Typhoon 18W(NORU) making landfall near Da Nang //TS 19W(KULAP)//Invest 97W//TC 02S(ASHLEY)//HU 09L(IAN): intensifying//2709utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 18W(NORU) AND 19W(KULAP). 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ARE ISSUED ON 02S(ASHLEY).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: HAVING RECENTLY UNDERGONE ANOTHER ROUND OF RAPID INTENSIFICATION, WHICH PEAKED AT 270000Z AT 130 KNOTS, TYPHOON (TY) 18W HAS RECENTLY STARTED TO WEAKEN. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND ENHANCED INFRARED (EIR) IMAGERY SHOWS THAT AFTER PEAKING AT 0000Z, THE EYE HAS SUBSEQUENTLY FILLED IN, WHILE CLOUD TOP TEMPS HAVE WARMED CONSIDERABLY, LEADING TO MUCH LOWER DVORAK CURRENT INTENSITY ESTIMATES. HOWEVER, THE SYSTEM HAS NOT GIVEN UP THE GHOST ENTIRELY JUST YET, WITH CONVECTIVE HOT TOWERS CONTINUING TO FIRE UP ON THE SOUTHERN SIDE OF THE CORE AND WRAP UPSHEAR, SO THE ONSET OF RAPID WEAKENING MAY STILL LIE A BIT IN THE FUTURE. 270609Z GMI AND 270611Z AMSR-2 37GHZ MICROWAVE IMAGES REVEALED A VERY SMALL INNER CORE AND WEAK 9NM EYE FEATURE, WHICH LENT HIGH CONFIDENCE TO THE INITIAL POSITION. THE MICROWAVE IMAGERY SUGGESTED DEVELOPMENT OF A WEAK OUTER EYEWALL OR CONVECTIVE BAND ABOUT 30-40NM OUT FROM THE CENTER AS WELL. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, WELL ABOVE THE SUBJECTIVE AND OBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES, WHICH ARE DECEIVINGLY LOW DUE TO THE WELL-KNOWN LOW BIASES IN THE DVORAK TECHNIQUE WITH VERY SMALL SYSTEMS. EVEN THOUGH SHEAR IS QUITE HIGH (25-30 KNOTS), THE SYSTEM SO FAR HAS BEEN ABLE TO SUSTAIN ENOUGH UPSHEAR CONVECTION TO PUSH BACK AGAINST THE STRONG SHEAR. OTHER THAN THE SHEAR, THE OVERALL ENVIRONMENT IS FAVORABLE WITH WARM SSTS BETWEEN THE STORM AND THE COAST AND STRONG WESTWARD AND MODERATE EQUATORWARD OUTFLOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: OVER THE PAST 12 HOURS, TY NORU TOOK A BIT OF A JOG TO THE SOUTH BUT HAS RECENTLY TURNED BACK TO THE NORTH AND NOW SEEMS TO HAVE STEADIED UP ON A WESTWARD HEADING. AS THE SYSTEM WOBBLED IT ALSO SLOWED SIGNIFICANTLY, CUTTING TRACK SPEED IN HALF, DOWN TO JUST 8 KNOTS SINCE 0000Z. WHILE SOME ADDITIONAL WOBBLE IS CERTAINLY A POSSIBILITY GOING FORWARD, THE OVERALL TRACK MOTION IS FORECAST TO REMAIN JUST A SHADE NORTH OF DUE WEST THROUGH LANDFALL, AS THE SYSTEM TRACKS ALONG THE SOUTHERN SIDE OF THE DEEP STR CENTERED TO THE NORTH OF HONG KONG. EVEN THOUGH THE SYSTEM CONTINUES TO FIGHT MIGHTILY AGAINST THE STRONG AND PERSISTENT EASTERLY SHEAR, IT WILL NOT BE ABLE TO SUSTAIN THAT FIGHT MUCH LONGER, AND WILL BEGIN TO WEAKEN FROM NOW THROUGH LANDFALL UNDER THE INFLUENCE OF THE SHEAR AND POSSIBLE EYEWALL REPLACEMENT CYCLE (ERC). HOWEVER, THE SYSTEM IS STILL ANTICIPATED TO BE A VERY STRONG TYPHOON WHEN IT CROSSES THE COAST IN THE VICINITY OF DA NANG AROUND TAU 18. ONCE ASHORE THE SYSTEM WILL RAPIDLY WEAKEN DUE TO FRICTIONAL EFFECTS OF THE RUGGED TERRAIN AND ULTIMATELY DISSIPATE OVER NORTHEAST THAILAND BY TAU 48.

MODEL DISCUSSION: NUMERICAL GUIDANCE IS IN VERY GOOD AGREEMENT ON THE TRACK THROUGH LANDFALL, WITH ALL CONSENSUS MEMBERS CONTAINED WITHIN A 25NM ENVELOPE WHICH IS CENTERED JUST SOUTH OF DA NANG. AFTER LANDFALL THE GUIDANCE SPREADS A BIT BUT REMAINS IN A RELATIVELY SMALL ENVELOPE. THE JTWC FORECAST LIES ON THE NORTHERN SIDE OF THE ENVELOPE IN LIGHT OF THE RECENT NEAR-TERM MOTION, WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT AS WELL, WITH ALL CONSENSUS MEMBERS AGREEING ON WEAKENING FROM NOW TO LANDFALL, FOLLOWED BY RAPID DISSIPATION THEREAFTER. AGAIN THE JTWC FORECAST LIES ON THE HIGHER END OF THE GUIDANCE THROUGH THE MAJORITY OF THE FORECAST PERIOD, WITH HIGH CONFIDENCE.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED JUST TO THE SOUTH OF FLARING DEEP CONVECTIVE BURSTS. BY AROUND THE 0700Z HOUR THE MSI SUGGESTS THE LLCC MAY BE TUCKING BACK UP UNDER THE STRONGEST OF THE CONVECTIVE BURSTS. A 270624Z SSMIS 37GHZ MICROWAVE IMAGE SHOWED A BROAD BAND OF DEEP CONVECTION WRAPPING CYCLONICALLY INTO A WELL-DEFINED CENTER, THOUGH NOT WRAPPING ALL THE WAY AROUND ENOUGH TO CALL IT A MICROWAVE EYE FEATURE. BASED ON THE HIGH CONFIDENCE INITIAL POSITION, THE SYSTEM HAS SLOWED DOWN AS IT HAS REACHED THE AXIS OF THE STEERING RIDGE AND HAS BEGUN TO TRACK NORTH OR SLIGHTLY NORTH-NORTHEAST. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE AT 50 KNOTS, BASED ON THE AVERAGE OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND THE SATELLITE CONSENSUS (SATCON), WHICH ALSO ALIGNS WELL WITH THE EXPERIMENTAL CIMSS DEEP MICRONET ESTIMATE OF 49 KNOTS AND AN OPEN-AIIR ESTIMATE OF 53 KTS. THE SYSTEM LIES IN A MARGINAL ENVIRONMENT CHARACTERIZED BY WARM SSTS (28-29C) AND ROBUST POLEWARD OUTFLOW COMPETING WITH STRONG SOUTHERLY VERTICAL WIND SHEAR (VWS). MID-LEVEL DRY AIR IS ALSO BEGINNING TO NOSE ITS WAY IN ON THE SOUTH-SOUTHEAST SIDE OF THE INNER CORE, INHIBITING CONVECTION THERE AND GIVING THE SYSTEM THE LOOK OF A MID-LATITUDE FRONTAL TYPE SYSTEM. BUT LOOKS CAN BE DECEIVING, AS SOUNDER PROFILES AND PHASE-SPACE DIAGRAMS CONFIRM THE SYSTEM IS STILL SOLIDLY A WARM-CORE TROPICAL CYCLONE.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: HAVING REACHED THE STEERING RIDGE AXIS, TROPICAL STORM 19W (KULAP) HAS BEGUN TO SHIFT OVER TO A NORTHEASTWARD TRACK OVER THE PAST FEW HOURS. THIS TREND WILL CONTINUE AS THE SYSTEM MOVES NORTH OF THE RIDGE AXIS AND ACCELERATE NORTHEASTWARD ALONG THE WESTERN SIDE OF THE STEERING RIDGE. WHILE THE OVERALL ENVIRONMENT WOULD SUGGEST WEAKENING DUE TO THE HIGH SHEAR, THE FORECAST CALLS FOR INTENSIFICATION THROUGH THE FORECAST PERIOD, FOR TWO PRIMARY REASONS; FIRST THE VERY ROBUST OUTFLOW ALOFT IS ENOUGH TO OFFSET THE SHEAR, AT LEAST IN THE NEAR-TERM AS THE RELATIVE SHEAR IS A BIT LOWER DUE TO THE STORM MOTION AND SHEAR VECTOR BEING IN PHASE. SECONDLY, BY AROUND TAU 24 TO 36, AS THE SYSTEM MOVES NORTHEASTWARD, IT WILL BEGIN TO INTERACT AND COME IN PHASE WITH A STRONG 500MB SHORTWAVE TROUGH, WHICH WILL INDUCE STRONG POSITIVE VORTICITY OVER TOP OF THE SYSTEM, AS WELL AS ENHANCED THERMAL ADVECTION LEADING TO STRONG BAROCLINIC FORCING AND INTENSIFICATION AS THE SYSTEM BEGINS EXTRATROPICAL TRANSITION (ETT). AS INDICATED BY PHASE-SPACE DIAGRAMS AND GLOBAL MODEL FIELDS, TS 19W WILL REMAIN A WARM-CORE SYSTEM AS IT TRANSITIONS, BECOMING AN INSTANT WARM-SECLUSION TYPE EXTRATROPICAL LOW BY TAU 48, WHICH WILL LIKELY CONTINUE TO INTENSIFY EVEN AFTER COMPLETION OF ETT (AND THE END OF THE FORECAST) AS IT MOVES INTO THE BERING SEA BY AROUND TAU 72.

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT WITH MINIMAL SPREAD IN THE CONSENSUS MEMBERS THROUGH THE FORECAST PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE IS MIXED, WITH THE COAMPS-TC (BOTH NAVGEM AND GFS VERSIONS) AND GFS INDICATING NEAR-RAPID INTENSIFICATION THROUGH TAU 24, PEAKING AT 77 KNOTS, WHILE THE REMAINDER OF THE GUIDANCE INDICATES A LESS-ROBUST RATE OF INTENSIFICATION, WITH PEAKS BETWEEN 55-65 KNOTS. HWRF SHOWS A DELAYED PEAK INTENSITY OF 65 KNOTS AT TAU 72. THE JTWC FORECAST LIES NEAR THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE, THROUGH THE FORECAST PERIOD. ADDITIONAL INTENSIFICATION IS POSSIBLE BEYOND THE END OF THE FORECAST PERIOD AS THE SYSTEM RAPIDLY MOVES NORTHEAST INTO THE BERING SEA.

THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED NEAR 14.0N 136.5E IS NOW LOCATED NEAR 17.9N 134.9E, APPROXIMATELY 537 NM SOUTHWEST OF IWO TO, JAPAN. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 270432Z AMSR2 89 GHZ IMAGE SHOW A BROAD AND ELONGATED CIRCULATION WITH DISORGANIZED DEEP CONVECTION ALONG THE NORTHERN AND SOUTHERN QUADRANTS OF THE AREA. AN EARLIER 270030Z ASCAT-B SCATTEROMETER PASS SHOWED TWO CIRCULATION CENTERS, A BROADER ONE TO THE SOUTH AND A SMALLER ONE TO THE NORTH. THE BEST TRACK POSITION HAS BEEN ADJUSTED TO FIT WITHIN THE CENTROID BETWEEN THESE TWO CIRCULATIONS. THE SAME FEATURES CAN BE SEEN WITHIN THE MSI, WITH A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) CAN BE SEEN PEAKING FROM BENEATH THE CIRRUS CLOUD SHIELD AND THE AFOREMENTIONED MICROWAVE IMAGE. ENVIRONMENTAL ANALYSIS REVEALS THE INVEST IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT DEFINED BY ZESTY (29-30C) SEA SURFACE TEMPERATURES, MODERATE POLEWARD OUTFLOW, AND LOW (5-10KTS) VERTICAL WIND SHEAR. THOUGH SHEAR HAS BEEN ON THE RISE, A LOOK AT THE 850MB VORTICITY CHART SHOWS PLENTY OF PVA TO POSSIBLY FIGHT OFF THE RISE OF SHEAR. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 97W WILL TRACK NORTHWEST OVER THE NEXT 36-48 HOURS AND CONTINUE TO CONSOLIDATE AND SLOWLY INTENSIFY. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 17 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH THE ASSOCIATED CONVECTION BEING DISPLACED TO THE SOUTHWEST. THIS DISPLACEMENT IS CAUSED BY STRONG (30-35 KTS) UPPER-LEVEL WIND FLOW FROM THE NORTH-NORTHEAST. A BULLSEYE 270340Z METOP-B ASCAT PASS, WHICH SHOWS A DEFINED LLCC SURROUNDED PREDOMINATELY BY 25 KNOT WIND BARBS WITH AN AREA OF 40 KNOT WINDS IN THE SOUTHWESTERN REGION AND 35 KNOT WINDS IN THE SOUTHEASTERN SEMI-CIRCLE. TROPICAL CYCLONE 02S IS IN A MARGINALLY UNFAVORABLE ENVIRONMENT, CHARACTERIZED BY STRONG (30-35 KTS) POLEWARD OUTFLOW ALOFT, OFFSET BY NOMINALLY WARM (25-26 C) SEAS SURFACE TEMPERATURES (SSTS), AND STRONG (20-25 KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION AND INITIAL INTENSITY ARE PLACED WITH HIGH CONFIDENCE BASED ON THE MSI LOOP, THE AVERAGE OF MULTIPLE AGENCY DVORAK ESTIMATES, AND THE PREVIOUSLY MENTIONED ASCAT IMAGE.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC ASHLEY WILL CONTINUE ON A WEST-SOUTHWESTWARD TRACK AS IT MOVES ALONG THE NORTHWEST SECTOR OF THE STR POSITIONED TO THE SOUTHEAST. TC ASHLEY APPEARS TO HAVE ALREADY PEAKED AT 40 KNOTS, AND WILL NOW BEGIN WEAKENING AS IT TRANSITS WEST-SOUTHWEST INTO A MORE UNFAVORABLE ENVIRONMENT, MARKED BY COOLER SSTS, HIGHER VWS, AND DRIER AIR SURROUNDING THE LLCC. AFTER TAU 12, TC 02S WILL MAKE A SOUTHWEST TURN AND TRACK INTO EVEN COOLER WATERS, WHILE THE CONVECTION CONTINUALLY IS STRIPPED AWAY FROM THE CENTER. AT TAU 24 THE SYSTEM WILL BEGIN DISSIPATING OUT OVER THE SOUTHERN INDIAN OCEAN FAR FROM ANY LANDMASS AND COMPLETE DISSIPATION BY TAU 36 IF NOT SOONER DUE TO THE HARSH ENVIRONMENT.

MODEL DISCUSSION: THE TRACK MODEL CONSENSUS MEMBERS ARE IN TIGHT AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH A MERE 36NM SPREAD AT TAU 12, INCREASING TO AN OVERALL SPREAD OF 120 NM BY TAU 36 AS THE LLCC WEAKENS. THE TIGHT AGREEMENT IN CONSENSUS LENDS HIGH CONFIDENCE IN THE FORECAST TRACK. THE SAME STORY IS TRUE FOR INTENSITY MODEL GUIDANCE. THERE IS ONLY A SPREAD OF 5 KNOTS BETWEEN THE HIGHEST INTENSITY OF HWRF, AND LOWEST COAMPS THROUGH THE DURATION OF THE FORECAST PERIOD, LENDING OVERALL HIGH CONFIDENCE IN THE JTWC INTENSITY FORECAST.

WTNT44 KNHC 270858 TCDAT4 Hurricane Ian Discussion Number 17 NWS National Hurricane Center Miami FL AL092022 500 AM EDT Tue Sep 27 2022 Ian's satellite presentation continued to improve up until the center reached the coast of western Cuba around 0830 UTC. An Air Force Reserve reconnaissance aircraft that was in the storm until around 0400 UTC reported peak 700-mb flight-level winds of 101 kt, and a peak SFMR wind of 97 kt. During the final pass through the center, dropsonde data supported a minimum pressure of 960 mb. Given the continued improvement in satellite imagery, Dvorak data T-numbers from SAB and TAFB of T5.5 (102 kt), and objective estimates from UW/CIMSS of T5.4 (100 kt), the intensity was increased to 100 kt shortly after 0600 UTC. The latest objective Dvorak estimates have increased to around 110 kt, and that is the estimated landfall intensity and initial intensity for this advisory. NOAA and Air Force Reserve reconnaissance aircraft are scheduled to investigate the storm as it moves off the northern coast of Cuba this morning. Ian is expected to spend only spend a few hours over western Cuba, and little overall change in strength is likely during that time. The center should emerge over the southeastern Gulf of Mexico later this morning, where warm water and generally low vertical wind shear conditions are expected to allow for additional intensification, and the NHC forecast calls for Ian to reach category 4 strength. By 24 to 36 hours, increasing southwesterly vertical wind shear and drier mid-level air are likely to result in some gradual weakening. However, Ian is still expected to be a major hurricane when it reaches the Florida west coast. The official intensity forecast is near the latest simple and corrected multi-model consensus predictions. Ian has turned northward and is moving 355/10 kt. The hurricane should continue on a northward motion today around the western periphery of a subtropical ridge. After that time, a broad trough over the eastern United States is expected to cause a north-northeastward turn. There continues to be larger-than-normal spread in the track guidance by 36-48 hours, however the trend in the global models has been more southward and eastward over the last cycle or two. As a result, the NHC track has been adjusted to the southeast of the previous forecast and it lies just west of the TVCA multi-model consensus aid. Users are reminded to not focus on the exact track as some additional adjustments to the track are possible, and wind, storm surge, and rainfall hazards will extend far from the center. The updated forecast track has necessitated several changes to the warnings and watches across the Florida Keys and Florida peninsula, including an extension of the Hurricane Warning southward to Bonita Beach on the west coast. Key Messages: 1. Life-threatening storm surge, hurricane-force winds, flash floods and possible mudslides are expected in portions of western Cuba today. Devastating wind damage is expected where the core of Ian moves across western Cuba this morning. 2. There is a danger of life-threatening storm surge along much of the Florida west coast where a storm surge warning has been issued, with the highest risk from Fort Myers to the Tampa Bay region. Residents in these areas should listen to advice given by local officials. 3. Hurricane-force winds are expected in the hurricane warning area in west-central Florida beginning Wednesday morning with tropical storm conditions expected by late today. 4. Heavy rainfall will spread across western Cuba through Tuesday. This will likely produce instances of flash flooding and possible mudslides in areas of higher terrain over western Cuba. 5. Heavy rainfall will increase across the Florida Keys and South Florida Tuesday, spreading into central to northern Florida Wednesday and Thursday, and the Southeast by Friday and Saturday, likely causing flash, urban, and small stream flooding. Considerable flooding is expected across Central Florida into southern Georgia and coastal South Carolina, with significant, prolonged river flooding expected across central to northern Florida.