Tropical Storm Harvey Forecast Discussion (Text)

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WTNT44 KNHC 191449

Tropical Storm Harvey Discussion Number   9
NWS National Hurricane Center Miami FL       AL092017
1100 AM AST Sat Aug 19 2017

Harvey has become less organized in visible imagery since this
time yesterday, with the convective pattern becoming elongated and
the circulation looking less well defined.  In addition, an Air
Force Reserve Hurricane Hunter aircraft could not close the
circulation at 850 mb, but was able to close the circulation at 1000
ft.  The plane has not yet reported tropical-storm-force winds, but
the northwestern quadrant was not well sampled.  Thus, the initial
intensity is held at a possibly generous 35 kt.

The initial motion is now 275/19.  A low- to mid-level ridge
extending across the western Atlantic should keep Harvey on a fast
westward course across the Caribbean Sea for the next 36-48 hours.
Thereafter, there should be a weakness in the ridge north of
Harvey caused by a strong mid/upper-level low currently seen in
water vapor imagery over the Gulf of Mexico.  This pattern should
cause a turn toward the west-northwest and a decrease in forward
speed. The track guidance is in good agreement that Harvey should
pass near or just north of northeastern Honduras, and then cross
Belize and/or the Yucatan Peninsula into the Bay of Campeche, and
based on this the new forecast track follows the guidance with only
minor changes from the previous track.

The ongoing moderate vertical shear should continue for another
12-24 h or so, and combined with the current lack of organization
should allow at best only slow strengthening.  After that, the
upper-level winds are expected to become favorable for strengthening
as the system moves over the deep warm waters of the western
Caribbean.  The intensity forecast follows the previous forecast in
calling for a peak intensity of 60 kt just before the system
reaches Belize or the Yucatan Peninsula.  Harvey should weaken as it
crosses the southern portion of the Yucatan Peninsula between 72-96
h, followed by some re-intensification over the Bay of Campeche.  It
should be noted that any additional loss of organization in the next
12-24 h would result in the cyclone degenerating into an easterly


INIT  19/1500Z 13.9N  68.1W   35 KT  40 MPH
 12H  20/0000Z 14.1N  70.9W   35 KT  40 MPH
 24H  20/1200Z 14.4N  74.9W   40 KT  45 MPH
 36H  21/0000Z 14.9N  78.7W   45 KT  50 MPH
 48H  21/1200Z 15.7N  82.4W   50 KT  60 MPH
 72H  22/1200Z 17.5N  88.0W   60 KT  70 MPH
 96H  23/1200Z 19.0N  91.5W   30 KT  35 MPH
120H  24/1200Z 19.5N  93.5W   40 KT  45 MPH

Forecaster Beven

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Page last modified: Saturday, 19-Aug-2017 14:50:10 UTC