802
WTPZ43 KNHC 092044
TCDEP3
TROPICAL STORM RACHEL DISCUSSION NUMBER 51
NWS NATIONAL HURRICANE CENTER MIAMI FL EP182026
200 PM PDT FRI OCT 09 2026
RACHEL IS PRODUCING LIMITED CONVECTION THIS AFTERNOON, WITH
RELATIVELY SHALLOW, WARM CLOUD TOPS CONFINED TO THE NORTHERN AND
EASTERN SEMICIRCLES. A SCATTEROMETER PASS AT 1753 UTC SHOWED PEAK
SATELLITE-DERIVED WINDS OF 37 KT. SATELLITE INTENSITY ESTIMATES FROM
UW-CIMSS AND TAFB RANGE BETWEEN 26 AND 41 KT. USING THIS DATA, THE
INITIAL INTENSITY IS LOWERED TO 40 KT FOR THIS ADVISORY.
THE SYSTEM IS STARTING TO GRADUALLY INCREASE ITS FORWARD SPEED AND
IS MOVING AT AN ESTIMATED 055/5 KT. RACHEL SHOULD BEGIN TO
ACCELERATE TOWARD THE NORTHEAST AND THEN NORTH-NORTHEAST TONIGHT AND
TOMORROW, EMBEDDED WITHIN THE FLOW OF A DEEPENING MID- TO
UPPER-LEVEL TROUGH APPROACHING THE WESTERN UNITED STATES. ON THE
FORECAST TRACK, THE SYSTEM IS EXPECTED TO MOVE INLAND OVER NORTHERN
BAJA CALIFORNIA LATE SATURDAY OR EARLY SUNDAY BEFORE CONTINUING
NORTH-NORTHEASTWARD INTO THE SOUTHWESTERN UNITED STATES ON SUNDAY.
TRACK GUIDANCE REMAINS SIMILAR TO THE PREVIOUS CYCLE, WITH THE
HURRICANE REGIONAL MODELS, THE GFS, AND THE ECMWF ON THE LEFT SIDE
OF THE ENVELOPE, AND THE GDMI AND HCCA ON THE RIGHT. THE NHC TRACK
FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE AND LIES IN
THE MIDDLE OF THE GUIDANCE ENVELOPE. NOTE THAT 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 CONTINUES TO STRUGGLE TO PRODUCE ANYTHING MORE THAN SHALLOW
CONVECTION, AS THE SYSTEM IS EMBEDDED WITHIN A DRY AND STABLE AIR
MASS OVER COOL SEA SURFACE TEMPERATURES. HOWEVER, AS THE SYSTEM
BEGINS TO ACCELERATE NORTHEASTWARD, A FAVORABLE TROUGH INTERACTION
IS EXPECTED, ALONG WITH AN INCREASE IN MID-LEVEL RELATIVE HUMIDITY.
ALSO, SEA SURFACE TEMPERATURES JUST OFFSHORE OF THE WESTERN BAJA
CALIFORNIA PENINSULA ARE ANOMALOUSLY WARM FOR THIS TIME OF YEAR.
GIVEN THESE CONDITIONS, RACHEL IS EXPECTED TO PRODUCE INTERMITTENT
BURSTS OF CONVECTION AND STRENGTHEN, UP UNTIL LANDFALL, EVEN THOUGH
VERTICAL WIND SHEAR WILL INCREASE SIGNIFICANTLY AS THE SYSTEM
APPROACHES THE COAST. 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 IS SIMILAR TO THE
PREVIOUS ADVISORY AND LIES NEAR THE UPPER END OF THE GUIDANCE
ENVELOPE, ALTHOUGH SOME OF THE HURRICANE REGIONAL MODELS AND THE
HCCA ARE SLIGHTLY HIGHER THAN THE OFFICIAL FORECAST JUST OFFSHORE AT
36 H.
KEY MESSAGES:
1. RACHEL IS EXPECTED TO APPROACH THE COAST OF THE NORTHERN BAJA
CALIFORNIA PENINSULA AND EXTREME SOUTHERN CALIFORNIA AT TROPICAL
STORM STRENGTH SATURDAY NIGHT. TROPICAL STORM CONDITIONS ARE
EXPECTED OVER PORTIONS OF WESTERN BAJA CALIFORNIA, MEXICO WHERE
TROPICAL STORM WARNINGS ARE IN EFFECT. TROPICAL STORM CONDITIONS ARE
POSSIBLE IN EXTREME SOUTHERN CALIFORNIA AND EASTERN BAJA CALIFORNIA
WHERE A TROPICAL STORM WATCH IS 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, SATURDAY NIGHT AND SUNDAY.
3. RACHEL AND ITS MOISTURE 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 FOR SIGNIFICANT 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 09/2100Z 23.3N 124.0W 40 KT 45 MPH
12H 10/0600Z 24.2N 122.4W 45 KT 50 MPH
24H 10/1800Z 26.7N 119.4W 50 KT 60 MPH
36H 11/0600Z 30.9N 117.2W 55 KT 65 MPH
48H 11/1800Z 36.4N 115.0W 40 KT 45 MPH...POST-TROP/INLAND
60H 12/0600Z...DISSIPATED
FORECASTER KELLY
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