September 21, 2020

Tropical Storm Debby forms in the Central Gulf of Mexico… …Tropical Storm Warning issued for a portion of the Louisiana Coast


Pin It

Aircraft reconnaissance…satellite…and buoy data indicate that

the circulation associated with the area of low pressure in the

Gulf of Mexico has become sufficiently defined to classify this

system as a tropical storm.  The initial intensity is based on a

highest 1000-ft flight-level wind of 61 kt and SFMR winds near

45kt.  These winds are only occurring to the east of the center.

 Debby is moving slowly northward…or 360 degrees at 5 kt.  The

cyclone is in a weak steering environment between two mid-level

ridges located over the Greater Antilles and the southern United

States…and Debby is not expected to move much during the next

couple of days.  The track guidance is split in two branches…with

the GFS and GFDL showing an eastward motion across Florida…and

the rest of the models bringing Debby westward across the northern

Gulf towards Texas.  Even though the deterministic GFS shows an

eastward track…more than half of the GFS ensemble members are in

agreement with the westward-moving models…making the westward

scenario seem more likely.  It is important to note too that the

ECMWF model shows a faster westward motion than indicated in the

NHC forecast…so it is possible that Debby could reach the coast

earlier than indicated.

Debby is currently a sheared cyclone with nearly all of the deep

convection located in a curved band to the east of the center.

However…an upper-level low over the northwestern Gulf of Mexico

is forecast to dig southwestward…which will result in a decrease

of vertical shear affecting the system…and a greater chance of

intensification over the next few days.  Because the official track

forecast is so different from the GFS solution…the GFS fields used

by the SHIPS and lgem models are not likely to be representative of

the conditions encountered by Debby.  The NHC forecast therefore

shows more strengthening than indicated by the intensity guidance.

Debby is the earliest 4th storm in the historical records…

surpassing Hurricane Dennis of 2005…which became a tropical storm

on July 5th.

Print Friendly, PDF & Email

Speak Your Mind