Advisories

WDPN32 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (SAUDEL) WARNING NR 
046//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.4N 118.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 198 NM WEST-SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A STILL
SHEARED CYCLONE, WITH MODEL ANALYSES INDICATING 10-20 KT OF
EASTERLY OR SOUTHEASTERLY SHEAR, CONSISTENT WITH THE LOPSIDED
CONVECTIVE DISTRIBUTION FOCUSED WEST-NORTHWEST OF THE LOW-LEVEL
CIRCULATION CENTER (LLCC) AND UPPER-LEVEL EASTERLIES BENEATH THE
OUTFLOW LAYER. THE LLCC ITSELF IS CHALLENGING TO IDENTIFY WITH
PRECISION, AS IT IS MOSTLY OBSCURED BY CIRRUS, AND RADAR IMAGERY
ONLY REVEALS THE SHAPE OF THE CURVED BANDS OUTLINING ITS WESTERN
SIDE. THE INITIAL INTENSITY IS SET AT 35 KT BASED ON 021337Z ASCAT
DATA SHOWING A BAND OF GALES JUST OFF THE CHINESE COASTLINE,
CONSISTENT WITH A BLEND OF OBJECTIVE SATELLITE-BASED INTENSITY
ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE OVER EASTERN CHINA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS AIDT: 38 KTS AT 021450Z
   CIMSS D-MINT: 39 KTS AT 021435Z
   CIMSS D-PRINT: 44 KTS AT 021720Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM 17W (SAUDEL) IS CURRENTLY
EXPERIENCING A TRANSFER OF STEERING MECHANISM FROM THE
NEAR-EQUATORIAL RIDGE OVER BORNEO TO THE SUBTROPICAL RIDGE (STR)
OVER EASTERN CHINA. THE STORM IS MOVING MORE SLOWLY AT THE MOMENT
AS IT TURNS NORTHWARD, AND IS EXPECTED TO TURN SHARPLY
NORTHWESTWARD ALONG THE SOUTHERN FLANK OF THE STR AND APPROACH THE
CHINESE COASTLINE OVER THE NEXT 12 HOURS. LANDFALL IS EXPECTED IN
AROUND 12 HOURS, FOLLOWED BY A GENERALLY WESTWARD TRAJECTORY
INLAND. WHILE THE STORM ENVIRONMENT IS NOT PARTICULARLY HOSTILE TO
INTENSIFICATION, THE LIMITED TIME REMAINING OVER WATER WILL NOT
ALLOW MUCH STRENGTHENING, IF ANY. DYNAMICAL MODELS ARE IN GOOD
AGREEMENT ON SAUDEL'S LANDFALL OCCURRING AT A SIMILAR INTENSITY TO
ITS PRESENT VALUE. THE JTWC FORECAST IS FOR 35 KT INTENSITY JUST
AFTER LANDFALL IN 12 HOURS, BUT A TEMPORARY BUMP ABOVE 35 KT IS
POSSIBLE PRIOR TO THAT POINT. QUICK DISSIPATION IS EXPECTED AFTER
TAU 12 AS THE STORM MOVES INLAND.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE OVERALL
BLEND OF AI-BASED AND PHYSICS-BASED MODEL GUIDANCE AND SIMILAR TO
THE PREVIOUS FORECAST, PLACED WITH HIGH CONFIDENCE. THE JTWC
INTENSITY FORECAST IS CLOSE TO THE MULTI-MODEL BLEND OF DYNAMICAL
AND STATISTICAL-DYNAMICAL INTENSITY AIDS, ALSO PLACED WITH HIGH
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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