Tropical Storm LAN Advisory Wed Oct 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (LAN)
WARNING NR 08//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 25W (LAN), LOCATED APPROXIMATELY 187 NM NORTHWEST
OF KAYANGEL, HAS TRACKED SOUTH-SOUTHEASTWARD AT 03 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A
170637Z 91 GHZ SSMIS IMAGE DEPICTS BROAD BANDING CONVECTION WITH
PULSATING CENTRAL CONVECTION SHOWING SLOW CONSOLIDATION OVER THE
LAST SIX HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION
WHICH IS BASED ON A LOW REFLECTIVITY FEATURE OBSERVED IN THE
AFOREMENTIONED MICROWAVE IMAGE AND A 170117Z METOP-B ASCAT IMAGE
SHOWING A WELL DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A
PATCH OF 45 KNOT WIND BARBS ON THE NORTHWESTERN QUADRANT. THE
INITIAL INTENSITY ASSESSMENT OF 50 KNOTS IS BASED ON SCATTEROMETRY
DATA, AGENCY DVORAK ESTIMATES OF T3.0 (45 KNOTS), AND A 170635Z
SATCON ESTIMATE OF 57 KNOTS. UPPER-LEVEL ANALYSIS SHOWS A POINT
SOURCE FORMING JUST SOUTHEAST OF THE LLCC WITH A WELL-ESTABLISHED
POLEWARD OUTFLOW CHANNEL FEEDING INTO A TUTT CELL SOME DISTANCE TO
THE EAST. VERTICAL WIND SHEAR IS FAVORABLE AND SHOWING SIGNS OF
IMPROVEMENT. AVAILABLE OCEANIC ENERGY IS ALSO NOTABLY HIGH WITH
EXTREMELY WARM SSTS BETWEEN 30 AND 31 CELSIUS AND ACCOMPANYING HIGH
OCEAN HEAT CONTENT. CURRENTLY TS 25W IS DRIFTING SOUTH-
SOUTHEASTWARD IN A WEAK STEERING ENVIRONMENT.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 25W IS FORECAST TO REMAIN QUASI-STATIONARY OVER THE NEXT 12
HOURS BEFORE A SUBTROPICAL RIDGE TO THE EAST BUILDS SUFFICIENTLY
DRIVING THE SYSTEM ON A STEADY NORTHWARD TRACK. ENVIRONMENTAL
CONDITIONS WILL IMPROVE OVER THE NEXT 12 TO 72 HOURS AS THE POINT
SOURCE ALIGNS WITH THE LOW-LEVEL CIRCULATION AND THE SYSTEM FURTHER
CONSOLIDATES. THE SLOW TO MODERATE TRACK MOTION OVER EXTREMELY HIGH
OCEANIC HEAT CONTENT WHICH WILL FUEL AN INTENSIFICATION PHASE
REACHING SUPER TYPHOON STRENGTH BY TAU 72. MODEL GUIDANCE SHOWS
GENERAL AGREEMENT WITH THE TRACK SPEED AND TRAJECTORY THROUGH TAU
72, BUT MINOR DIFFERENCES IN TRACK SEPARATION ARE NOTED AND
ATTRIBUTED TO THE UNCERTAINTY OVER THE NEXT 12 HOURS WHILE IN A WEAK
STEERING ENVIRONMENT. THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK
UP TO TAU 72.
   C. IN THE EXTENDED PERIOD, TS 25W WILL MAINTAIN ITS INTENSITY AS
A SUPER TYPHOON THROUGH TAU 96. THE EXTENT OF GALE FORCE WINDS ARE
FORECAST TO EXTEND A NOTABLE DISTANCE FROM THE SYSTEM CENTER,
ENHANCED BY A COLD SURGE OVER THE EAST CHINA SEA. AROUND TAU 120 TS
25W WILL BEGIN INTERACTING WITH THE MID-LATITUDE JET AND START
TRANSITIONING INTO AN EXTRATROPICAL SYSTEM. DYNAMIC MODEL GUIDANCE
SHOWS GENERAL AGREEMENT IN THE TRACK TRAJECTORY, BUT DIFFERS GREATLY
IN SPEED WITH A 590NM SEPARATION BETWEEN POSITIONS AT TAU 120. ECMWF
IS NOW THE WESTERN OUTLIER WITH THE WIDEST AND SLOWEST TURN TO THE
NORTHEAST. THE EXTENDED FORECAST TRACK IS PLACED NEAR THE MULTI-
MODEL CONSENSUS WITH LOW CONFIDENCE.//
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