WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (NONGFA) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.5N 108.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 90 NM NORTH OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
LIKE A COLLEGE GRADUATE FINALLY LEAVING ITS PARENTS BASEMENT,
TROPICAL CYCLONE 20W MANAGED TO GET ITSELF TOGETHER OVER THE 
PAST SIX HOURS AND RAMPED UP INTO A VIGOROUS, MATURE SYSTEM. 
THE INTENSITY IS ASSESSED AT 40 KNOTS, STEPPING UP A NOTCH FROM THE 
JTWC DVORAK BASED ON A DATA T OF T3.0 FROM JTWC AND A RAW ADT T3.0 
FROM CIMSS. JMA HAS NOW UPGRADED THE SYSTEM TO TROPICAL STORM STATUS 
AND NAMED THE SYSTEM NONGFA. WHICH IS FITTING, GIVEN THAT NONGFA IS A 
LAO NAME FOR FLOWER AND THE SYSTEM IS CARRYING PLENTY OF MOISTURE FOR 
WATERING THE FLOWERS DEEP INTO THE MOUNTAINS OF LAOS. ANIMATED VISUAL 
AND INFRARED IMAGERY DURING THE PAST SIX HOURS SHOWED TIGHTENING 
BANDS OF VIGOROUS DEEP CONVECTION WITH OVERSHOOTING TOPS THAT WERE
MEASURED AS COLD AS NEGATIVE 92 CELSIUS. TEMPERATURES HAVE SINCE
WARMED AS THE SYSTEM MOVES OUT OF THE DIURNAL MAX PERIOD, BUT ONLY
MODERATELY AS THE LATEST SAMPLES SHOW TEMPERATURES IN THE MID MINUS
80'S. THERE IS, HOWEVER, AN OVERALL REDUCTION IN THE AREA OF THE
COLDEST TOPS. IT DOES APPEAR THAT WE HAVE SEEN ITS BEST. 
INFRARED AND WATER VAPOR IMAGERY ALSO SHOW A DISTINCT
LINE OVER THE NORTHEASTERN QUADRANT INDICATING THE SYSTEM IS STILL 
FIGHTING BACK AND HOLDING ITS OWN AGAINST ROUGHLY 20KTS OF VERTICAL
WIND SHEAR. THE LOW LEVEL CIRCULATION CENTER HAS ALSO BEEN MOVING
FURTHER UNDERNEATH THE CONVECTIVE CANOPY. RADAR ANIMATION ALSO
SHOWS EXPANSION AND TIGHTENING OF THE RAINBANDS OVER THE SOUTHEAST
QUADRANT. ALTHOUGH SURFACE REPORTS ALONG THE HAINAN AND VIETANAMESE
COAST REMAIN UNDER 25KTS, THE SYSTEM STILL HAS ANOTHER 90 MILES TO
GO OVER VERY WARM SEAS AND COMPLETELY SATURATED AIR BEFORE LANDFALL. 

INITIAL WIND RADII BASIS: ESTIMATED VIA BANDING FEATURES SHOWING IN
THE 37 GHZ SPECTRUM OF A 292308Z SSMIS SERIES AND CONSTRAINED USING
SFC REPORTS FROM VIETNAM AND HAINAN. 

CURRENT STEERING MECHANISM: THE EXTREME SOUTHWESTERN FLANK OF THE
SUBTROPICAL RIDGE.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 292030Z
   CIMSS AIDT: 36 KTS AT 292030Z
   CIMSS D-MINT: 26 KTS AT 292054Z
   CIMSS D-PRINT: 32 KTS AT 300020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 17-22 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: THE VORTEX OF TS NONGFA IS STILL HONING IN ON
A LANDFALL JUST NORTH OF DONG HOI NEAR 0330Z, WITH THE MOST VIGOROUS 
WINDS AND HEAVIEST RAINS EXPECTED BETWEEN DONG HOI AND DA NANG.
THE MOST RECENT SATELLITE ANIMATION AND SURFACE REPORTS INDICATE
THE SYSTEM WILL COME ASHORE AT A MINIMUM OF GALE FORCE (35KTS) BUT
NOT MORE THAN 45KTS. THE GALE FORCE INTENSITY AND ABUNDANT DEEP
MOISTURE WILL ALLOW THE SYSTEM TO REMAIN A VIGOROUS WEATHER MAKER
AT LEAST INTO LAOS, BUT THE RUGGED TERRAIN WILL TEAR APART THE LLCC
AND MAKE THE SYSTEM UNTRACKABLE BEFORE IT MOVES VERY FAR INTO
THAILAND. IT REMAINS WORTH NOTING THAT AN ABUNDANCE OF GUIDANCE
CONTINUES TO INDICATE THAT THE ENERGY FROM THE SYSTEM MAY TRANSLATE
ALL THE WAY INTO THE BAY OF BENGAL. 

MODEL DISCUSSION: MODEL GUIDANCE IS FINE, HOWEVER AT THIS LATE
PHASE OF DEVELOPMENT THE PREFERRED GUIDANCE IS SYNOPTIC REPORTS,
RADAR, AND SATELLITE IMAGERY. THIS FORECAST EMBRACES REALITY.   

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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