GFS Forecast Review NCEP EMC GCWMB Bi-weekly Briefing Fanglin Yang, August 25, 2011

Hurricane Irene Courtesy 00Z 23Aug2011 Cycle 00Z 25Aug2011 Cycle GFS has performed well in terms of track forecast.

Hurricane Irene Courtesy GFS track forecast is one of the best

Hurricane Irene: GFS 00Z 25AUG2011 Forecast 5PM, Friday 5PM, Saturday 5PM, Sunday 11AM, Saturday DC area: 40 mph wind, lots of rain

Hurricanes, Typhoons …… Pacific Atlantic Nanmadol Talas Both basins are active

GFS Four Cycles In the past few months, GFS 00Z cycle fell behind the 12Z and 06Z cycles. NH 500hPa Height AC SH 500hPa Height AC In the past few months, GFS 00Z cycle became better than all other cycles.

IMD T382 GFS—no dropouts below.7 But average score.028 lower Courtesy: Glenn White GFS had two dropouts in July; The T382 GFS run in Indian had no dropouts.

In the Past 31 Days NH 500hPa Height AC SH 500hPa Height AC No dropout Tied with CMC No dropout

In the Past 31 Days Tropical Wind CONUS QPF Score 00-72hr accumulated rainfall; Better than all but ECMWF Slightly better than ECM and UKM for day-1 in the lower troposphere and lower stratosphere

NH 500-hPa Height AC GFS forecast skill has been steadily improving; falls behind ECMWF and Met Office; better than Canadian and Navy. After 2007, UK Met Office improved summer forecast.

SH 500-hPa Height AC The gap between GFS and ECMWF hasn’t changed for decades. Met Office surpassed GFS in CMC improved after 2008

Tropical 850hPa Wind GFS significantly improved after 2007 GSI implementation and July-2010 T574 implementation.

Tropical 200hPa Wind GFS hasn’t improved much in the past decade. Modest improvement after July-2010 implementation. CMC significantly improved after 2006.