739
WTPZ43 KNHC 101453
TCDEP3
TROPICAL STORM RACHEL DISCUSSION NUMBER 54
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182026
800 AM PDT SAT OCT 10 2026
RACHEL APPEARS TO BE IN THE MIDST OF ITS TRANSITION TO A
POST-TROPICAL STORM. CONVECTION IS BECOMING SHALLOWER AND IS BEING
SHEARED OFF TO THE NORTHEAST OF THE CENTER DUE TO 25-35 KT OF
SOUTHWESTERLY SHEAR, AND THE SYSTEM IS TAKING ON A
FRONTAL STRUCTURE WITH A DRIER AIR MASS OF STRATOCUMULUS
CLOUDS WRAPPING AROUND THE SOUTHERN SIDE OF THE CIRCULATION. BASED
ON THE ASCAT-B SCATTEROMETER PASS FROM OVERNIGHT, THE INITIAL
INTENSITY IS HELD AT 50 KT.
RACHEL HAS BEEN MOVING A BIT EAST OF THE PREVIOUS TRACK, AND THE
CURRENT MOTION IS ESTIMATED TO BE NORTHEASTWARD, OR 055/19 KT. A
TURN TOWARD THE NORTH-NORTHEAST WITH AN INCREASE IN FORWARD SPEED
IS EXPECTED BY TONIGHT WHILE RACHEL INTERACTS WITH A MID-LEVEL
CUT-OFF LOW LOCATED TO ITS NORTHWEST. THE TRACK GUIDANCE IS IN GOOD
AGREEMENT THAT RACHEL'S CENTER WILL MOVE ONSHORE THE EXTREME
NORTHERN PORTION OF BAJA CALIFORNIA TONIGHT, WITH THE SYSTEM
CONTINUING QUICKLY NORTH-NORTHEASTWARD ACROSS THE SOUTHWESTERN U.S.
ON SUNDAY. THE NEW NHC TRACK FORECAST HAS BEEN NUDGED EAST OF THE
PREVIOUS TRACK AND IS CLOSE TO THE LATEST HCCA AID.
MODEL-DERIVED PHASE SPACE DIAGRAMS INDICATE THAT RACHEL NOW HAS AN
ASYMMETRIC, SHALLOW WARM-CORE STRUCTURE AND IS LIKELY TO BECOME
DEEPER COLD CORE, AND HENCE FULLY POST TROPICAL, IN ABOUT 24 HOURS
ONCE IT HAS MOVED ONSHORE. IN THE MEANTIME, BAROCLINIC INTERACTION
WITH THE UPPER-LEVEL TROUGH COULD CAUSE SOME SLIGHT INTENSIFICATION
OVER THE NEXT 12 HOURS OR SO, WHICH IS SUPPORTED BY MUCH OF THE
INTENSITY MODELS. WEAKENING IS EXPECTED AFTER RACHEL MOVES ONSHORE,
ALTHOUGH STRONG GUSTY WINDS ARE LIKELY ACROSS MUCH OF THE
SOUTHWESTERN U.S. THROUGH EARLY NEXT WEEK AS LOW PRESSURE MOVES
INTO THE ROCKY MOUNTAINS. A 36-HOUR POST-TROPICAL POINT IS PROVIDED
FOR CONTINUITY, BUT IT'S LIKELY THAT THE LOW WILL NOT HAVE A
WELL-DEFINED CIRCULATION BY THAT POINT.
KEY MESSAGES:
1. RACHEL IS EXPECTED TO APPROACH AND MOVE ASHORE ALONG THE COAST OF
NORTHERN BAJA CALIFORNIA AT TROPICAL STORM STRENGTH TONIGHT.
TROPICAL STORM CONDITIONS ARE EXPECTED IN PORTIONS OF BAJA
CALIFORNIA AND NORTHERN BAJA CALIFORNIA SUR, MEXICO, WHERE TROPICAL
STORM WARNINGS ARE IN EFFECT. TROPICAL STORM CONDITIONS ARE ALSO
POSSIBLE IN EXTREME SOUTHERN CALIFORNIA, EASTERN BAJA CALIFORNIA,
AND PORTIONS OF NORTHWESTERN MEXICO WHERE TROPICAL STORM WATCHES ARE
IN EFFECT.
2. DAMAGING WIND GUSTS ASSOCIATED WITH RACHEL AND ITS REMNANTS ARE
EXPECTED TO SPREAD OVER PORTIONS OF NORTHWESTERN MEXICO AND INTERIOR
PORTIONS OF THE SOUTHWEST UNITED STATES, ESPECIALLY IN AREAS OF
HIGHER TERRAIN, TONIGHT AND SUNDAY.
3. RACHEL AND ITS MOISTURE WILL CONTINUE TO SPREAD OVER PORTIONS OF
THE SOUTHWEST UNITED STATES AND NORTHERN BAJA CALIFORNIA PENINSULA.
THIS WILL LEAD TO INCREASING COVERAGE OF RAINFALL AND FOR THE
POTENTIAL FOR SIGNIFICANT FLASH AND URBAN FLOODING THIS WEEKEND.
4. WAVES GENERATED BY RACHEL, COMBINED WITH AN INCOMING LONG-PERIOD
SOUTHERLY SWELL, WILL PRODUCE LIFE-THREATENING SURF AND RIP CURRENT
CONDITIONS ALONG THE COASTS OF SOUTHERN CALIFORNIA AND NORTHERN BAJA
CALIFORNIA. MAJOR COASTAL FLOODING HAS ALREADY BEEN OCCURRING IN
SOME AREAS, WITH OBSERVED WATER LEVELS RUNNING AS MUCH AS 1.5 FEET
ABOVE PREDICTIONS. COASTAL FLOODING AND EROSION ARE EXPECTED TO
WORSEN TONIGHT INTO SUNDAY MORNING AS THE HIGHEST WAVES ASSOCIATED
WITH RACHEL COINCIDE WITH HIGH TIDES AND ALREADY ELEVATED WATER
LEVELS. HAZARDOUS COASTAL CONDITIONS ARE EXPECTED TO CONTINUE INTO
EARLY NEXT WEEK. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER
OFFICE.
FORECAST POSITIONS AND MAX WINDS
INIT 10/1500Z 25.5N 119.6W 50 KT 60 MPH
12H 11/0000Z 28.2N 117.5W 55 KT 65 MPH
24H 11/1200Z 33.0N 115.3W 40 KT 45 MPH...POST-TROP/INLAND
36H 12/0000Z 38.5N 112.5W 30 KT 35 MPH...POST-TROP/INLAND
48H 12/1200Z...DISSIPATED
FORECASTER BERG
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