000WTNT41 KNHC 060236TCDAT1Hurricane Irma Discussion Number 28NWS National Hurricane Center Miami FL AL1120171100 PM AST Tue Sep 05 2017The satellite view of Irma remains quite spectacular, with anextremely well-defined eye and a large, symmetrical CDO. Reportsfrom NOAA and Air Force Hurricane Hunter aircraft indicate that thecentral pressure had fallen at about 1 mb per hour since thismorning, although very recently the deepening trend has leveledoff. Based on SFMR-observed winds from the aircraft, the currentintensity remains at 160 kt. The Meteo-France radar imagerysuggests a concentric eyewall structure and observations from theaircraft hinted at a secondary wind maximum. If an eyewallreplacement becomes more definitive, this would likely haltadditional strengthening, and could even lead to some weakening.The official intensity forecast is near or above the modelconsensus. Given the favorable atmospheric and oceanic environment,Irma is likely to remain a Category 4 or 5 hurricane for the nextfew days.Latest center fixes from satellite imagery and the aircraftindicate that Irma is now moving west-northwestward, or 285/13 kt.A strong ridge extending southwestward from the central Atlantic isexpected to steer Irma west-northwestward during the next couple ofdays. A large mid-latitude trough over the eastern United States isforecast to lift northeastward, allowing the ridge to build westwardand keep Irma on a westward to west-northwestward heading throughFriday. In 4 to 5 days, a small trough diving southward overthe east-central U.S. is expected to weaken the western portion ofthe ridge, causing Irma to turn poleward. Some of the dynamicalmodels have shifted northward a bit from the previous cycle, withthe normally reliable GFS looking like a northeast outlier. Theofficial track forecast leans toward the ECMWF solution. Users arereminded to not focus on the exact forecast track, especially at thelonger ranges, since the average NHC track errors are about 175 and225 statute miles at days 4 and 5, respectively.KEY MESSAGES:1. Irma is a potentially catastrophic category 5 hurricane and willbring life-threatening wind, storm surge, and rainfall hazards toportions of the northern Leeward Islands, including the VirginIslands and Puerto Rico, on Wednesday. Preparations should berushed to completion.2. A Hurricane Warning is in effect for the northern coast of theDominican Republic, with hurricane watches for Haiti, thesoutheastern Bahamas and the Turks and Caicos. Irma is likely tobring dangerous wind, storm surge, and rainfall to these areas fromWednesday night through Friday.3. Irma could directly affect the remainder of the Bahamas and Cubaas an extremely dangerous major hurricane later this week. Residentsin these areas should monitor the progress of Irma and listen toadvice given by officials.4. The chance of direct impacts from Irma beginning later this weekand this weekend from wind, storm surge, and rainfall continues toincrease in the Florida Keys and portions of the Florida Peninsula.However, it is too soon to specify the timing and magnitude of theseimpacts.FORECAST POSITIONS AND MAX WINDSINIT 06/0300Z 17.4N 61.1W 160 KT 185 MPH 12H 06/1200Z 18.1N 63.1W 155 KT 180 MPH 24H 07/0000Z 19.1N 65.9W 150 KT 175 MPH 36H 07/1200Z 20.1N 68.5W 145 KT 165 MPH 48H 08/0000Z 21.0N 71.2W 140 KT 160 MPH 72H 09/0000Z 22.0N 76.2W 135 KT 155 MPH 96H 10/0000Z 23.2N 79.5W 125 KT 145 MPH120H 11/0000Z 25.0N 81.5W 120 KT 140 MPH$$Forecaster Pasch