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Tropical Storm Pilar Discussion Number 2
NWS National Hurricane Center Miami FL EP182017
1000 PM CDT Sat Sep 23 2017
The structure of the cyclone near Mexico has improved over the past
6 hours. Dvorak intensity estimates from TAFB and SAB now support
an estimated intensity of 35 kt, so the system is now classified as
Tropical Storm Pilar.
The initial motion based on recent satellite fixes is 350/4 kt.
Pilar is still expected to move generally toward the north-northwest
or north to the east of a mid-level ridge centered over Mexico for
the next couple of days, and the primary source of uncertainty in
the forecast is possible interaction with land. Due in part to
initial position uncertainty, the global models vary on whether
Pilar will clip the coast of Jalisco or remain just offshore, but
the model consensus now shows a landfall in about 24 hours. The
NHC forecast has been adjusted slightly to the east toward the
model consensus, but it is certainly possible that the tropical
storm could remain offshore and enter the Gulf of California.
Regardless of whether the center makes landfall or not, heavy rain
is still likely along the coast of Mexico through early next week.
The possibility of land interaction makes the intensity forecast
particularly difficult. Very warm SSTs and only moderate shear
should allow for some strengthening for at least the next 36 hours.
However, if Pilar makes landfall sooner than that, it will likely
quickly weaken. Since my track forecast shows Pilar making
landfall in about 24 hours, my intensity forecast peaks at that
time, and shows steady weakening thereafter. Beginning around 48
h, the GFS and ECMWF show that the shear will increase
substantially, which should cause Pilar to quickly become a remnant
low, even if it remains over water.
FORECAST POSITIONS AND MAX WINDS
INIT 24/0300Z 18.7N 105.3W 35 KT 40 MPH
12H 24/1200Z 19.3N 105.5W 45 KT 50 MPH
24H 25/0000Z 20.3N 105.6W 50 KT 60 MPH
36H 25/1200Z 21.1N 105.7W 45 KT 50 MPH
48H 26/0000Z 21.9N 105.9W 40 KT 45 MPH
72H 27/0000Z 23.3N 106.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 28/0000Z 24.7N 107.3W 25 KT 30 MPH...POST-TROP/REMNT LOW