Tropical Storm LAN Advisory 10月19日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (LAN)
WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 25W (LAN), LOCATED APPROXIMATELY 441 NM NORTH-NORTHWEST
OF KAYANGEL, HAS TRACKED NORTH-NORTHWESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A
181536Z METOP-A 89 GHZ GMI IMAGE DEPICTS A BROAD AREA OF DEEP
CONVECTIVE BANDING IN THE SOUTHERN SEMI-CIRCLE WRAPPING INTO A LOW-
LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE MICROWAVE IMAGE AND MULTI AGENCY
POSITION FIXES. THE INITIAL INTENSITY IS ASSESSED AT 65 KNOTS BASED
ON DVORAK ESTIMATES FROM PGTW AND RJTD OF T4.0 (65 KNOTS) AND IS
SUPPORTED BY A SATCON ESTIMATE OF 59 KNOTS. ENVIRONMENTAL ANALYSIS
REVEALS THAT THE SYSTEM IS IN AN AREA OF LOW (10-15 KNOTS) VERTICAL
WIND SHEAR (VWS) AND IS TRACKING THROUGH AN AREA OF WARM (30 TO 31
CELSIUS) SEA SURFACE TEMPERATURES (SSTS) AND HIGH OCEAN HEAT
CONTENT. THE SYSTEM HAS A WELL DEFINED POLEWARD OUTFLOW CHANNEL THAT
IS FEEDING INTO A TUTT CELL LOCATED TO THE EAST. CURRENTLY TY 25W IS
TRACKING NORTHWARD ALONG THE WESTERN EXTENT OF A SUBTROPICAL RIDGE
(STR) BUILDING TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 25W IS FORECAST TO TRACK NORTH-NORTHWESTWARD OVER THE NEXT
24 HOURS UNDER THE INFLUENCE OF THE BUILDING STR LOCATED TO THE
EAST. AFTER TAU 24 THE TRACK WILL TURN DUE NORTH AND THEN BEGIN TO
RECURVE TO THE NORTHEAST AS IT ROUNDS THE NORTHWESTERN EXTENT OF THE
STR. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST ALLOWING FOR A
RAPID INTENSIFICATION OF TY LAN, REACHING A PEAK INTENSITY OF 125
KNOTS BY TAU 48. DYNAMIC MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT
IN THE TRACK DIRECTION AND SPEED, LENDING HIGH CONFIDENCE IN THIS
PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TY 25W WILL CONTINUE TO TRACK TO THE NORTHEAST
AROUND THE SUB TROPICAL RIDGE AXIS AS IT BEGINS TO INTERACT WITH THE
MID-LATITUDE WESTERLIES. AN APPROACHING MID-LATITUDE TROUGH WILL
INITIALLY ENHANCE OUTFLOW FOR A SHORT PERIOD, THEN LIMIT OUTFLOW
CONTRIBUTING TO A WEAKENING TREND. AS THE SYSTEM INTERACTS WITH THE
MID-LATITUDE TROUGH IT WILL ALSO BEGIN EXTRA-TROPICAL TRANSITION
AROUND TAU 96 AT WHICH TIME IT WILL BEGIN TO GRADUALLY ACCELERATE.
DYNAMIC MODEL GUIDANCE IS IN STRONG AGREEMENT AS TO THE TRACK
DIRECTION, HOWEVER, THE TRACK SPEED VARIES IN THE LATER TAUS LEADING
TO A LARGE SPREAD BY TAU 120. DUE TO THE HIGH DEGREE OF UNCERTAINTY
IN STORM SPEED, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
TRACK FORECAST.//
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