Sunny and Warm Posted June 12, 2013 Share Posted June 12, 2013 The following was part of the Charleston NWS office AFD today: HIGHS WELL INTO THE 90S WITH MOST AREAS TOPPING OUT IN THE MID 90S BY MID AFTERNOON...WITH SOME UPPER 90S POSSIBLE ACROSS INTERIOR SOUTHEAST GEORGIA. DEWPOINTS ARE FORECAST TO MIX OUT INTO THE UPPER 60S TO LOWER 70S LATER TODAY WHICH WILL PRODUCE HEAT INDEX VALUES OF 100-104 DEGREES FOR SEVERAL HOURS DURING PEAK HEATING. A FEW SPOTS COULD TOUCH 105 FOR ABOUT AN HOUR...ESPECIALLY WHERE DEWPOINTS POOL SLIGHTLY NEAR THE SEA BREEZE...BUT DURATIONS OF 105+ HEAT INDICES ARE NOT EXPECTED TO BREACH TEMPORAL REQUIREMENTS FOR A HEAT ADVISORY. NOTE...HEAT ADVISORIES ARE ISSUED FOR HEAT INDICES OF 105-114 DEGREES OCCURRING FOR TWO HOURS OR MORE THROUGH JUNE 30TH...AFTER WHICH THE CRITERIA IS RAISED TO 110-114 DEGREES FOR THE REMAINDER OF THE SUMMER. A SPECIAL WEATHER STATEMENT WAS ISSUED EARLIER TO HIGHLIGHT THE FIRST REAL TASTE OF HEAT AND HUMIDITY FOR THE SUMMER SEASON. Does Mt Holly migrate the Heat Index as the summer wear on like Charleston does, and if not, why not? I don't recall the HI criteria change over the course of a summer when I lived in PA, but may have missed it. Thanks in advance! Link to comment Share on other sites More sharing options...
phlwx Posted June 13, 2013 Share Posted June 13, 2013 criteria changes in Philly and immediate metro between May and June. They use the Kalkstein method on heat advisory issuance here (and it's a quasi-sliding scale based on time of the year, impact/duration, etc.)...the NWS guys can probably talk more detail into it but I think our guidelines are much more conservative here than in even DC or NYC simply due to the amount of brick housing stock and # of places that still lack AC. Philly & suburban counties are treated a bit differently on head advisories than say Allentown & Reading are because of the row home factor and the high mortality in the '93 heatwaves. More on that: http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-85-8-1067 Link to comment Share on other sites More sharing options...
Rainshadow Posted June 17, 2013 Share Posted June 17, 2013 Yes, Heat Index criteria changes for metro areas from 96 before June 15th to 98 the second half of June and then 100 the rest of the summer. Link to comment Share on other sites More sharing options...
phlwx Posted July 16, 2013 Share Posted July 16, 2013 Is this the longest duration excessive heat warning we've had in the region since the '95 redo of the heat warnings in the metro? I could only thumb back to 2009 on Iowa State's servers and couldn't see anything longer than 4 days in any single warning. Gotta think the '95 heat wave probably kicked more of these out but I can't find data that old floating around. Link to comment Share on other sites More sharing options...
Rainshadow Posted July 19, 2013 Share Posted July 19, 2013 Might even be back to 1993 judging that it had the record for most consecutive days of 95F or higher and all of the heat related deaths. Link to comment Share on other sites More sharing options...
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