WDPS31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (MAILA) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.3S 154.6E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 687 NM NORTHEAST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYSTEM
RELATIVELY SYMMETRICAL CENTRAL DENSE OVERCAST (CDO) WHICH HAS
REMAINED FOR THE MOST PART UNCHANGED FOR THE PAST 12 HOURS. WHILE
AN EYE HAS YET TO APPEAR IN THE CDO, A 050753Z WSF-M COLOR-ENHANCED
37GHZ IMAGE REVEALED A WELL-FORMED MICROWAVE EYE IS PRESENT UNDER
THE CDO. ONE POSSIBLE REASON FOR THE LACK OF A FASTER PACE OF
INTENSIFICATION IS THE PRESENCE OF SOME EVIDENT DRY MID-LEVEL AIR,
EVIDENCED BY A MOAT BETWEEN RAIN BANDS IN THE MICROWAVE IMAGERY,
WEDGING UP THE WESTERN SIDE OF THE EYE FEATURE. ADDITIONALLY,
MESOSCALE MODEL-DERIVED SOUNDINGS INDICATE THE PRESENCE OF HIGH
(20-25 KNOT) MID-LEVEL EASTERLY SHEAR, WHICH IF PRESENT, WOULD ALSO
INHIBIT A FASTER RATE OF INTENSIFICATION. EVEN WITH THESE NEGATIVE
FACTORS, TC 30P HAS STEADILY INTENSIFIED OVER THE PAST 12 HOURS.
THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE, WITH THE
WSF-M IMAGE PROVIDING THE ONLY LOOK UNDER THE HOOD. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE AS WELL, BASED ON A
BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED
BELOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH WARM SSTS,
MODERATE WESTERLY OUTFLOW ALOFT, AND LOW DEEP-LAYER SHEAR, OFFSET
BY DRY MID-LEVEL AIR AND MODERATE TO HIGH MID-LEVEL EASTERLY SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING AND BALANCED STEERING
PATTERN, WITH A DEEP-LAYER NEAR EQUATORIAL RIDGE (NER) ALONG THE
EQUATOR, AND A SUBTROPICAL RIDGE (STR) OVER NORTHERN AUSTRALIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   ABRF: T4.0 - 65 KTS
   CIMSS ADT: 61 KTS AT 051130Z
   CIMSS AIDT: 65 KTS AT 051130Z
   CIMSS D-MINT: 86 KTS AT 050754Z
   CIMSS D-PRINT: 88 KTS AT 051200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: MODERATE TO HIGH MID-LEVEL SHEAR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 30P HAS MAINTAINED A
QUASI-STATIONARY MOTION OVER THE LAST 12 HOURS AND REMAINS TRAPPED
IN A COMPETING STEERING ENVIRONMENT AS DESCRIBED ABOVE. THERE ARE
AS OF YET NO SIGNS OF ANY SIGNIFICANT CHANGE IN THE STEERING
PATTERN FOR THE NEXT 48 TO 60 HOURS AND TC 30P WILL MEANDER SLOWLY
AROUND THE SOLOMON SEA THROUGH THAT TIMEFRAME. THE FORECAST CALLS
FOR A SLOW EASTWARD PROGRESSION THROUGH TAU 36, THEN A TURN
NORTHWARD BY TAU 48. HOWEVER, THE BOTTOM LINE IS THAT THE TRACK
WILL BE BOTH HIGHLY ERRATIC AND HIGHLY UNCERTAIN, THOUGH THE SYSTEM
IS EXPECTED TO REMAIN IN A FAIRLY SMALL AREA THROUGH TAU 48. BY TAU
72, THE NER TO THE NORTH MOVES AWAY TO THE NORTH AND THE TROUGH
ASSOCIATED WITH TC 31P NEAR FIJI MOVES AWAY TOWARDS THE SOUTHEAST,
WHICH WILL ALLOW THE STR OVER AUSTRALIA TO BUILD EASTWARD TO THE
SOUTH OF TC 30P. BEYOND TAU 96, THE STR OVER AUSTRALIA MOVES
QUICKLY EASTWARD, POSITIONING ITSELF TO THE SOUTH OF TC 30P. THIS
EVOLUTION OF THE STEERING PATTERN WILL ALLOW TC 30P TO BE EJECTED
WESTWARD AFTER TAU 72, ULTIMATELY TRANSITING CLOSE TO THE SOUTHEAST
TIP OF PAPUA NEW GUINEA BY THE END OF THE FORECAST PERIOD.
REGARDING INTENSITY, DEEP-LAYER SHEAR IS FORECAST TO CONTINUE TO
WEAKEN IN THE NEAR-TERM, AND MID-LEVEL SHEAR IS ALSO EXPECTED TO
SLACKEN, ALLOWING THE VORTEX TO FULLY ALIGN. ONCE THIS OCCURS, THE
SYSTEM IS FORECAST TO RAPIDLY INTENSIFY (RI), TO A PEAK OF 110
KNOTS BY TAU 36. OCEAN HEAT CONTENT IN THE REGION IS HIGH (125-150
KJ PER CM2), SO THE WARM WATER IS DEEP ENOUGH TO ALLOW FOR ABOUT 36
HOURS OF UPWELLING BEFORE THE COOL WATERS REACH THE SURFACE.
BEGINNING AT TAU 48, THE SYSTEM RAPIDLY WEAKENS AS IT LOSES ITS
ENERGY SOURCE. BY TAU 72, TC 30P WILL REACH ITS MINIMUM AND AS IT
BEGINS TO MOVE TO THE WEST AND AWAY FROM THE COOL UPWELLED POOL, IT
WILL BEGIN TO INTENSIFY ONCE MORE. HOWEVER, PROXIMITY TO TERRAIN
AND A MARGINAL INCREASE IN SHEAR WILL SERVE TO CAP THE INTENSITY
THROUGH THE END OF THE FORECAST PERIOD.   

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN SIGNIFICANT
DISAGREEMENT, PARTICULARLY IN THE LONGER-RANGE FORECAST TAUS.
THROUGH TAU 48, THE BULK OF THE CONSENSUS MEMBERS, AS WELL AS BOTH
GEFS AND ECEPS, DEPICT A SLOWLY MEANDERING, BUT GENERALLY EASTWARD
TRAJECTORY. THE AI MODELS (EC-AIFS, GDM AND THE AI CONSENSUS) BEGIN
TO DEVIATE EQUATORWARD AND BREAK FROM THE PACK BY TAU 48. BY TAU
72, THE BULK OF THE CONSENSUS TRACKERS LOOP THE SYSTEM BACK TOWARDS
WEST OR SOUTHWEST WHILE THE AI MODELS CONTINUE THEIR TRACK
EQUATORWARD. BY THE END OF THE FORECAST PERIOD, THE AI MODELS ARE
ARRAYED IN A FAN HEADED WEST-NORTHWEST FURTHER INTO THE SOLOMON
SEA. THE REMAINDER OF THE CONSENSUS (ECMWF, ECEPS, GFS, GEFS,
NAVGEM, EGRR AND GALWEM) FAN OUT ON A SOUTHWESTWARD TRAJECTORY,
WITH A 210NM SPREAD BETWEEN THE GFS AND GEFS ON THE NORTHERN EDGE
AND THE NAVGEM ON THE SOUTHERN. THE JTWC FORECAST IS PLACED CLOSE
TO THE CONSENSUS MEAN THROUGH TAU 96, THEN MUCH SLOWER, IN A BLEND
BETWEEN THE ECMWF AND GEFS AT TAU 120. CONFIDENCE IS LOW,
ESPECIALLY GIVEN THE VERY WIDE SPREAD IN THE ENSEMBLE MEMBERS.
INTENSITY GUIDANCE IS MIXED. NEARLY EVERY RI AID IS TRIGGERED,
DEPICTING A PEAK INTENSITY BETWEEN 110-130 KNOTS BY TAU 36.
MEANWHILE, THE HWRF AND COAMPS-TC SUGGEST LITTLE IN THE WAY OF
ADDITIONAL INTENSIFICATION AND THE HAFS-A IS ROUGHLY BETWEEN THE
TWO EXTREMES. AFTER THE PEAK AT TAU 36, THE GUIDANCE IS SPLIT, WITH
THE SHIPS, GFS AND CONSENSUS INDICATING A FLAT INTENSITY TREND
THROUGH THE REMAINDER OF THE FORECAST, WHILE THE COUPLED MODELS
DEPICT A SHARP WEAKENING THROUGH TAU 72 BEFORE RESUMING A SLIGHT
INTENSIFICATION. THE JTWC FORECAST IS PLACED GENERALLY NEAR THE
HAFS-A, BUT CONFIDENCE IS LOW DUE TO THE FACT THAT THE TREND WILL
IN LARGE PART BE DRIVEN BY THE FORECAST TRACK, CONFIDENCE IN WHICH
IS LOW. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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