I have slightly bumped my odds of subtropical cyclone formation from Paulette's remnant upward to 60% as Paulette is already producing a circular clump of showers in its northeast quadrant and it has not yet made it to the 26 deg C waters. Odds are trimmed donward with time as Paulette will continue to weaken with time under the cut-off upper vorticity if it does not develop into a subtropical cyclone early on....and by late in the forecast period the upper vorticity and Paulette will be pushed southeastward toward cooler waters by the upper ridging to the west according to the 0600Z GFS model run.

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

IOH 24 Hr Outlook (1800Z Sep 20)...60% chance of subtropical cyclone formation (eastern Atlantic near 33N-30W)

IOH 48 Hr Outlook (1800Z Sep 21)...60% chance of subtropical cyclone formation (eastern Atlantic near 33N-30W)

IOH 72 Hr Outlook (1800Z Sep 22)...50% chance of subtropical cyclone formation (eastern Atlantic near 32.5N-30W)

IOH 96 Hr Outlook (1800Z Sep 23)...10% chance of subtropical cyclone formation (west of the Canary Islands near 31N-25W)

IOH 120 Hr Outlook (1800Z Sep 24)...0% chance of subtropical cyclone formation (just west of the southern Canary Islands near 27.5N-22.5W)

AREA OF INTEREST #2....The tropical wave of low pressure that recently exited western Africa remains in the National Hurricane Center tropical weather outlook. So far the tropical wave is disorganized....with the offshore thunderstorm acitvity weakening and activity over far Western Africa not yet showing signs of organization. The two separate areas of activity are separated by dry Saharan air. Given the amount of dry saharan air entangled with this wave I still give a 0% chance of tropical cyclone formation from it at this time. This is my planned final statement on this wave as the National Hurricane Center has also lowered odds to 0%...unless this wave shows signs of organization later.

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

IOH 24 Hr Outlook (1800Z Sep 20)...0% chance of tropical cyclone formation (eastern tropcial Alantic near 12.5N-23W)

...COMPUTER MODEL SUMMARY...

Temporarily cancelled to avoid further delays in completing this post.

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