BIRDSEYE VIEW POSTS

Since 2012 on the now retired Weather Underground 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 at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at IOHurricanes@outlook.com 

 
 
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MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #160

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


...THURSDAY NOVEMBER 11 2021 9:45 AM EDT...

Satellite image as of 1240Z. Areas of interest circled in yellow are not mentioned in the NHC tropical weather outlook. Areas circled in a green dashed line are in the NHC 5-day tropical weather outlook. Areas circled in a solid green are in the NHC 2-day tropical weather outlook:

NHC TAFB Surface Analysis 0000Z:

GFS Model Upper-Level Winds 0000Z:

The current non-tropical surface cyclone in the open central Atlantic is running out of time to acquire tropical characteristics… as it will be absorbed by a rapidly developing cyclone to its immediate northwest in the next 24 hours. See area of interest #1 section below for more details.


Elsewhere... the current upper trough entering the northwest Atlantic from southeastern Canada is slated to amplify as it heads toward the northeast Atlantic over the next few days. The south part of the trough is likely to become a cut-off cold-core upper vortex that glides south into mild eastern Atlantic water temps... potentially resulting in enough instability to allow acquisition of tropical characteristics for any surface low pressure to be generated by the vortex. Therefore the east Atlantic region may require monitoring for signs of subtropical development by next week… see area of interest #2 section below for details.

AREA OF INTEREST #1...A surface frontal cyclone has moved briskly eastward into the open central Atlantic from the western Atlantic while moving in tandem with its parent upper trough. The shower and thunderstorm activity of the cyclone has become increasingly concentrated in a thick band just north of the swirl. This band is associated with the incoming frontal zone driven by an amplifying upper trough fast-approaching from southeastern Canada… and as a result the surface cyclone is becoming less tropical. The frontal zone features a new and rapidly intensifying frontal low just to the west supported by the divergence zone of the Canadian amplifying upper trough… and in the next 24 hours is expected to swing the surface cyclone north into the far North Atlantic cool waters while also absorbing the surface cyclone as it becomes the dominant weather feature in the region. With this outlook… the surface cyclone has ran out of time to acquire tropical characteristics… and this is my final statement on this cyclone on this blog.

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

IOH 24 Hr Outlook (0600Z Nov 12)... 0% chance of subtropical cyclone formation (northeast Atlantic near 50N-37.5W)


AREA OF INTEREST #2…The current upper trough entering the northwest Atlantic from southeastern Canada is producing a pair of surface frontal lows… one that has departed mainland Canada and is now passing southeast of Greenland… and a new one that is located offshore of Newfoundland and Nova Scotia. The new frontal low is forecast to explosively intensify and absorb area of interest #1 in the next 24 hours. This intensification is to be driven by the amplification of the upper trough which results in an increase in upper divergence over the frontal low… with the trough’s amplification caused by adjacent amplification of adjacent warm core deep-layered ridging to the west in the warm sector of the vigorous frontal system currently over the central US. The amplification of the upper trough is expected to be continuous in the days ahead… with the deep-layered ridging expected to cut-off the south part of the upper trough into a cold core upper vortex over or near the Azores at 72+ hours. Models have converged on possible subtropical development in association with this upper vortex as it glides south toward mild waters while steered by the deep-layered ridging… and I have declared an area of interest for this situation as a result.


The eastern divergence zone of the upper vortex is expected to trigger a surface frontal low over or near the Azores in 72 hours. As the surface low and upper vortex move in tandem to the south through 96 hours… the system is likely to have enough instability to generate thunderstorms and possible tropical characteristics from the combination of water temps in the mid-20s of deg C and cold upper air temps associated with the upper vortex (200 mb heights below 1200 dekameters). I have already assigned 30% odds of subtropical development due to this favorable thermodynamic profile… however these odds are on the low side as the model convergence on this solution has only been recent and I am waiting to see if the models hold on this solution before issuing higher odds. At 120 hours… the deep-layered ridge is forecast to have its upper layer to the west… and surface layer (supported by the eastern convergence zone of the upper layer) passing to the north. This will result in the upper vortex continuing a south drift while the surface layer of the ridge pushes the surface low on a more southwest angle… resulting in the surface low entering the west side of the upper vortex where northerly wind shear is likely. Thus I trim down subtropical development odds to 20% during that timeframe.

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

IOH 24 Hr Outlook (0600Z Nov 12)... 0% chance of subtropical cyclone formation (north Atlantic near 42N-40W)

IOH 48 Hr Outlook (0600Z Nov 13)… 0% chance of subtropical cyclone formation (northwest of the Azores near 42N-30W)

IOH 72 Hr Outlook (0600Z Nov 14)… 0% chance of subtropical cyclone formation (over the Azores near 38N-28W)

IOH 96 Hr Outlook (0600Z Nov 15)… 30% chance of subtropical cyclone formation (eastern Atlantic near 34N-28W)

IOH 120 Hr Outlook (0600Z Nov 16)… 20% chance of subtropical cyclone formation (eastern Atlantic near 32N-32W)


…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 Area of Interest #1......at 18+ hours becomes absorbed by much larger and rapidly intensifying frontal cyclone and its amplifying upper trough that ejects from southeastern Canada.

**Area of Interest #2… For upper trough that ejects from southeast Canada… south part becomes cut-off by deep-layered ridge to the west as a vortex… surface frontal low forms with support from the divergence zone of the vortex at a location just south of the Azores at 84 hours… frontal low becomes a subtropical storm at 33N-32.5W at 108 hours… weakens to a subtropical depression near 32N-36.5W at 120 hours.

0000Z ECMWF Model Run...

**For Area of Interest #1... at 24+ hours becomes absorbed by much larger and rapidly intensifying frontal cyclone and its amplifying upper trough that ejects from southeastern Canada

**Area of Interest #2…For upper trough that ejects from southeast Canada… south part becomes cut-off by deep-layered ridge to the west as a vortex… surface frontal low forms with support from the divergence zone of the vortex at a location just northeast of the Azores at 72 hours… surface frontal low and upper vortex track south-southwest and reaches 32N-32.5W at 120 hours while potentially acquiring tropical characteristics.


0000Z GFS Model Run...

**For Area of Interest #1... at 21+ hours becomes absorbed by much larger and rapidly intensifying frontal cyclone and its amplifying upper trough that ejects from southeastern Canada

**Area of Interest #2…For upper trough that ejects from southeast Canada… south part becomes cut-off by deep-layered ridge to the west as a vortex… surface frontal low forms with support from the divergence zone of the vortex at a location over the eastern Azores at 72 hours…surface frontal low and upper vortex track south-southwest and reaches 32.5N-32W at 120 hours while potentially acquiring tropical characteristics.


0000Z NAVGEM Model Run...

**For Area of Interest #1... at 18+ hours begins merging with much larger and rapidly intensifying frontal cyclone and its amplifying upper trough that ejects from southeastern Canada...in the process becoming the dominant of the two in the merger...the remnant frontal cyclone loses identity between Greenland and Iceland at 102 hours as the current frontal system over the central US approaches

**Area of Interest #2…For upper trough that ejects from southeast Canada… south part becomes cut-off by deep-layered ridge to the west as a vortex… surface frontal low forms with support from the divergence zone of the vortex at 32.5N-36.5W at 102 hours… weakens to a surface trough at 30N-31W at 120 hours

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