MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #2A (Special Update)
*******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 MAY 20 2021 10:15 PM EDT...
Tropical disturbance forms in the western Gulf of Mexico...as of 8 PM EDT is being monitored by the National Hurricane Center (NHC) for signs of additional development. An upper trough from the central US...associated with a surface front that recently dissipated...has become stalled against the west side of the deep-layered ridge over the eastern US. The eastern divergence zone of the upper trough has produced showers and thunderstorms in the western Gulf of Mexico which have been able to organize beneath low shear and upper outflow under the southwest quadrant of the deep-layered ridge...into a rotating surface trough of low pressure as of this evening. The 1200Z cycle of the CMC and ECMWF have picked up on this feature while the GFS and NAVGEM showed no development. This new disturbance has been introduced into the NHC outlook perhaps from the usually conservative ECMWF showing some development.
On satellite animation...this disturbance is already moving NNW towards the general direction of the Texas coast under the steering influence of the eastern US deep-layer ridge. Therefore I assess the ECMWF...which keeps this system over southern 26+ deg C water for the next 24 hours....maybe inaccurate. Due to the current absence of thunderstorms near the center of rotation...I only forecast a very low 5% chance of tropical cyclone tonight...followed by a 0% chance of development by 24 hours once the current NNW motion of this disturbance moves it over water below 26 deg C. Unlike the disturbance currently east of Bermuda in which tropical development is likely over water below 26 deg C due to cold upper air temps....the upper air temps in the Gulf of Mexico are much warmer due to the deep-layered ridge and so 26+ deg C water temperatures are needed for development in this case. For more information on the disturbance east of Bermuda...refer to birdseye view post #2 on the home page of this site.
Should this system redevelop thunderstorms in the next 24 hours...heavy rainfall will become possible over southeast Texas.
******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********
IOH 12 Hr Outlook (0600Z May 21)...5% chance of tropical cyclone formation (western Gulf of Mexico near 26.2N-94.5W)
IOH 24 Hr Outlook (1800Z May 21)...0% chance of tropical cyclone formation (offshore of Texas near 28.5N-95W)