432
WTPZ42 KNHC 242040
TCDEP2
HURRICANE VANCE DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP222026
300 PM CST SAT OCT 24 2026
VANCE HAS BECOME SIGNIFICANTLY LESS ORGANIZED SINCE THE LAST
ADVISORY DUE TO A COMBINATION OF COLD WATER NEAR THE CENTER AND
INCREASING SOUTHWESTERLY SHEAR. MICROWAVE DATA INDICATES THAT THE
EYEWALL HAS BROKEN OPEN, WITH THE REMAINING CONVECTION LIMITED TO
NORTH OF THE CENTER. IN ADDITION, VISIBLE IMAGERY SHOWS THE
LOW-LEVEL CENTER TO BE NEAR OR A LITTLE SOUTH OF THE SOUTHERN EDGE
OF THE CONVECTIVE MASS. THE VARIOUS SATELLITE INTENSITY ESTIMATES
HAVE DROPPED, AND BASED ON THEM THE INITIAL INTENSITY IS LOWERED TO
80 KT. THIS COULD BE QUITE GENEROUS, AS THE CURRENT STRUCTURE DOES
NOT LOOK MUCH LIKE A HURRICANE.
THE INTENSITY FORECAST IS STILL PROBLEMATIC, BUT PERHAPS A LITTLE
LESS SO THAN EARLIER. VANCE IS LIKELY TO WEAKEN DURING THE NEXT
12-18 H AS IT CROSSES A POOL OF COLDER WATER WITH TEMPERATURES NEAR
27C THAT HAS BEEN UPWELLED BY SEVERAL PREVIOUS TROPICAL CYCLONES,
WHILE AT THE SAME TIME IT EXPERIENCES AT LEAST MODERATE
SOUTHWESTERLY SHEAR. BEYOND THAT TIME, THE CENTER IS EXPECTED TO
MOVE OVER SEA SURFACE TEMPERATURES NEAR 29C CLOSER TO THE COAST OF
MEXICO. THIS COULD ALLOW INTENSIFICATION IF THE SHEAR IS LIGHT
ENOUGH AND THE STORM STRUCTURE IS STILL GOOD ENOUGH TO ALLOW IT. THE
GFS AND ECMWF CONTINUE SHOW A PERIOD OF REDUCED, BUT STILL MARGINAL,
SHEAR THAT COULD ALLOW SOME INTENSIFICATION, AND BASED ON THIS AND
TRENDS IN THE GUIDANCE SLIGHT RE-INTENSIFICATION IS SHOWN AT 48 H.
BY THE END OF THE FORECAST PERIOD, INCREASING SHEAR IS LIKELY TO
CAUSE VANCE TO STEADILY WEAKEN. IT IS STILL POSSIBLE THAT VANCE
COULD WEAKEN MORE THAN FORECAST BEFORE REACHING WARMER WATER AND
THAT THE SHEAR MAY BE TOO STRONG TO ALLOW RE-INTENSIFICATION AFTER
36 H. THE NEW INTENSITY FORECAST HAS MAJOR DOWNWARD ADJUSTMENTS FROM
THE PREVIOUS FORECAST.
THE INITIAL MOTION REMAINS NORTH-NORTHWESTWARD OR 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 OR SO. THE TRACK FORECAST BEYOND THAT TIME IS DEPENDENT ON THE
CYCLONE'S STRENGTH AND 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 OR NORTH-NORTHWESTWARD. THE TRACK
GUIDANCE ENVELOPE HAS SHIFTED WESTWARD SINCE THE PREVIOUS ADVISORY,
AND THE NEW FORECAST TRACK HAS BEEN NUDGED WESTWARD AS WELL.
ADDITIONAL WESTWARD ADJUSTMENTS TO THE TRACK MAY BE NECESSARY IF
VANCE CONTINUES TO LOSE ORGANIZATION.
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 24/2100Z 13.3N 103.3W 80 KT 90 MPH
12H 25/0600Z 14.0N 103.6W 75 KT 85 MPH
24H 25/1800Z 14.9N 104.0W 70 KT 80 MPH
36H 26/0600Z 15.6N 104.4W 70 KT 80 MPH
48H 26/1800Z 16.0N 104.6W 75 KT 85 MPH
60H 27/0600Z 16.4N 104.8W 70 KT 80 MPH
72H 27/1800Z 17.0N 104.9W 65 KT 75 MPH
96H 28/1800Z 18.1N 105.2W 50 KT 60 MPH
120H 29/1800Z 19.3N 105.6W 40 KT 45 MPH
FORECASTER BEVEN
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