756
WTPZ41 KNHC 082039
TCDEP1
TROPICAL DEPRESSION SIXTEEN-E DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL EP162023
400 PM CDT SUN OCT 08 2023
SINCE THE PRIOR ADVISORY, 1-MINUTE VISIBLE IMAGES FROM THE GOES-18
MESOSECTOR HAVE BEEN QUITE HELPFUL IN SHOWING THAT THE SYSTEM WE
HAVE BEEN MONITORING JUST SOUTH OF ZIHUATANEJO HAS DEVELOPED A
WELL-DEFINED CIRCULATION LOCATED A BIT FARTHER NORTHWEST OF PREVIOUS
ESTIMATIONS. THIS CIRCULATION WAS FARTHER SUPPORTED BY A 1702 UTC
GMI PASS WHICH SHOWED TIGHTLY CURVED BANDS WRAPPING MOST OF THE WAY
AROUND THIS APPARENT CENTER ON THE 37 GHZ CHANNEL. THUS, THE SYSTEM
NOW CAN BE CONSIDERED A TROPICAL DEPRESSION, AND THE INITIAL
INTENSITY IS 30 KT FOR THIS ADVISORY, WHICH IS IN BETWEEN THE
T1.5/25-KT ESTIMATES FROM TAFB AND SAB VERSUS 35-KT FROM THE D-PRINT
ESTIMATE FROM UW-CIMSS.
NOW THAT THE CENTER HAS BECOME WELL-DEFINED, IT HAS FORMED FARTHER
NORTHWEST THAN EARLIER ESTIMATED. THIS SHOULD NOT BE CONSIDERED AN
ACCELERATION IN THE SHORT-TERM MOTION THOUGH, WHICH STILL APPEARS TO
BE SLOWLY OFF TO THE NORTH-NORTHWEST AT 340/4 KT. THIS SLOW MOTION
IS EXPECTED TO CONTINUE WITH A GRADUAL TURN NORTHWARD AND THEN
NORTH-NORTHEASTWARD AS THE SYSTEM IS STEERED AROUND MID-LEVEL
RIDGING LOCATED EAST OF IT OVER THE CARIBBEAN SEA IN ADDITION TO THE
OUTER CIRCULATION OF TROPICAL STORM LIDIA TO ITS WEST. GIVEN THE
FARTHER NORTHWESTWARD INITIAL POSITION, THE TIMING FOR LANDFALL HAS
MOVED UP A BIT TO BETWEEN 24-36 H, BY TOMORROW EVENING. THERE
CONTINUES TO BE SOME SPREAD IN THIS LANDFALL TIMING, WITH THE GFS
REMAINING ON THE FASTER END VERSUS THE SLOWER CMC AND ECMWF
SOLUTIONS. THE LATEST NHC TRACK FORECAST MORE OR LESS SPLITS THE
DIFFERENCE, WHICH IS CLOSE TO BOTH THE TVCE AND HCCA CONSENSUS AIDS,
THOUGH MOST OF THE GUIDANCE NOW AGREES THE SYSTEM SHOULD BE INLAND
AFTER 36 HOURS.
INTENSIFICATION IS STILL FORECAST UP UNTIL THE SYSTEM MOVES INLAND
OVER MEXICO. WITH LANDFALL NOW BETWEEN 24-36 H, THERE MIGHT NOT BE
QUITE AS MUCH TIME FOR INTENSIFICATION AS PREVIOUSLY EXPECTED. WITH
THAT SAID, BOTH THE RAW MODEL OUTPUT FROM THE ECMWF AND CMC SUGGEST
SIGNIFICANT INTENSIFICATION OVER THE NEXT 24 HOURS BEFORE THE
DEPRESSION MAKES LANDFALL, AND OUT OF RESPECT OF THESE MODELS, A
PEAK INTENSITY OF 45 KT CONTINUES TO BE SHOWN JUST BEFORE LANDFALL.
THIS IS ON THE HIGHER END OF THE INTENSITY GUIDANCE ENVELOPE. THE
SYSTEM SHOULD QUICKLY WEAKEN AFTER MOVING INLAND, ULTIMATELY
DISSIPATING OVER THE HIGHER RUGGED TERRAIN OF SOUTH-CENTRAL MEXICO
BY 48 HOURS. HOWEVER, THE SIGNIFICANT UP-SLOPE FLOW THAT WILL RESULT
IS ANTICIPATED TO CONTINUE PRODUCING VERY HEAVY RAINFALL INTO
TUESDAY OVER COASTAL AND INLAND MEXICO AS THE CYCLONE AND ITS
REMNANTS MOVE FARTHER INLAND.
KEY MESSAGES:
1. THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM BEFORE IT
APPROACHES THE COAST OF SOUTHERN MEXICO ON MONDAY. A TROPICAL STORM
WARNING REMAINS IN EFFECT FOR A PORTION OF THE COAST OF SOUTHERN
MEXICO.
2. HEAVY RAINS FROM THIS SYSTEM WILL LIKELY PRODUCE FLASH AND URBAN
FLOODING, ALONG WITH POSSIBLE MUDSLIDES IN AREAS OF HIGHER TERRAIN
ACROSS THE STATES OF GUERRERO, MICHOACAN AND COASTAL SECTIONS OF
WESTERN OAXACA.
FORECAST POSITIONS AND MAX WINDS
INIT 08/2100Z 15.9N 101.7W 30 KT 35 MPH
12H 09/0600Z 16.5N 101.8W 35 KT 40 MPH
24H 09/1800Z 17.2N 101.7W 45 KT 50 MPH
36H 10/0600Z 18.0N 101.4W 30 KT 35 MPH...INLAND
48H 10/1800Z...DISSIPATED
FORECASTER PAPIN
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