{"id": "1203981566662770690", "title": "Tropical Cyclone Discussion", "adv_date": "2026-08-23T15:00:00Z", "msg": "639\nWTPZ44 KNHC 231446\nTCDEP4\n \nTropical Storm Iselle Discussion Number   1\nNWS National Hurricane Center Miami FL       EP092026\n800 AM MST Sun Aug 23 2026\n\nThe area of low pressure that we have been monitoring for the past \nseveral days (EP92) has had gale-force winds and sufficiently \nwell-organized convection for the past 12 h or so.  The ASCAT-C pass \nfrom 23/0517Z showed winds of 40 kt, and that the system did not yet \nhave a well-defined circulation, although it was closer than it was \non the previous pass from 12 h earlier.  An OSCAT pass a couple \nhours later around 23/0716Z suggested that the surface circulation \nwas continuing to become better-defined.  Since that time, satellite \nimagery indicates continued consolidation of deep convection over \nthe low-level center, and the system very likely has a well-defined \ncirculation by now.  Thus, EP92 is upgraded to Tropical Storm \nIselle, and the current intensity is estimated at 40 kt based on the \nscatterometer data.\n\nThere have been no other recent microwave passes, and the confidence \nin the initial position is low. The initial motion is estimated to \nbe west-northwestward, or 300 degrees at 10 kt.  A northwestward \nmotion is expected through Monday while Iselle is steered by ridging \nover the southwestern United States and northwestern Mexico. As the \nridge builds in a bit more to the north of the cyclone, a gradual \nturn toward the west-northwest is expected on Tuesday and Wednesday. \n The NHC track forecast closely follows the HFIP Corrected Consensus \n(HCCA) model and the Google DeepMind (GDMI), which is on the \nnorthern side of the guidance envelope.  There is a healthy amount \nof spread in the track guidance, and confidence in the track \nforecast is slightly below average.\n\nIselle will be traveling over warm water and within a moist \nenvironment with weak vertical wind shear for the next couple of \ndays.  Only slow intensification is forecast during the next 12 h as \nthe cyclone attempts to consolidate and form a core.  Given the \nfavorable environment, steady strengthening is forecast tonight and \nMonday, and the NHC forecast shows Iselle reaching hurricane \nstrength Monday night.  By Tuesday night, a modest increase in \nwest-southwesterly vertical wind shear and decreasing sea-surface \ntemperatures along Iselle's path should lead to gradual weakening.  \nThe NHC intensity forecast lies near the intensity consensus and the \nhurricane regional model solutions.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  23/1500Z 15.3N 114.2W   40 KT  45 MPH\n 12H  24/0000Z 16.5N 115.6W   45 KT  50 MPH\n 24H  24/1200Z 17.9N 117.2W   55 KT  65 MPH\n 36H  25/0000Z 19.3N 118.7W   65 KT  75 MPH\n 48H  25/1200Z 20.5N 120.3W   65 KT  75 MPH\n 60H  26/0000Z 21.4N 121.9W   60 KT  70 MPH\n 72H  26/1200Z 22.0N 123.6W   55 KT  65 MPH\n 96H  27/1200Z 23.0N 127.2W   45 KT  50 MPH\n120H  28/1200Z 23.9N 130.8W   35 KT  40 MPH\n \n"}