Tropical Storm THIRTEEN Advisory Wed Aug 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W
(THIRTEEN) WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 22.1N 132.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 350 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH TIGHTLY WRAPPING
LOW LEVEL CLOUD LINES. A 310750Z SSMIS 91GHZ MICROWAVE IMAGE
REVEALS THAT 13W IS UNDER RELENTLESS NORTHEASTERLY SHEAR DUE TO THE
OUTFLOW FROM 12W WHICH IS 260NM NORTHWEST. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON EIR AND SSMIS MICROWAVE
IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON PGTW AND RJTD DVORAK INTENSITY ESTIMATES
REFLECTING 30 KNOTS WHILE KNES REMAINS LOW AT T1.0 AND CIMSS ADT
REMAINS HIGHER AT 35KTS.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM:  COMBINATION OF A SUBTROPICAL RIDGE
(STR) TO THE EAST AND BINARY INTERACTION WITH STY 12W TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.0 - 25 KTS
   CIMSS ADT: 35 KTS AT 311140Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: NORTHEASTERLY SHEAR FROM TY 12W.
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TD 13W IS FORECAST TO TRACK GENERALLY
NORTHWESTWARD ALONG THE EASTERN PERIPHERY OF TY 12W. WHILE THE
SYSTEM IS CURRENTLY BEING LIMITED BY THE OUTFLOW FROM 12W WHICH HAS
FULLY EXPOSED THE LLCC, THERE IS A SHRINKING OPPORTUNITY FOR
DEVELOPMENT NEAR TAU 12. ONCE 13W ESCAPES THIS REPRESSIVE OUTFLOW
AND MOVES PARALLEL TO 12W THE OUTFLOW ENVIRONMENT SHOULD IMPROVE
DRAMATICALLY, MODEL FIELDS SUGGEST LIMITED EASTWARD AND POLEWARD
OUTFLOW FROM TY 12W AND DEVELOPMENT OF AN EQUATORWARD AND EASTWARD
OUTFLOW CHANNEL FOR TD 13W. THIS NEW OUTFLOW PATTERN COUPLED WITH
THE ALREADY WARM SEA SURFACE TEMPERATURES AND MILD VERTICAL WIND
SHEAR COULD ALLOW FOR A PERIOD OF BRIEF INTENSIFICATION TO A PEAK
OF APPROXIMATELY 40 KNOTS BY TAU 24. AFTER TAU 24, 13W WILL
CONTINUE TO INTERACT WITH TY 12W UNTIL FULLY DISSIPATING AS A
SEPARATE AND DISTINCT CIRCULATION CENTER BY TAU 36 WITH AN
INTENSITY NEAR 40KTS. UNLIKE PREVIOUSLY FORECASTS THE LATEST RUN OF
HWRF-P IS NO LONGER INDICATING THE LONGSHOT INTENSIFICATION TO
TYPHOON STRENGTH BEFORE STRIKING KADENA AND ORBITING 12W,
NEVERTHELESS, JTWC WILL CONTINUE TO MONITOR ALL POSSIBLE
PERMUTATIONS AS BINARY INTERACTION CAN BE HIGHLY COMPLEX AND
UNPREDICTABLE.
MODEL DISCUSSION: WITH THE EXCEPTION OF COAMPS-TC (NAVGEM VERSION),
NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT 13W WILL TRANSLATE
ALONG THE EASTERN AND NORTHERN PERIPHERY OF 12W BEFORE FULLY
INTEGRATING AND THEREBY DISSIPATING NEAR TAU 36. FOR THIS REASON
THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE. RELIABLE
MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT 13W WILL
INITIALLY STRUGGLE TO INTENSIFY AFTER WHICH THE SYSTEM WILL ACHIEVE
A PEAK OF 40KTS BEFORE ITS INEVITABLE INTEGRATION WITH 12W.
NOTWITHSTANDING THE LONGSHOT HWRF-P PREDICTION MENTIONED ABOVE, THE
JTWC FORECAST INTENSITY IS PLACED WITH MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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