{"id": "1204049620543995906", "title": "Tropical Cyclone Discussion", "adv_date": "2026-08-23T21:00:00Z", "msg": "356\nWTPZ44 KNHC 232032\nTCDEP4\n \nTropical Storm Iselle Discussion Number   2\nNWS National Hurricane Center Miami FL       EP092026\n200 PM PDT Sun Aug 23 2026\n\nRecent satellite imagery over Iselle shows a shear pattern, with a \nlarge area of very deep convection located in the southwest \nsemicircle of Iselle.  Visible imagery shows a partially exposed \nlow-level center at the northeast edge of the convection.  A recent \n23/1748Z ASCAT-C overpass shows an elongated, but well-defined \nsurface circulation, with a radius of maximum winds (RMW) of about \n70 nautical miles, with gales in the NE, SE and SW quadrants.  There \nare several 40-45 kt vectors on the south side, and the intensity is \nincreased to 45 kt for this advisory.  This is above the latest \nsubjective Dvorak estimate from TAFB, which is T2.5/35 kt.\n\nThe initial motion estimate is northwestward, or 315 degrees at 14 \nkt.  A continued northwest motion is expected through Monday while \nIselle is steered by ridging over the southwestern United States and \nnorthwestern Mexico. As the ridge builds in a bit more to the north \nof the cyclone, a gradual turn toward the west-northwest is expected \non Tuesday and Wednesday.  The NHC track forecast has been shifted \nwell to the right (or northeast) of the previous forecast through 48 \nh, mainly due to the farther north initial position and is nearly on \ntop of the previous forecast thereafter.  The NHC forecast is very \nclose to the latest HFIP Corrected Consensus (HCCA) model and the \nGoogle DeepMind (GDMI).  There is still a healthy amount of spread \nin the track guidance, and confidence in the track forecast is \nslightly below average.\n \nIselle will be traveling over warm water and within a moist \nenvironment with weak to moderate vertical wind shear for the next \nday or so, but westerly vertical wind shear should increase to the \n15-20 kt range by Tuesday or sooner.  Strengthening is expected for \nthe next 36 h.  Thereafter, Iselle will be moving into a more \nstable environment, with gradually decreasing sea-surface \ntemperatures, so weakening is expected to begin by Tuesday night \nor Wednesday.  Only small changes have been made to the NHC \nintensity forecast, which lies between the middle and high end of \nthe guidance envelope for most of the forecast period.  Rapid \nintensification is becoming less likely because the RMW is still\nlarge, and the system has at most 36-48 h left to strengthen.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  23/2100Z 16.9N 115.1W   45 KT  50 MPH\n 12H  24/0600Z 18.2N 116.3W   50 KT  60 MPH\n 24H  24/1800Z 19.6N 117.8W   60 KT  70 MPH\n 36H  25/0600Z 20.8N 119.4W   65 KT  75 MPH\n 48H  25/1800Z 21.4N 121.1W   65 KT  75 MPH\n 60H  26/0600Z 21.9N 122.8W   60 KT  70 MPH\n 72H  26/1800Z 22.4N 124.6W   50 KT  60 MPH\n 96H  27/1800Z 23.3N 128.4W   45 KT  50 MPH\n120H  28/1800Z 24.2N 132.2W   30 KT  35 MPH...POST-TROP/REMNT LOW\n \n"}