Tropical Storm NALGAE Advisory lun, 31-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING
NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 15.4N 117.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 225 NM WEST-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 26W HAS MOVED WEST-SOUTHWEST OVER THE PAST SIX
HOURS, AND THE CENTER NOW LIES FIRMLY IN THE SOUTH CHINA SEA, WEST
OF THE CENTRAL PHILIPPINE ISLAND OF LUZON. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) SUGGEST THE SYSTEM IS STILL RATHER BROAD,
DISORGANIZED, WITH FLARING CONVECTION CONFINED TO THE SOUTHWESTERN
PERIPHERY OF THE LOW LEVEL CIRCULATION CENTER (LLCC). A 300516Z
AMSR2 89 GHZ MICROWAVE IMAGE REVEALS FORMATIVE CONVECTIVE BANDING
IN THE NORTHWEST AND SOUTHWESTERN QUADRANTS OF THE LOW LEVEL
CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON AN EARLIER 300208Z  ASCAT-B IMAGE, WHICH SHOWS
AN ELONGATED BUT DEFINED CIRCULATION WITH 40-45 KNOT WIND OVER THE
NORTHWESTERN PERIPHERY. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE PGTW, RJTD, KNES DVORAK
ESTIMATES AND ASCAT DATA. ENVIRONMENTAL CONDITIONS ARE GENERALLY
FAVORABLE, CHARACTERIZED BY LOW (5-10 KNOTS) WARM (28-29C) SSTS AND
GOOD POLEWARD AND EQUATORWARD OUTFLOW.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: DEEP-LAYER STR CENTERED TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 45 KTS AT 300454Z
   CIMSS ADT: 43 KTS AT 300540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: OVER THE PAST 12 HOURS, TROPICAL STORM 26W HAS
EMERGED INTO THE SOUTH CHINA SEA (SCS) MOVING WEST-SOUTHWEST. THE
CURRENT CONVECTIVE STRUCTURE STILL SUGGEST THE LACK OF PROGRESS
TOWARD A VERTICALLY STACKED, SYMMETRICAL CORE, THEREFORE THE SYSTEM
WILL CONTINUE TO DEVELOP SLOWLY. BY TAU 12, TS 26W WILL BEGIN TO
TURN AND TRACK NORTHWESTWARD, AS MODEL GUIDANCE INDICATES THE
WESTERN SIDE OF THE STR WILL ERODE AND WEAKEN AHEAD OF AN
APPROACHING MID-LATITUDE TROUGH. AFTER TAU 12, TS 26W WILL HOLD
STEADY ON A NORTH-NORTHWEST TRACK THROUGH TAU 48, HOWEVER TRACK
SPEED IS FORECAST TO BE RATHER SLOW AS THE STEERING GRADIENTS ARE
NOT STRONG. ADDITIONALLY, THE SYSTEM IS EXPECTED TO SLOWLY
RECONSOLIDATE, AS AN UPPER-LEVEL POINT SOURCE ALOFT IS ANTICIPATED
TO DEVELOP ALOFT ALONG WITH THE POSSIBILITY OF INCREASED POLEWARD
OUTFLOW BY TAU 36. THESE IMPROVED ENVIRONMENTAL FACTORS WILL ALLOW
FOR STEADY INTENSIFICATION TO A PEAK OF 65 TO 70 KNOTS BY TAU 48.
HOWEVER, BY TAU 72, THE SYSTEM WILL BE IMPACTED BY COOLING SSTS,
INCREASING VERTICAL WIND SHEAR, ALONG WITH DRY AIR ENTRAINMENT
WHICH WILL LEAD TO A STEADY WEAKENING TREND THROUGH TAU 120.
FURTHERMORE, THE STEERING PATTERN EVOLVES, AS THE STR TO THE EAST
BUILDS WESTWARD, ALONG WITH LOWER-LEVEL FLOW OUT OF THE
NORTH-NORTHEAST WHICH WILL THEN STEER THE SYSTEM SHARPLY TO THE
NORTHWEST AND THEN WEST-NORTHWEST THROUGH TAU 120.
MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN FAIR
AGREEMENT, WITH THE PRIMARY OUTLIERS BEING NAVGEM, COMAPS-TC
(NAVGEM) ON THE WESTERN EDGE OF THE AIDS ENVELOPE, AND GALWEM ON
THE EASTERN EDGE. THE REMAINDER OF THE TRACKERS ARE TIGHTLY GROUPED
IN AN ENVELOPE WHICH GRADUALLY EXPANDS TO 110NM AT TAU 72.
THEREAFTER, AS THE TRACK GUIDANCE DIVERGES SIGNIFICANTLY BY
TAU 120. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS
FORECAST, AND LIES JUST WEST AND SOUTH OF THE MULTI-MODEL CONSENSUS
MEAN THROUGH THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE IS IN FAIR AGREEMENT, WITH THE GFS AND HWRF ON THE HIGH
END OF THE SPECTRUM WITH A PEAK OF 70-75 KNOTS, WHILE CTCI, COTI
REPRESENT THE LOW END OF INTENSITY GUIDANCE. THE JTWC INTENSITY
FORECAST IS PLACED WITH MEDIUM CONFIDENCE AND LIES CLOSE TO THE GFS
AND HWRF SOLUTIONS, SLIGHTLY ABOVE THE CONSENSUS MEAN.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
NNNN
NNNN