ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
Tropical Depression Norma Discussion Number 20
NWS National Hurricane Center Miami FL EP172017
300 AM MDT Tue Sep 19 2017
Conventional satellite imagery shows continued deterioration of
Norma's cloud pattern this evening. All that remains of the
associated deep convection is fragments in the northeast quadrant.
A 0518 UTC ASCAT-B overpass indicated winds of only 30 kt in the
north and east portions of the cyclone. Therefore, Norma is
downgraded to a depression for this advisory. Norma is forecast to
further weaken while traversing decreasing oceanic temperatures. An
intruding drier and more stable marine layer will also contribute to
Norma's demise. The official forecast is just an update of the
previous one and shows Norma becoming a remnant low in 36 hours and
dissipating in 2 days.
The initial motion is estimated to be west-northwestward, or
280/5 kt. Norma is expected to move west during the next 24 hours,
within the southwestern peripheral mid-tropospheric flow of a
subtropical ridge extending westward from northern Mexico over the
eastern Pacific. Afterward, the cyclone is forecast to gradually
turn northwestward as a remnant low. The NHC forecast is just a bit
south of the previous package due to the position adjustment based
on the scatterometer data, and is nudged toward the HFIP Corrected
Consensus model.
FORECAST POSITIONS AND MAX WINDS
INIT 19/0900Z 21.6N 113.9W 30 KT 35 MPH
12H 19/1800Z 21.7N 114.7W 30 KT 35 MPH
24H 20/0600Z 22.1N 115.6W 25 KT 30 MPH
36H 20/1800Z 22.6N 116.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 21/0600Z...DISSIPATED
$$
Forecaster Roberts
NNNN