TS 23W(NAMTHEUN) Smap and Ascat-c suggested winds just below Typhoon intensity near the center, 16/03utc

JTWC IS ISSUING 6 HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TS 23W.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING, HOWEVER, TRACK SPEEDS HAVE BEEN ADJUSTED SLIGHTLY FASTER BASED ON RECENT ACCELERATION OF FORWARD MOTION. FORECAST DISCUSSION: TS 23W IS IN THE PROCESS OF SHIFTING TO A MORE NORTHERLY TRACK AS THE STEERING RIDGE TO THE EAST CONTINUES TO STRENGTHEN. HIGH AMPLITUDE FLOW IS ALLOWING NAMTHEUN TO MAINTAIN TROPICAL CHARACTERISTICS AS IT TRAVELS WELL INTO THE MID-LATITUDES, AND IT HAS SO FAR REMAINED RESILIENT TO THE EFFECTS OF VWS. SST WILL REMAIN GENERALLY SUPPORTIVE FOR THE NEXT 12-18 HOURS. TS NAMTHEUN SHOULD BE ABLE TO MAINTAIN STRONG TROPICAL STORM INTENSITY OVER THE NEXT 12 HOURS GIVEN THE VERY FAVORABLE OUTFLOW SUPPORT, HOWEVER, AFTER THAT TIME DECLINING SST AND THE EFFECTS OF DRY AIR ENTRAINMENT WILL DRIVE A SLOW WEAKENING TREND. EXTRA-TROPICAL TRANSITION (ETT) WILL BEGIN AROUND 36H, AND BE WELL UNDERWAY BY 48H AS THE SYSTEM BEGINS TO ROUND THE RIDGE. AT THE SAME TIME, TS 23W WILL INCREASINGLY FEEL THE INFLUENCE OF INCREASING VWS DUE TO AN APPROACHING TROUGH. TS 23W WILL COMPLETE ETT BY 72H, WITH THE REMNANT GALE-FORCE LOW ACCELERATING TO THE NORTHEAST.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TIGHTLY CURVED BANDING WRAPPING INTO A COMPACT CENTRAL DENSE OVERCAST FEATURE. BANDING IS PARTIALLY EXPOSED ON THE WESTERN SEMI-CIRCLE DUE TO HIGH-LEVEL VERTICAL WIND SHEAR (VWS) AND THE PRESENCE OF DRY AIR. DESPITE WARMING CLOUD TOPS AND DEGRADATION OF THE PRIMARY FEEDER BAND ON THE SE SIDE, A TIMELY 152324Z ASCAT-B PASS REVEALED WINDS OF AT LEAST 55 KNOTS IN THE SE QUADRANT. A 152233Z ASCAT-C ULTRA-HIGH RESOLUTION PRODUCT AND A 151936Z SMAP PASS SUGGESTED THE PRESENCE OF A VERY SMALL AREA OF POSSIBLE 60 KNOT WINDS. SUBJECTIVE DVORAK ESTIMATES REMAINED UNCHANGED, RANGING FROM T3.0 TO T3.5 (45 TO 55 KNOTS). SATCON AND ADT HAVE ALSO REMAINED STEADY AT 52 AND 51 KNOTS, RESPECTIVELY. BASED ON ALL AVAILABLE DATA, THE INITIAL INTENSITY WAS ASSESSED AT 55 KNOTS, AND THE 151800Z INTENSITY WAS REVISED UPWARDS TO 55 KNOTS GIVEN THE LATE-ARRIVING SMAP DATA. THE INITIAL POSITION WAS PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT-B DATA, AND INDICATES THE TRACK SPEED HAS ACCELERATED OVER THE PAST SIX HOURS. AN UPPER-LEVEL JET TO THE NORTHEAST IS PROVIDING ROBUST OUTFLOW SUPPORT. ADDITIONALLY, VWS HAS BACKED OFF SLIGHTLY, AND SSTS REMAIN SUPPORTIVE.

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN VERY TIGHT AGREEMENT ON THE TRACK SOLUTION, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST THAT IS LAID CLOSE TO THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE HAS CONSISTENTLY UNDERESTIMATED NAMTHEUNS RECENT INTENSIFICATION; HOWEVER, THERE IS VERY LIMITED TIME REMAINING FOR ANY FURTHER INTENSIFICATION. CONFIDENCE IN THE INTENSITY FORECAST IS SET AT MEDIUM DUE TO UNCERTAINTIES ASSOCIATED WITH ETT.

16/04UTC.