Advisories

WDPN31 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) 
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 142.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 174 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT THE
CONVECTION THAT WAS DEVELOPING AROUND THE 0600Z HOUR, HAS EXPANDED
AND PERSISTED, AND NOW COVERS AND OBSCURES THE LOW-LEVEL
CIRCULATION CENTER (LLCC). A DEARTH OF HIGH-RESOLUTION MICROWAVE
IMAGERY PRECLUDES ANALYSIS OF WHETHER OR NOT THE CONVECTION IS
TRULY ORGANIZING OR JUST FLARING IN ISOLATED POCKETS. THERE APPEARS
TO BE TWO DISTINCT CONVECTIVE MASSES, ONE NORTHWEST AND ONE
SOUTHEAST OF THE ASSESSED LLCC, AND CURRENTLY THERE IS NO SIGN OF
ROTATION, SUGGESTING THAT THE STRUCTURE REMAINS DISORGANIZED. AS
THE MESOSCALE MODELS HAD SUGGESTED, THE MOISTURE FIELD SOMEWHAT
IMPROVED IN THE OVERNIGHT HOURS, AND THE UPPER-LEVEL LOW (ULL)
REPOSITIONED TO A MORE FAVORABLE POSITION, INCREASING UPPER-LEVEL
OUTFLOW. ANIMATED WATER VAPOR IMAGERY HOWEVER SHOWS VERY DRY AIR
LURKING TO THE WEST AND NORTHWEST. THE INITIAL POSITION IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON A LONG EXTRAPOLATION OF A 140736Z
GPM COLOR-ENHANCED 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, BASED ON AN OVERALL INCREASE IN
BOTH THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES AND THE
IMPROVING CONVECTIVE STRUCTURE. ENVIRONMENTAL CONDITIONS ARE
MARGINALLY FAVORABLE, WITH WARM SSTS, LOW SHEAR AND MARGINALLY
IMPROVED OUTFLOW ALOFT, OFFSET BY THE PRESENCE OF DRY MID-LEVEL AIR
ALL AROUND THE LLCC, WHICH IS ITSELF COCOONED IN A TINY POCKET OF
ENHANCED MOISTURE.

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

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 31 KTS AT 141210Z
   CIMSS AIDT: 33 KTS AT 141210Z
   CIMSS D-PRINT: 26 KTS AT 141140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: COMPACT SIZE OF THE SYSTEM; DRY MID-LEVEL AIR
SURROUNDING THE INNER CORE; RESTRICTED OUTFLOW ALOFT. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN EXTENDED TO 48
HOURS. 

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 28W IS FORECAST TO
CONTINUE TRACKING NORTHWESTWARD THROUGH TAU 24, THEN BEGIN A
GRADUAL WESTWARD TURN THROUGH THE END OF THE FORECAST PERIOD AS THE
PRIMARY STEERING INFLUENCE SHIFTS FROM THE STR TO THE NORTHEAST, TO
A LOW- TO MID-LEVEL RIDGE WEST OF KYUSHU. IN TERMS OF INTENSITY,
THE CONVECTION THAT DEVELOPED ABOUT SIX HOURS AGO HAS BEEN SOMEWHAT
SURPRISINGLY PERSISTENT. HOWEVER, THE CONVECTION IS LIKELY PEAKING
IN ITS INTENSITY CURRENTLY, OR WILL REACH ITS PEAK IMMINENTLY AND
IS EXPECTED TO COLLAPSE WITHIN THE NEXT SIX HOURS. ALL GLOBAL AND
MESOSCALE MODELS DEPICT AN EXTREMELY DRY AIR MASS TO THE
WEST-NORTHWEST OF TD 28W, AND THE SYSTEM WILL BEGIN MOVING INTO THE
DRY AIR WITHIN THE NEXT 12 HOURS. AFTER TAU 24, SHEAR BEGINS
TO GRADUALLY INCREASE AS WELL, AND THE COMBINED EFFECTS WILL RESULT
IN A GENERAL WEAKENING TREND FROM TAU 12 THROUGH THE END OF THE
FORECAST PERIOD. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT ON A
NORTHWESTWARD TRACK THROUGH TAU 24, THEN A GRADUAL TURN WESTWARD
THEREAFTER. SEVERAL OF THE CONSENSUS MEMBERS LOSE THE VORTEX AFTER
TAU 12 AND ONLY ABOUT HALF THE MEMBERS REMAIN THROUGH THE REMAINDER
OF THE FORECAST PERIOD. OF THESE, ALL BUT THE GALWEM ARE TIGHTLY
CLUSTERED ABOUT THE JTWC FORECAST, WHICH IS PLACED NEAR THE GFS
WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD OVERALL
AGREEMENT, SHOWING 28W MAINTAINING INTENSITY FOR ABOUT 12 HOURS,
THEN A VERY GRADUAL WEAKENING TREND THROUGH TAU 48. 

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