Advisories

WDPN32 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (TWENTYNINE) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4N 160.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 950 NM EAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 29W AS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH A THIN PLUME OF CENTRAL DEEP CONVECTION SHEARED
TO THE WEST. THERE IS A CONSIDERABLE AMOUNT OF DEEP CONVECTION
DISPLACED WESTWARD OF THE CENTER, WITH DEEP CONVECTION BEGINNING TO
BLOOM AROUND THE NORTHERN AND SOUTHERN PERIPHERIES. A PATCH OF DRY
MID-LEVEL AIR TO THE NORTHEAST OF THE CENTER IS SUPPRESSING
CONVECTION WITHIN THE EASTERN SEMICIRCLE. THE 141801Z SSMIS
MICROWAVE DATA CONFIRMS THE SYSTEM REMAINS SHALLOW WITH THE CENTRAL
CONVECTION DISPLACED TO THE WEST. ENVIRONMENTAL ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT, CHARACTERIZED BY WARM (29-30 C) SEA SURFACE
TEMPERATURES (SST), ROBUST WESTWARD OUTFLOW, AND LOW TO MODERATE
(15-20 KTS) EASTERLY VERTICAL WIND SHEAR, OFFSET SLIGHTLY BY THE
REGION OF RELATIVELY DRIER AIR AND THE SLOW VORTEX CONSOLIDATION.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
MOSTLY EXPOSED LLCC. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND THE CIMSS
AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

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

CURRENT STEERING MECHANISM: THE SOUTHERN PERIPHERY OF THE
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   CIMSS SATCON: 29 KTS AT 141720Z
   CIMSS ADT: 30 KTS AT 141910Z
   CIMSS AIDT: 27 KTS AT 141910Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG WESTWARD
   OTHER FACTORS: SMALL PATCH OF MID-LEVEL DRY AIR TO THE NORTHEAST

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 29W RECENTLY CONCLUDED ITS LOOPING MOTION
AND HAS TRACKED NORTH-NORTHWESTWARD FOR THE PAST SEVERAL HOURS. THE
STORM IS FORECAST TO CONTINUE ITS NORTH-NORTHWESTWARD TRACK BRIEFLY
THROUGH TAU 12. AFTER TAU 12, 29W IS EXPECTED TO ASSUME A STEADY
NORTHWESTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD, WHILE
IT REMAINS UNDER THE STEERING INFLUENCE OF THE EXPANSIVE STR
CENTERED FAR TO THE NORTH. 29W IS FORECAST TO MAINTAIN A VERY
CONSISTENT FORWARD MOTION THROUGH TAU 120, SUSTAINING A TRACK SPEED
OF 13 KTS FROM TAU 12 TO TAU 72, BEFORE SLOWING SLIGHTLY TO 12 KTS
BETWEEN TAU 72-120. REGARDING INTENSITY, 29W IS FORECAST TO
GRADUALLY INTENSIFY THROUGH TAU 24 WHILE THE SYSTEM CONTINUES TO
CONSOLIDATE AND ORGANIZE. FOLLOWING TAU 24, THE ENVIRONMENT IS
EXPECTED TO BECOME MORE FAVORABLE, WITH VWS EXPECTED TO DROP TO
5-10 KTS AND THE DRY AIR BEGINNING TO REDUCE. IN RESPONSE TO THE
IMPROVED CONDITIONS, 29W IS FORECAST TO STEADILY INTENSIFY FROM TAU
24 TO TAU 60. BY ABOUT TAU 60, THE ENVIRONMENT IS EXPECTED TO
BECOME HIGHLY FAVORABLE, WITH THE DRY AIR ELIMINATED AND THE SYSTEM
NOW STRONG ENOUGH TO EASILY RESIST THE PERSISTENT 10-15 KTS OF VWS.
ADDITIONALLY, THE EQUATORWARD AND WESTWARD OUTFLOW IS EXPECTED TO
STRENGTHEN AROUND TAU 36 AND REMAIN ROBUST THROUGH TAU 120, FURTHER
AIDING IN INTENSIFICATION. THEREFORE, 29W IS FORECAST TO UNDERGO A
PERIOD OF RAPID INTENSIFICATION (RI) BETWEEN TAU 60-96. JUST AFTER
TAU 72, 29W IS EXPECTED TO PASS JUST OFF THE NORTHERN COAST OF
GUAM, BRINGING ELEVATED WINDS TO THE NORTHERN MARIANAS ISLANDS. 29W
IS EXPECTED TO PEAK AT TAU 120, WITH ADDITIONAL INTENSIFICATION
POSSIBLE OUTSIDE THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH THE DURATION OF THE FORECAST PERIOD, THOUGH A FEW
OUTLIERS ARE PRESENT: NAVGEM, GEFS, ECMWF, AND ECENS. DISCOUNTING
THOSE MEMBERS, THE BULK OF THE MODEL GUIDANCE IS IN TIGHT AGREEMENT
WITH A 75 NM CROSS-TRACK SPREAD AT THE CLOSEST POINT OF APPROACH TO
THE NORTHERN MARIANAS (JUST AFTER TAU 72). THE JTWC TRACK FORECAST
IS HEDGED SLIGHTLY SOUTH OF THE MULTI-MODEL CONSENSUS AND CLOSER TO
GUAM, IN RESPONSE TO THE MOST RELIABLE MODEL SOLUTIONS DEPICTING A
TRACK CLOSE TO THE NORTHERN COAST OF GUAM. THERE IS A MODERATE
AMOUNT OF ALONG-TACK SPREAD CAUSED BY THE SAME GROUP OF MODEL
OUTLIERS AS MENTIONED EARLIER (WITH THE EXCEPTION OF NAVGEM AND
INCLUDING GSM). AS A RESULT, THE JTWC IS HEDGED SLIGHTLY FASTER
THEN THE MULTI-MODEL CONSENSUS, CLOSE TO THE MOST RELIABLE MODEL
SOLUTIONS. OVERALL, THE JTWC TRACK FORECAST LIES IN STRONG
AGREEMENT WITH UKMET, GALWEM, AND THE FOLLOWING EXPERIMENTAL AL
MODELS: GOOGLE DEEPMIND, AIGEFS, AIGFS, AIFS; WITH OVERALL HIGH
CONFIDENCE. RELIABLE INTENSITY AIDS ARE IN STRONG AGREEMENT FROM
TAU 0 UNTIL TAU 36, DEPICTING A GRADUAL INTENSIFICATION AS THE
SYSTEM CONSOLIDATES, AND STRONGLY SUPPORTING THE JTWC INTENSITY
FORECAST DURING THAT TIME. FROM TAU 36, GUIDANCE DIVERGES, WITH
GOOGLE DEEPMIND INDICATING RI BEGINNING AS SOON AS TAU 36, AND
HAFS-A INDICATING RI AS LATE AS TAU 72. THE TIMING OF THE RI
PERIOD IS UNCERTAIN AND SOLELY DEPENDS ON HOW 29W IS ABLE TO
CONSOLIDATE AND VERTICALLY ALIGN ITSELF. AS A RESULT, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FROM TAU 0-72
AND LOW CONFIDENCE FROM TAU 72-120. THE JTWC INTENSITY FORECAST IS
ALIGNED CLOSELY WITH COAMPS-TC AND HWRF THROUGH TAU 48, THEN HEDGED
BETWEEN HWRF AND HAFS-A FROM TAU 60 TO 120. 

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