WDPN32 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (SAOLA) WARNING 
NR 043//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 109.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 190 NM EAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT THE
REMNANT CIRCULATION ASSOCIATED WITH TROPICAL DEPRESSION (TD) 09W
(SAOLA) HAS MOVED OFFSHORE TO THE EAST OF BEIHAI AND EMERGED INTO
THE NORTHERN PORTION OF THE GULF OF TONKIN. HOWEVER, THE MSI ALSO
SHOWS THAT THE ROTATION IS VERY BROAD AND DISORGANIZED, WITH THE
CLOUD STRUCTURE INDICATING RELATIVELY COOLER, DRIER AIR MOVING OVER
THE WARM WATERS OF THE GULF. CONVECTION IS SPARSE AND LIMITED IN
VERTICAL STRENGTH, NOT EVEN SHOWING UP IN THE ANIMATED RADAR DATA.
THE INITIAL POSITION IS THUS ASSESSED WITH LOW CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE DUE TO A LACK OF 
AGENCY FIXES. THE AVAILABLE OBJECTIVE INTENSITY ESTIMATES INCLUDING
ADT, AIDT AND DPRINT (25 KTS, 35 KTS AND 27 KTS RESPECTIVELY),
GENERALLY SUPPORT THE INITIAL INTENSITY. THE SYSTEM IS TRACKING
SOUTHWESTWARD ALONG THE SOUTHERN SIDE OF A LOW TO MID-LEVEL
ANTICYCLONE OVER CENTRAL CHINA. ENVIRONMENTAL CONDITIONS ARE
UNFAVORABLE, WITH MODERATE TO HIGH SOUTHEASTERLY WIND SHEAR AND DRY
MID-LEVEL AIR ENVELOPING THE SYSTEM, OFFSETTING THE WARM SSTS OF
THE GULF OF TONKIN.

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

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A LOW TO
MID-LEVEL ANTICYCLONE OVER CENTRAL CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS ADT: 25 KTS AT 030530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: VERY DRY AIR ENVELOPING THE SYSTEM. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TD 09W WILL CONTINUE TO TRACK SOUTHWESTWARD,
STAYING WEST OF HAINAN ISLAND, THROUGH THE FORECAST PERIOD. WHILE
SSTS ARE VERY WARM AND WOULD NORMALLY BE EXPECTED TO FUEL
INTENSIFICATION OF A TROPICAL CYCLONE IN THIS REGION, THE LACK OF A
WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), THE PRESENCE OF
MODERATE TO HIGH SOUTHEASTERLY SHEAR AND DRY MID-LEVEL AIR OVER THE
SYSTEM, WILL PROHIBIT ANY SUCH PLANS. THE SYSTEM IS FORECAST TO
STEADILY WEAKEN AND ULTIMATELY DISSIPATE TO THE WEST OF HAINAN NO
LATER THAN TAU 48. 

MODEL DISCUSSION: DYNAMICAL MODEL GUIDANCE IS IN FAIRLY GOOD
AGREEMENT ON THE OVERALL TRACK SCENARIO, THOUGH THE HAFS-A AND ECMWF
CONTINUE TO STUBBORNLY INSIST ON A STRAIT SOUTHWEST TRACK INTO
VIETNAM. THE REMAINDER OF THE GUIDANCE SUPPORTS A TRACK FURTHER TO
THE EAST, ROUGHLY PARALLEL TO THE HAINAN COASTLINE. INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT ON A STEADY WEAKENING TREND
THROUGH THE FORECAST, ENDING IN DISSIPATION BY TAU 48. 

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