MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #153
*******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 4 2021 1:44 AM EDT...
Satellite image as of 0410Z. 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 3):
GFS Model Upper-Level Winds 1800Z (Nov 3):
See Wanda section below for an update on the tropical storm 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. So far there are no signs of a western or southern Caribbean disturbance developing with the support of the upper ridge’s outflow.
And finally in approximately four days...the currently amplified upper trough over the Texas/New Mexico border is forecast to be heading into the western Atlantic and drive the formation of a rapidly intensifying surface frontal cyclone offshore of the United States east coast with its eastern divergence zone. 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 as hinted by the 1800Z NAVGEM model run… there may be enough instability to allow the surface cyclone to acquire tropical characteristics in approximately six days from today. If model trends move toward a more amplified upper trough/vortex...will consider adding an area of interest for tropical development in regards to this situation. Regardless...another round of coastal sea swells for the east coast of North America is likely by next week...similar to what was seen with the precursor surface cyclone that eventually became Wanda.
TROPICAL STORM WANDA...Persistent Wanda is continuing north in response to a solid wall of surface ridging to the east and upper trough to the west. Despite being over water temps in the low 20s of deg C and under upper-level air that is not very cold (200 mb heights above 1200 dekameters)… Wanda continues to hang on to tropical characteristics while featuring a core of broken and weak bands of showers and thunderstorms around its center. This activity and Wanda’s long stretch of having 50 mph maximum sustained winds is likely attributed to the supportive eastern divergence zone of the upper trough in the region.
A shortwave trough impulse is expected to ejecting from the current eastern North American longwave upper trough in the next 48 hours. However models continue to agree that the shortwave trough will approach too slowly to continue the north track of Wanda… as the currently approaching western Atlantic surface ridge which has also ejected from North America beats it to the punch and shifts Wanda back south. Once the longwave upper trough and a northwest Atlantic surface frontal cyclone it produces finally approaches and erodes the ridge… Wanda will finally be shot northeast into the high latitudes at 96+ hours. The only model that took exception to this was the NAVGEM model run… which as mentioned in the intro section of this post develops a subtropical cyclone offshore of the southeast US in the days ahead. The NAVGEM shows a warm deep-layer ridge developing west of Wanda in the warm southerly flow on the east side of the subtropical cyclone… which keeps Wanda drifting south through 96+ hours. Given the NAVGEM is not the most reliable model… I am taking its solution with a grain of salt at this time.
My updated forecast for Wanda is now extended through day 5 (120 hours) as my forecast track is adjusted south in the short-term to reflect the ongoing strong model consensus that the Storm will not be dragged further north by the soon to arrive shortwave upper trough. This will prolong Wanda’s tropical status with the new track keeping Wanda over waters in the low 20s of deg C instead of cooler waters… which is why I have extended the forecast. Over the next 72 hours Wanda will remain in the same conditions that have kept it going as a 50 mph wind tropical storm (see first paragraph of this Wanda discussion for details on these conditions) … and so my intensity forecast is kept steady-state through that time. By 96 hours… the longwave North American upper trough will approach while retaining 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. By 120 hours Wanda is expected to have reached much cooler waters… and as a result is expected to finally lose tropical character by that timeframe.
The short-term south turn is expected to 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 (0000Z Nov 4)… 50 mph maximum sustained wind tropical storm centered at 40.6N-39.6W
IOH 24 Hr Forecast (0000Z Nov 5)… 50 mph maximum sustained wind tropical storm centered at 42.5N-39W
IOH 48 Hr Forecast (0000Z Nov 6)… 50 mph maximum sustained wind tropical storm centered at 38N-37.5W
IOH 72 Hr Forecast (0000Z Nov 7)… 50 mph maximum sustained wind tropical storm centered at 37.5N-37.5W
IOH 96 Hr Forecast (0000Z Nov 8)… 60 mph maximum sustained wind tropical storm centered at 42.5N-32.5W
IOH 120 Hr Forecast (0000Z Nov 9)… Remnant non-tropical frontal cyclone centered at 50N-21W
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z (Nov 3) CMC Model Run...
**For Tropical Storm Wanda...moves north and reaches 42.5N-40W at 30 hours… turns south-southeast and reaches 37N-38W at 78 hours while weakening to a tropical depression… afterwards accelerates north-northeast and by 114 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)
1200Z (Nov 3) ECMWF Model Run...
**For Tropical Storm Wanda... moves north and reaches 42N-40W at 24 hours… turns south and reaches 37.5N-39W at 72 hours… afterwards accelerates north-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 3) GFS Model Run...
** For Tropical Storm Wanda... moves north and reaches 42N-40W at 24 hours… turns south-southeast and reaches 37N-37.5W at 75 hours… afterwards accelerates northeast and by 120 hours transitions into a non-tropical frontal low located at 48.5N-24W… along the 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 3) NAVGEM Model Run...
**For Tropical Storm Wanda... moves north and reaches 42N-38.5W at 24 hours… turns south and stalls near 32.5N-37.5W as a weaker tropical cyclone by 120 hours
**Rapidly intensifying surface frontal cyclone develops offshore of the southeast US coast at 84 hours with the support of amplifying upper trough that approaches from its current position over the Texas/New Mexico border…while overhead upper trough amplifies into an upper vortex the surface cyclone whirls southwest and becomes a strong subtropical Storm just offshore of the Carolinas at 138 hours