*******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 NOVEMBER 2 2021 3:45 AM EDT...
The Atlantic Hurricane Season remains active with Wanda acquiring fully tropical character in the open central Atlantic and two additional areas of Interest being monitored for tropical development. See area of interest and Wanda sections below for more information.
Elsewhere… in the wake of Area of Interest #1… upper-level winds in the southern Caribbean Sea will remain divergent in the split flow between the south side of the western Caribbean upper ridge and eastern Caribbean upper vorticity. And in a few days as the upper vorticity dissipates while remaining cut-off from high-latitude cold air… the upper ridge in the Caribbean is forecast to expand which will provide an area of low shear and upper outflow. Some model runs hint that another tropical low pressure could form in the southern Caribbean after Area of Interest #1 exits the region… either with the support of the split flow upper divergence and/or with the support of the expanding Caribbean upper ridge. Therefore additional monitoring for tropical activity in the southern Caribbean may be needed in the days ahead.
TROPICAL STORM WANDA…More recent satellite image of Tropical Storm Wanda… taken at 0400Z:
As forecast… Wanda has been undergoing a cyclonic loop around the south side of its parent upper vortex… which has caused the direction of heading to be southwest…south… and now east. Meanwhile a solid wall of surface ridging to the north and east is expected to soon dampen the eastward progress of Wanda and force a north turn. Also aiding in the north turn is the approaching western Atlantic upper trough which will be near Wanda by 24+ hours. By 72 hours… an east lean in the north track is likely as the current North American upper vortex shifts east toward the north Atlantic and Wanda as a stronger upper trough capable of pushing the storm more east.
The structure and intensity forecast has been more challenging. After seeming to shed its tropical character yesterday while showing weaker and more scattered thunderstorms… due to the warming of the overhead upper vortex which decreased the instability… Wanda has developed a new circular thunderstorm shield. This is probably explained by the fact that Wanda in its recent eastward swing in track has reached the east side of the upper vortex where upper divergence is present… which has probably counteracted the decreased instability. As of 5 PM EDT on Monday… the NHC upgraded Wanda from subtropical to fully tropical status. Although there is a lack of cirrus warm core outflow on the edge of the thunderstorm shield as of this writing… the NHC cited the consolidation of the wind field (from satellite scans of surface winds) to a smaller area near the center as evidence of a now fully tropical storm (subtropical systems often have a wider area of winds away from the center… fully tropical systems have the strongest wind close to the center).
Given that upper divergence will continue over Wanda as the west Atlantic upper trough approaches in an amplified state… and that Wanda has done well with the existing upper divergence… I have bumped up the short-term intensity forecast to indicate possible strengthening to 60 mph max sustained winds in the next 24 hours. By 48 hours Wanda will be nearing the even cooler 20 deg C sea surface temp isotherm… and I lower the intensity forecast as I anticipate Wanda losing thunderstorm intensity due to the upper trough not being that cold (200 mb heights well above 1200 dekameters)… even with the aid of the upper trough’s divergence. By 72 hours I project Wanda to lose tropical characteristics while reaching cold water temps in the mid-teens of deg C… and as the upper vortex from North America approaches as a strong upper trough and overspreads Wanda with a surface cold front.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Nov 2)… 45 mph maximum sustained wind tropical storm centered at 34.5N-41.6W
IOH 24 Hr Forecast (0000Z Nov 3)…60 mph maximum sustained wind tropical storm centered at 37.5N-40W
IOH 48 Hr Forecast (0000Z Nov 4)…50 mph maximum sustained wind tropical storm centered at 41.5N-40W
IOH 72 Hr Forecast (0000Z Nov 5)… Remnant non-tropical frontal cyclone centered at 47.5N-37.5W
AREA OF INTEREST #1… The southern Caribbean tropical low pressure that formed from the tail end of a surface front has continued to be defined by occasional thunderstorm banding features on its south and west sides and an area of cyclonic turning in satellite animation. The tropical low pressure has been aided by the outflow of an ongoing upper ridge in the western Caribbean. The upper flow is also split between the south side of this upper ridge and south side of upper vorticity located in the eastern Caribbean… with the split flow upper divergence also aiding the tropical low. The tropical low has little time over water to develop further as a surface ridge building over the central US is expected to begin steering it west into Nicaragua and Costa Rica. Also going against development is the recent decline in the thunderstorm activity seen in the more recent satellite frames. Therefore I have dropped tropical cyclone development odds to 0%… and plan this to be my final statement on this area of interest on this blog unless it continues to be mentioned in the NHC outlook at the time of my next update.
It should be noted that locally heavy rains are possible in Nicaragua and Costa Rica over the next day or so as the tropical low crosses through the region. It is also possible that the tropical low afterwards reaches the eastern Pacific and develops there. This site is dedicated for Atlantic tropical activity… visit the NHC site hurricanes.gov (hurricanes dot gov) and refer to the eastern Pacific tropical weather outlook product for more information.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Nov 3)… 0% chance of tropical cyclone formation (Costa Rica/Nicaragua border near 11N-83.5W)
AREA OF INTEREST #2… The tropical low pressure in the eastern tropical Atlantic continues its northwest march toward the surface ridge weakness associated with Tropical Storm Wanda. As such the tropical low has left the low shear haven of the upper ridge in the region and is now beneath a belt of upper southwesterly shearing winds located ahead of the upper vortex associated with Wanda. The shear is displacing the thunderstorm activity to the east of the tropical low’s center… and tropical cyclone formation here is no longer expected. This is my final statement on this area of interest on this blog.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 24 Hr Outlook (0000Z Nov 3)… 0% chance of tropical cyclone formation (eastern tropical Atlantic near 19N-36W)
...COMPUTER MODEL SUMMARY...
Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)
1200Z CMC Model Run...
**For Tropical Storm Wanda…moves northeast and reaches 44N-28W at 120 hours as a non-tropical remnant frontal low
**For area of interest #1…no development shown
**For area of interest #2… no development shown
1200Z ECMWF Model Run...
** For Tropical Storm Wanda…moves northeast to 42N-39.5W at 72 hours as a potentially stronger Tropical Storm… turns south-southeast and reaches 36.5N-38.5W by 120 hours
**For area of interest #1…no development shown
**For area of interest #2… no development shown
1800Z GFS Model Run...
** For Tropical Storm Wanda…moves northeast into the British Isles by 120 hours as a non-tropical remnant frontal low
**For area of interest #1…no development shown
**For area of interest #2… no development shown
**Additional southern Caribbean tropical low develops near 11.5N-81.5W at 69 hours… becomes a possible tropical depression near 12.5N-82W at 96 hours… drifts south toward western Panama while weakening into a remnant low thru 126 hours
1200Z NAVGEM Model Run...
**For Tropical Storm Wanda…moves northeast to the southeast coast of Iceland by 120 hours as a rapidly intensifying remnant non-tropical frontal cyclone
**For area of interest #1…no development shown
**For area of interest #2… no development shown