Tropical Storm CHAMPI Advisory Di, 22.06.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING
NR
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 13.3N 143.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 70 NM WEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) CONTINUES TO DEPICT A
SHEARED COMPACT CYCLONE, WITH A LOW-LEVEL CENTER (LLC) BECOMING
PARTIALLY EXPOSED ON THE WESTERN EDGE OF A MASS OF RAGGED
CONVECTION. A TUTT CELL OVER THE PHILIPPINE SEA CAN BE SEEN PUSHING
CIRRUS FRAGMENTS TOWARD THE LLC FROM THE WEST-SOUTHWEST, DENOTING
MODERATE SOUTHWESTERLY SHEAR. DRY MID-LEVEL AIR ASSOCIATED WITH THE
TUTT CELL IS STILL PREVENTING UPSHEAR PROPAGATION OF CONVECTION,
EVIDENCED BY THE IMMEDIATE EVAPORATION OF NASCENT THUNDERSTORMS IN
THE WESTERN SEMICIRCLE DURING THE PAST 6 HOURS. THE INITIAL POSITION
AND INTENSITY ARE BOTH LARGELY BASED ON EXTRAPOLATION FROM A
BULLSEYE 212214Z ASCAT METOP-A PASS INDICATING MAXIMUM WINDS OF 25-
30 KTS. OVERALL ORGANIZATION OF THE VORTEX HAS CHANGED LITTLE DURING
THE PAST 6 HOURS.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA. 25-30KTS INDICATED ON
THE BULLSEYE 212214Z ASCAT METOP-A PASS.
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 40 KTS AT 211840Z
   CIMSS ADT: 35 KTS AT 220110Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK 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 DEPRESSION (TD) 06W WILL CONTINUE
TRACKING NORTHWESTWARD AROUND THE SOUTHWESTERN PERIPHERY OF A DEEP-
LAYER SUBTROPICAL RIDGE TO THE NORTHEAST, EVENTUALLY TURNING
NORTHWARD BY 72 HOURS. THE SPEED WITH WHICH TD 06W ROUNDS THIS RIDGE
WILL DEPEND ON HOW FAR NORTHEAST THE CYCLONE TRACKS DURING
THE NEXT 48-72 HOURS, AS A MORE RIGHTWARD TRACK, WOULD PLACE THE
CYCLONE CLOSER TO THE STRONG BELT OF DEEP-LAYER SOUTHERLY FLOW,
LEADING TO FASTER FORWARD MOTION. NUMERICAL MODEL GUIDANCE IS THUS
SPREAD BETWEEN SLOWER, LEFTWARD TRACKS AND FASTER, RIGHTWARD TRACKS.
THE JTWC TRACK FORECAST LEANS SLIGHTLY TOWARD THE NUMERICAL MODEL
GUIDANCE IS THUS SPREAD BETWEEN SLOWER, LEFTWARD TRACKS AND FASTER,
RIGHTWARD TRACKS. THE JTWC TRACK FORECAST CONTINUES TO LEAN SLIGHTLY
TOWARD THE RIGHT SIDE OF THE GUIDANCE ENVELOPE DURING THE FIRST 72
HOURS, IN PART DUE TO A SLIGHT JOG NORTH OF GUIDANCE DURING THE PAST
6 HOURS. THE JTWC TRACK FORECAST IS SLIGHTLY FASTER DURING THE 72-
120 HOUR PERIOD COMPARED TO THE PREVIOUS FORECAST, FOLLOWING THE
RECENT GUIDANCE TREND, WHICH IS NOW ONLY SPREAD AT 135NM BY TAU 72.
THE LARGE-SCALE ENVIRONMENT IS EXPECTED TO REMAIN ONLY MARGINALLY
FAVORABLE FOR INTENSIFICATION, AS CONTINUED ENTANGLEMENT WITH THE
NEARBY UPPER-LEVEL TROUGH RESULTS IN MODERATE SHEAR FOR THE NEXT 12
HOURS AND CONTINUES TO COMBAT AGAINST A DRIER AIR MASS TO THE WEST-
NORTHWEST. THE SHEAR WILL BEGIN TO LESSEN OVER THE NEXT 24 TO 48
HOURS AS THE SYSTEM BEGINS TO ROUND THE RIDGE AXIS AND REACHES A
PEAK INTENSITY OF 55KTS BY TAU 72. SHEAR WILL BEGIN INCREASING AGAIN
AS THE CYCLONE PASSES BENEATH AN UPPER-LEVEL RIDGE AXIS. STRONG LOW-
MID LEVEL SOUTHERLY FLOW BETWEEN THE STR AND MEI-YU FRONTAL BOUNDARY
WILL RESULT IN MODERATE NORTHERLY SHEAR AND DECREASE THE SYSTEMS
INTENSITY TO 45KTS BY TAU 96. TD 06W WILL APPROACH COOLER SSTS OF 24-
25C, WEAKEN, AND SIMULTANEOUSLY BEGIN UNDERGOING AN EXTRATROPICAL
TRANSITION, AND DECREASE TO 30 KTS BY TAU 120. GIVEN THE SMALL SIZE
OF THE CYCLONE THAT IS FORECAST TO PERSIST, POTENTIAL INTERACTION
WITH THE MEI-YU BOUNDARY INDUCES LOWER CONFIDENCE IN THE TRACK
FORECAST AFTER 72 HOURS.
MODEL DISCUSSION: THE JTWC TRACK FORECAST GENERALLY LIES SLIGHTLY TO
THE RIGHT AND SLOWER THAN THE MULTI-MODEL CONSENSUS, IN PART DUE TO
THE LEFTWARD OUTLIERS AFUM AND UKMET ENSEMBLE WHICH DO NOT PROPERLY
RESOLVE THE SMALL TROPICAL CYCLONE VORTEX, AS WELL AS THE SPEEDY
OUTLIER NAVGEM. THE JTWC INTENSITY FORECAST IS SLIGHTLY
BELOW THE MULTI-MODEL CONSENSUS AFTER 48 HOURS.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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