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TROPICAL STORM HOWARD DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092016
800 AM PDT MON AUG 01 2016
Howard's convective structure has gradually been increasing in
organization. The cyclone's cloud pattern is characterized by a
long curved band, at the head of which is a clearing around the
low-level center. Subjective Dvorak satellite classifications are
T2.5/35 kt and T3.5/55 kt from SAB and TAFB, respectively. A blend
of these is used to arrive at the initial intensity estimate of 45
kt.
The initial motion estimate is 295/09. Howard's primary steering
mechanism is the western extension of a subtropical ridge located
over the south-central United States, which is imparting a mostly
westerly course. However, a mid- to upper-level low west of the
cyclone is allowing for a greater northerly component of motion.
This general movement with some increase in forward speed is likely
during the next 2 days, after which time a turn toward the west
is likely. This should occur when Howard weakens and becomes a
shallower cyclone in the trade-wind flow. The official NHC track
forecast is hardly unchanged from the previous one and is closest
to a blend of the GFS and ECMWF model solutions.
Ships model output shows some westerly shear over the cyclone,
perhaps related to Howard's outrunning the upper-level anticyclone
over it. Otherwise, large-scale conditions are expected to be
sufficiently conducive for some additional intensification during
the next 24 hours or so. By 36-48 hours, Howard should reach much
cooler waters and enter an increasingly drier and more stable
environment, all of which should lead to weakening. This should
result in a fast rate of weakening, and the system is forecast to
become post-tropical in 48 hours. The NHC intensity forecast is
close to the multi-model consensus in the short term and then
follows the LGEM during the weakening phase.
FORECAST POSITIONS AND MAX WINDS
INIT 01/1500Z 16.7N 123.6W 45 KT 50 MPH
12H 02/0000Z 17.5N 125.4W 50 KT 60 MPH
24H 02/1200Z 18.7N 128.0W 55 KT 65 MPH
36H 03/0000Z 19.9N 130.8W 45 KT 50 MPH
48H 03/1200Z 21.0N 133.6W 40 KT 45 MPH...POST-TROPICAL
72H 04/1200Z 22.3N 139.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 05/1200Z 22.9N 144.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 06/1200Z 22.9N 150.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Kimberlain
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