076
WTPZ43 KNHC 091456
TCDEP3
TROPICAL STORM RACHEL DISCUSSION NUMBER 50
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182026
800 AM PDT FRI OCT 09 2026
SATELLITE IMAGES INDICATE THAT RACHEL IS STRUGGLING TO MAINTAIN DEEP
CONVECTION, WITH ONLY LIMITED AND SHALLOW CONVECTION REMAINING NEAR
THE CENTER OF CIRCULATION. A SCATTEROMETER PASS RECEIVED SHORTLY
AFTER THE PREVIOUS ADVISORY INDICATED PEAK WINDS OF AROUND 43 KT.
SATELLITE INTENSITY ESTIMATES FROM UW-CIMSS RANGE FROM 31 TO 44 KT,
WHILE THE TAFB SUBJECTIVE DVORAK ESTIMATE IS T2.5/35 KT. GIVEN THE
SCATTEROMETER DATA, THE INITIAL INTENSITY IS HELD AT 45 KT FOR THIS
ADVISORY.
THE STORM IS MOVING NORTHEASTWARD AT AN ESTIMATED 055/4 KT. A
DEEPENING MID-TO UPPER-LEVEL TROUGH MOVING INTO THE EASTERN PACIFIC
TOWARD THE WESTERN UNITED STATES IS EXPECTED TO STEER RACHEL
NORTHEASTWARD TO NORTH-NORTHEASTWARD WITH AN INCREASING FORWARD
SPEED THROUGHOUT THE FORECAST PERIOD. ON THE FORECAST TRACK, THE
SYSTEM IS EXPECTED TO MOVE INLAND OVER NORTHERN BAJA CALIFORNIA LATE
SATURDAY OR EARLY SUNDAY BEFORE CONTINUING NORTHEASTWARD INTO THE
SOUTHWESTERN UNITED STATES ON SUNDAY. THERE HAS BEEN A NORTHWARD
SHIFT IN THE LATEST TRACK GUIDANCE, WITH THE GLOBAL AND HURRICANE
REGIONAL MODELS NOW BRINGING THE CENTER NEAR THE U.S./MEXICO BORDER
OR INTO EXTREME SOUTHERN CALIFORNIA. THE LATEST NHC TRACK FORECAST
HAS BEEN NUDGED NORTHWARD AND LIES BETWEEN THE GLOBAL AND REGIONAL
HURRICANE MODELS TO THE LEFT, AND THE HCCA AND GDMI SLIGHTLY TO THE
RIGHT. GIVEN THIS TRACK FORECAST, TROPICAL STORM WATCHES HAVE BEEN
ISSUED FOR PORTIONS OF NORTHERN BAJA CALIFORNIA AND SOUTHERN
CALIFORNIA. THERE WILL BE A SHARP GRADIENT IN THE WIND FIELD, WITH
THE STRONGEST WINDS ANTICIPATED TO REMAIN PRIMARILY IN THE EASTERN
AND SOUTHERN SEMICIRCLES OF THE CIRCULATION.
RACHEL REMAINS EMBEDDED WITHIN A VERY DRY AIR MASS, WITH MID-LEVEL
RELATIVE HUMIDITY VALUES IN THE LOWER 30 PERCENT RANGE. SEA SURFACE
TEMPERATURES OF AROUND 24-25C WILL ALSO LIMIT CONVECTIVE
ORGANIZATION. HOWEVER, INTERACTION WITH THE AFOREMENTIONED DEEPENING
TROUGH IS EXPECTED TO INCREASE MID-LEVEL MOISTURE AND IMPROVE
UPPER-LEVEL DIVERGENCE, ALLOWING RACHEL TO PRODUCE INTERMITTENT
BURSTS OF DEEP CONVECTION AND MAINTAIN TROPICAL CYCLONE STATUS.
FURTHERMORE, THERE ARE ANOMALOUSLY WARM WATERS JUST OFFSHORE OF
NORTHERN BAJA CALIFORNIA FOR THIS TIME OF YEAR, RUNNING ROUGHLY 6-7C
ABOVE NORMAL. THERE HAS BEEN A NOTABLE UPWARD TREND IN THE INTENSITY
GUIDANCE FROM THE GLOBAL AND REGIONAL MODELS THIS CYCLE, AND THE NHC
FORECAST HAS BEEN ADJUSTED ACCORDINGLY. AS THE SYSTEM APPROACHES THE
COAST, INCREASING VERTICAL WIND SHEAR IS EXPECTED TO DISPLACE THE
REMAINING CONVECTION DOWNSHEAR TOWARD THE NORTHEASTERN PORTION OF
THE CIRCULATION. RACHEL IS FORECAST TO REMAIN A STRONG TROPICAL
STORM AS IT MAKES LANDFALL. ONCE INLAND, RAPID WEAKENING IS
EXPECTED, AND THE SYSTEM IS FORECAST TO BECOME POST-TROPICAL OVER
THE SOUTHWESTERN UNITED STATES. THE LATEST NHC INTENSITY FORECAST
LIES NEAR THE UPPER END OF THE GUIDANCE ENVELOPE, REFLECTING THE
COMPLEX INTERACTIONS BETWEEN RACHEL AND THE APPROACHING TROUGH, AS
WELL AS THE INHERENT UNCERTAINTY IN HOW MODELS HANDLE THESE
PROCESSES.
KEY MESSAGES:
1. RACHEL IS EXPECTED TO APPROACH THE COAST OF THE NORTHERN BAJA
CALIFORNIA PENINSULA AND SOUTHERN CALIFORNIA AT TROPICAL STORM
STRENGTH SATURDAY NIGHT, AND A TROPICAL STORM WATCH IS NOW IN EFFECT
FROM SAN JOSE DE LAS PALOMAS, MEXICO NORTHWARD INTO SOUTHERN
CALIFORNIA TO THE SAN DIEGO/ORANGE COUNTY LINE.
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, SATURDAY NIGHT AND SUNDAY.
3. RACHEL AND THE MOISTURE ASSOCIATED WITH THE SYSTEM WILL SPREAD
OVER PORTIONS OF THE SOUTHWEST UNITED STATES AND NORTHERN BAJA
CALIFORNIA PENINSULA THROUGH THIS WEEKEND. THIS WILL LEAD TO
INCREASING COVERAGE OF RAINFALL AND FOR THE POTENTIAL OF FLASH AND
URBAN FLOODING.
4. SWELLS PARTLY GENERATED BY RACHEL WILL CONTINUE TO BUILD ALONG
THE COAST OF SOUTHERN CALIFORNIA AND NORTHERN BAJA CALIFORNIA.
THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP
CURRENT CONDITIONS, AS WELL AS MODERATE TO ISOLATED MAJOR COASTAL
FLOODING, THROUGH EARLY NEXT WEEK. PLEASE CONSULT PRODUCTS FROM
YOUR LOCAL WEATHER OFFICE.
FORECAST POSITIONS AND MAX WINDS
INIT 09/1500Z 22.8N 124.6W 45 KT 50 MPH
12H 10/0000Z 23.4N 123.6W 45 KT 50 MPH
24H 10/1200Z 25.1N 121.0W 50 KT 60 MPH
36H 11/0000Z 28.5N 118.1W 55 KT 65 MPH
48H 11/1200Z 33.3N 116.0W 45 KT 50 MPH...INLAND
60H 12/0000Z 38.1N 114.0W 35 KT 40 MPH...POST-TROP/INLAND
72H 12/1200Z...DISSIPATED
FORECASTER KELLY
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