MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #154
*******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.**********
...FRIDAY NOVEMBER 5 2021 8:00 AM EDT...
Satellite image as of 0420Z. 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 1800Z (Nov 4):
GFS Model Upper-Level Winds 1800Z (Nov 4):
See Wanda section below for an update on the tropical storm located in the open north-central Atlantic. Elsewhere... the upper ridge in the western Caribbean is expanding as the upper vorticity that has been in the eastern Caribbean weakens while removing cut-off from high-latitude cold air. There are no signs of a western or southern Caribbean disturbance developing with the support of the upper ridge’s outflow… and development of one is not anticipated with model forecasts remaining silent in regards to future activity here.
And finally in approximately three days...the currently amplified southern US upper trough and western Gulf of Mexico frontal low pressure it is generating is forecast to be located just offshore of the eastern US. The frontal low is forecast to become a rapidly intensifying frontal cyclone beneath the strong upper divergence zone of the amplified upper trough. If the upper trough amplifies into a sufficiently cold upper vortex that keeps the surface cyclone on a more south track over mild/warmer waters… there may be enough instability to allow the surface cyclone to acquire tropical characteristics in approximately five days from today. At present… the model guidance has not trended toward forecasting an amplified upper trough/vortex. And regardless of acquisition of tropical character or not...expect the surface cyclone to generate coastal sea swells for the east coast of North America by late this weekend and/or early next week.
TROPICAL STORM WANDA...Two features are moving east toward Wanda this morning… a western Atlantic surface ridge and east Canada shortwave upper trough. It is clear that the surface ridge has begun to dictate the steering as Wanda has begun reversing to a southward track. Meanwhile the shortwave upper trough is driving a surface cold front into the northwest quadrant of Wanda. However the NHC is assuming Wanda is maintaining tropical characteristics as the western core of the storm continues to generate distinct curved shower and weak thunderstorm bands located at the south end of the frontal cloud band. Wanda’s tropical character is ongoing despite being over 20 deg C waters and under upper-level air that is not very cold (200 mb heights above 1200 dekameters). The shower and weak thunderstorm activity and Wanda’s long stretch of having 50 mph maximum sustained winds is likely attributed to the supportive eastern divergence zone of the central Atlantic upper trough in the region.
By 48+ hours… the current eastern North America longwave upper trough and a northwest Atlantic surface frontal cyclone it produces will finally approach and erode steering surface ridge… which will finally sling Wanda northeast into the high latitudes after spending the last several days in a twisting meandering path. Over the next 48 hours Wanda will remain in the same conditions that have kept it going as a 50 mph wind tropical storm (see prior paragraph for details on these conditions) … and so my intensity forecast is kept steady-state through that time. Between 48 and 72 hours… the approaching longwave North American upper trough will retain cold upper air temps and it’s amplified structure… which will increase the instability and upper divergence over Wanda while it remains over low-20 deg C waters. I project Wanda to strengthen in this environment. Once Wanda crosses the 20 deg C isotherm and reaches cooler waters in the teens of deg C by 72 hours… I anticipate Wanda will finally begin losing its tropical characteristics.
The short-term south turn that Wanda is starting now will bring Wanda closer to the Azores in the days ahead. This could result in coastal sea swells for the Azores by this weekend and/or early next week.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0600Z Nov 5)… 50 mph maximum sustained wind tropical storm centered at 41.8N-38W
IOH 24 Hr Forecast (0600Z Nov 6)… 50 mph maximum sustained wind tropical storm centered at 37.8N-37.5W
IOH 48 Hr Forecast (0600Z Nov 7)… 50 mph maximum sustained wind tropical storm centered at 37.5N-36W
IOH 72 Hr Forecast (0600Z Nov 8)… 60 mph maximum sustained wind tropical storm transitioning into a non-tropical frontal cyclone… centered at 45N-31W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Nov 4) CMC Model Run...
**For Tropical Storm Wanda...turns south-southeast and reaches 35.5N-37.5W at 66 hours… afterwards accelerates northeast and by 120 hours is located at 47N-26.5W as a non-tropical remnant frontal low
1200Z (Nov 4) ECMWF Model Run...
**For Tropical Storm Wanda... turns south and reaches 37N-39W at 48 hours… afterwards accelerates northeast and by 120 hours loses identity along cold front of northwestern Atlantic frontal cyclone (the frontal cyclone is supported by the current eastern North America upper trough as it later shifts toward the Atlantic)
1800Z (Nov 4) GFS Model Run...
** For Tropical Storm Wanda... turns south-southeast and reaches 37N-38W at 48 hours… afterwards accelerates northeast and by 99 hours loses identity along cold front of northwestern Atlantic frontal cyclone while nearing the British Isles (the frontal cyclone is supported by the current eastern North America upper trough as it later shifts toward the Atlantic)
1800Z (Nov 4) NAVGEM Model Run...
**For Tropical Storm Wanda... turns south-southeast and reaches 37N-38.5W at 48 hours while weakening to a remnant low… absorbed by cold front of northwest Atlantic frontal cyclone by 60 hours (the frontal cyclone is supported by the current eastern North America upper trough as it later shifts toward the Atlantic)