WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SONGDA)
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.4N 126.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 270 NM SOUTH OF KUNSAN AB, KOREA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT,
CONSOLIDATING SYSTEM WITH IMPROVED CONVECTIVE BANDING WRAPPING INTO
A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). MSI ALSO SUGGESTS 
THE LOW-LEVEL STRUCTURE HAS IMPROVED WITH EXPOSED LOW-LEVEL CLOUD 
LINES OVER THE EASTERN SEMICIRCLE WRAPPING INTO THE LLCC. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI. THE INITIAL 
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 
RJTD, KNES DVORAK ESTIMATES, CONSISTENT WITH THE IMPROVED 
CONSOLIDATION. ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH MODERATE 
POLEWARD OUTFLOW, LOW VERTICAL WIND SHEAR AND WARM SST VALUES (27-
28C).

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

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A LOW- TO MID-
LEVEL SUBTROPICAL RIDGE CENTERED OVER CENTRAL JAPAN.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 292350Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: INCREASED THE PEAK INTENSITY TO 45 
KNOTS BASED ON THE RECENT CONSOLIDATION AND COMPACT SIZE OF THE 
SYSTEM.

FORECAST DISCUSSION: TD 06W HAS CLEARLY BECOME BETTER ORGANIZED
OVER THE PAST SIX HOURS AS IT TRACKED WEST-NORTHWESTWARD CLEARING
THE ISLANDS SOUTH OF KYUSHU. TD 06W SHOULD CONTINUE TO TRACK WEST-
NORTHWESTWARD THROUGH TAU 12 THEN TURN SHARPLY NORTHWARD ALONG
THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR), WHICH IS
EXPECTED TO ERODE WITH THE APPROACH OF A MIDLATITUDE SHORTWAVE
TROUGH. DUE TO THE COMPACT NATURE OF THE SYSTEM AND FAVORABLE
CONDITIONS THROUGH TAU 12, THE SYSTEM IS EXPECTED TO INTENSIFY TO
40-45 KNOTS. AFTER TAU 24, SST IS FORECAST TO COOL TO 24-25C WITH
INCREASING VERTICAL WIND SHEAR, WHICH WILL LEAD TO STEADY
WEAKENING. AFTER TAU 48, TD 06W WILL RECURVE NORTHEASTWARD AND
TRACK OVER SOUTHERN NORTH KOREA WITH DISSIPATION ANTICIPATED BY TAU
72.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 170NM SPREAD IN SOLUTIONS AT TAU 72. NAVGEM AND UKMO ARE THE
EASTERN OUTLIERS AND INDICATE A SHARP NORTHWARD TO NORTH-
NORTHEASTWARD TURN BY TAU 24 WHILE GFS TRACKS THE SYSTEM NORTHWARD 
INTO THE NORTHERN YELLOW SEA BEFORE RECURVING THE SYSTEM EASTWARD 
INTO NORTH KOREA. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE 
MULTI-MODEL CONSENSUS WITH THE BULK OF THE GUIDANCE WITH MEDIUM 
OVERALL CONFIDENCE. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY 
FORECAST BASED ON UNCERTAINTY IN THE PEAK INTENSITY ASSOCIATED WITH 
THE COMPACT SYSTEM. 

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