GFS Forecast Review

NCEP EMC GCWMB

Bi-weekly Briefing

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/

Fanglin Yang, August 25, 2011

Hurricane Irene Courtesy

00Z 23Aug2011 Cycle00Z 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 .7But 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 DaysTropical 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 2005.

• 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.