MY 2021 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #41A (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.**********
…UPDATE…TUESDAY JULY 6 2021 2:04 PM EDT…
Aircraft recon measures Elsa is now just below hurricane force with 70 mph max sustained winds. A hurricane warning is now in effect for the northwest Florida peninsula. See update written at 2 PM EDT below for more information on recent developments…which discusses the fact that Elsa could become a hurricane shortly.
…TUESDAY JULY 6 2021 2:00 PM EDT...
Satellite image of strengthening Tropical Storm Elsa as of 1706Z:
Early this morning as the center of Elsa emerged from Cuba…the thunderstorm activity on colorized infrared satellite suggested the tropical storm had become disorganized from southwesterly upper shearing winds being driven by upper vorticity over the northern Gulf of Mexico and southeastern US. However the storm was measured to re-strengthen to 60 mph max sustained winds regardless. As the center passed just west of the Florida Keys and now into the waters just offshore of the Florida peninsula west coast…a strong thunderstorm flare has persisted over and just east of the surface center with the cloud swirl signature of the surface center becoming more sharply defined in the most recent satellite pictures. This means that Elsa could actually be strengthening due to the divergent nature of the shearing upper winds…as divergence tends to occur on the east side of mid-latitude upper troughs and upper vorticity features. This was something hinted at in the 11 AM EDT advisory package from the NHC…as well as recent runs of the ECMWF and GFS model. And since 5 AM EDT today a Hurricane watch was posted for the northwest Florida coast.
Here are the expected impacts going forward with Elsa:
(1) The western Bahamas and western Cuba may see coastal sea swells and perhaps additional locally heavy rain from a stray outer band generated by Elsa throughout the day.
(2) The Florida Keys have been raked with tropical storm force winds all morning (most notable national weather service station observation was at Key West which logged sustained winds of 44 mph with a gust to 70 mph at 11:53 AM EDT). Tropical storm force winds will soon wind down…but coastal sea swells and additional heavy rain from outer bands will linger throughout the day.
(3) Coastal storm surge will remain a concern for the western part of the Florida peninsula throughout the day. Tropical storm to category 1 hurricane force winds are expected to arrive across Port Charlotte…Tampa Bay…and other parts of northwest Florida in the coming hours as the intense area of thunderstorms just east of the center arrives onshore. The prior preparation for tropical storm conditions should encompass the new potential for category 1 hurricane force winds…it just means that now more people could see some wind damage and power outages.
(4) The east side of the Florida peninsula could still see sea swells and rip currents and some breezy winds today.
(5) All of the Florida peninsula could see heavy rains with flash flooding potential today.
(6) Interests in the Florida panhandle could still see coastal sea swells today. The heaviest rainfall will likely stay to the east due to the shearing upper southwesterly winds over Elsa.
(7) The ECMWF model still forecasts a more east track of Elsa along the Georgia and Carolina coast tomorrow and Thursday with potential for Elsa to re-strengthen after its landfall in north Florida…as the storm taps into warm Gulf Stream water. The current steering flow in the atmosphere does not support such an eastward track…it will take Elsa to reform to the east under a sheared off thunderstorm burst for this scenario to happen. However I now recommend interests along the coastal areas of Georgia and the Carolinas to begin preparing for possible tropical storm force winds and coastal sea swells in case this scenario does happen…especially as Elsa could get aided by the divergent nature of the shearing upper southwesterly flow as we are currently seeing…even if the center never quiet makes it back over water after its north Florida landfall. Heavy rain with possible flash flooding is also another hazard to consider here.