552
WTPZ43 KNHC 252042
TCDEP3
TROPICAL STORM SONIA DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182025
200 PM PDT SAT OCT 25 2025
SONIA APPEARS TO HAVE BECOME BETTER ORGANIZED DURING THE PAST
SEVERAL HOURS. GMI MICROWAVE IMAGERY VALID NEAR 18Z SHOWED A
BETTER-DEFINED CENTER IN 37 GHZ IMAGERY. SATELLITE-BASED INTENSITY
ESTIMATES RANGE FROM NEAR 45 KT TO NEAR 55 KT. ASCAT-C WIND DATA
VALID AT 1701 UTC ONLY CAPTURED A PART OF THE CIRCULATION OF SONIA
ON THE EDGE OF THE PASS SWATH, BUT IT DID NOT SHOW ANY WINDS OF
TROPICAL-STORM FORCE. BASED ON ALL THESE DATA, THE INTENSITY
ESTIMATE REMAINS 45 KT FOR THIS ADVISORY.
THE AFOREMENTIONED GMI DATA HELPED IDENTIFY THE CENTER OF SONIA, SO
THE INITIAL POSITION AND MOVEMENT OF THE TROPICAL STORM IS HIGHER
CONFIDENCE NOW. HOWEVER, THERE IS STILL UNUSUALLY LARGE SPREAD IN
THE TRACK GUIDANCE. THE MODELS APPEAR TO BE SPLIT OVER WHETHER SONIA
WILL BEGIN A SHORT PERIOD OF INTENSIFICATION IN ABOUT A DAY, OR NOT.
THE STRONGER SOLUTIONS, INCLUDING THE GFS AND ALL OF THE HURRICANE
REGIONAL MODELS, SHOW SONIA GAINING MORE LATITUDE, WHILE THE WEAKER
ONES, INCLUDING THE GOOGLE DEEPMIND AND ECMWF, KEEP THE CYCLONE
MOVING GENERALLY WESTWARD TO WEST-NORTHWESTWARD. THE NHC TRACK
FORECAST ALREADY SPLIT THESE SOLUTIONS, AND NO SIGNIFICANT CHANGE
HAS BEEN MADE FOR THIS ADVISORY SINCE THERE IS NO OBVIOUS REASON TO
DISCOUNT EITHER SOLUTION AT THIS TIME.
LIKEWISE, NO CHANGE OF NOTE WAS MADE TO THE OFFICIAL INTENSITY
FORECAST. SONIA COULD STRENGTHEN SLIGHTLY OVER THE WEEKEND, SINCE
ITS STRUCTURE AND ORGANIZATION APPEAR TO BE IMPROVING AND THERE ARE
NO IMMEDIATE SIGNIFICANT INHIBITING FACTORS. HOWEVER, BY EARLY NEXT
WEEK THE CYCLONE WILL MOVE INTO A DRIER ENVIRONMENT AND MOVE TOWARD
AN UPPER-LEVEL LOW THAT WILL RESULT IN AN INCREASE IN SHEAR. THIS
SHOULD CAUSE WEAKENING, AND ALL AVAILABLE DYNAMICAL GUIDANCE STILL
INDICATES SONIA WILL BECOME POST-TROPICAL BY DAY 4, REGARDLESS OF
HOW STRONG IT GETS BETWEEN NOW AND THEN. THE NHC INTENSITY FORECAST
IS NOW NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
FORECAST POSITIONS AND MAX WINDS
INIT 25/2100Z 13.5N 118.9W 45 KT 50 MPH
12H 26/0600Z 13.6N 119.7W 50 KT 60 MPH
24H 26/1800Z 13.7N 120.3W 55 KT 65 MPH
36H 27/0600Z 14.1N 120.9W 60 KT 70 MPH
48H 27/1800Z 14.7N 121.9W 60 KT 70 MPH
60H 28/0600Z 15.0N 123.1W 50 KT 60 MPH
72H 28/1800Z 15.1N 124.7W 40 KT 45 MPH
96H 29/1800Z 15.0N 128.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 30/1800Z...DISSIPATED
FORECASTER D. ZELINSKY
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