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Tropical Storm Gonzalo Discussion Number 6
NWS National Hurricane Center Miami FL AL072020
1100 PM AST Wed Jul 22 2020
A series of earlier microwave passes over Gonzalo reveal a small
eye feature beneath a relatively ragged, Central Dense Overcast
with associated -75.5C cloud tops. Based on the evidence
of the small eye and a blend of the subjective and objective
satellite intensity estimates, the initial intensity is raised to 50
kt for advisory.
The intensity forecast philosophy remains the same as the previous
advisory with a higher than normal degree of uncertainty in the
latter half of the period as the cyclone moves through the
Caribbean. Gonzalo should remain in an environment of relatively
low shear, although the impacts of dry, stable air and large-scale
subsidence could hamper further intensification in a few days. It's
worth noting that the ECMWF Ensemble model is showing a pretty
significant low- to mid-level easterly surge that spreads
just to the north of the cyclone's forecast track and over the
northeastern Caribbean in a couple of days. This predicted event
could possibly curtail strengthening at that time. On the
other hand, with the exception of the ECMWF, the global models now
show the cyclone maintaining tropical storm strength while moving
into the eastern Caribbean. The official intensity forecast is
adjusted slightly above the previous forecast, hedging toward the
HFIP HCCA consensus and the IVCN multi-model intensity aid
solutions. It should also be noted that the small size of this
system makes it susceptible to significant fluctuations in
intensity, both upward and downward.
The initial motion is estimated to be due west, or 270/10 kt.
There is no change to the track forecast philosophy. Gonzalo is on
the south side of a low- to mid-level tropospheric ridge, and this
feature should steer the storm generally westward at a faster
forward speed for the next few days. After that time, a motion
toward the west-northwest is expected. The NHC track forecast is
nudged a bit to the north of the previous one and is close to the
various consensus aids.
Interests in the Windward Islands should continue to monitor the
progress of this system. A Hurricane Watch is now issued for
Barbados.
Key Messages
1. Gonzalo is expected to move near or over the southern Windward
Islands this weekend, and could bring direct impacts from winds and
heavy rainfall. While it is too soon to determine the magnitude and
timing of those impacts, interests in the southern Windward Islands
should monitor the progress of Gonzalo.
FORECAST POSITIONS AND MAX WINDS
INIT 23/0300Z 9.9N 45.9W 50 KT 60 MPH
12H 23/1200Z 10.0N 47.6W 60 KT 70 MPH
24H 24/0000Z 10.2N 50.0W 65 KT 75 MPH
36H 24/1200Z 10.6N 52.7W 70 KT 80 MPH
48H 25/0000Z 11.2N 55.5W 75 KT 85 MPH
60H 25/1200Z 11.8N 58.6W 70 KT 80 MPH
72H 26/0000Z 12.6N 61.8W 60 KT 70 MPH
96H 27/0000Z 14.3N 67.6W 50 KT 60 MPH
120H 28/0000Z 15.6N 73.1W 40 KT 45 MPH
$$
Forecaster Roberts
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