104
WTPZ43 KNHC 050840
TCDEP3
HURRICANE RACHEL DISCUSSION NUMBER 33
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182026
200 AM PDT MON OCT 05 2026
RACHEL HAS THE SATELLITE APPEARANCE OF A HURRICANE THAT RECENTLY
UNDERWENT AN EYEWALL REPLACEMENT CYCLE (ERC), WITH A BROAD RING OF
OUTER CONVECTION WHILE THE SMALLER CORE IT HAD YESTERDAY IS DECAYING
WITHIN. ON MICROWAVE IMAGERY, A 0302 UTC GMI PASS ALSO SHOWED A MORE
PROMINENT OUTER EYEWALL THAT WAS OPEN ON THE NORTHWEST SIDE ON THE
89 GHZ CHANNEL. THIS STRUCTURE SUGGESTS SOME DRY AIR IS ALSO BEING
ENTRAINED INTO THE CIRCULATION, LIKELY DUE TO 15-20 KT OF
NORTHEASTERLY VERTICAL WIND SHEAR DIAGNOSED BY UW-CIMSS. THE D-MINT
INTENSITY ESTIMATE ASSOCIATED WITH THAT GMI MICROWAVE PASS WAS
83 KT, BUT OTHER SUBJECTIVE AND OBJECTIVE SATELLITE ESTIMATES
CONTINUE TO GRADUALLY DECREASE, SO THE INITIAL INTENSITY IS BEING
LOWERED TO 80 KT FOR THIS ADVISORY.
THE HURRICANE CONTINUES TO MOVE NORTH OF DUE WEST, ESTIMATED AT
280/7 KT. A MID-LEVEL RIDGE OVER THE SOUTHWESTERN UNITED STATES
EXTENDS INTO THE EAST PACIFIC AND IS EXPECTED TO CONTINUE STEERING
RACHEL OFF IN A GENERAL WESTWARD TO WEST-NORTHWESTWARD MOTION OVER
THE NEXT 2-4 DAYS. NEAR THE END OF THE FORECAST PERIOD, A MID- TO
UPPER-LEVEL TROUGH IS FORECAST TO DIG IN TO THE NORTHWEST OF RACHEL,
WITH THE GUIDANCE SHOWING THE TROPICAL CYCLONE'S MOTION COMING TO A
HALT AND POTENTIALLY TURNING NORTHEASTWARD BY 120 H. WHILE BOTH THE
DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE ARE TIGHTLY CLUSTERED OVER
THE FIRST 3-4 DAYS, THE POSSIBLE TROUGH INTERACTION RESULTS IN A
LARGE INCREASE IN TRACK SPREAD BY 120 H. THE LATEST NHC TRACK
FORECAST IS JUST A TOUCH NORTH OF THE PREVIOUS ONE, FOLLOWING THE
BLEND IN THE LATEST HFIP CORRECTED CONSENSUS APPROACH (HCCA), GOOGLE
DEEPMIND ENSEMBLE MEAN (GDMI), AND ITS NEWER VERSION (WN3I).
THE INTENSITY FORECAST FOR RACHEL IS A LITTLE INTERESTING. PART OF
THE RECENT WEAKENING IS LIKELY DUE TO THE COMBINATION OF THE
HURRICANE UNDERGOING AN ERC WHILE THERE WAS A SUBTLE INCREASE IN
NORTHEASTERLY SHEAR OVER THE PAST DAY. BOTH THE GFS AND EC-SHIPS
GUIDANCE SHOW THIS SHEAR PERSISTING FOR THE NEXT 12-24 H BEFORE
DIMINISHING BELOW 10 KT AS THE HURRICANE CONTINUES TO TRAVERSE
SEA-SURFACE TEMPERATURES (SSTS) IN THE 26-27 C RANGE. THUS, WHILE A
LITTLE ADDITIONAL WEAKENING IS SHOWN IN THE SHORT-TERM, THE
HURRICANE MIGHT STABILIZE FOR A BIT IF THE SHEAR DECREASES, AND I
CAN'T RULE OUT THE POSSIBILITY IT MIGHT STILL DEVELOP ANNULAR
CHARACTERISTICS IN THE 36-48 H TIME FRAME. THEREAFTER, WHILE SHEAR
WILL LIKELY REMAIN LOW, SSTS DECREASE TO AROUND 25 C, AND MOST OF
THE GUIDANCE RESPONDS BY SHOWING SLOW WEAKENING RESUMING. RACHEL MAY
START TO STRUGGLE TO PRODUCE ORGANIZED CONVECTION BY 120 H. HOWEVER,
THIS IS A TRICKIER-THAN-USUAL FORECAST, BECAUSE DURING THAT TIME IT
MAY ALSO INTERACT WITH AN UPPER-LEVEL TROUGH WHICH COULD PROVIDE
SOME BAROCLINIC SUPPORT TO HELP MAINTAIN CONVECTION. IN FACT, THIS
POSSIBILITY IS SHOWN IN THE SIMULATED INFRARED IMAGERY FROM THE 00
UTC GFS AND ECMWF RUNS. THUS, POST-TROPICAL STATUS IS NOT SHOWN AT
120 H QUITE YET. THE LATEST NHC INTENSITY FORECAST LIES CLOSEST TO
THE HCCA INTENSITY AID.
FORECAST POSITIONS AND MAX WINDS
INIT 05/0900Z 20.4N 115.6W 80 KT 90 MPH
12H 05/1800Z 20.5N 116.7W 75 KT 85 MPH
24H 06/0600Z 20.6N 118.2W 75 KT 85 MPH
36H 06/1800Z 20.7N 119.7W 75 KT 85 MPH
48H 07/0600Z 21.0N 121.0W 75 KT 85 MPH
60H 07/1800Z 21.5N 122.5W 65 KT 75 MPH
72H 08/0600Z 22.0N 124.1W 60 KT 70 MPH
96H 09/0600Z 22.4N 126.7W 50 KT 60 MPH
120H 10/0600Z 22.6N 126.5W 40 KT 45 MPH
FORECASTER PAPIN
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