Tropical Storm NOCK-TEN Advisory Seg, 26-12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (NOCK-TEN) WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 30W (NOCK-TEN), LOCATED APPROXIMATELY 73 NM
WEST-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 16 KNOTS OVER THE PAST SIX HOURS. ANIMATED HIGH
RESOLUTION VISIBLE SATELLITE IMAGERY INDICATES THAT TY NOCK-TEN HAS
DRAMATICALLY WEAKENED AFTER PASSING OVER LUZON SOUTH OF MANILA, WITH
THE SYSTEM BECOMING MUCH MORE ASYMMETRIC AND RAGGED. CONVECTIVE
BANDING HAS BEEN VERY DIFFICULT TO IDENTIFY, THOUGH NOW THAT THE
SYSTEM HAS REEMERGED OVER THE SOUTH CHINA SEA (SCS), THERE ARE HINTS
THAT BANDING MAY BE TRYING TO REESTABLISH. A 26/0436Z AMSR-2 89 GHZ
MICROWAVE IMAGE CONFIRMS THIS, SHOWING DEEP CONVECTIVE ACTIVITY
CURVING INTO THE WESTERN SIDE OF THE LOW LEVEL CIRCULATION CENTER
(LLCC). THE INITIAL POSITION IS BASED ON AVAILABLE SATELLITE
IMAGERY, AS WELL AS COMPOSITE RADAR REFLECTIVITY DATA FROM THE
DOPPLER RADAR AT TAGAYTAY. THE INITIAL INTENSITY IS BASED ON
ANALYSIS OF FIX DATA FROM PGTW, WITH A CURRENT INTENSITY VALUE OF
T4.5 (77 KNOTS) AS WELL ADVANCED DVORAK TECHNIQUE (ADT) AUTOMATED
INTENSITY OF T4.1 (67 KNOTS). UPPER-LEVEL ANALYSIS INDICATES THAT TY
30W IS TRAVERSING THROUGH A WEAKLY FAVORABLE ENVIRONMENT WITH
MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS) AND WEAK WESTWARD
OUTFLOW. THE CYCLONE HAS BEGUN TO TRACK WEST-NORTHWESTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR)
WHICH EXTENDS FROM CENTRAL THAILAND ACROSS THE BASHI CHANNEL AND
INTO THE PHILIPPINE SEA.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.	
B. TY NOCK-TEN IS FORECAST TO CONTINUE TRACKING GENERALLY
NORTHWESTWARD AS THE STEERING RIDGE REORIENTS TO A NORTH-SOUTH AXIS
VICE ITS CURRENT EAST-WEST AXIS. AFTER TAU 24, THE LLCC WILL START
TO BECOME DECOUPLED FROM THE CONVECTION, COMPLETING THIS PROCESS BY
TAU 48. CONCURRENTLY, THE LLCC OF TY 30W WILL TURN SOUTHWESTWARD AS
IT BECOMES EMBEDDED IN THE BROAD NORTHEASTERLY FLOW ASSOCIATED WITH
A COLD SURGE EVENT. AS TY NOCK-TEN EMERGES INTO THE SCS, THERE IS A
18-24 HOUR WINDOW FOR IT TO REMAIN AT TYPHOON STRENGTH, AS IT TAPS
INTO MORE POLEWARD ORIENTED OUTFLOW AND BEFORE THE NORTHEASTERLY
SURGE COMBINE TO SHEAR THE SYSTEM APART. AFTER TAU 24, TY 30W WILL
RAPIDLY WEAKEN DUE TO INCREASED VWS (20-25 KNOTS) AND EXPOSURE TO THE
STRONG COLD AND DRY NORTHEASTERLY SURGE IN THE SCS, FULLY
DISSIPATING BY TAU 72. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT WITH SOME ALONG TRACK SPREAD IN THE SCS AFTER THE
DECOUPLING. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-
MODEL CONSENSUS AND REMAINS CONSISTENT WITH PREVIOUS FORECASTS,
LEADING TO HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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