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> GEFS Upgrade, Info on the GFS Ensembles
post Feb 15 2012, 08:20 AM
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Technical Implementation Notice 11-47, Amended

National Weather Service Headquarters Washington DC

1045 AM EST Wed Jan 18 2012

To: Subscribers:

-Family of Services

-NOAA Weather Wire Service

-Emergency Managers Weather Information Network


Other NWS Partners, Users and Employees

From: Timothy McClung

Chief, Science Plans Branch

Office of Science and Technology

Subject: Amended: Global Ensemble Forecast System (GEFS)

Changes: Effective February 14, 2012

Amended to reschedule the implementation for Tuesday, February 14, 2012 and to add specific mention that the increased run time of the Global Ensemble will result in a delay of the associated Global Wave Ensemble products.

On or about Tuesday, February 14, 2012, beginning with the 1200 Coordinated Universal Time (UTC) run, the NCEP Global Ensemble Forecast System (GEFS) will be updated.

The upgrade in the GEFS production suite includes:

1. Running the latest Global Forecast System (GFS) model with improved physics scheme GFS v9.1.0 to replace the currently used GFS v8.0

2. Increasing the horizontal resolution from T190 (about 70km) to T254 (about 50-55km) for the first 192 hours (8days) of model integration

3. Increasing vertical resolution from 28 levels to 42 levels for 0-384 hours (0-16 days) forecasts

4. Improving the ensemble initialization method by inflating the initial perturbations between Earth’s surface and 500mb.

5. Optimizing the stochastic Total Tendency Perturbation (STTP) scheme, implemented in February 2010, to represent model related uncertainty by adjusting its parameters to match the increased model resolution

Due to the increase in model resolution and limitations in computational resources, the delivery of some GEFS products will be delayed. Files for the early hours (06h forecast) will experience virtually no delay. Files for the longer forecast hours may be subject to a delay of up to 20 minutes depending on the lead time. This change was announced earlier this year in a Public Information Statement. The delivery times of the GFS and North American Ensemble Forecast System (NAEFS) products will not be affected. The delivery times of the associated Global Wave Ensemble will be affected by this change in the GEFS. The Global Wave Ensemble products will be available roughly
20 minutes later after this implementation.

There will be several changes in the GEFS product data files affecting files with names pgrba/pgrbb. The GEFS products disseminated over NOAAPORT will not change in format or content. The GEFS products disseminated via the NWS and NCEP servers will have some changes in content. A small increase in the GRIB product data volumes is expected due to these changes. These products are available at the following locations:

NCEP server: http://www.ftp.ncep.noaa.gov/data/nccf/com...efs.YYYYMMDD/xx


ftp://ftp.ncep.noaa.gov/pub/data/nccf/com...efs.YYYYMMDD/xx , where YYYYMMDD is the date and xx is the model cycle

NWS server:


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