WDPN31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (TWENTYTWO) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 132.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 669 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL DEPRESSION (TD) 22W (TWENTYTWO) CONTINUES TO SLOWLY
CONSOLIDATE WHILE TRACKING A WEST-SOUTHWESTWARD COURSE IN THE
PHILIPPINE SEA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A BROAD ROTATION, WITH AN ELONGATED AXIS RUNNING SOUTHWEST
TO NORTHEAST. THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC)
REMAINS EMBEDDED WITHIN THE LARGER TROUGH, WHICH EXTENDS FROM THE
PHILIPPINE ISLANDS EASTWARD ALMOST TO GUAM. THE ANIMATED MSI
SUGGESTS THE POSSIBILITY OF MULTIPLE VORTICES WITHIN THE LARGER
CIRCULATION, COMPLICATING LOCATION OF THE INITIAL POSITION. A
FORTUITOUS 210113Z GMI 37GHZ MICROWAVE IMAGE SHOWS EXTENSIVE SPIRAL
BANDS COVERING AN LARGE PORTION OF THE PHILIPPINE SEA (THE OUTERMOST
SPIRAL BAND LIES JUST OF LEYTE ISLAND, AND A SMALL, DISCRETE
CENTER, WHICH PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION. THE
INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, HEDGED SLIGHTLY
HIGHER THAN THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES IN LIGHT
OF THE CIMSS ADT, AIDT, DPRINT AND DMINT WHICH ARE BETWEEN 27-33
KNOTS. THE ENVIRONMENT REMAINS FAVORABLE, WITH LOW VERTICAL WIND
SHEAR, WARM SSTS AND STRONG EQUATORWARD OUTFLOW.

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

CURRENT STEERING MECHANISM: THE SYSTEM IS TRACKING
WEST-SOUTHWESTWARD ALONG THE SOUTHEASTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER THE TAIWAN STRAIT. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 38 KTS AT 210100Z
   CIMSS ADT: 32 KTS AT 202340Z
   CIMSS AIDT: 33 KTS AT 210000Z
   CIMSS DPRINT: 30 KTS AT 210000Z
   CIMSS DMINT: 29 KTS AT 210108Z 

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: EASTWARD AND WESTWARD OUTFLOW CHANNELS.

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 22W IS FORECAST TO CONTINUE TRACKING
GENERALLY WESTWARD FOR THE NEXT 12 TO 18 HOURS, ALONG THE
SOUTHEASTERN PERIPHERY OF THE STR TO THE NORTHWEST. A DEEP
MID-LATITUDE TROUGH CURRENTLY MOVING OVER MONGOLIA AND WESTERN
CHINA WILL RAPIDLY MOVE EASTWARD WHILE DEEPENING. BY TAU 24, THIS
TROUGH WILL BEGIN TO ERODE THE STR, AND ULTIMATELY SPLIT IT INTO
TWO DISTINCT PARTS, ONE OVER SOUTHERN CHINA AND A SECOND IN THE
VICINITY OF IWO TO, OPENING UP A BREAK IN THE RIDGE PATTERN IN THE
AREA OF TAIWAN. IN RESPONSE, TD 22W WILL BEGIN TO TRACK
WEST-NORTHWEST AFTER TAU 24. THE JET MAX ASSOCIATED WITH THE TROUGH
MOVES PAST THE TROUGH AXIS BY TAU 48 AND RAPIDLY MOVES
NORTHEASTWARD OVER JAPAN, WITH THE TROUGH WEAKENING AND RETREATING
NORTHWARD IN RESPONSE, SUCH THAT IT IS NOT STRONG ENOUGH TO PULL TD
22W FURTHER NORTHWARD THAN THE 18 DEG LATITUDE LINE. A LOW TO
MID-LEVEL POST-FRONTAL HIGH PRESSURE AREA WILL MOVE INTO EASTERN
CHINA BY TAU 72, AND CONTINUE TO BUILD AND MOVE EASTWARD
THEREAFTER, SPREADING EAST-NORTHEASTERLY FLOW ACROSS THE ENTIRE
REGION. TD 22W WILL IN RESPONSE TURN WESTWARD AFTER TAU 72, MOVING
ALONG THE SOUTHERN EDGE OF THIS STRONG ANTICYCLONE OVER EASTERN
CHINA. LANDFALL ALONG THE EASTERN COAST OF LUZON IS EXPECTED AROUND
TAU 84, WITH THE SYSTEM MOVING TO THE WEST COAST OF LUZON BY TAU 96
AND THEN MOVING INTO THE NORTHERN PORTION OF THE SOUTH CHINA SEA BY
THE END OF THE FORECAST PERIOD. IN TERMS OF INTENSITY, THE SYSTEM
HAS A SHORT WINDOW WITH FAVORABLE SHEAR CONDITIONS TO FURTHER
CONSOLIDATE, WHICH SHOULD ALLOW IT TO REACH TROPICAL STORM STRENGTH
IN THE NEXT 12 HOURS. SHEAR IS EXPECTED TO DRAMATICALLY INCREASE BY
TAU 18, INCREASING UP TO 25-30 KNOTS IN SOME MODELS. THE RESULT
WILL BE A LEVELING OFF OF THE INTENSITY BETWEEN 35 TO 40 KNOTS
BETWEEN TAU 12 AND TAU 48. SHEAR IS FORECAST TO DECREASE SHARPLY
AFTER TAU 48, WHICH WILL ALLOW THE SYSTEM TO QUICKLY INTENSIFY. THE
PEAK INTENSITY IN THE FORECAST IS 60 KNOTS AT TAU 72, BUT IT IS
LIKELY THAT THE SYSTEM WILL CONTINUE TO INTENSIFY PRIOR TO
LANDFALL, AND REACH TYPHOON STRENGTH PRIOR TO REACHING LUZON.
SIGNIFICANT WEAKENING IS FORECAST AS THE SYSTEM CROSSES LUZON, WITH
A STEADY INTENSITY EXPECTED ONCE THE SYSTEM IS BACK OVER WATER DUE
TO THE IMPACT OF MODERATE SHEAR. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE HAS STARTED TO
CONVERGE ONTO A TRACK OVER THE NORTHERN PORTION OF LUZON. THE
NAVGEM AND JGSM ARE THE LAST TWO HOLDOUTS TAKING THE SYSTEM
NORTHWARD TOWARDS TAIWAN. THE GFS AND GEFS REMAIN THE SOUTHERN SIDE
OUTLIER, BUT THE BULK OF THE GUIDANCE HAS SHIFTED SOUTHWARD AND THE
DISTANCE FROM THE PACK TO THE GFS HAS SIGNIFICANTLY LOWERED.
CROSS-TRACK SPREAD AT TAU 72 REMAINS AROUND 105NM, WHILE THE SPREAD
AT TAU 120, DISCARDING THE NAVGEM, HAS IMPROVED TO JUST 150NM.
ENSEMBLE GUIDANCE IS ALSO CONVERGING ON A TRACK OVER NORTHERN
LUZON, LENDING HIGHER CONFIDENCE TO THE JTWC FORECAST, WHICH IS
PLACED ON THE SOUTHERN EDGE OF THE INNER GROUPING OF CONSENSUS
MODELS, AND VERY CLOSE TO THE ECMWF ENSEMBLE MEAN TRACKER.
INTENSITY GUIDANCE FOR THE MOST PART REMAINS VERY BULLISH ON THE
SYSTEM, SEEMINGLY NOT BEING INFLUENCED BY THE FORECASTED INCREASE
IN DEEP-LAYER SHEAR. THE HAFS-A INDICATES A PEAK INTENSITY OF 55
NOTS AT TAU 48 FOLLOWED BY WEAKENING, WHILE THE HWRF SHOWS STEADY
INTENSIFICATION UP TO A PEAK OF 85 KNOTS AT TAU 96, WHERE IT
REMAINS EAST OF LUZON. THE JTWC FORECAST IS BELOW ALL OF THE
GUIDANCE BY UP TO 15 KNOTS THROUGH TAU 72, THEN SHIFTS SLIGHTLY
ABOVE THE CONSENSUS MEAN THROUGH THE REMAINDER OF THE FORECAST.   

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