098
WTPZ44 KNHC 230850
TCDEP4
TROPICAL STORM NARDA DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP142025
200 AM MST TUE SEP 23 2025
NARDA CONTINUES TO STRENGTHEN WELL OFF THE COAST OF SOUTHWESTERN
MEXICO THIS EVENING, WITH SATELLITE IMAGERY SHOWING A CENTRAL DENSE
OVERCAST AND VERY COLD CLOUD TOPS, COLDER THAN -80C, OVER THE
LOW-LEVEL CENTER. A 0248 UTC GPM MICROWAVE PASS AND A 0350 UTC
METOP-C ASCAT PASS WERE HELPFUL IN ESTIMATING THE CENTER LOCATION,
DETERMINING THE MOTION, AND ASSESSING THE STRUCTURE OF THE CYCLONE.
SUBJECTIVE DVORAK ESTIMATES FROM TAFB AND SAB WERE 4.0/65 KT AND
3.5/55 KT, RESPECTIVELY, WHILE OBJECTIVE ESTIMATES FROM UW-CIMSS
RANGED FROM 54 TO 60 KT. A BLEND OF THESE DATA, ALONG WITH THE
IMPROVED SATELLITE PRESENTATION, SUPPORTS RAISING THE INITIAL
INTENSITY TO 60 KT FOR THIS ADVISORY.
NARDA IS NOW ESTIMATED TO BE MOVING JUST SOUTH OF DUE WEST, OR 265
DEGREES, AT 11 KT. A GENERAL WESTWARD MOTION IS EXPECTED TO
CONTINUE DURING THE NEXT FEW DAYS AS THE CYCLONE IS STEERED BY A
STRENGTHENING SUBTROPICAL RIDGE TO ITS NORTH AND NORTHWEST. A TURN
TOWARD THE NORTHWEST AND A DECREASE IN FORWARD SPEED ARE EXPECTED BY
DAYS 4 AND 5 AS A MID-LEVEL LOW OVER SOUTHERN CALIFORNIA ERODES THE
EASTERN PORTION OF THE SUBTROPICAL RIDGE. THE OFFICIAL FORECAST
TRACK HAS BEEN ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS
FORECAST DURING THE NEXT COUPLE OF DAYS TO ACCOUNT FOR THE
SOUTH-OF-DUE-WEST MOTION, AND THEN SLIGHTLY TO THE RIGHT OF THE
PRIOR FORECAST BY DAYS 4 AND 5 DUE TO AN EASTWARD SHIFT IN THE
GUIDANCE. THE TRACK FORECAST FOLLOWS A BLEND OF THE HCCA, TVCE, AND
FSSE CONSENSUS AIDS, AS WELL AS THE GOOGLE DEEPMIND/NOAA EAGLE AI
GUIDANCE.
NARDA WILL REMAIN EMBEDDED WITHIN A MOIST AIR MASS, OVER VERY WARM
WATERS, AND IN AN ENVIRONMENT OF LIGHT TO MODERATE EASTERLY SHEAR
DURING THE NEXT DAY OR SO. THESE FACTORS SHOULD SUPPORT STEADY
STRENGTHENING. THE LATEST GFS- AND ECMWF-BASED SHIPS GUIDANCE
INDICATES ABOUT A 30 TO 40 PERCENT PROBABILITY OF A 25-KT INCREASE
WITHIN 24 HOURS, AND THE INTENSITY FORECAST REFLECTS THIS, WITH
NARDA EXPECTED TO BECOME A HURRICANE SOON. LITTLE CHANGE IN
STRENGTH IS FORECAST BETWEEN 36 AND 60 HOURS AS EASTERLY SHEAR
INCREASES TO AROUND 20–25 KT, WHICH MAY DISRUPT THE CYCLONE ENOUGH
TO PREVENT FURTHER INTENSIFICATION DESPITE OTHERWISE FAVORABLE
CONDITIONS. BEYOND 60 HOURS, SHEAR IS EXPECTED TO DECREASE, WHICH
MAY ALLOW NARDA TO APPROACH MAJOR HURRICANE STATUS BEFORE MOVING
OVER COOLER WATERS AND INTO A DRIER MID-LEVEL ENVIRONMENT BY DAY 5.
THE OFFICIAL INTENSITY FORECAST REMAINS NEAR THE UPPER END OF THE
GUIDANCE ENVELOPE AND IS MOST CLOSELY ALIGNED WITH THE HCCA AID.
FORECAST POSITIONS AND MAX WINDS
INIT 23/0900Z 15.7N 106.1W 60 KT 70 MPH
12H 23/1800Z 15.5N 107.8W 75 KT 85 MPH
24H 24/0600Z 15.3N 109.8W 85 KT 100 MPH
36H 24/1800Z 15.2N 112.0W 90 KT 105 MPH
48H 25/0600Z 15.3N 114.3W 90 KT 105 MPH
60H 25/1800Z 15.6N 116.6W 90 KT 105 MPH
72H 26/0600Z 16.1N 119.0W 95 KT 110 MPH
96H 27/0600Z 17.5N 122.5W 95 KT 110 MPH
120H 28/0600Z 19.4N 123.5W 70 KT 80 MPH
FORECASTER JELSEMA (CPHC)
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