MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #27
*******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.**********
...TUESDAY JUNE 9 2020 2:00 PM EDT...
Tropical Depression Cristobal weakens to a remnant inland tropical low pressure centered over northeast Missouri...heading into Wisconsin and the western Great Lakes region. See remnants of Cristobal section below for additional details. Also see area of interest section below on the potential for subtropical cyclone development east of Bermuda over the next few days.
REMNANTS OF CRISTOBAL...Southerly surface flow on the west side of the surface ridge that has moved into the Atlantic from the northeast United States...and also out ahead of the broad frontal low pressure area across the central United States...supported by the upper divergence zone of the vigorous upper trough located over the western United States...continues to channel the remnant tropical low pressure of Cristobal northward toward Wisconsin and the western Great Lakes region. Evidence for the current tropical structure of the remnant low presusre include a well-defined swirl of showers and thunderstorms near the center...in addition to warm core upper outflow supporting Cristobal supplied by the longwave upper ridge passing overhead. In the next 24 hours...the remnats of Cristobal will align with the eastern upper divergence maximum of the approaching 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 over the central United States will end up as a second lobe of low pressure orbiting eastward around the south side of Cristobal's remnant circulation while also intensifying under the support of the upper trough....therefore on the home page of this site there are plenty of states/Candian provnices being mentioned for possible wind impacts for tomorrow and into Thursday. This is my final statement on Cristobal on this blog as it is no longer a tropical cyclone (30+ mph max sustained wind depression/storm).
AREA OF INTEREST #1...The upper trough from eastern Canada that has recently amplified southward into the northwestern Atlantic supports two broad surface frontal low pressures along its surface cold front thanks to its eastern upper divergence zone...one on the east coast of Newfoundland...and a second brand new one located well southeast of Bermuda near 30N-58W. Its the second new feature southeast of Bermuda that is being monitored for possible acquisiton of tropical characteristics which could later make it transition into a subtropical cyclone...especially as the strong upper ridge over central North America cuts-off the south part of the upper trough into a cold core upper vortex that would keep wind shear low and help with instability for thunderstorms as the water temps are below 26 deg C. Evidence that the new surface frontal low is broad and not yet consolidated is shown on visible satellite imagery which seems to depict a faint cloud swirl west of the main one at 30N-59W. Based on the latest model runs...the updated outlook below shows the surface frontal low drifting northeast from its current position to the vicnity of 32.5N-55W over the next 1 to 2 days...and this makes sense based on the latest GFS model run of upper winds which shows the upper divergence maximum on the east side of the forecast upper vortex at this location. Water temperatures at this locaton are 22 deg C...and the upper vortex at 200 mb is forecast to measure in the mid-1210s of dekameters in height. Although I would like to see a cooler upper vortex (lower than mid-1210s) for subtropical development at 22 deg C waters...showers and thunderstorms are currently in a well-organized band on the east side of the current main swirl...which is enough for me to bump my odds of subtropical cyclone development up from 10% to now 20%...which still keeps the odds on the low side due to my low confidence in the thermodynamic picture. My slight rise in odds also has to do with the latest NAVGEM and ECMWF models that show the surface frontal low developing a more consoldiated circulation needed for subtropical cyclone status. I drop odds of development back to 0% by 72 hours as the models all taken together suggest that the surface frontal low pressure will have weakened due to the lack of upper divergence at the core of the upper vortex. My forecast positions show a stall at 32.5N-55W between 24 and 48 hours...with some westward drifting by 72 hours based on the foercast postions of the upper vortex in the 1200Z GFS. 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 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 quickly becoming 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 (1200Z Jun 10)...20% chance of subtropical cyclone formation (east of Bermuda near 32.5N-55W)
IOH 48 Hr Outlook (1200Z Jun 11)...20% chance of subtropical cyclone formation (east of Bermuda near 32.5N-55W)
IOH 72 Hr Outlook (1200Z Jun 12)...0% chance of subtropical cyclone formation (east of Bermuda near 32.5N-57.5W)
...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 remnants of Cristobal...has circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 30 hours. For area of interest #1...drifts surface low pressure northeastward from current position (30N-58W) to 35N-55W by 48 hours...weakens to a surface trough by 54 hours.
0000Z ECMWF Model Run...For remnants of Cristobal...has circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone between 24 and 48 hours. For area of interest #1..drifts surface low pressure northeastward from current position (30N-58W) to 32.5N-55W by 48 hours at which point the surface low is at its maximum intensity...weakens to a surface trough by 96 hours as it drifts westward to 60W.
1200Z GFS Model Run...For remnants of Cristobal...has circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 24 hours. For area of interest #1...drifts surface low pressure northeastward from current position (30N-58W) to 33N-55W by 30 hours...weakens to a westward-drifting surface trough at same location by 48 hours.
0600Z NAVGEM Model Run...For remnants of Cristobal...has circulation crossing western Great Lakes region and entering eastern Canada as a large intensifying frontal cyclone at 24 hours. For area of interest #1...drifts surface low pressure northeastward from current position (30N-58W) to 32.5N-55W by 24 hours at which pont the surface low is at its maximum intensity...weakens to a westward-drifting surface trough around 57W by 66 hours.