WDPS31 PGTW 152100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19P (NINETEEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.6S 137.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 397 NM EAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 19P (NINETEEN) HAS RAPIDLY CONSOLIDATED AFTER MOVING
OVER WATER AND IS BEGINNING TO QUICKLY INTENSIFY. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN AREA OF FLARING DEEP
CONVECTION, WHICH REMAINS SOMEWHAT DISORGANIZED IN THE EIR, WITH
THE BULK OF THE DEEPEST CONVECTION DISPLACED TO THE WEST OF THE
ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). A 151814Z SSMIS 89GHZ
MICROWAVE IMAGE SHOWED THE INITIAL PHASE OF MICROWAVE EYE
DEVELOPMENT, WITH STRONG SPIRAL BANDING FEATURES WRAPPING INTO THE
CENTER, PARTICULARLY ON THE WEST SIDE. HOWEVER, COMPARISON WITH THE
36GHZ IMAGE REFLECTS A FAIR AMOUNT OF VORTEX TILT TOWARDS THE WEST
WITH HEIGHT DUE TO MODERATE TO HIGH MID-LEVEL EASTERLY SHEAR. THE
INITIAL POSITION WAS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
ANALYSIS OF RADAR DATA FROM THE GOVE, AUSTRALIA STATION. THE SYSTEM
IS AT THE FAR RANGE OF THE RADAR AND THUS SEEING THE UPPER-LEVEL
ROTATION, WHICH ALIGNS WELL WITH THE MICROWAVE DEPICTION, BUT THE
LLCC IS LIKELY DISPLACED FURTHER EAST, THUS THE REDUCED CONFIDENCE.
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON
THE BULK OF THE AGENCY FIXES OF T2.5, COMBINED WITH THE ADT, AIDT,
DPRINT AND DMINT ESTIMATES NOTED BELOW. ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT, WITH VERY WARM (30-31C) SSTS, HIGH OHC
EXCEEDING 100 KJ PER CM3 AND MODERATE POLEWARD OUTFLOW, OFFSET BY
MODERATE EASTERLY SHEAR. ANIMATED WATER VAPOR IMAGERY SUGGESTS THAT
OUTFLOW FROM THE PERSISTENT CONVECTION IS BEGINNING TO PUSH BACK
AGAINST THE SHEAR, AS FILAMENTS OF CIRRUS ARE PUSHING EASTWARD,
WHICH WILL ALLOW FOR A MESOSCALE REDUCTION IN SHEAR VALUES NEAR THE
CENTER OF THE TC. IT SHOULD BE NOTED THAT THE RAW ADT VALUES HAVE
SHOT UP TO 3.4 AS OF 1830Z, WHICH MUST BE WATCHED CLOSELY AS THIS
MAY BE THE FIRST INDICATIONS OF POTENTIAL RAPID INTENSIFICATION
(RI) SCENARIO.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT, GENERALLY
TOWARDS A WEAKNESS IN THE SUBTROPICAL (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   ADRM: T2.5 - 35 KTS
   CIMSS SATCON: 52 KTS AT 151630Z
   CIMSS ADT: 38 KTS AT 151800Z
   CIMSS DPRINT: 35 KTS AT 151800Z
   CIMSS DMINT:  38 KTS AT 151503Z 

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: MODERATE TO HIGH EASTERLY 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: TC NINETEEN IS CURRENTLY TRACKING SLOWLY
TOWARDS THE SOUTHEAST TOWARDS A WEAKNESS IN THE STR SITUATED TO THE
SOUTHEAST OF THE CURRENT POSITION. OVER THE NEXT 24 TO 36 HOURS THE
SYSTEM IS ANTICIPATED TO SLOWLY CURVE TO A SOUTHWARD THEN
SOUTHWESTWARD TRACK AS THE A LOW- TO MID-LEVEL RIDGE BUILDS IN TO
THE SOUTH, OVER CENTRAL AUSTRALIA. THE SYSTEM IS EXPECTED TO SLOW
EVEN MORE, DOWN TO JUST TWO KNOTS OR SO, AFTER TAU 36 AS THE
BUILDING RIDGE TO THE SOUTH WILL BLOCK ITS TRACK TOWARDS THE COAST
FOR A BRIEF PERIOD. LANDFALL ALONG THE SOUTHERN COAST OF THE GULF
OF CARPENTARIA IS EXPECTED AROUND TAU 60. THEREAFTER, THE SYSTEM
WILL ACCELERATE WESTWARD AS THE RIDGE TO THE SOUTH CONTINUES TO
STRENGTHEN. IN TERMS OF INTENSITY, AS NOTED ABOVE, WE MAY BE SEEING
IN FIRST HINTS OF A POSSIBLE RI SCENARIO. THE SYSTEM WILL BE
TRACKING OVER VERY WARM WATERS WITH A LARGE AMOUNT OF OHC TO DRAW
FROM. IF THE DEEP CONVECTION CAN PERSIST AND CONTINUE TO PUSH BACK
AGAINST THE SHEAR AT THE MESOSCALE LEVEL, RI IS A DEFINITE
POSSIBILITY. THE FORECAST CALLS FOR A FAST PACE OF INTENSIFICATION,
BUT JUST BELOW THE THRESHOLD OF RI FOR NOW. THE PEAK INTENSITY OF
80 KNOTS IS EXPECTED JUST PRIOR TO LANDFALL, AT TAU 48. AFTER
LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN DUE TO FRICTIONAL EFFECTS
AS IT TRANSITS OVER NORTH-CENTRAL AUSTRALIA, AND ULTIMATELY
DISSIPATES BY THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
FAIRLY GOOD AGREEMENT ON THE OVERALL TRACK SCENARIO, WITH ALL OF
THE CONSENSUS MODELS AGREEING ON A GENTLY ARCING TRACK TOWARDS
THE COAST WHICH TURNS WESTWARD AFTER LANDFALL. THE TRACK ENVELOPE
IS MARKED BY NAVGEM TO THE EAST AND SOUTH AND THE ECMWF ENSEMBLE
MEAN ON THE NORTH AND WEST RESPECTIVELY. CROSS-TRACK SPREAD IS
ABOUT 110NM AT LANDFALL, OPENING UP TO ROUGHLY 150NM BY THE END OF
THE FORECAST PERIOD. THE JTWC FORECAST TRACK IS PLACED CLOSE TO THE
GFS ENSEMBLE AND ECMWF DETERMINISTIC SOLUTIONS WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS MIXED, WITH BOTH VERSIONS OF THE
COAMPS-TC MARKING THE LOW-END OF THE ENVELOPE, PEAKING THE SYSTEM
AT JUST 55 KNOTS, WHILE THE GFS SHIPS AND HAFS-A PEAK THE SYSTEM
CLOSER TO 85 KNOTS. ADDITIONALLY, THE RIPA, RI45 AND RI25 RI AIDS
HAVE BEEN TRIGGERED ON THIS CYCLE, ALSO PEAKING AS HIGH AS 85
KNOTS. LASTLY, THE GFS, COAMPS-TC AND ECMWF ENSEMBLE INTENSITY
PROBABILITY PRODUCTS ALL SHOW A HIGH LIKELIHOOD OF STRONG
INTENSIFICATION UP THROUGH TAU 48, THOUGH ONLY LOW PROBABILITIES
(LESS THAN 20 PERCENT) OF RI. THE JTWC FORECAST IS ON THE HIGHER
END OF THE GUIDANCE, BUT REMAINS BELOW THE MOST AGGRESSIVE RI
GUIDANCE, WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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