ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM Hurricane Simon Discussion Number 25 NWS National Hurricane Center Miami FL EP202026 800 AM MST Tue Oct 13 2026 Small stubborn Simon continues to defy expectations this morning. First light visible satellite imagery shows the hurricane still has a small eye, and is also located farther south than was analyzed by satellite imagery last night. This is further supported by microwave images from AMSR-3 at 09 UTC and SSMIS at 1125 UTC which both show an eyewall that is little better organized, though it remains open on the west side. This structure could be due to some residual shear or dry air that was ingested into the circulation. Satellite intensity estimates are all over the place this morning, ranging from as low as 47 kt from UW-CIMSS ADT, and as high as 95 kt by SATCON. Given the small eye signature surrounded by -65 to -70 C cold cloud tops, the initial intensity will be held at 80 kt, on the upper side of these estimates, but should be considered more uncertain than usual. Simon continues to move south of the previous forecast track, and the initial motion is a slow westward drift at 270/2 kt. The farther south initial position and current motion necessitates some pretty significant changes to the short-term track forecast. As mentioned yesterday, Simon is very close to a saddle point, or col, in the deep-layer steering flow. This feature means that Simon's future track is very sensitive to which side of the saddle point the storm is located. Yesterday, a plurality of the guidance was maintaining Simon on a northwestward to northward track, causing it to be on the north side of the saddle point, resulting in continued poleward motion. However, Simon has gained very little latitude over the past 24 h, and thus now finds itself on the south side of the saddle point. Consequently, the track guidance over the past few cycles has shifted substantially southward. The NHC track forecast is now shifted in a similar fashion, showing a very slow motion over the next 36-48 h as Simon makes a small cyclonic loop. The first part of the track forecast is substantially farther south than the prior one, but still not as far south as the HFIP Corrected Consensus Approach (HCCA), or any of the latest hurricane-regional models. After 48 h, deep-layer steering finally begins to shift out of the south as a deep-layer cutoff low digs into southern California, and Simon will finally start moving northward in earnest during the 48-72 h time frame. Towards the end of the forecast, Simon could bend back more north-northwestward, potentially entering the Gulf of California and finally making landfall in Mexico between 96-120 h. However, this forecast should be considered very low confidence at that time frame, as there are a host of solutions from landfall in mainland Mexico even before reaching the Gulf of California, direct impacts to Baja California Sur, or solutions that stay south of Mexico entirely over the next 5 days. The intensity forecast is not much easier either. Simon has managed to maintain a small inner-core and hurricanes of this size are known to be sensitive to small changes in their environmental conditions that could result in rapid changes in intensity, either up or down. This is also exhibited in the intensity guidance this morning, which ranges from Simon weakening to a tropical depression all the way to it regaining major hurricane intensity over the next 48-60 h. While shear over Simon is expected to remain low for the next 48 h and sea-surface temperatures (SSTs) are in the 29-30 C range, one wild card is how Simon's slow motion might cause some cool ocean upwelling. There is one ocean glider providing subsurface ocean temperature data near Simon, and it depicts 28 C waters down to about 80 m below the ocean surface. Assuming Simon does not completely stall, this is likely to support it maintaining hurricane intens…

ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM Tropical Depression Twenty-One-E Discussion Number 1 NWS National Hurricane Center Miami FL EP212026 900 AM CST Tue Oct 13 2026 Satellite images show that the area of low pressure located to the south of southern Mexico has become better organized over the past 24 hours. Large areas of banded deep convection are seen to the north and the east of the low-level center. An OSCAT pass from 0630 UTC this morning showed a closed circulation, but it was a bit short of being considered well-defined at that time since the data still showed a broad and somewhat elongated area of weak winds within about 75 n mi of the center. However, the convective organization and curved banding has increased since that time, and the circulation appears to have tightened up a bit over the past several hours. The subjective Dvorak estimate from TAFB is T2.0/30 kt, and it is estimated that a tropical depression has formed with an initial intensity of 30 kt. The initial motion of Tropical Depression Twenty-One-E is estimated to be northwestward, or 305/9 kt. A west-northwestward to northwestward motion should continue over the next 36 hours while a mid-level ridge persists over the northwestern Gulf of America. Thereafter, a turn to the northwest or north-northwest is likely as the ridge weakens. A decrease in forward speed is also expected after day 2 as the cyclone gets caught in weaker steering currents in between the weak ridge to its north and Hurricane Simon to its northwest. Spread in the track forecast is larger than normal from day 3 to 5, and some of this uncertainty is likely also due to uncertainty in Simon's track. A cold front moving southward from Texas into Mexico toward the end of the forecast period could help draw Simon closer to the coastline of Mexico, if the front is potent enough. Regardless, Tropical Depression 21-E could potentially be very close to the coast of Mexico as a hurricane over the weekend, and several Google DeepMind Ensemble members show the cyclone making landfall in southwestern or west-central Mexico. The NHC forecast closely follows the HFIP Corrected Consensus Approach (HCCA), and isn't too far off from the Google DeepMind Ensemble Mean. Confidence in the track forecast is low, especially beyond day 3. The cyclone is forecast to traverse extremely favorable oceanic and atmospheric conditions for at least the next 3 to 4 days. The NHC intensity forecast shows steady strengthening over the next 24 hours as the cyclone works to develop a convective core. After that time, rapid intensification is forecast during the 24 to 72 h time window. The DTOPS in the ECMWF-based SHIPS guidance is forecasting a 74 percent chance of a 65-kt increase over the next 72 h. The NHC intensity forecast is even more aggressive and shows 85 knots of strengthening over the next 72 h. The NHC forecast is slightly below the HCCA and GDMI in the short term, but very near the HCCA and GDMI beyond Day 2. The HAFS-A and HAFS-B models strengthen the cyclone to a category 4, and 36 of the 50 Google DeepMind members make it a category 4 or stronger, so the NHC forecast will aggressively show this system reaching category 4 strength at days 3 and 4. Beyond day 4, the possibility of increasing vertical wind shear and land interaction could induce some weakening, and most of the guidance shows the system losing some intensity after day 4. Confidence in the intensity forecast is above average. We are fairly confident it will become a strong hurricane due to the favorable environmental conditions and model guidance. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 9.8N 96.5W 30 KT 35 MPH 12H 14/0000Z 10.5N 97.6W 40 KT 45 MPH 24H 14/1200Z 11.3N 99.3W 50 KT 60 MPH 36H 15/0000Z 12.0N 100.5W 65 KT 75 MPH 48H 15/1200Z 12.8N 101.4W 80 KT 90 MPH 60H 16/0000Z 13.7N 101.9W 100 KT 115 MPH 72H 16/1200Z 14.5N …

WDPN33 PGTW 131500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KOGUMA) WARNING NR 035// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 36.8N 155.5E INITIAL INTENSITY: 60 KTS GEOGRAPHIC REFERENCE: 704 NM EAST-SOUTHEAST OF MISAWA, JAPAN MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 20 KTS SIGNIFICANT WAVE HEIGHT: 30 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) UNDERGOING RAPID SUBTROPICAL TRANSITION (STT). THE MID-LEVEL CIRCULATION AND ASSOCIATED DEEP CONVECTION SEEN EARLIER HAVE COMPLETELY COLLAPSED AND ARE NO LONGER DETECTABLE IN ANIMATED EIR IMAGERY. BASED ON THE LATEST MODEL FIELDS, THERMAL CONVECTION REMAINS MARGINAL, THE SYSTEM HAS YET TO ACQUIRE DEFINITIVE FRONTAL CHARACTERISTICS, AND IT REMAINS WELL EQUATORWARD OF THE POLAR FRONT JET AND ASSOCIATED BAROCLINIC ZONE. DEEP-LAYER VERTICAL WIND SHEAR (VWS) REMAINS EXTREMELY HIGH, AND DRY MID-LEVEL AIR NOW COMPLETELY OVERLIES THE SHALLOW VORTEX, WHICH IS CONFINED BELOW 700MB. ACCORDINGLY, THE SYSTEM IS ASSESSED AS UNDERGOING SUBTROPICAL TRANSITION (STT). THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC RESOLVED IN EIR. A 130744Z S1D SYNTHETIC APERTURE RADAR (SAR) PASS REVEALED A SLIGHTLY ELONGATED LLCC WITH A MEAN VMAX OF 62 KNOTS AND AN OBSERVED PEAK OF 68 KNOTS. BECAUSE THE RAPID COLLAPSE OF CONVECTION TENDS TO INTRODUCE A SIGNIFICANT LOW BIAS IN OBJECTIVE SATELLITE ESTIMATES, CONTINUITY WITH THIS HIGH-RESOLUTION SAR INSTRUMENT PROVIDES STRONG EMPIRICAL JUSTIFICATION FOR HOLDING INITIAL INTENSITY AT 60 KNOTS, ASSESSED WITH MEDIUM CONFIDENCE. ENVIRONMENTAL CONDITIONS ARE HIGHLY UNFAVORABLE FOR TROPICAL DEVELOPMENT, CHARACTERIZED BY STRONG VWS EXCEEDING 40 KNOTS, COOL SSTS (24-25C), DRY AIR ENTRAINMENT, AND VORTEX DECOUPLING. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHWESTERN FLANK OF A DEEP-LAYER SUBTROPICAL RIDGE (STR). AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS RJTD: T3.5 - 55 KTS RCTP: T3.0 - 45 KTS CIMSS ADT: 39 KTS AT 131200Z CIMSS AIDT: 45 KTS AT 131200Z CIMSS D-MINT: 47 KTS AT 131018Z CIMSS D-PRINT: 45 KTS AT 131200Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE VWS: 30+ KTS SST: 24-25 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: VORTEX DECOUPLING, DRY MID-LEVEL AIR ENTRAINMENT. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TS 27W CONTINUES ITS STEADY PROGRESSION NORTHEASTWARD ALONG THE NORTHWESTERN SIDE OF THE STR POSITIONED TO THE SOUTHEAST. NO SIGNIFICANT TRACK CHANGES ARE EXPECTED; THE SYSTEM WILL GRADUALLY CURVE TOWARD THE EAST AS IT TRANSITS THE POLEWARD PERIPHERY OF THE STR. TRANSLATION SPEED WILL REMAIN STABLE AT APPROXIMATELY 20 KNOTS THROUGHOUT THE FORECAST WINDOW, AS LOW- TO MID-LEVEL RIDGING EXTENDING TO THE EAST BLOCKS THE TYPICAL ACCELERATION CHARACTERISTIC OF CYCLONES LEAVING THE SUBTROPICS. REGARDING INTENSITY: 27W WILL CONTINUE TO STEADILY WEAKEN AND GRADUALLY SPIN DOWN AS IT TRANSITIONS THROUGH STT AND SUBSEQUENT EXTRATROPICAL TRANSITION (ETT) OVER THE NEXT 48 HOURS. AS OUTLINED ABOVE, 27W IS CURRENTLY ASSESSED TO BE IN STT MODE, PROJECTED TO COMPLETE WITHIN THE NEXT 12 HOURS. ALOFT, THE REMNANT VORTEX WILL PASS BENEATH AN UPPER-LEVEL RIDGE AXIS THAT DISPLACES THE POLAR JET STREAM FAR TO THE NORTH OVER KAMCHATKA. IN THE LOWER LEVELS, EXTENSIVE HIGH PRESSURE EXTENDS POLEWARD TO THE EAST OF 27W TOWARD THE ALEUTIANS. THE LACK OF AN ACTIVE BAROCLINIC ZONE WILL SU…

WDPN31 PGTW 131500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) WARNING NR 007// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.4N 145.4E INITIAL INTENSITY: 25 KTS GEOGRAPHIC REFERENCE: 253 NM NORTH OF SAIPAN MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 11 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH PERSISTENT CONVECTION CONFINED ALONG THE SOUTHEASTERN CONVERGENT ASYMPTOTE. WHILE THIS DEEP CONVECTION HAS PERSISTED IN THE SOUTHEASTERN QUADRANT FOR BEYOND SIX HOURS, IT HAS BEEN SYSTEMATICALLY UNABLE TO WRAP INWARD TOWARD THE LLCC. TRANSIENT, ISOLATED CONVECTIVE BURSTS RESIDE WITHIN THE WESTERN INFLOW BANDS, BUT LACK CONTINUITY AND DISSIPATE RAPIDLY. A 131110Z ASCAT-C PASS RESOLVES AN ASYMMETRIC SURFACE WIND FIELD, CHARACTERIZED BY LIGHT, DISORGANIZED FLOW ACROSS THE WESTERN SEMICIRCLE AND A 20-25 KNOT WIND BAND ALONG AN ARC EXTENDING FROM SOUTH OF THE LLCC UP THE EASTERN FLANK. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN EIR. THE INITIAL INTENSITY IS ALSO ASSESSED WITH HIGH CONFIDENCE, BASED ON THE SCATTEROMETER SWATH AND ALIGNED WITH THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW. ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE FOR TROPICAL DEVELOPMENT. ALTHOUGH DEEP-LAYER SHEAR IS MINIMAL (0-5 KTS), TD 28W RESIDES DIRECTLY BENEATH A WEAK UPPER-LEVEL LOW (ULL) AND INVERTED UPPER-LEVEL TROUGH, HEAVILY RESTRICTING UPPER- LEVEL OUTFLOW AND INTRODUCING DRY, SUBSIDENT AIR DIRECTLY OVER THE VORTEX CORE. THE 131200Z GUAM SOUNDING (THE NEAREST EMPIRICAL RAWINSONDE STATION) CONFIRMS A STRONG SUBSIDENCE INVERSION CAP AT 730MB, WITH DEEP DRY AIR EXTENDING TO 300MB. NUMERICAL FIELDS SUPPORT A SYNOPTIC PROFILE OVER THE CORE OF 28W THAT IS ROUGHLY ANALOGOUS. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS CIMSS SATCON: 42 KTS AT 130910Z CIMSS ADT: 25 KTS AT 131140Z CIMSS AIDT: 25 KTS AT 131140Z CIMSS D-MINT: 27 KTS AT 131201Z CIMSS D-PRINT: 27 KTS AT 131140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 0-5 KTS SST: 28-29 CELSIUS OUTFLOW: WEAK WESTWARD OTHER FACTORS: HIGHLY CONSTRAINED UPPER-LEVEL OUTFLOW AND DRY MID-LEVEL AIR. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 28W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD AT APPROXIMATELY 10 KNOTS ALONG THE SOUTHWESTERN PERIPHERY OF THE EXPANSIVE STR THROUGHOUT THE FORECAST PERIOD. REGARDING INTENSITY, 28W REMAINS IN CLOSE PROXIMITY TO THE UPSTREAM ULL AND INVERTED TROUGH. OVER THE FORECAST TIMELINE, WHILE THE ULL IS PROJECTED TO DRIFT SOUTHWESTWARD, THE ASSOCIATED TROUGH AXIS WILL REMAIN COUPLED WITH THE LLCC. THE RESULTANT UPPER-LEVEL SUBSIDENCE, PERSISTENT DRY AIR ENTRAINMENT, AND THE LACK OF A ROBUST OUTFLOW MECHANISM WILL SUPPRESS INTENSIFICATION. MESOSCALE MODELS CONTINUE TO RESOLVE A BRIEF WINDOW OF MODEST MOISTURE IMPROVEMENT NEAR TAU 24, WHICH DRIVES AN INCORRECT MODEL PROJECTED RE- INTENSIFICATION (DISCUSSED BELOW). HOWEVER, WHILE TRANSIENT CONVECTIVE CELLS MAY TEMPORARILY DEVELOP, PERSISTENCE IS UNLIKELY DUE TO THE ABSENCE OF AN ESTABLISHED UPPER-LEVEL EXHAUST MECHANISM. ACCORDINGLY, 28W WILL GRADUALLY WEAKEN AND DECAY, WITH DISSI…