MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #124A (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.**********
...SATURDAY SEPTEMBER 19 2020 2:35 AM EDT...
As if we didn’t need any more surprises in the Atlantic tropics with Wilfred and Alpha becoming named storms over the last 24 hours....tropical depression twenty-two became Tropical Storm Beta yesterday afternoon...becoming the third storm to be named in the Atlantic yesterday. And now Beta has more surprises up it’s sleeve by regenerating northeastward into its sheared off thunderstorms...and quickly intensifying to 60 mph maximum sustained winds in the process. This special update is to make adjustments to my forecast for what is now Beta accordingly.
Despite the jump to the northeast...a westward turn is still soon expected from the current central United States surface ridge building under the western convergence zone of the large upper trough over eastern North America. However the west motion is expected to be slow as the western convergence zone of the southwestern lobe of the upper trough will extend the central United States surface ridge southwestward in the next 24 hours...with the southwestern lobe of the ridge blocking west progress. Also Beta is now strong and hence tall enough to be slowed by the upper southwesterly flow ahead of the upper trough. However I show a slightly faster west motion than before for the next 24 hours as Beta’s strong thunderstorm latent heat release will likely weaken the south part of the upper trough into an upper vortex as the GFS model has been insisting....with the weaker vortex not producing as much upper westerly flow to slow Beta and not producing as much western upper convergence such that the blocking southwestern surface ridge lobe is not as strong. As the upper vortex dissipates by 48 hours....so does the blocking southwestern surface ridge lobe...so I forecast a slightly faster west track into the southern Texas coast. A second upper trough to pass over North America will be too far north to play a role with Beta...which leaves the question of how Beta interacts with a third upper trough to move into the southwestern US. Based on the 0000Z GFS run...I don’t think this upper trough will produce enough westerly flow to stop Beta from moving into southern Texas after 48 hours...but just enough upper flow to instead slow the forward speed a bit as Beta tries to round the Southwest side of the central US surface ridge. As the upper westerly flow finally arrives by 72 hours...I think there will have been enough land interaction to make Beta more weak and shallow such that it still continues around the surface ridge and further inland into southern Texas by 96 hours. However if for any reason the system takes longer to make landfall and stays stronger/taller at a location along the Texas coast or just offshore...that opens the door for the upper westerly flow at 72+ hours to more strongly influence the track...pushing Beta northeastward against the central United States surface ridge...creating an erratic and very slow northeastward track near or along the Texas coastline and toward the Louisiana coastline as the latest NHC official forecast and models currently show.
Regarding intensity...given that Beta appears to be weakening the south side of the current upper trough in the region as noted in the previous paragraph....wind shear will be less and thus I now significantly raise my intensity to show a category 2 hurricane landfall along the south Texas coast by Sunday night. Given the north shift in track and the increase in intensity...the threat to the Mexico Tamaulipas coast has reduced...and has significantly increased for the Texas coast where hurricane and tropical storm advisories have been raised. I recommend interests along the Texas coast to prepare for tropical storm and possible hurricane force conditions (damaging winds...coastal storm surge...and heavy rainfall with flooding potential)...and when shopping during preparation to also frequently hand sanitize and wear a mask to reduce your risk of contracting the COVID-19 virus amid the outbreak in the region. Although there is some uncertainty in the exact track of this system...weather conditions could deteriorate as early as Sunday night. Think of a hotel or family/friend residence if you live along a vulnerable section of coastline...as you may have to relocate for example if storm surge becomes severe...as a public storm shelter may not be as ideal to controlling your exposure to COVID-19. Interests further north along the southwest Louisiana coast are under tropical storm advisories and should also start preparing in case Beta does take a slow and erratic track further north as some of the latest model runs still indicate. If indeed a slow and erratic track sets in...rainfall flooding could become a severe problem as well.
******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********
0 Hr Position (0000Z Sep 19)...60 mph maximum sustained wind tropical storm centered in the western Gulf of Mexico at 25.5N-92.3W
IOH 24 Hr Forecast (0000Z Sep 20)...75 mph maximum sustained wind hurricane centered in the western Gulf of Mexico at 26.5N-94W
IOH 48 Hr Forecast (0000Z Sep 21)...100 mph maximum sustained wind hurricane centered just offshore of the southern Texas coast at 26.5N-97W
IOH 72 Hr Forecast (0000Z Sep 22)...50 mph maximum sustained wind tropical storm centered over southern Texas at 27.5N-98.5W
IOH 96 Hr Forecast (0000Z Sep 23)...Remnant low pressure centered over southern Texas at 28.5N-99.5W