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 #22

*******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 JUNE 4 2020 11:21 AM EDT...

Tropical Storm Cristobal has recently been downgraded to a tropical depression while moving further inland into the Guatemala/Mexico border region...see Cristobal section below for additional details.


TROPICAL STORM CRISTOBAL (RECENTLY DOWNGRADED TO TROPICAL DEPRESSION)...My track forecast from yesterday remains spot-on...with the circulation of Cristobal tracking southeast further inland into the Guatemala/Mexico border while pulled in by the remainder of the broad low pressure area to the southeast that has been supported by the upper ridge/outflow persisting over Central America. Therefore my updated track forecast below is unchanged and simply a continuity of the previous one. The intensity of Cristobal is the only surprising thing...as the circulation has maintained tropical storm intensity after being centered inland for so long. However I am still maintaing my previous intensity forecast as Cristobal is finally looking quiet less organized...particularly on colorized infrared schemes...in the latest satellite loops such that I believe it will still weaken to a remnant low pressure in the short-term...then re-emerge over the Gulf of Mexico and redevelop in the longer term. It is conceivable that Cristobal completely loses its identity within the broader low pressure area to the southeast over the next 24 hours...with the broader low pressure area later lifting northward into the Gulf of Mexico and becoming a second seperate tropical cyclone. However in my forecasting...I am still assuming that this will be one long continuous tropical cyclone event retaining the name of Cristobal...with the assumption that Cristobal's current circulation keeps its identity. In addition even if Cristobal technically loses its entire identity within the broad low pressure area...I think the National Hurricane Center will err on the side of caution and try not to confuse the public by introducing another name to this storm...especially considering that this storm system is already near land area and has made headlines with its rainfall flooding...and consider the broad low pressure area as a continuation of Cristobal.


Meanwhile...upper vorticity energy offshore of Mexico and California...and another piece of energy currently south of Alaska...will merge into a highly amplified upper trough across the western Untied States during the forecast period. Even though these features have not yet merged...their eastern upper divergence zones are already producing a large area of low surface pressure over the western United States...with southerly warm air advection out ahead of the expansive surface low pressure field amplifying the longwave upper ridge that has been over western North America. This will cause the upper vorticity that has been over Texas and north Mexico...which has now arrived to a position just northwest of Cristobal...to also amplify into an upper vortex that covers the west half of the Gulf of Mexico. The eventual shift northward into the Gulf of Mexico will occurr as the broad low pressure system/remnants of Cristobal transitions into a feature supported by the eastern divergence zone of the upper vortex. A northward track will also be supported as the surface ridge over the southeastern United States is already being eroded by the eastern divergence zone of this upper vorticity. The Euro (ECMWF) has been aggressive in strengthening Cristobal over the Gulf of Mexico...and today's NAVGEM has joined the party. But I am maintaing an intensity forecast below hurricane force as I think it is less likely that Cristobal will be able to focus enough thunderstorm latent heat release to combat the negative effects of the cold upper vortex...especially considering that the storm is currently unraveling into a broader circulation over land and will need time to re-consolidate when it goes into the Gulf of Mexico. Another factor that supports a broader/weaker tropical cyclone is that the region of upper divergence on the east side of the upper vortex will be large...keeping the low surface pressures spread over a larger/broader area.


After landfall over southeastern Louisiana (just after 72 hours)...I support the idea of a northwestward swing in track as the current upper trough energy over southwestern Canada will dive south and amplify over the northeastern United States due to the highly amplified nature of the western 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 potentially add a west component to the storm track. Also in the upper layers the steering supports a west component as the longwave upper ridge will be shifting eastward to a position directly north of Cristobal. The eastward shift of the longwave ridge will be from the merger of the vigorous energy south of Alaska and offshore of California as they become a vigorous upper trough sliding into the western United States...with the current western US broad surface low pressure area supported by the eastern divergence zone of these pieces of energy likewise shifting eastward and driving warm air advection into the cold core western Gulf upper vortex. This should cause the upper vortex to fade around Cristobal's landfall time...the absence of the vortex making it easier for Cristobal to also lean west post-landfall. In the long range...well after 120 hours...the GFS and Euro (ECMWF) are increasingly suggesting that the remants of Cristobal could align with the eastern upper divergence maximum of the forecast strong western US upper trough...resulting in the remnant circulation possibly intensifying into an intense frontal cyclone that moves through the Great Lakes and southeastern Canada. If modeling continues to insist on this solution...may have to also be concerned about a wind impact over these regions.


Interests on the United States Gulf coast from Louisiana to the Florida panhandle should continue to monitor the progress of Cristobal for possible storm surge and wind impact...thinking about what preparations would be needed but not necessarily acting upon them till its clear what the state of Cristobal will be when it emerges into the Gulf of Mexico in a couple of days. In the immediate-term we remain concerned about the extreme flooding risk to southeastern Mexico and parts of Central America as Cristobal and the adjacent broad surface low pressure area will continue to linger in the area over the next day...see bulletins at the home page of this site for details.

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

0 Hr Position (1200Z Jun 4)...40 mph maximum susatained wind tropical storm centered over the northwestern Mexico/Guatemala border at 17.8N-91.2W

IOH 24 Hr Forecast (1200Z Jun 5)...Remnant low pressure centered over the southwestern Yucatan peninsula at 19N-89.5W

IOH 48 Hr Forecast (1200Z Jun 6)...35 mph maximum sustained wind tropical depression centered in the Gulf of Mexico at 24N-88.5W

IOH 72 Hr Forecast (1200Z Jun 7)...60 mph maximum sustained wind tropical storm centered just offshore of southeastern Louisiana at 29N-88W

IOH 96 Hr Forecast (1200Z Jun 8)...35 mph maximum sustained wind tropical depression centered over southwestern Mississippi at 31.5N-91W

IOH 120 Hr Forecast (1200Z Jun 9)...Remnant low pressure centered over southern Arkansas at 34N-93W


...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 Tropical Storm Cristobal...through 30 hours moves the circulation inland to the northwestern Guatemala/Mexico border where it loses its identity within broad low pressure area to the southeast...through 42 hours lifts broad low pressure area northward across west Yucatan coast while suggesting tropical cyclone formation (not clear if this is the remnants of Cristobal or a second seperate tropical cyclone). Has tropical cyclone shift northward across the Gulf of Mexico and reach waters just offshore of southeast Louisiana by 90 hours...then turns cyclone northwestward then northward into central inland Louisiana by 120 hours.


0000Z ECMWF Model Run...For Tropical Storm Cristobal...through 24 hours moves the circulation inland to the northwestern Guatemala/Mexico border where it loses its identity within broad low pressure area to the southeast...through 48 hours lifts broad low pressure area northward across west Yucatan coast while suggesting rapid tropical cyclone formation (not clear if this is the remnants of Cristobal or a second seperate tropical cyclone). Has tropical cyclone shift northward across the Gulf of Mexico and reach southeast Lousiana coast at 96 hours (suggests possibly strong tropical cyclone from 72 to 96 hours)...then turns cyclone northwestward inland into the northwest corner of Lousiana by 120 hours.

0600Z GFS Model Run...For Tropical Storm Cristobal...through 18 hours moves the circulation inland into northern Guatemala where it loses is identity within broad low pressure area to the southeast...through 30 hours lifts broad low pressure area northward across interior Yucatan peninsula...suggesting possible tropical cyclone formation on the north coast of the peninsula at 36 hours (not clear if this is the remnants of Cristobal or a second seperate tropical cyclone). Has tropical cyclone shift northward across the Gulf of Mexico and reach the southeast Lousiana coast at 90 hours...then accelerates the cyclone northwestward into the southeast corner of Oklahoma by 120 hours.


0600Z NAVGEM Model Run...For Tropical Storm Cristobal...through 24 has the circulation merge with the broad low pressure area to the southeast and then reach the east coast of the Yucatan peninsula at the Belize/Mexico border...through 42 hours lifts Cristobal north-northwest across the northeastern Yucatan peninsula while suggesting re-strengthening...then suggests possibly strong tropical cyclone while lifting Cristobal northward across the Gulf of Mexico thru landfall time over southeast Lousiana at 90 hours...drifts Cristobal northwestward into central inland Louisiana at 120 hours.

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