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 #25

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


...SUNDAY JUNE 7 2020 5:40 PM EDT...


Tropical Storm Cristobal accelerates northward into the United States Gulf coast...see Cristobal section below for details. See area of interest section below on the potential for subtropical cyclone development east of Bermuda over the next few days


TROPICAL STORM CRISTOBAL...Southerly surface flow out ahead of the broad frontal low pressure area over the western United States...supported by the upper divergence zone of the vigorous upper trough also located over the western United States...continues to channel Tropical Storm Cristobal northward...with the center of circulation currently making landfall over southeastern Louisiana. The warm southerly surface flow steering Cristobal has caused the unfavorable cool core western Gulf upper vorticity to dissipate over the northwestern Gulf of Mexico...with the remainder of the upper vorticity still lingering over the southwestern Gulf but away from Cristobal. This has allowed some warm anticyclonic outflow directly over Cristobal's center as the longwave upper ridge approaching from central North America has attempted to bridge with the upper ridging currently covering the east half of Cristobal. While Cristobal had postively responded to this more favorable upper air pattern while developing pockets of thunderstorms over and just around the core of the circulation...which has this morning reorganized into a ragged ring around the center...the thunderstorm activity did not become widespread enough to strengthen Cristobal above 50 mph max sustained winds. Water vapor satellite shows an axis of rather dry and sinking air over eastern Texas as the Central America longwave upper ridge approaching from the northwest appears to be dumping upper northerly flow against the northwest side of Cristobal's outflow...with the two flows colliding into an upper convergent pattern promoting this dry sinking air. It is likely then this dry air has been infiltrating Cristobal and preventing the formation of widespread thunderstorms. Therefore my updated intensity forecast thus shows a slightly weaker tropical depression centered over northeastern Louisiana at 24 hours.


After the center makes landfall over southeastern Louisiana shortly...a northwest lean in track is expected as the current upper trough energy over eastern Canada will dive south and amplify over the northeastern United States due to the highly amplified nature of the central North America longwave upper ridge. This will position the western convergence zone of the upper trough and resulting surface ridge to the northeast of Cristobal...close enough for the ridge to add a west component to the storm track. Also in the upper layers the steering supports a west component as the central North America longwave upper ridge will soon pass directly north of Cristobal. Forecast track is the same as previous...except that I have slightly adjusted the 48-hour point further north due to the latest model consensus that moves Cristobal more rapidly north. Computer models are in unanimous agreement that the remants of Cristobal will align with the eastern upper divergence maximum of the western United States upper trough...resulting in the remnant circulation intensifying into a vigorous and possibly intense frontal cyclone that moves through the Great Lakes and into eastern Canada. Models also show that the remainder of the broad frontal low pressure area over the western United States will end up as a second lobe of low pressure orbiting eastward around the south side of Cristobal's remnant circulation duirng this time while also intensifying under the support of the upper trough....therefore on the home page of this site I have extended the wind impact in the Great Lakes region eastward to include all of Michigan instead of just the western part of the state. Impacts to the Great Lakes region on the United States and Canada side is likely in 3 days. For the shorter-term impacts going on due to the current landfall...also see bulletins on home page of this site.

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

0 Hr Position (1800Z Jun 7)...50 mph maximum sustained wind tropical storm making landfall on the southeast Louisiana coast at 28.8N-89.9W

IOH 24 Hr Forecast (1800Z Jun 8)...30 mph maximum sustained wind tropical depression centered over northeastern Louisiana at 32N-92W

IOH 48 Hr Forecast (1800Z Jun 9)...Remnant frontal low pressure centered over the northern Illinois/Missouri border at 39N-91W


AREA OF INTEREST #1...The National Hurricane Center in their 5-day tropical weather outlook continues to highlight the central tropical Atlantic to the east of Bermuda as an area of interest for subtropical development. This is response to continued computer model solutions that show a surface low pressure area developing in about 2 days in response to current upper trough over eastern Canada diving southward and amplifying into a cut-off upper vortex in the Atlantic along the east side of the upper ridge emerging from central North America...as the upper ridge later amplifies in the eastern warm air advection zone of what is expected to be the remnant frontal cyclone of Cristobal moving into the Great Lakes region and Ontario Canada. The cold temperatures of the forecast cut-off upper vortex may allow for subtropical development despite central Atlantic water temperatures of 22 deg C in the central Atlantic region. However at this time I have dropped odds of subtropical cyclone development to 5% for multiple reasons. First the models consensus taken together at 48 hours shows an elongated surface low pressure area instead of a consolidated circulation needed for subtropical cyclone formation. Second...today's 1200Z GFS model run shows the upper vortex becoming moreso streteched southwest-to-northeast in the 48 to 72 hour timeframe by the ridge approaching from central North America as it moves into the northwest Atlantic. This could keep the surface circulation elongated instead of consolidated. Third...even though the upper vortex is shown in the GFS to be circular again by 96 hours...its 200 mb height is forecast to be in the mid-1220s of dekameters...a warmer upper vortex than shown before...would like to see mid 1210-s or even 1200s for subtropical development at 22 deg C water temperatures. I drop the odds of development back down to 0% by 120 hours as the models all taken together suggest that the surface circualtion will have weakened due to the lack of upper divergence at the core of the upper vortex. My forecast positions show a slower track with some southwest drifting by 120 hours based on the foercast postions of the upper vortex in the 1200Z GFS...which shows the upper vortex at a more east position overall compared to yesterday and then drifts the upper vortex southwest at 120 hours. This steering will be caused by the upper ridge approaching from central North America as it enters the northwest Atlantic...during that time the ridge will have a southwest lobe directly west of this system such that the forward west/southwest progress of this system will be slow as the rest of the ridge to be located to the north tries to steer the system. Not mentioning any impacts to Bermuda on the home page bulletins of this site as the models taken together show this system either quickly becoming or staying weak during its lifecycle as it whirls into a position directly below the upper vortex where a lack of supportive divergence causes the weakening.

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

IOH 24 Hr Outlook (1800Z Jun 8)...0% chance of subtropical cyclone formation (east of Bermuda near 32.5N-61W)

IOH 48 Hr Outlook (1800Z Jun 9)...5% chance of subtropical cyclone formation (east of Bermuda near 32.5N-55W)

IOH 72 Hr Outlook (1800Z Jun 10)...5% chance of subtropical cyclone formation (east of Bermuda near 32.5N-57W)

IOH 96 Hr Outlook (1800Z Jun 11)...5% chance of subtropical cyclone formation (east of Bermuda near 32.5N-59W)

IOH 120 Hr Outlook (1800Z Jun 12)...0% chance of subtropical cyclone formation (southeast of Bermuda near 30.5N-62.5W)


...COMPUTER MODEL SUMMARY...

Source...Tropical Tidbits (https://www.tropicaltidbits.com/analysis/models/)


1200Z CMC Model Run...For Tropical Storm Cristobal...has remnant circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 72 hours. For area of interest #1...develops weak central Atlantic surface low at 35N-58W at 48 hours in response to current eastern Canada upper trough diving south and amplifying into the Atlantic...has surface low drift slowly west-southwestward and weakened into a surface trough over Bermuda at 108 hours.


1200Z ECMWF Model Run...For Tropical Storm Cristobal...has remnant circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 72 hours. For area of interest #1...develops elongated north-south surface low pressure circulation in the central Atlantic at 48 hours spanning from 34N-58W to 30N-58W in response to current eastern Canada upper trough diving south and amplifying into the Atlantic. By 72 hours has northern lobe at 34N-58W become the dominant center of circulation. Circulation shown to drift west-sothwestward and weakened into a surface trough over Bermuda at 120 hours.


1200Z GFS Model Run...For Tropical Storm Cristobal...has remnant circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 72 hours. For area of interest #1...develops weak central Atlantic surface low at 33N-57W at 48 hours in response to current eastern Canada upper trough diving south and amplifying into the Atlantic...has surface low drift slowly west-southwest and quickly weakens it into a surface trough east of Bermuda in the vicinity of 60W by 90 hours.


1200Z NAVGEM Model Run...For Tropical Storm Cristobal...has remnant circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 72 hours. For area of interest #1...develops weak surface trough of low pressure east and southeast of Bermuda in the vicnity of 60W around 60 hours in response to current eastern Canada upper trough diving south and amplifying into the Atlantic. Does not show a well-defined closed circulation developing along the surface trough through 120 hours.

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