{"id": "1204262126378516482", "title": "Tropical Cyclone Discussion", "adv_date": "2026-08-24T15:00:00Z", "msg": "679\nWTPZ44 KNHC 241433\nTCDEP4\n \nTropical Storm Iselle Discussion Number   5\nNWS National Hurricane Center Miami FL       EP092026\n800 AM PDT Mon Aug 24 2026\n\nDespite being affected by moderate west-northwesterly shear, \nIselle's cloud pattern has continued to improve, with a core of very \ndeep convection that has now rotated over and north of the center, \nand a deep convective band extending southward on the east side of \nthe cyclone.  A 24/0903 UTC AMSR-2 pass also shows the improving \nstructure of the inner core.  The latest subjective Dvorak \nclassification from TAFB is T3.5/55 kt, and objective satellite \nintensity estimates range from 50 to 59 kt.  The initial intensity \nhas been set at 55 kt for this advisory, in agreement with the \nestimates.\n\nThe initial motion estimate is northwestward, or 310/11 kt.  A \nmid-level ridge north of Iselle is forecast to strengthen, causing \nIselle to turn west-northwestward on Tuesday, and that motion should \nthen continue through the end of the week.  The latest NHC track \nforecast is a little faster and to the left of the previous \nforecast, and lies very close to the HFIP Corrected Consensus (HCCA) \nand the Google DeepMind Ensemble Mean (GDMI).\n\nIselle remains over warm waters and within a moist environment.  \nHowever, SHIPS and UW-CIMSS both currently analyze 17 kt of vertical \nwind shear.  Water temperatures and moisture will remain quite \nfavorable for another 24 h, but the shear is forecast to increase to \nat least 20 kt between the 12 to 24 h period.  Given the recently \nimproving structure, the NHC forecast continues to call for \nstrengthening and system to become a  hurricane in 12 to 24 h, which \nis at the high end of the intensity model guidance suite.  However, \ngiven the increasing shear, there is some uncertainty as to whether \nIselle will become a hurricane.  Beyond 24 h, gradually decreasing \nocean temperatures and moisture will lead to steady weakening, and \nthe NHC intensity forecast lies in the middle of the guidance \nenvelope from hour 48 onward.  The latest ECMWF and GFS simulated \nsatellite imagery suggest that Iselle could become a remnant low as \nearly as Thursday.  I have moved forward the forecast time for \nIselle becoming post-tropical to hour 96, but it's possible the \ncyclone could lose its convection sooner than forecast.  After that, \nthe models indicate the remnant low opening up into a trough by day \n5.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  24/1500Z 18.5N 117.1W   55 KT  65 MPH\n 12H  25/0000Z 19.4N 118.3W   65 KT  75 MPH\n 24H  25/1200Z 20.5N 120.2W   65 KT  75 MPH\n 36H  26/0000Z 21.1N 122.1W   60 KT  70 MPH\n 48H  26/1200Z 21.5N 123.8W   50 KT  60 MPH\n 60H  27/0000Z 22.0N 125.6W   40 KT  45 MPH\n 72H  27/1200Z 22.5N 127.6W   35 KT  40 MPH\n 96H  28/1200Z 23.1N 131.9W   30 KT  35 MPH...POST-TROP/REMNT LOW\n120H  29/1200Z...DISSIPATED\n \n"}