641
WTPZ44 KNHC 030244
TCDEP4
TROPICAL STORM PILAR DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL EP192023
1000 PM CDT THU NOV 02 2023
ON REGULAR GEOSTATIONARY SATELLITE IMAGERY, PILAR'S STRUCTURE IS NOT
THAT IMPRESSIVE, WITH PULSING DEEP CONVECTION NEAR THE CENTER AND A
CONTINUED LACK OF BANDING FEATURES. HOWEVER, AN EARLIER AMSR-2
MICROWAVE PASS AT 2003 UTC AND A MORE RECENT 2231 UTC GPM PASS SHOW
THE CYCLONE'S LOW-LEVEL STRUCTURE IS MORE FORMIDABLE, WITH A CYAN
RING EVIDENT ON THE 37-GHZ CHANNEL. HOWEVER, THE 89-GHZ CHANNEL
SHOWS THE DEEPER CONVECTION IS DISPLACED NORTHEAST OF THE CENTER,
POSSIBLY A RESULT OF MODERATE WESTERLY VERTICAL WIND SHEAR DUE TO
THE BRISK GULF OF TEHUANTEPEC GAP-WIND FLOW PILAR IS EMBEDDED IN.
WHILE SUBJECTIVE DVORAK ESTIMATES REMAINS ON THE LOWER SIDE, AT
T3.0/45 KT FROM TAFB, AND T2.5/35 KT FORM SAB, THE INITIAL INTENSITY
WILL REMAIN 50 KT THIS ADVISORY, OUT OF RESPECT FOR THE EARLIER
SCATTEROMETER DATA. THE MAXIMUM WINDS ON PILAR'S NORTH SIDE ARE
LIKELY A RESULT OF PILAR'S CYCLONIC VORTEX SUPERIMPOSED ON THE
LARGER GAP-WIND FLOW IN THE AREA.
THIS SAME FLOW APPEARS TO HAVE CAUSED PILAR TO ACCELERATE TODAY, AND
ITS ESTIMATED MOTION IS CURRENTLY RAPID TO THE WEST-SOUTHWEST AT
250/19 KT. A CONTINUED WEST-SOUTHWESTWARD MOTION WITH A GRADUAL
SLOWDOWN IS EXPECTED FOR THE NEXT DAY OR SO AS THE SMALL CYCLONE IS
STEERED BY THE LOW-LEVEL GAP WINDS IN ADDITION TO A MID-LEVEL RIDGE
DRAPED ALONG TO ITS NORTHWEST. FARTHER UPSTREAM, AN UPPER-LEVEL
TROUGH IS FORECAST TO DIG INTO THE BAJA CALIFORNIA PENINSULA, WHICH
WILL ULTIMATELY ERODE THE RIDGING AT THE SAME TIME PILAR LEAVES THE
INFLUENCE OF THE GAP WIND FLOW, ALLOWING FOR A TURN WESTWARD AND
WEST-NORTHWESTWARD BY THE END OF THE FORECAST. THE TRACK AIDS THIS
EVENING HAVE SHIFTED FASTER AND A BIT FARTHER SOUTH, INFLUENCED SOME
BY THE INITIAL POSITION ASSISTED BY THE MICROWAVE DATA. THE NHC
TRACK FORECAST IS A BLEND OF THE PRIOR INTERPOLATED TRACK WITH THE
CONSENSUS AIDS.
AS EARLIER STATED, THE ENVIRONMENTAL CONDITIONS DO NOT APPEAR ALL
THAT FAVORABLE FOR PILAR, AS THE GAP WINDS THE STORM IS EMBEDDED IN
ALSO CONTRIBUTE TO MODERATE WESTERLY VERTICAL WIND SHEAR. THE SHEAR
DIRECTION IS IMPORTANT, BECAUSE THAT COULD RESULT IN PILAR IMPORTING
DRY AIR UPSTREAM AS SEEN IN THE GOES-18 WATER VAPOR IMAGERY. IN
ADDITION, THE CYCLONE IS QUITE SMALL, POTENTIALLY MAKING IT MORE
SUSCEPTIBLE THAN USUAL TO LESS FAVORABLE ENVIRONMENTAL CONDITIONS.
THUS, THE NHC INTENSITY FORECAST CONTINUES TO SLOW LITTLE CHANGE IN
INTENSITY OR VERY GRADUAL WEAKENING, DESPITE THE STORM MOVING OVER
WARMER SEA-SURFACE TEMPERATURES. THE LATEST NHC INTENSITY FORECAST
FAVORS A BLEND OF THE HAFS-A/B HURRICANE-DYNAMICAL GUIDANCE AND IVCN
CONSENSUS AID. BY EARLY NEXT WEEK, EVEN STRONGER VERTICAL WIND SHEAR
WILL LEAD TO A FASTER RATE OF WEAKENING, AND IT'S POSSIBLE PILAR
COULD BECOME A REMNANT LOW OR DISSIPATE BY THE END OF THE FORECAST
PERIOD.
FORECAST POSITIONS AND MAX WINDS
INIT 03/0300Z 10.7N 99.2W 50 KT 60 MPH
12H 03/1200Z 10.0N 101.8W 50 KT 60 MPH
24H 04/0000Z 9.7N 105.0W 45 KT 50 MPH
36H 04/1200Z 9.6N 108.0W 45 KT 50 MPH
48H 05/0000Z 9.8N 110.6W 45 KT 50 MPH
60H 05/1200Z 10.1N 112.7W 45 KT 50 MPH
72H 06/0000Z 10.8N 114.5W 40 KT 45 MPH
96H 07/0000Z 11.8N 116.7W 35 KT 40 MPH
120H 08/0000Z 13.6N 118.8W 30 KT 35 MPH
FORECASTER PAPIN
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