TC 11P// TC 10P(NAT)// INVEST 94P// INVEST 97P// INVEST 99S// 0715utc updates

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 11P. 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ARE ISSUED ON TC 10P. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON INVEST 94P.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A MIDGET-SIZED SYSTEM WITH SHALLOW RAIN BANDS FEEDING INTO THE LOW LEVEL CIRCULATION (LLC) THAT IS OBSCURED BY A COLD DENSE OVERCAST THAT HAS DEEPENED SLIGHTLY IN THE LAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED LLC FEATURE IN THE 071211Z ATMS MICROWAVE IMAGE. THE INITIAL INTENSITY IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE AVERAGE OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SLIGHT CONVECTIVE IMPROVEMENT. ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SST AND STRONG POLEWARD OUTFLOW OFFSET BY MODERATE-HIGH VWS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 11P WILL CONTINUE SOUTHEASTWARD UNDER THE STEERING NER UP TO TAU 24. AFTERWARD, A SUBTROPICAL RIDGE (STR) TO THE SOUTH WILL BLOCK ITS FORWARD MOTION AND COMPETE FOR STEERING. THE MARGINALLY FAVORABLE ENVIRONMENT WILL BECOME UNFAVORABLE WITH INCREASING VWS AS THE SYSTEM DRIFTS INTO THE PREVAILING WESTERLIES, LEADING TO GRADUAL DECAY AND EVENTUAL DISSIPATION BY TAU 36.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH AN EVEN SPREAD TO 95NM BY TAU 24. AFTERWARD, A WESTWARD AND EASTWARD TRACK BIFURCATION SCENARIO ENSUES WITH THE STR AND THE NER COMPETING FOR STEERING. IN VIEW OF THIS, THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC NAT WILL CONTINUE EASTWARD UNDER THE STEERING INFLUENCE OF THE NER TO THE NORTH. THE MARGINAL ENVIRONMENT WILL SUSTAIN THE CURRENT INTENSITY AT BEST BEFORE VWS AND DRY AIR ENTRAINMENT WILL DOMINATE AND DISSIPATE THE SYSTEM BY TAU 36, POSSIBLY SOONER.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH AN EVEN SPREAD TO 107NM BY TAU 36, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. THERE IS ONLY MEDIUM CONFIDENCE IN THE INTENSITY FORECAST DUE TO THE POSSIBILITY OF AN EARLIER DISSIPATION.

THE AREA OF CONVECTION (INVEST 94P) PREVIOUSLY LOCATED NEAR 18.0S 159.5E IS NOW LOCATED NEAR 16.6S 159.2E, APPROXIMATELY 519 NM WEST OF PORT VILA, VANUATU. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 070341Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT A BROAD, PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FRAGMENTED BANDING IN THE SOUTHERN SEMICIRCLE. ENVIRONMENTAL ANALYSIS INDICATES THAT 94P IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN PARTIAL DISAGREEMENT ON THE TRACK OF 94P. GFS HAS 94P TRACKING SOUTHEASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHWARD TOWARD NEW CALEDONIA, WHILE ECMWF HAS IT TRACKING SLOWLY EASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHEASTWARD, NORTH OF NEW CALEDONIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 997 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

GLOBAL MODELS ARE IN PARTIAL DISAGREEMENT ON THE TRACK OF 94P. GFS HAS 94P TRACKING SOUTHEASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHWARD TOWARD NEW CALEDONIA, WHILE ECMWF HAS IT TRACKING SLOWLY EASTWARD OVER THE NEXT 48 HOURS BEFORE TURNING SOUTHEASTWARD, NORTH OF NEW CALEDONIA.