Advisories

WDPN32 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 29W (TWENTYNINE) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.7N 159.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 883 NM EAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL 
DEPRESSION (TD) 29W AS A MOSTLY EXPOSED LOW-LEVEL CIRCULATION CENTER 
(LLCC) STRUGGLING TO CONTEND WITH THE ELEVATED VERTICAL WIND SHEAR 
(VWS) AND THE DRY AIR DIRECTLY TO ITS EAST. THE THIN PLUME OF CENTRAL 
CONVECTION IS CONTINUOUSLY SHEARED OFF TO THE WEST. THE 142320Z ASCAT 
DATA REVEALS A COMPACT LLCC WITH ELEVATED WINDS TO THE NORTH AND SOUTH 
OF THE SYSTEM. ENVIRONMENTAL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT, 
CHARACTERIZED BY LOW TO MODERATE (15-20 KTS) VWS, WARM (29-30 C) SEA 
SURFACE TEMPERATURES (SST), ROBUST WESTWARD OUTFLOW, 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 PREVIOUSLY MENTIONED ASCAT, 
SUPPORTED BY 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 ADT: 28 KTS AT 150110Z
   CIMSS AIDT: 29 KTS AT 150110Z

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 IN THE EASTERN
SEMICIRCLE

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 IS FORECAST TO CONTINUE STEADILY TRACKING 
NORTHWESTWARD THROUGH TAU 120 WHILE IT REMAINS ON THE SOUTHERN 
PERIPHERY 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 12-13 KTS FOR THE ENTIRE FORECAST PERIOD. 
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 THE DRY AIR BEGINNING TO MOISTEN. IN RESPONSE TO THE 
IMPROVED CONDITIONS, 29W IS FORECAST TO STEADILY INTENSIFY FROM TAU 24 
TO TAU 48. BY ABOUT TAU 48, THE ENVIRONMENT IS EXPECTED TO BECOME 
HIGHLY FAVORABLE, WITH THE DRY AIR ELIMINATED AND THE SYSTEM NOW 
STRONG ENOUGH TO EASILY RESIST THE PERSISTENT APPROXIMATE 15 KTS OF 
VWS EXPECTED THROUGHOUT THE FORECAST DURATION. 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 PROLONGED 
PERIOD OF RAPID INTENSIFICATION (RI) BETWEEN TAU 48-96. 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 
CURRENTLY EXPECTED TO PEAK AT TAU 120. 

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 (AROUND TAU 72). MODEL GUIDANCE HAS COME INTO 
TIGHTER AGREEMENT IN A TRACK PASSING JUST NORTH OF GUAM, WITH RELIABLE 
PHYSICS-BASED AND EXPERIMENTAL AI-BASED MODELS IN STRONG AGREEMENT 
THAT 29W WILL PASS BETWEEN GUAM AND ROTA. THE JTWC TRACK FORECAST LIES 
CLOSE TO THE MULTI-MODEL CONSENSUS 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 24, AND GFS INDICATING RI AS LATE AS TAU 72. 
THE TIMING OF THE RI PERIOD IS UNCERTAIN AND 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 HAFS-A, COAMPS-TC, AND HWRF THROUGH TAU 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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