827
WTPZ41 KNHC 042033
TCDEP1
TROPICAL STORM PRISCILLA DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL EP162025
200 PM MST SAT OCT 04 2025
THE SATELLITE PRESENTATION OF INVEST 99E HAS CONTINUED TO IMPROVE
TODAY, WITH AN ELONGATED CONVECTIVE BAND HAVING FORMED THROUGH
THE WESTERN AND NORTHERN PART OF THE CIRCULATION. GIVEN THE
SYSTEM’S BROAD NATURE, ITS CENTER DEFINITION HAD BEEN QUESTIONABLE,
PARTICULARLY BASED ON ASCAT DATA FROM YESTERDAY EVENING. HOWEVER, A
RECENT 1645 UTC ASCAT PASS SHOWED THAT THE CENTER HAS BECOME
SIGNIFICANTLY BETTER DEFINED, WITH 35-40 KT WINDS OCCURRING NORTH
AND NORTHWEST OF THE CENTER. BASED ON THESE DATA, ADVISORIES ARE
BEING INITIATED ON TROPICAL STORM PRISCILLA, WITH AN ESTIMATED
INTENSITY OF 40 KT.
PRISCILLA IS MOVING NORTHWESTWARD (315 DEGREES) AT 8 KT. A
LARGE-SCALE TROUGH IS CURRENTLY LOCATED OVER THE WESTERN UNITED
STATES AND EXTENDS SOUTHWARD OVER BAJA CALIFORNIA, LEAVING
PRISCILLA IN AN ENVIRONMENT OF WEAK STEERING CURRENTS. IN THE
SHORT TERM, THAT SHOULD CAUSE THE STORM TO SLOW DOWN AND DRIFT IN A
GENERAL NORTHWARD DIRECTION FOR THE NEXT 36 HOURS. AFTER THAT
TIME, PRISCILLA IS EXPECTED TO SETTLE IN TO A MORE STEADY
NORTHWESTWARD TRACK AS A STRONGER MID-LEVEL RIDGE BUILDS OVER
NORTHERN MEXICO AND THE DEEP-LAYER TROUGH REMAINS ENTRENCHED OVER
THE WESTERN UNITED STATES. FOR MOST OF THE FORECAST PERIOD, THE
NHC TRACK FORECAST LEANS ON THE EASTERN SIDE OF THE GUIDANCE
ENVELOPE, IN THE VICINITY OF THE ECMWF, HCCA CONSENSUS AID, AND
GOOGLE DEEPMIND ENSEMBLE MEAN.
PRISCILLA WILL BE MOVING OVER SEA SURFACE TEMPERATURES OF ABOUT 29
DEGREES CELSIUS DURING THE NEXT COUPLE OF DAYS, COINCIDENT WITH A
PERIOD OF STRONG UPPER-LEVEL DIVERGENCE. THESE CONDITIONS SHOULD
SUPPORT STRENGTHENING, ALTHOUGH THE SYSTEM'S LARGE SIZE COULD LIMIT
THE RATE OF INTENSIFICATION IN THE SHORT TERM. THAT SAID, SOME OF
THE RAPID INTENSIFICATION (RI) INDICES ARE GREATER THAN 50% WITHIN
36 AND 48 HOURS, SO IF PRISCILLA CAN DEVELOP A TIGHTER INNER CORE
WITHIN THE LARGER WIND FIELD, MORE SIGNIFICANT STRENGTHENING WOULD
BE POSSIBLE. THE NHC INTENSITY FORECAST CALLS FOR PRISCILLA TO
BECOME A HURRICANE BY SUNDAY NIGHT, WITH STRENGTHENING CONTINUING
THROUGH TUESDAY. COOLER WATER TEMPERATURES AND A LESS FAVORABLE
ATMOSPHERE SHOULD INDUCE WEAKENING BY WEDNESDAY AND THURSDAY.
KEY MESSAGES:
1. TROPICAL STORM CONDITIONS ARE POSSIBLE ALONG PORTIONS OF THE
COAST OF SOUTHWESTERN MEXICO WITHIN THE WATCH AREA SUNDAY AND
MONDAY. INTERESTS IN THE SOUTHERN PORTION OF BAJA CALIFORNIA SUR
SHOULD ALSO MONITOR THE PROGRESS OF PRISCILLA.
2. HEAVY RAINFALL ASSOCIATED WITH PRISCILLA WILL IMPACT COASTAL
SECTIONS OF SOUTHWESTERN MEXICO THROUGH MONDAY, WHICH COULD RESULT
IN FLASH FLOODING, PARTICULARLY IN AREAS OF HIGHER TERRAIN.
3. SWELLS GENERATED BY PRISCILLA ARE AFFECTING PORTIONS OF
THE COAST OF SOUTHWESTERN MEXICO AND WILL REACH THE COASTS OF
WEST-CENTRAL MEXICO AND THE SOUTHERN BAJA CALIFORNIA PENINSULA BY
MONDAY. THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND
RIP CURRENT CONDITIONS.
FORECAST POSITIONS AND MAX WINDS
INIT 04/2100Z 15.5N 106.6W 40 KT 45 MPH
12H 05/0600Z 15.8N 106.8W 45 KT 50 MPH
24H 05/1800Z 16.3N 106.9W 55 KT 65 MPH
36H 06/0600Z 17.0N 107.3W 65 KT 75 MPH
48H 06/1800Z 17.8N 108.2W 75 KT 85 MPH
60H 07/0600Z 18.8N 109.4W 80 KT 90 MPH
72H 07/1800Z 19.7N 110.7W 85 KT 100 MPH
96H 08/1800Z 21.7N 113.3W 80 KT 90 MPH
120H 09/1800Z 24.1N 115.4W 60 KT 70 MPH
FORECASTER BERG
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