Re : An Upgrade to what?

Environmental Protection's (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

Semi-Lagrangian dynamic scheme and improved physics scheme, GSM

v12.1.0, to replace the currently used GFS v9.1.0.



2. Increasing the horizontal resolution from T254 (about 55km) to

TL574 (about 33km) for the first 192 hours (8 days) of model

integration, and from T190 (about 70km)to TL382 (about 55km)

between 192 hours and 384 hours of model integration.



3. Increasing vertical resolution from 42 levels to 64 levels for

0-384 hours (0-16 days) forecasts.



4. Modifying the ensemble initialization method by replacing the

Bred Vector with Ensemble Transform and Rescaling (BV-ETR) scheme

with Ensemble Kalman Filter (EnKF) scheme. The 6-hour forecasts

of the 80 EnKF ensemble members of the Hybrid Data Assimilation

system, from the previous cycle, are used to initialize the

ensemble perturbations.



5. Improving the Stochastic Total Tendency Perturbation (STTP)

scheme by (1) turning off perturbations in the surface pressure,

(2) increasing the perturbation amplitude of other model state

variables around the time of model truncation (192 hours), and

(3) adjusting its parameters to match the Semi-Lagrangian scheme,

the increased model resolution and improved model physics.