WDPN31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.7N 157.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 1031 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH PERSISTENT DEEP
CONVECTION SHEARED TO THE SOUTHWEST OF THE LLCC AND FLARING
CONVECTIVE ACTIVITY TO THE SOUTHEAST NEAR A SECONDARY CIRCULATION.
THE EXPOSED LLCC PROVIDED HIGH CONFIDENCE TO THE INITIAL POSITION.
THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS, ON THE HIGHER END OF
THE SUBJECTIVE AND OBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES.
THE OVERALL ENVIRONMENT IS MARGINAL, WITH RELATIVELY WARM SSTS, AND
LOW TO MODERATE VWS. THE OUTFLOW ENVIRONMENT IS RELATIVELY WEAK
DIRECTLY OVER THE LLCC AS THE SYSTEM IS BELOW A 200MB RIDGE, BUT IS
MORE ROBUST FURTHER SOUTHWEST, AS EVIDENCED BY THE PRONOUNCED
CIRRUS FLOW SOUTHWEST INTO A TUTT CELL POSITIONED WELL TO THE
SOUTHEAST. RECENT ANIMATED VISIBLE IMAGERY SHOWS THAT THE MOVEMENT
OF THE LLCC HAS SLOWED SIGNIFICANTLY IN THE PAST SIX HOURS, NOW
DRIFTING SLOWLY NORTHWARD, CONFIRMING THE SYSTEM LIES IN COL REGION
BETWEEN TWO STR CENTERS, ONE TO THE EAST AND ANOTHER LYING TO THE
WEST-SOUTHWEST.

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

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT BETWEEN TWO
STR CENTERS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 37 KTS AT 022041Z
   CIMSS ADT: 26 KTS AT 022340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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: THOUGH TD 17W CURRENTLY LIES IN A WEAK
STEERING ENVIRONMENT, TRAPPED BETWEEN TWO STR CENTERS AS IT
APPROACHES THE RIDGE AXIS. THE EASTERN STR CENTER IS EXPECTED TO
STRENGTHEN AND BECOME THE DOMINATE STEERING MECHANISM OVER THE NEXT
12 HOURS, AND TD 17W SHOULD RESPOND BY TURNING NORTHWARD AND
ACCELERATING. AFTER ROUNDING THE AXIS BY TAU 24, THE SYSTEM WILL
CONTINUE ACCELERATING NORTHEASTWARD THROUGH THE REMAINDER OF THE
FORECAST PERIOD. FROM AN INTENSITY STANDPOINT, WHILE THE SYSTEM
LIES OVER WARM WATERS FOR ANOTHER 24 HOURS AND VWS WILL REMAIN LOW,
THE LACK OF A STRONG OUTFLOW ALOFT AND THE PRESENCE OF A POCKET OF
DRY AIR BETWEEN 700MB AND 400MB WILL INHIBIT CONVECTIVE DEVELOPMENT
AND THUS INTENSIFICATION. VWS IS FORECAST TO DRAMATICALLY INCREASE
TO ABOVE 35 KTS BY TAU 36, SIMULTANEOUS TO THE SYSTEM MOVING OVER
COOLER WATERS, WHICH WILL LEAD TO RAPID WEAKENING AFTER TAU 36.
WHILE THE SYSTEM IS EXPECTED TO INTERACT WITH THE LOW-LEVEL
BAROCLINIC ZONE, THETA-E ANALYSIS REVEALS THAT IT WILL NOT FULLY
EMBED WITHIN THE BAROCLINIC ZONE, AND 500MB ANALYSIS SHOWS THE
SYSTEM WILL TRACK AHEAD OF A 500MB RIDGE. HENCE, THE SYSTEM IS NOT
EXPECTED TO TRANSITION TO AN EXTRA-TROPICAL LOW, BUT IS FORECAST
FULLY DISSIPATE OVER WATER BY TAU 48.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU
48, WITH NAVGEM AS THE SINGULAR OUTLIER ON THE POLEWARD SIDE OF THE
ENVELOPE. THE REMAINDER OF THE CONSENSUS REMAIN TIGHTLY PACKED WITH
A 120NM SPREAD AT TAU 48. THE JTWC FORECAST LIES ALONG THE WESTERN
SIDE OF THE GUIDANCE ENVELOPE THROUGH THE FORECAST PERIOD IN LIGHT
OF THE NEAR-TERM MOTION VECTOR, WHICH WAS MORE WEST-NORTHWEST. THE
INTENSITY GUIDANCE REMAINS CONSISTENT WITH THE PREVIOUS RUN, WITH
THE MAJORITY OF THE GUIDANCE INDICATING STEADY INTENSITY THROUGH
TAU 24, THEN INTENSIFICATION TO 35 KNOTS THEREAFTER. BASED ON THE
EXPECTED SHEAR VALUES OVER 50 KTS BY TAU 48, IT IS UNLIKELY THAT
THE SYSTEM WILL BE ABLE TO INTENSIFY, HENCE THE JTWC FORECAST
BREAKS WITH THE CONSENSUS AFTER TAU 24, AND DISSIPATES THE SYSTEM
BY TAU 48. CONFIDENCE IN THE TRACK AND INTENSITY FORECAST IS HIGH. 


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