JTWC Prognosis for NANMADOL

[Jeb]

WDPN31 PGTW 031500

MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//

SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W WARNING NR 20//

RMKS/

1. FOR METEOROLOGISTS.

2. PROGNOSTIC REASONING FOR 021200Z5 DEC TO 071200Z0 DEC 2004.

A. TYPHOON (TY) 30W (NANMADOL), LOCATED APPROXIMATELY 210 NM

SOUTHWEST OF KAOSHIUNG, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD

AT 12 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED

ON 031130Z8 ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING

INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF

55, 65 AND 75 KNOTS. THE LATEST ENHANCED WATER VAPOR IMAGERY

SHOWS THAT TY 30W HAS DEVELOPED THE ASYMMETRIC CLOUD PATTERN

CONSISTENT WITH EXTRATROPICAL TRANSITION WITH THE LOW LEVEL

CIRCULATION CENTER 130 NM SOUTH OF OF THE DEEP CONVECTION.

B. TY 30W IS FORECAST TO CONTINUE TO TRACK POLEWARD TOWARDS

SOUTHERN TAIWAN AND THEN MERGE WITH THE MAJOR SHORTWAVE TROUGH

EXITING ASIA AND ACCELERATE RAPIDLY TO THE NORTHEAST AS AN

EXTRATROPICAL LOW. THE AVAILABLE DYNAMIC AIDS CONSISTING OF NOGAPS,

COAMPS, GFDN, AFWA MM5, JGSM, JTYM, TLAPS, AND WBAR ARE IN POOR

AGREEMENT WITH THIS SCENARIO. JGSM AND COAMPS LOSE THE VORTEX AT

THE 36 HOUR TAU WHILE THE OTHER MODELS VARY GREATLY IN SPEED. THIS

FORECAST IS BASED ON A CONSENSUS OF THE AVAILABLE MODELS AND THE

EXPECTED SPEED OF A SYSTEM UNDERGOING TRANSITION TO AN EXTRATROPICAL

LOW.

C. THE INTENSITY OF TY 30W IS FORECAST TO CONTINUE TO DECREASE

AS IT ENCOUNTERS AN ENVIRONMENT OF UNFAVORABLE VERTICAL SHEAR.

D. CURRENT AND FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR

A LARGE SIZED SYSTEM UNDERGOING EXTRATROPICAL TRANSITION.

3. FORECAST TEAM: GRUBER/CHRISTIAN/LEWIN