Nice discussion from JTWC on the complex steering pattern with this one.
WDPN32 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 19.6N 125.3E
INITIAL INTENSITY: 25 KTS
GEOGRAPHIC REFERENCE: 388 NM NORTHEAST OF MANILA, PHILIPPINES
MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
SIGNIFICANT WAVE HEIGHT: 11 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
QUICKLY CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) WITH
FLARING, DISORGANIZED CONVECTION, SCATTERED ACROSS THE SOUTHERN
PORTION OF THE ROTATION. A 231323Z ASCAT-C BULLSEYE DEPICTED A
SMALL, BUT WELL-DEFINED LLCC WITH 25-30 KNOT WINDS EXTENDING FROM
SOUTHWEST TO EAST OF THE CIRCULATION CENTER, PROVIDING THE IMPETUS
FOR THE FIRST WARNING. A 231937Z COLOR-ENHANCED 89GHZ MICROWAVE
IMAGE SHOWS WHAT COULD BE A NASCENT MICROWAVE EYE FEATURE AND
WELL-DEFINED BANDING FEATURES WRAPPING INTO THE CENTER. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON A PARTIALLY
EXPOSED LLCC IN ANIMATED PROXY VISIBLE IMAGERY, AND EXTRAPOLATION
TO THE MICROWAVE CENTER IN THE AFOREMENTIONED MICROWAVE IMAGERY.
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE PREVIOUSLY DISCUSSED ASCAT DATA, AND ANALYSIS OF THE AVAILABLE
AGENCY FIX ESTIMATES, THOUGH THE ACTUAL INTENSITY IS VERY LIKELY
CLOSER TO 30 KNOTS THAN 25 KNOTS AT THIS POINT BASED ON THE LATE
RECEIPT OF THE DISCUSSED MICROWAVE IMAGERY. ANIMATED WATER VAPOR
IMAGERY INDICATES THE DEVELOPMENT OF A WEAK AND STILL-DEVELOPING
POINT SOURCE OVER TOP OF THE SYSTEM, AS WELL AS A ROBUST TUTT-CELL
FAR TO THE NORTHEAST, JUST EAST OF KYUSHU. THE FORMER IS PROVIDING
LOCALIZED RADIAL OUTFLOW AND MODERATE EQUATORWARD FLOW, WHILE THE
LATER IS SUPPORTING WEAK POLEWARD OUTFLOW. THE SYSTEM LIES IN A
FAVORABLE ENVIRONMENT, WITH GOOD OUTFLOW, LOW (10-15 KNOTS) VWS,
ZESTY (30-31C) SSTS, HIGH OHC WATERS (110 KJ PER CM2). THE SYSTEM
IS CURRENTLY MOVING TOWARDS THE NORTH-NORTHWEST ALONG THE WESTERN
SIDE OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST NEAR 135E.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T1.5 - 25 KTS
RJTD: T1.0 - 25 KTS
KNES: T2.5 - 35 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 30-31 CELSIUS
OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 09W (NINE) HAS DEVELOPED RAPIDLY OVER THE
PAST 24 HOURS, AFTER HAVING TRAVERSED SOUTHWARD ALONG THE WEST SIDE
OF A MONSOON GYRE OVER THE PREVIOUS SEVERAL DAYS. HAVING REACHED
ITS FURTHER EQUATORWARD POINT, THE SYSTEM IS NOW MOVING TOWARDS THE
NORTHWEST ALONG THE WEST SIDE OF A STRONG STR EXTENSION THAT HAS
DEVELOPED TO ITS EAST. THIS GENERAL MOTION IS EXPECTED TO CONTINUE
FOR THE NEXT 24 HOURS AS THE SYSTEM CONTINUES TO CONSOLIDATE AND
STRENGTHEN. BY TAU 24, MULTIPLE, FAIRLY DRASTIC CHANGES IN THE
UPPER-LEVEL PATTERN BEGIN TO EMERGE. FIRST, THE STR CENTER
CURRENTLY STEERING THE SYSTEM IS FORECAST TO QUICKLY WEAKEN AND
DISAPPEAR AROUND TAU 36. SECOND, THE STR WILL BE REPLACED BY A
MONSOON GYRE THAT SETS UP TO THE EAST IN THE DEEP-LAYER MEAN
PATTERN, WITH THE OUTLINES OF THE CYCLONIC FLOW REACHING ALMOST
1700NM. THIRD, A NEW STR CENTER DEVELOPS NEAR HONG KONG. THE
COMBINATION OF THIS TRIFECTA WILL RESULT IN THE SYSTEM SLOWING AS
IT REACHES THE POLEWARD INFLECTION POINT AROUND TAU 24, HANG OUT
THERE FOR A FEW HOURS, THEN TURN SHARPLY EQUATORWARD AS STEERING
TRANSITIONS TO THE GRADIENT BETWEEN THE STRONG GYRE TO THE EAST AND
THE STR CENTER TO THE WEST. THE SYSTEM TRACKS GENERALLY SOUTHWARD
ABOUT TAU 96, WHERE IT ENCOUNTERS ANOTHER SEISMIC SHIFT IN THE
STEERING PATTERN AS THE GYRE DISSIPATES AND IS REPLACED BY A
MONSTROUS STR CENTERED AROUND 40N 160E. THE FAR WESTERN EXTENSION
OF THIS RIDGE WILL ASSUME THE DOMINANT STEERING ROLE AFTER TAU 96,
AND THE SYSTEM WILL BEGIN TO SLOWLY TURN BACK TO THE NORTH BY THE
END OF THE FORECAST PERIOD. IN TERMS OF INTENSITY, THE FAVORABLE
ENVIRONEMNT WILL FUEL STEADY INTENSIFICATION THROUGH TAU 72, WHERE
AN INFLUX OF NORTHERLY SHEAR WILL LEAD TO A 24 HOUR PERIOD OF
STAGNATION IN THE INTENSIFICATION TREND. INTENSIFICATION RESUMES
AFTER TAU 96 THROUGH TH REMAINDER OF THE FORECAST. LATE RECEIPT OF
THE LATEST COAMPS-TC ENSEMBLE DATA SUGGESTS A HIGH PROBABILITY OF
RAPID INTENSIFICATION BETWEEN TAU 48 AND TAU 72 (80-100 PERCENT),
WHICH ALIGNS WITH THE HAFS-A 1200Z DATA AS WELL. THEREFORE, THERE
IS A POSSIBILITY OF A HIGHER PEAK IN THE FORECAST THAN IS CURRENTLY
ANTICIPATED, AND THE POTENTIAL FOR RAPID INTENSIFICATION (RI) AFTER
TAU 48.
MODEL DISCUSSION: TRACK GUIDANCE IS FOR THE MOST PART IN
SURPRISINGLY GOOD AGREEMENT IN LIGHT OF THE UNUSUAL TRACK FORECAST.
THE TWO OUTLIERS ARE THE UKMET ENSEMBLE WHICH TAKES THE SYSTEM INTO
A LANDFALL ON THE NORTHEAST COAST OF LUZON THEN INTO THE SOUTH
CHINA SEA, AND THE NAVGEM WHICH TURNS THE SYSTEM EAST, THEN SOUTH
AND ENDS UP NORTH OF PALAU. REMOVING THESE TWO OUTLIERS, THE
REMAINDER OF THE CONSENSUS MEMBERS ARE IN GOOD AGREEMENT ON THE
TURN TO THE SOUTH AROUND TAU 24, FOLLOWED BY A NEARLY
QUASI-STATIONARY PERIOD BY TAU 96 AND A TURN TO POLEWARD
THEREAFTER. THE JTWC FORECAST TRACK LIES CLOSE TO THE CONSENSUS
MEAN AND LIES AMONGST THE TIGHTEST GROUPING OF TRACKERS. CONFIDENCE
HOWEVER IS LOW DUE TO THE UNCERTAINTY IN THE SYNOPTIC STEERING
ENVIRONMENT AND JUST HOW THE GYRE-STR COMBINATION WILL ULTIMATELY
SET UP. INTENSITY GUIDANCE IS IN GOOD AGREEMENT ON STEADY
INTENSIFICATION, THOUGH MULTIPLE RI TRACKERS ARE TRIGGERING,
INCLUDING THE FRIA, RICN, RI70 AND RI45. THE HAFS-A AND CTCX
DETERMINISTIC GUIDANCE ARE ON THE HIGH END OF THE PACKAGE, PEAKING
THE SYSTEM NEAR 120 KNOTS, WHILE THE COTC, SHIPS AND GFS ARE
SIGNIFICANTLY LOWER. THE JTWC FORECAST IS IN LINE WITH THE
CONSENSUS MEAN, WITH LOW CONFIDENCE IN LIGHT OF THE LATE-BREAKING
RI GUIDANCE COMING IN.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: MEDIUM
TRACK 72-120 HR: MEDIUM
INTENSITY 0 - 72 HR: LOW
INTENSITY 72-120 HR: LOW//
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