781
WTPZ42 KNHC 180239
TCDEP2
TROPICAL STORM NORMA DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP172023
900 PM MDT TUE OCT 17 2023
NORMA IS BECOMING BETTER ORGANIZED ON SATELLITE IMAGERY. THERE IS
A DEVELOPING CENTRAL DENSE OVERCAST WITH VERY COLD CLOUD TOPS, AND
SOME CONVECTIVE BANDING IS EVIDENT. UPPER-LEVEL OUTFLOW IS FAIRLY
WELL DEFINED OVER THE WESTERN SEMICIRCLE OF THE CIRCULATION. THE
CURRENT INTENSITY ESTIMATE IS SET AT 45 KT IN AGREEMENT WITH THE
LATEST DVORAK CLASSIFICATIONS FROM TAFB AND SAB.
BASED ON RECENT CENTER FIXES, THE MOTION IS NOW NORTHWESTWARD, OR
AROUND 305/7 KT. A WEAK MID-LEVEL RIDGE TO THE EAST OF NORMA
SHOULD MAINTAIN A SLOW NORTHWESTWARD TO NORTH-NORTHWESTWARD TRACK
FOR THE NEXT 48 TO 72 HOURS. LATER IN THE FORECAST PERIOD, THERE IS
SIGNIFICANT UNCERTAINTY IN THE TRACK, SINCE THE MODEL GUIDANCE AT 3
TO 5 DAYS IS NOT IN VERY GOOD AGREEMENT. THE ECMWF AND UKMET SHOW A
WEAKENING CYCLONE MOVING ALONG THE WESTERN SIDE OF THE GUIDANCE
ENVELOPE WHEREAS THE GFS SHOW A STRONG SYSTEM MOVING MUCH MORE TO
THE NORTHEAST. THE 4- AND 5-DAY OFFICIAL FORECAST POSITIONS
ARE CLOSE TO THE SIMPLE AND CORRECTED MODEL CONSENSUS PREDICTIONS.
HOWEVER THERE IS LOW CONFIDENCE IN THIS FORECAST, GIVEN THE SPREAD
IN THE MODEL TRACKS.
FOR THE NEXT COUPLE OF DAYS, THE STORM SHOULD BE IN AN ATMOSPHERIC
AND OCEANIC ENVIRONMENT THAT WILL BE QUITE CONDUCIVE FOR
STRENGTHENING. THE SHIPS RAPID INTENSIFICATION (RI) INDICES AND
THE DTOPS PROBABILITIES FOR RI SUGGEST A HIGH LIKELIHOOD FOR
SIGNIFICANT STRENGTHENING DURING THE NEXT 48 HOURS OR SO. THIS IS
ALSO REFLECTED IN THE NHC INTENSITY FORECAST, WHICH EXPLICITLY
SHOWS RI IN THE EARLIER PART OF THE PERIOD. IN 3 TO 5 DAYS, HIGHER
SOUTH-SOUTHWESTERLY VERTICAL WIND SHEAR AND DRIER AIR IS LIKELY TO
INHIBIT STRENGTHENING. THE OFFICIAL FORECAST IS NEAR OR ABOVE THE
INTENSITY MODEL CONSENSUS.
FORECAST POSITIONS AND MAX WINDS
INIT 18/0300Z 13.7N 107.8W 45 KT 50 MPH
12H 18/1200Z 14.4N 108.2W 55 KT 65 MPH
24H 19/0000Z 15.5N 108.5W 70 KT 80 MPH
36H 19/1200Z 16.5N 108.6W 85 KT 100 MPH
48H 20/0000Z 17.3N 108.8W 90 KT 105 MPH
60H 20/1200Z 18.2N 109.2W 95 KT 110 MPH
72H 21/0000Z 19.2N 109.6W 95 KT 110 MPH
96H 22/0000Z 21.3N 110.2W 90 KT 105 MPH
120H 23/0000Z 22.5N 109.8W 85 KT 100 MPH
FORECASTER PASCH
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