338
WTPZ42 KNHC 241454
TCDEP2
HURRICANE VANCE DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL EP222026
900 AM CST SAT OCT 24 2026
THE SATELLITE APPEARANCE OF VANCE HAS DETERIORATED A BIT DURING THE
PAST FEW HOURS, LIKELY DUE TO THE COMBINED EFFECTS OF COLDER SEA
SURFACE TEMPERATURES NEAR THE CENTER AND INCREASING SOUTHWESTERLY
SHEAR. WHILE THE EYEWALL CLOUD TOPS REMAIN QUITE COLD, THE EYE HAS
BECOME LESS DISTINCT AND THE CENTRAL DENSE OVERCAST HAS BECOME MORE
RAGGED. THE SUBJECTIVE AND OBJECTIVE SATELLITE INTENSITY ESTIMATES
HAVE NUDGED DOWNWARD, AND THE INITIAL INTENSITY IS REDUCED TO 90 KT.
THE INTENSITY FORECAST IS STILL PROBLEMATIC AND LOW CONFIDENCE.
VANCE IS LIKELY TO WEAKEN DURING THE NEXT 24 H AS IT CROSSES A POOL
OF COLDER WATER WITH TEMPERATURES NEAR 27C THAT HAS BEEN UPWELLED BY
SEVERAL PREVIOUS TROPICAL CYCLONES, AND AT THE SAME TIME
SOUTHWESTERLY SHEAR IS FORECAST TO INCREASE TO NEAR 20-25 KT. THE
CYCLONE IS LIKELY TO TAKE 24 H OR SO TO CROSS THE COLD POOL, THEN IT
IS EXPECTED TO MOVE OVER SEA SURFACE TEMPERATURES NEAR 29C CLOSER TO
THE COAST OF MEXICO. THIS SHOULD ALLOW INTENSIFICATION IF THE SHEAR
IS LIGHT ENOUGH. THE GFS AND ECMWF BOTH SHOW A PERIOD OF REDUCED,
BUT STILL MARGINAL, SHEAR THAT COULD ALLOW SOME INTENSIFICATION, AND
THIS IS REFLECTED IN THE INTENSITY FORECAST. THE NEW INTENSITY
FORECAST HAS SOME ADJUSTMENTS FROM THE PREVIOUS FORECAST,
PARTICULARLY AFTER 60 H. THERE ARE THREE ISSUES THAT SHOULD BE NOTED
FOR THIS FORECAST. FIRST THE 06Z GFS CALLS FOR VANCE TO MAKE
LANDFALL ALONG THE MEXICAN COAST AS A HURRICANE, ALTHOUGH AT THE
MOMENT NO OTHER GUIDANCE EXPLICITLY SHOWS THIS. SECOND, IT IS
POSSIBLE THAT VANCE COULD WEAKEN MORE THAN CURRENTLY FORECAST DURING
THE NEXT 24 H AS IT PASSES OVER THE COLD POOL. THIRD, IT IS POSSIBLE
THAT THE SHEAR MAY INCREASE TO THE POINT WHERE NO RE-INTENSIFICATION
COULD OCCUR, AS THE UKMET AND CANADIAN MODELS SHOW STRONGER SHEAR
THAN THE GFS AND ECMWF.
THE INITIAL MOTION IS 340/5 KT. VANCE IS BEING STEERED BY A WEAK
LOW- TO MID-LEVEL RIDGE OVER EASTERN MEXICO, AND IT IS APPROACHING A
LARGE MID-LATITUDE TROUGH OVER THE WESTERN UNITED STATES AND
NORTHWESTERN MEXICO. WHILE NEITHER OF THESE FEATURES WILL CHANGE
MUCH DURING THE NEXT FEW DAYS, VANCE IS LIKELY TO MOVE INTO AN AREA
OF LIGHTER STEERING CURRENTS NEAR THE BASE OF THE TROUGH AND SLOW
ITS FORWARD MOTION DURING THE NEXT 24-36 H. THE TRACK FORECAST
AFTER 36 H IS DEPENDENT ON HOW STRONG VANCE IS AND HOW WELL VANCE
MAINTAINS ITS VERTICAL STRUCTURE. A WEAKER SYSTEM THAT SHEARS APART
LIKE SHOWN IN THE UKMET AND CANADIAN IS LIKELY TO MOVE
WEST-NORTHWESTWARD TO NORTHWESTWARD BEFORE RESUMING A MORE NORTHERLY
MOTION, WHILE A STRONGER AND VERTICALLY DEEPER SYSTEM IS LIKELY TO
CONTINUE SLOWLY NORTHWARD. THE NEW FORECAST TRACK IS ON THE EAST
SIDE OF THE GUIDANCE ENVELOPE NEAR THE HFIP CORRECTED CONSENSUS,
GOOGLE DEEPMIND, AND FLORIDA STATE SUPERENSEMBLE, AND IT HAS ONLY
MINOR ADJUSTMENTS FROM THE PREVIOUS FORECAST.
KEY MESSAGES:
1. DUE TO THE UNCERTAINTIES IN BOTH THE TRACK AND INTENSITY
FORECASTS, IT IS TOO EARLY TO SAY WHAT WIND AND STORM SURGE
IMPACTS VANCE MAY CAUSE ALONG THE COAST OF MEXICO. INTERESTS IN
SOUTHWESTERN MEXICO SHOULD CONTINUE TO MONITOR THE PROGRESS OF THE
HURRICANE.
2. HEAVY RAINFALL ASSOCIATED WITH SLOW-MOVING HURRICANE VANCE WILL
IMPACT THE WESTERN COAST OF MEXICO FROM MICHOACáN TO JALISCO DURING
MUCH OF NEXT WEEK. THIS RAINFALL MAY PRODUCE LIFE-THREATENING
FLOODING AND MUDSLIDES ACROSS COLIMA AND WESTERN PORTIONS OF
MICHOACáN AND JALISCO, ESPECIALLY IN AREAS ALONG STEEP TERRAIN.
FORECAST POSITIONS AND MAX WINDS
INIT 24/1500Z 12.9N 103.0W 90 KT 105 MPH
12H 25/0000Z 13.6N 103.3W 85 KT 100 MPH
24H 25/1200Z 14.6N 103.6W 80 KT 90 MPH
36H 26/0000Z 15.5N 104.0W 80 KT 90 MPH
48H 26/1200Z 16.0N 104.3W 85 KT 100 MPH
60H 27/0000Z 16.3N 104.4W 90 KT 105 MPH
72H 27/1200Z 16.7N 104.4W 80 KT 90 MPH
96H 28/1200Z 17.7N 104.5W 65 KT 75 MPH
120H 29/1200Z 18.7N 104.7W 50 KT 60 MPH
FORECASTER BEVEN
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