WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 07W (SEVEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.9N 143.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 116 NM WEST-SOUTHWEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED,
COMPACT LOW LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION
CONFINED TO THE SOUTHERN PERIPHERY AND HEALTHY EQUATORWARD OUTFLOW
ALOFT. AN 182058Z WSF-M MWI PASS AND RADAR IMAGERY SHOWED THE
MID-LEVEL CIRCULATION SEPARATED FROM THE LLCC. THE CONVECTIVE
STRUCTURE HAS NOT IMPROVED SINCE 181800Z AS THE SYSTEM CONTENDS
WITH SOME EASTERLY VERTICAL WIND SHEAR (VWS) AND DRIER AIR AT
500-300 MB, EVIDENCED BY A TIMELY 190000Z ATMOSPHERIC SOUNDING AT
GUAM. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR
DEVELOPMENT, CHARACTERIZED BY VERY HIGH SEA SURFACE TEMPERATURE
(SST) AND OCEAN HEAT CONTENT (OHC), MODERATE EQUATORWARD OUTFLOW
ALOFT, AND LOW TO MODERATE VWS. THE INITIAL POSITION IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE LLCC BECOMING UNTUCKED FROM THE
CONVECTIVE MASS IN ANIMATED MSI AND RADAR IMAGERY. DUE TO THE
UNFORTUNATE LACK OF ASCAT PASSES OVER THE SYSTEM CENTER FOR THE
PAST 36 HOURS, SURFACE OBSERVATIONS FROM ANDERSEN AFB AND GUAM
INTERNATIONAL AIRPORT HAVE BEEN CRUCIAL FOR ESTABLISHING THE
INITIAL INTENSITY, WHICH REMAINS AT 30 KTS WITH MEDIUM CONFIDENCE.
THE INTENSITY IS SET BETWEEN THE ADT AND AIDT OBJECTIVE ESTIMATES
FROM CIMSS ON THE HIGH END AND THE AGENCY SUBJECTIVE DVORAK FIXES
RANGING FROM T1.0 TO T1.5 ON THE LOW END.

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

CURRENT STEERING MECHANISM: WESTERN EXTENSION OF A LOW-MID LEVEL
SUBTROPICAL RIDGE (STR) CENTERED OVER MIDWAY ATOLL

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 34 KTS AT 190030Z
   CIMSS AIDT: 34 KTS AT 190030Z
   CIMSS D-MINT: 23 KTS AT 182101Z
   CIMSS D-PRINT: 24 KTS AT 182300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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: THE TROPICAL DEPRESSION IS NOW ON A
WEST-NORTHWEST TRAJECTORY, STEERED BY A LOW- TO MID-LEVEL STR TO
THE NORTH. AS 07W DEEPENS, THE WESTERN EXTENSION OF A DEEP-LAYER
STR WILL KEEP THE STORM MOTION STEADY. FROM TAU 96 TO TAU 120, A
RIDGE BUILDING OVER THE SOUTH CHINA SEA WILL SLOW DOWN THE SYSTEM,
AND A WEAKNESS IN THE STR NEAR THE RYUKYU ISLANDS WILL ENABLE 07W
TO TURN POLEWARD. ENVIRONMENTAL CONDITIONS WILL BE HIGHLY FAVORABLE
FOR DEVELOPMENT FOR THE FIRST 3 DAYS. HIGH SST AND OHC, LOW VWS,
AND MODEST DEEP-LAYER MOISTURE WILL FUEL INTENSIFICATION. THE
INITIAL DEVELOPMENT WILL BE SLOW WHILE THE SYSTEM UNDERGOES
AXISYMMETERIZATION. HOWEVER, ONCE THE INNER CORE SOLIDIFIES, THE
COMPACT SYSTEM WILL INTENSIFY QUICKLY, POTENTIALLY AT AN EXTREMELY
RAPID RATE. THE FORECAST CALLS FOR A 55 KT INCREASE FROM TAU 48 TO
TAU 72 TO 115 KTS, THOUGH THE PEAK WILL OCCUR BETWEEN TAU 72 AND
TAU 96 AND IS NOT SHOWN. TOWARDS TAU 96, 07W WILL BEGIN TO WEAKEN
AS THE SLOWER MOTION WILL INDUCE UPWELLING OF COOLER SUB-SURFACE
WATERS. THE SYSTEM WILL FURTHER APPROACH THE SOUTHERN PERIPHERY OF
AN UPPER LEVEL RIDGE, WHICH WILL CAUSE AN INCREASE IN EASTERLY VWS.
THESE FACTORS WILL LEAD TO MORE STEADY WEAKENING AT TAU 120.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT ON TAKING 07W
WEST-NORTHWESTWARD THROUGH TAU 96. THE CROSS-TRACK SPREAD
SUBSTANTIALLY INCREASES BEYOND TAU 72 DUE TO DIFFERENCES IN THE
STRENGTH OF THE DEEP-LAYER STR. THE HWRF, HAFS-A, GFS, AND ECMWF
MODELS REPRESENT THE POLEWARD SIDE OF THE GUIDANCE ENVELOPE, WHILE
THE AI MODELS ENCOMPASS THE OTHER END. THE FORECAST TRACK LARGELY
FOLLOWS THE MULTI-MODEL CONSENSUS THROUGH TAU 96 AND HEDGES CLOSER
TO THE AI GUIDANCE AT TAU 120. VIRTUALLY ALL RELIABLE INTENSITY
AIDS DEPICT INTENSIFICATION THROUGH TAU 72-96. COAMPS-TC AND HAFS-A
REMAIN THE MOST AGGRESSIVE MODELS AND RAPIDLY INTENSIFY 07W TO
125-135 KTS. NOTABLY, OUTPUT FROM THE 181800Z NESTED HAFS-A MODEL
RUN SHOWS 07W ACHIEVING A MAXIMUM POTENTIAL INTENSITY OF 170 KTS.
THE SHIPS STATISTICAL-DYNAMICAL MODEL ESTIMATES A 70 PERCENT CHANCE
OF A 55 KT INCREASE IN 48 HOURS AND A 65 KT INCREASE IN 72 HOURS,
AND THE AI-RI CIMSS ALGORITHM CONCURS WITH A 60 PERCENT CHANCE OF A
65 KT INCREASE IN 72 HOURS. SUPPORTED BY THE LARGELY FAVORABLE
ENVIRONMENT THROUGH WHICH 07W WILL TRAVEL AND MULTIPLE INDICATIONS
FROM THE AVAILABLE GUIDANCE, THE INTENSITY FORECAST CALLS FOR
EXTREMELY RAPID INTENSIFICATION TO OCCUR BETWEEN TAU 36 AND TAU 72.
IF 07W CAN QUICKLY DEVELOP THE INNER CORE, THE SYSTEM WILL DEEPEN
MORE QUICKLY AND POTENTIALLY ACHIEVE A HIGHER MAXIMUM INTENSITY.
THE FORECAST PEAK IS SET BELOW HAFS-A AND COAMPS-TC BUT IS HIGHER
THAN GFS AND THE EXPERIMENTAL GOOGLE DEEPMIND MODELS.

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