#242 Postby euro6208 » Mon Jul 31, 2017 11:22 pm
WDPN31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (NORU) WARNING NR
46//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 07W (NORU), LOCATED APPROXIMATELY 179 NM WEST-SOUTHWEST
OF IWO TO, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A SYSTEM
WHICH CONTINUES TO WEAKEN, WITH STRONG CONVECTIVE BANDING INTO A
WELL-DEFINED, CLOUD-FILLED EYE. THE CONVECTIVE STRUCTURE HAS
CONTINUED TO WEAKEN OVER THE PAST SIX HOURS. THE EYEWALL APPEARS TO
HAVE REESTABLISHED ITSELF, THOUGH IN A MUCH WEAKER STATE. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE LARGE
EYE FEATURE. A 312213Z AMSU 89GHZ MICROWAVE PASS CONFIRMED THE
EXISTENCE OF A VERY WEAK EYEWALL, WITH SOMEWHAT STRONGER CONVECTION
LIMITED TO THE SOUTHEAST PORTION OF THE SYSTEM. THE INITIAL
INTENSITY HAS BEEN LOWERED TO 105 KNOTS, BASED ON MULTI-AGENCY
SUBJECTIVE INTENSITY ESTIMATES OF T4.5 TO T5.5 (77 TO 105 KNOTS) AND
THE OVERALL WEAKENED APPEARANCE IN BOTH THE MULTISPECTRAL AND
MICROWAVE IMAGERY. WHILE THE SYSTEM IS WEAKENING, ENVIRONMENTAL
ANALYSIS INDICATES IT REMAINS IN AN OVERALL FAVORABLE AREA. THE
PREVIOUS WEAK EASTWARD OUTFLOW CHANNEL HAS NOW BEEN CUT OFF, WITH
ONLY A WEAK POINT SOURCE NOW PROVIDING LIMITED OUTFLOW TO THE
SYSTEM. VERTICAL WIND SHEAR (VWS) IS LOW (5-10 KNOTS) AND SEA
SURFACE TEMPERATURES (SSTS) ARE 30 DEG CELSIUS, AND THE SYSTEM IS
CURRENTLY TRANSITING OVER AN AREA OF LOW OCEAN HEAT CONTENT (OHC).
ALL OF THESE FACTORS ARE CONTRIBUTING TO THE WEAKENING TREND
OBSERVED OVER THE PAST SIX HOURS. 07W IS TRACKING NORTHWESTWARD
WITHIN A COMPETING STEERING ENVIRONMENT WITH RIDGES TO THE NORTH,
WEST AND SOUTHEAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST TRACK PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 07W WILL CONTINUE TRACKING NORTHWESTWARD OVER THE NEXT 36
HOURS AS THE RIDGE TRIPLET ENCAPSULATING TY 07W ITSELF MOVES
WESTWARD IN RESPONSE TO THE SOUTHEASTERN RIDGE BUILDING AND THE
NORTHERN RIDGE RETREATING TO THE NORTHWEST. AN UPPER-LEVEL TROUGH
WILL MOVE BY TO THE NORTH AROUND TAU 36, WEAKENING THE NORTHERN
RIDGE FOR SHORT PERIOD AND ALLOWING TY 07W TO TURN NORTH-
NORTHWESTWARD AFTER TAU 36. BUT THIS TURN NORTH WILL BE SHORT LIVED,
AND TY 07W RESUMES A WEST-NORTHWEST TRACK BY TAU 72, AS THE NORTHERN
RIDGE AGAIN BUILDS IN ACROSS THE NORTH OF THE SYSTEM. TY 07W IS
FORECAST TO SLOWLY WEAKEN THROUGH TAU 24 AS THE OUTFLOW CHANNEL
REMAINS LIMITED TO THE WEAK POINT SOURCE, AND THE SYSTEM TRACKS OVER
AN AREA OF LOW OHC VALUES. A SHORT PERIOD OF STEADY INTENSITY IS
EXPECTED BETWEEN TAUS 24 AND 36 AS THE LIMITED OUTFLOW IS OFFSET BY
INCREASING OHC AS THE SYSTEM CROSSES A HIGH OHC POOL. THE SYSTEM
WILL REINTENSIFY YET AGAIN BETWEEN TAUS 48 AND 72 AS THE SYSTEM TAPS
INTO A STRONG POLEWARD OUTFLOW CHANNEL AHEAD OF A MID-LATITUDE
TROUGH. MODEL GUIDANCE HAVE COME TIGHT AGREEMENT THROUGH TAU 48,
WITH ALL MODELS AGREEING ON THE OVERALL FORECAST SCENARIO AND ONLY
MODERATE SPREAD THROUGH TAU 72. GFS AND JGSM ARE THE OUTLIERS TO THE
NORTH AND SOUTH RESPECTIVELY, WITH ROUGHLY 200 NM SPREAD AT TAU 72.
DUE TO THE INCREASING MODEL AGREEMENT THERE IS HIGH CONFIDENCE IN
THIS PORTION OF THE FORECAST TRACK.
C. BY AROUND TAU 72, THE NORTHERN RIDGE IS FORECAST TO BUILD BACK
IN ACROSS THE NORTH OF TY 07W LEADING TO A MORE WEST-NORTHWESTWARD
TRACK THROUGH TAU 120. THE EXACT POSITION AND TIMING OF THE TURN
DEPENDS ON THE SPEED, STRENGTH AND ORIENTATION OF THE NORTHERN
STEERING RIDGE, WHICH IN TURN WILL BE DRIVEN BY THE DEVELOPMENT OF
ANOTHER MID-LATITUDE TROUGH DIGGING SOUTHWARDS BEGINNING AT TAU 120.
TY 07W IS EXPECTED TO SLOWLY WEAKEN AFTER TAU 72, DUE TO INCREASING
NORTHERLY PRESSURE AND VWS AND MOVEMENT OVER LOWER OHC POOL. THE
SYSTEM WILL REACH A MINIMUM OF 85 KNOTS BY TAU 96 BUT INCREASE
SLIGHTLY BY TAU 120 AS RADIAL OUTFLOW AND GREATER OHC VALUES COMBINE
TO GIVE THE SYSTEM A SLIGHT BOOST. DYNAMIC MODEL GUIDANCE HAS COME
INTO MUCH BETTER AGREEMENT IN THE LONGER RANGE FORECAST IN THIS RUN
WITH ALL MODELS EXCEPT UKMET AND JGSM AGREEING ON THE FORECAST
SCENARIO. MODEL SPREAD AT TAU 120 HAS NOW DROPPED TO LESS THAN 400
NM. WHILE MODELS GUIDANCE HAS IMPROVED, DUE TO THE LARGE DEGREE OF
COMPLEXITY IN THE STEERING ENVIRONMENT, THERE REMAINS LOW CONFIDENCE
IN THE FORECAST TRACK.//
NNNN
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Remember, all of my post aren't official. For official warnings and discussions, Please refer to your local NWS products...
NWS for the Western Pacifichttps://www.weather.gov/gum/
, if that projected peak verifies, that would surely be the story of the year. 
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