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Tropical Storm KATIA
ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM 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 NNNN