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Tropical Storm Katia Discussion Number  15
NWS National Hurricane Center Miami FL       AL132017
Issued by the NWS Weather Prediction Center College Park MD
400 AM CDT Sat Sep 09 2017

Convection has substantially diminished with Katia, with satellite
imagery showing a significantly degraded structure. In fact, it
seems that the low-level circulation may be decoupled from the
low center aloft now, as a distinct circulation in diminishing
colder cloud tops moved more quickly off to the southwest. There was
already evidence of this occurring from the recon flight earlier
tonight. The initial position was determined via the circulation in
warmer clouds in the lower troposphere on IR satellite. Katia is
very close to the higher terrain of the Sierra Madre Mountains, and
thus the forecast shows very little movement this morning as the
increasingly shallow circulation would be less likely to propagate
west through the mountainous areas.

The initial intensity is set at 35 knots out of respect for the
hurricane strength Dvorak fixes only nine hours ago, and the extent
of tropical storm force winds sampled by the recon plane shortly
thereafter, although this could be generous. The most likely
location of tropical storm force winds would be away from the center
and over the water or near the coast in the eastern semicircle of
Katia's circulation. The wind field should continue to weaken this
morning, and we show a dissipation of Katia by 18Z today.

Although convection has generally diminished as of 09Z, lingering
elevated levels of atmospheric moisture associated with Katia could
continue to produce heavy rains in the region, which could lead to
flash floods and mudslides even after Katia dissipates.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 20.3N  97.5W   35 KT  40 MPH
 12H  09/1800Z 20.2N  97.6W   20 KT  25 MPH...INLAND
 24H  10/0600Z...DISSIPATED

$$
Forecaster Lamers/Roth

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