470
WTPZ42 KNHC 220244
TCDEP2
TROPICAL STORM NORMA DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL EP172023
900 PM MDT SAT OCT 21 2023
NORMA CONTINUES TO MOVE ACROSS THE SOUTHERN PORTION OF THE BAJA
CALIFORNIA PENINSULA THIS EVENING. THE SATELLITE DEPICTION OF THE
ILL-DEFINED LOW-LEVEL CENTER HAS BEEN DIFFICULT TO TRACK THROUGH THE
TERRAIN AS THE SYSTEM HAS DECOUPLED FROM THE MID-LEVEL CENTER.
INFRARED SATELLITE IMAGERY INDICATES THAT THERE CONTINUES TO BE
BURSTS OF CONVECTION ON THE NORTHWEST SIDE. THE LAND INTERACTION,
INCREASINGLY SOUTHERLY SHEAR AND DRY AIR IS CAUSING NORMA TO WEAKEN.
SUBJECTIVE AND OBJECTIVE DVORAK ESTIMATES FOR THIS ADVISORY RANGE
FROM 55 TO 60 KT. GIVEN THE CURRENT SATELLITE DEPICTION AND THE
SATELLITE INTENSITY ESTIMATES, THE INITIAL INTENSITY FOR THIS
ADVISORY IS SET TO 55 KT.
THE TROPICAL STORM IS MOVING NORTH-NORTHEASTWARD OR 30 DEGREES AT
5 KT. THE SYSTEM WILL MOVE ACROSS THE SOUTHERN PORTION OF BAJA
CALIFORNIA SUR THROUGH TONIGHT. NORMA SHOULD EMERGE OVER THE
SOUTHERN GULF OF CALIFORNIA EARLY SUNDAY, THEN MOVE NORTHEASTWARD TO
EAST-NORTHEASTWARD AND MAKE LANDFALL ALONG THE COAST OF SINALOA IN
WESTERN MEXICO WITHIN THE TROPICAL STORM WARNING AREA. THE UPDATED
NHC TRACK FORECAST IS SIMILAR TO THE PREVIOUS, AND LIES BETWEEN
THE SIMPLE AND CORRECTED CONSENSUS AIDS.
NORMA IS EXPECTED TO CONTINUE WEAKENING DUE TO THE AFOREMENTIONED
VERTICAL WIND SHEAR, DRIER AIR, AND LAND INTERACTION. ONCE NORMA
MOVES INLAND OVER MAINLAND MEXICO, IT WILL QUICKLY DISSIPATE OVER
THE HIGH TERRAIN. THE INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS ADVISORY. THE OFFICIAL FORECAST SHOWS A 48 HOUR REMNANT
LOW POINT FOR CONTINUITY, HOWEVER IT IS POSSIBLE THAT THE SYSTEM
COULD BE DISSIPATED BY THAT TIME.
KEY MESSAGES:
1. HEAVY RAINS FROM NORMA WILL CONTINUE TO IMPACT SOUTHERN PORTIONS
OF BAJA CALIFORNIA SUR THROUGH SUNDAY, AND THROUGH SINALOA INTO
MONDAY. THIS RAINFALL WILL PRODUCE FLASH AND URBAN FLOODING, ALONG
WITH MUDSLIDES IN AREAS OF HIGHER TERRAIN.
2. TROPICAL STORM CONDITIONS WILL CONTINUE THROUGH TONIGHT WITHIN
THE TROPICAL STORM WARNING AREA OVER THE SOUTHERN BAJA CALIFORNIA
PENINSULA.
3. NORMA IS FORECAST TO BRING TROPICAL STORM CONDITIONS TO PORTIONS
OF THE WEST COAST OF MAINLAND MEXICO WITHIN THE TROPICAL STORM
WARNING AREA BEGINNING EARLY SUNDAY.
FORECAST POSITIONS AND MAX WINDS
INIT 22/0300Z 23.5N 109.7W 55 KT 65 MPH
12H 22/1200Z 24.1N 109.2W 50 KT 60 MPH...OVER WATER
24H 23/0000Z 24.5N 108.4W 45 KT 50 MPH
36H 23/1200Z 24.9N 107.7W 30 KT 35 MPH...INLAND
48H 24/0000Z 25.2N 106.8W 25 KT 30 MPH...POST-TROP/INLAND
60H 24/1200Z...DISSIPATED
FORECASTER KELLY
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