987
WTPZ42 KNHC 260237
TCDEP2
TROPICAL STORM VANCE DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL EP222026
900 PM CST SUN OCT 25 2026
VANCE'S STRUCTURE CONTINUES TO DEGRADE AS SEEN IN VISIBLE SATELLITE
IMAGERY AND THE GPM AND AMSR3 MICROWAVE PASSES, DUE TO STRONG
VERTICAL WIND SHEAR AND RELATIVELY DRY MID-LEVEL AIR. CONVECTION
CONTINUES TO DEVELOP TO THE NORTHEAST OF THE CENTER, BUT IT IS
MOSTLY LIMITED TO THAT QUADRANT. THE TAFB DVORAK FIX WAS T3.5/55 KT
AND THE OBJECTIVE INTENSITY ESTIMATES FROM UW-CIMSS ARE IN 37-52 KT
RANGE. BASED ON THAT DATA, THE INITIAL INTENSITY HAS BEEN LOWERED
TO 55 KT.
VANCE IS CURRENTLY MOVING TOWARD THE NORTHWEST, 305/6 KT. THE
TROPICAL STORM IS BEING STEERED BY A MID-LEVEL RIDGE CENTERED OVER
THE SOUTH-CENTRAL UNITED STATES, ALONG WITH A CLOSED UPPER-LEVEL LOW
MOVING ACROSS THE SOUTHWESTERN UNITED STATES. THE CYCLONE IS
EXPECTED TO CONTINUE TO MOVE TOWARD THE NORTHWEST TO WEST-NORTHWEST
WITH A DECREASE IN FORWARD SPEED AS THE STEERING CURRENTS WEAKEN. A
TURN BACK TO THE NORTH IS EXPECTED BY THE MIDDLE OF THE WEEK AS AN
AMPLIFIED MID TO UPPER-LEVEL TROUGH MOVES OVER THE EASTERN PACIFIC.
THE CURRENT NHC TRACK FORECAST HAS BEEN ADJUSTED A LITTLE TO THE
WEST OF THE PREVIOUS ONE. FUTURE ADJUSTMENTS TO THE WEST ARE LIKELY
IF THE GUIDANCE TRENDS CONTINUE.
THE COMBINATION OF SOUTHWESTERLY WIND SHEAR AND RELATIVELY DRY
MID-LEVEL AIR ARE EXPECTED TO CONTINUE TO GRADUALLY WEAKEN THE
STORM. BY THE MIDDLE OF THIS WEEK, AN UPPER-LEVEL TROUGH WILL
FURTHER ENHANCE THE WIND SHEAR, RESULTING IN ADDITIONAL WEAKENING.
BOTH THE GFS AND ECMWF SIMULATED SATELLITE IMAGERY SUGGEST THAT
VANCE WILL STRUGGLE TO HOLD ON TO ORGANIZED DEEP CONVECTION BY LATE
THIS WEEK. THE CURRENT INTENSITY FORECAST STILL CALLS FOR VANCE
TO BECOME POST-TROPICAL AT 96 H AND DEGENERATE INTO A REMNANT LOW BY
120 H. HOWEVER, THE CURRENT INTENSITY FORECAST IS ON THE UPPER END
OF THE GUIDANCE ENVELOPE, AS MOST OF THE GUIDANCE SHOWS THE RATE OF
WEAKENING MUCH FASTER THAN WHAT IS CURRENTLY FORECAST. IT IS
CERTAINLY POSSIBLE THAT THE CYCLONE COULD WEAKEN FASTER, WHICH WILL
MEAN THAT IT COULD BECOME A REMNANT LOW SOONER THAN WHAT IS
FORECASTED.
KEY MESSAGES:
1. ALTHOUGH THE THREAT TO SOUTHWEST MEXICO IS DECREASING
AS THE FORECAST TRACK SHIFTS WESTWARD AWAY FROM THE COAST,
INTERESTS THERE SHOULD CONTINUE TO MONITOR VANCE'S PROGRESS.
2. PERIODS OF HEAVY RAINFALL ASSOCIATED WITH VANCE WILL IMPACT
PORTIONS OF WESTERN MEXICO DURING MUCH OF THIS WEEK. THIS RAINFALL
MAY PRODUCE FLOODING AND MUDSLIDES ACROSS COLIMA, NAYARIT, AND
SINALOA, ALONG WITH WESTERN PORTIONS OF MICHOACáN, JALISCO, AND
DURANGO, ESPECIALLY IN AREAS ALONG STEEP TERRAIN.
FORECAST POSITIONS AND MAX WINDS
INIT 26/0300Z 15.0N 104.7W 55 KT 65 MPH
12H 26/1200Z 15.3N 105.3W 50 KT 60 MPH
24H 27/0000Z 15.7N 106.0W 45 KT 50 MPH
36H 27/1200Z 16.5N 106.8W 40 KT 45 MPH
48H 28/0000Z 17.4N 107.3W 40 KT 45 MPH
60H 28/1200Z 18.5N 107.6W 40 KT 45 MPH
72H 29/0000Z 20.0N 107.7W 40 KT 45 MPH
96H 30/0000Z 22.0N 107.8W 35 KT 40 MPH...POST-TROPICAL
120H 31/0000Z 24.0N 107.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
FORECASTER KATZ/CANGIALOSI
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page