Aircraft reconnaissance…satellite…and buoy data indicate that
Gulf of Mexico has become sufficiently defined to classify this
system as a tropical storm.Â The initial intensity is based on a
highest 1000-ft flight-level wind of 61 kt and SFMR winds near
45kt.Â These winds are only occurring to the east of the center.
Â Debby is moving slowly northward…or 360 degrees at 5 kt.Â 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.Â 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.Â 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.Â 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.Â 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.Â 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.