
WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (JEBI) WARNING NR
08//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 25W (JEBI), LOCATED APPROXIMATELY 451 NM EAST-
NORTHEAST OF SAIPAN, CNMI, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MSI SHOWS FURTHER STRENGTHENING AS
EVIDENCED BY OVERSHOOTING TOPS NEAR THE STORM CENTER. CONSOLIDATION
ALSO CONTINUED WITH DEEP/SOLID FORMATIVE BANDS (MOSTLY FROM THE
SOUTHERN FLANK) WRAPPING TIGHTER INTO AN OBSCURED LLCC. SUSTAINED
POLEWARD OUTFLOW INTO A TUTT CELL TO THE NORTHEAST IS ALSO VISIBLE
ON THE MSI LOOP. THE INITIAL POSITION IS BASED WITH HIGH CONFIDENCE
ON A 282254Z ASCAT TIGHT BULLS-EYE PASS. THE INITIAL INTENSITY OF 55
KNOTS IS BASED ON THE DVORAK ESTIMATES OF T3.5/55KTS FROM PGTW AND
RJTD AND REFLECTS THE IMPROVED STATE OF THE SYSTEM. THE ENVIRONMENT
REMAINS CONDUCIVE WITH WARM SSTS (29-30 CELSIUS), LOW VWS (10-15
KTS) AND A STEADY OUTFLOW. THE CYCLONE IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF AN EAST-WEST ORIENTED STR TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
WARNING.
B. TS 25W WILL REMAIN ON ITS CURRENT TRACK UP TO TAU 48 UNDER THE
STEERING INFLUENCE OF THE STR. AFTERWARD, IT WILL TURN TO A MORE
NORTHWESTWARD DIRECTION TOWARD A BREAK IN THE RIDGE. THE FAVORABLE
ENVIRONMENT WILL PREVAIL AND FUEL A CLIMATOLOGICAL RATE OF
INTENSIFICATION, REACHING 115 KNOTS BY TAU 72. NUMERICAL MODEL TRACK
FORECASTS ARE IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THIS
PORTION OF THE JTWC TRACK FORECAST.
C. BEYOND TAU 72, TS JEBI WILL TURN MORE NORTH-NORTHWESTWARD
TOWARD MAINLAND JAPAN AS IT BEGINS TO ROUND THE WESTERN EDGE OF THE
STR. THE ENVIRONMENT WILL CONTINUE TO SUPPORT STEADY
INTENSIFICATION, REACHING A PEAK OF 120 KNOTS BY TAU 96 BEFORE A
WEAKENING PHASE BEGINS DUE TO INCREASING VWS. THE NUMERICAL MODEL
GUIDANCE IS IN OVERALL GOOD AGREEMENT WITH THE POLEWARD TURN BUT
REMAINS SIGNIFICANTLY SPREAD OUT - ABOUT 380 NM BY TAU 120 - WITH
THE ECMWF SUITE (ECM2 AND EEM2) AS THE NOTABLE LEFT-OF-TRACK
OUTLIER. IN VIEW OF THIS, AND GIVEN THE DEGREE OF UNCERTAINTY
NORMALLY ASSOCIATED WITH STORM TRACK CHANGES, CONFIDENCE IN THE JTWC
TRACK FORECAST BEYOND TAU 72, THAT IS LAID JUST TO THE RIGHT OF
CONSENSUS TO OFFSET THE LEFT OUTLIERS, REMAINS LOW.//
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