Advisories

WDPN31 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.7N 143.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 274 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 28W CONTINUING TO HAVE A FULLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH ONLY A FEW ISOLATED PUFFS OF
CONVECTION FLARING UP ALONG THE SOUTHWESTERN TAIL OF THE SYSTEM
THAT ARE QUICK TO DISSIPATE. A 132317Z METOP-B ASCAT PASS REVEALS
THE WIND FIELD HAS REMAINED CONSISTENT, WITH 25 KTS ISOLATED TO THE
NORTHEASTERN QUADRANT AND THE WEAKEST WINDS OF 5-10 IN THE 
SOUTHWESTERN QUADRANT, WITH THE WRAPPING IN THIS AREA BECOMING 
SLIGHTLY ELONGATED, WHILE THE CIRCULATION IN MSI REMAINS QUITE 
SYMMETRICAL. DESPITE THE WARM (28-29 C) SEA SURFACE TEMPERATURES 
(SSTS) AND LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), ENVIRONMENTAL 
CONDITIONS ARE ASSESSED TO BE UNFAVORABLE FOR DEVELOPMENT DUE TO THE 
UPPER-LEVEL TROUGH THAT REMAINS DIRECTLY ABOVE 28W, SUPPRESSING 
OUTFLOW ALOFT AND CAUSING SUBSIDENCE OF DRY MID-LEVEL AIR. THE INITIAL 
POSITION AND INTENSITY ARE ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
EXPOSED LLCC AND AFOREMENTIONED ASCAT DATA.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF SUBTROPICAL RIDGE
CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS SATCON: 42 KTS AT 132027Z
   CIMSS ADT: 25 KTS AT 132340Z
   CIMSS AIDT: 24 KTS AT 132340Z
   CIMSS D-MINT: 25 KTS AT 132257Z
   CIMSS D-PRINT: 25 KTS AT 132340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: UPPER-LEVEL TROUGH SITUATED ABOVE 28W INTRODUCING
SUBSIDENT DRY AIR AND SUPPRESSING OUTFLOW

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 28W IS FORECAST TO CONTINUE STEADILY
NORTHWESTWARD FOR THE REMAINDER OF THE FORECAST PERIOD UNDER THE
STEERING INFLUENCE OF THE LOW-LEVEL FLOW ASSOCIATED WITH THE WESTERN 
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 
REGARDING INTENSITY, 28W IS EXPECTED TO BEGIN DISSIPATING AT TAU 12 
AND DISSIPATE BY TAU 24 OVER WATER. AS DISCUSSED ABOVE, SOME NEGATIVE 
IMPACTS OF THE UPPER-LEVEL TROUGH ARE BEGINNING TO APPEAR AS THE WIND 
FIELD GROWS MORE ASYMMETRICAL, AND ENVIRONMENTAL CONDITIONS WILL 
REMAIN LARGELY THE SAME, WITH THE UPPER-LEVEL TROUGH EXPECTED TO 
PROPAGATE WESTWARD TO REMAIN OVER TOP OF 28W, CONTINUING TO SUBSIDE 
DRY AIR AND SUPPRESS OUTFLOW, DENYING 28W THE CHANCE OF ANY FURTHER
DEVELOPMENT. 

MODEL DISCUSSION: TRACK MODEL GUIDANCE CONTINUES TO BE IN GOOD
AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD ON A
NORTHWESTWARD TRACK. THE OFFICIAL JTWC FORECAST TRACK IS THUS
PLACED WITH HIGH CONFIDENCE, IN LINE WITH THE MULTI-MODEL
CONSENSUS. INTENSITY MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT,
WITH ALL MESOSCALE AND GLOBAL MODELS NOW DEPICTING A STEADY
INTENSITY OF 25 KTS FOR THE NEXT 12 TO 24 HOURS. THE GFS AND GOOGLE
DEEPMIND SHOW DISSIPATION THEREAFTER, WHEREAS THE MESOSCALE MODELS GO 
ON TO HOLD IT AT 25-30 KTS FOR ANOTHER 24 HOURS, AND ONLY THE DECAY
SHIPS (GFS AND NAVGEM) STILL DEPICT FURTHER INTENSIFICATION AFTER
TAU 72, WHILE THE REMAINDER LOSE THE VORTEX. THE OFFICIAL JTWC
INTENSITY FORECAST IS ASSESSED WITH HIGH CONFIDENCE, CLOSELY IN
LINE WITH THE GFS AND GOOGLE DEEPMIND, WHICH HAVE REMAINED
CONSISTENT IN A QUICKER DISSIPATION.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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