WDPN31 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (CONSON) 
WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3N 109.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 67 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WEAK,
SHALLOW, BUT PERSISTENT LOW LEVEL CIRCULATION CENTER (LLCC) EAST OF
QUANG NGAI, VIETNAM, WHICH HAS REMAINED STATIONARY OVER THE PAST 12
HOURS. ANIMATED RADAR IMAGERY SHOWS THAT THE SYSTEM IS DEVOID OF
ANY SIGNIFICANT CONVECTION WITH ONLY SHALLOW BANDS OF PRECIPITATION
WRAPPING INTO THE CIRCULATION CENTER. THE INITIAL POSITION IS
ASSESSED WITH  HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN EIR AND
RADAR DATA. SURFACE PRESSURE READINGS OF 1000MB FROM QUANG NGAI
SUPPORT A 30 KNOT INITIAL INTENSITY WITH MEDIUM CONFIDENCE, HEDGED
SLIGHTLY ABOVE THE JTWC CURRENT INTENSITY ESTIMATE OF 25 KNOTS. THE
ENVIRONMENT REMAINS MARGINALLY UNFAVORABLE, WITH MODERATE TO HIGH
VWS OFFSETTING WARM SSTS AND DIVERGENT WESTWARD OUTFLOW. THE SYSTEM
REMAINS FIRMLY ENSCONCED IN A WEAK STEERING PATTERN, LEADING TO THE
STATIONARY MOVEMENT.

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

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN BETWEEN A
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHWEST, A SUBTROPICAL RIDGE
(STR) TO THE NORTH AND AN EXTENSION OF A DEEP-LAYER STR TO THE
EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS SATCON: 38 KTS AT 120629Z
   CIMSS ADT: 29 KTS AT 121140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK WESTWARD

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: TD 18W REMAINS VERY FIRMLY IN A STATIC
POSITION JUST OFFSHORE OF QUANG NGAI, VIETNAM IN A VERY WEAK
STEERING ENVIRONMENT BETWEEN A TRIO OF COMPETING RIDGES. OVER THE
NEXT 12 HOURS, THE EASTERN RIDGE IS FORECAST TO BUILD IN FROM THE
EAST AND ASSUME THE DOMINANT STEERING POSITION. THIS WILL FINALLY
PUSH TD 18W TO THE NORTHWEST, ULTIMATELY MAKING LANDFALL NEAR DA
NANG WITHIN THE NEXT 24 HOURS. THE SYSTEM IS EXPECTED TO CONTINUE
TO WEAKEN TO 25 KNOTS IN THE NEXT 12 HOURS, AND ULTIMATELY
DISSIPATE OVER THE RUGGED TERRAIN WEST OF HUE BY TAU 36. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN OVERALL AGREEMENT THAT
THE SYSTEM WILL START MOVING NORTHWEST OVER THE NEXT 12 HOURS.
HOWEVER THE GFS AND HWRF CONTINUE TO WANT TO HOLD THE TRACK
OFFSHORE WHILE THE REMAINDER OF THE CONSENSUS MEMBERS SUPPORT THE
JTWC FORECAST TRACK. WHILE GUIDANCE IS GENERALLY IN AGREEMENT THERE
IS LOW CONFIDENCE IN THE TRACK FORECAST DUE TO THE UNCERTAINTY
SURROUNDING THE TIMING OF THE PUSH TO THE NORTHWEST. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT ON THE SCENARIO, BUT ONCE AGAIN THE
UNCERTAINTY OF WHETHER THE ULTIMATE TRACK MOVES ONSHORE OR OFFSHORE
LENDS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST.  

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