980211: Early Eta Model

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 980211: Early Eta Model
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Wed, 11 Feb 1998 08:21:57 -0700 (MST)

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NATIONAL TECHNICAL IMPLEMENTATION MESSAGES 98-04
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
940 AM EST WED FEB 11 1998

TO:       FAMILY OF SERVICES /FOS/ SUBSCRIBERS...NOAA WEATHER
          WIRE SERVICE /NWWS/ SUBSCRIBERS...OTHER NATIONAL
          WEATHER SERVICE /NWS/ CUSTOMERS...NWS EMPLOYEES

FROM:     LEROY SPAYD...CHIEF...SCIENCE AND TRAINING CORE

SUBJECTS: CHANGES TO THE OPERATIONAL "EARLY" ETA MODEL MADE ON
          FEB 9 1998

AT 1200 UTC 09 FEBRUARY 1998 A SERIES OF CHANGES TO THE
OPERATIONAL "EARLY" ETA WAS IMPLEMENTED.   A BRIEF DESCRIPTION OF
THESE CHANGES FOLLOWS.

A/ MODEL/ANALYSIS CHANGES

1/ THE RESOLUTION OF THE ETA FORECAST MODEL HAS BEEN INCREASED
FROM 48 KM / 38 LEVELS TO 32 KM / 45 LEVELS WITH LITTLE CHANGE IN
THE SIZE OF THE HORIZONTAL DOMAIN.

2/ THE ETA OPTIMUM INTERPOLATION ANALYSIS HAS BEEN REPLACED WITH
A 3-DIMENSIONAL VARIATIONAL ANALYSIS /3DVAR/ DESIGNED FOR USE IN
THE ETA DATA ASSIMILATION SYSTEM /EDAS/...WHICH IS USED TO
INITIALIZE THE EARLY ETA FORECAST

3/ THE EDAS HAS BEEN MODIFIED TO RUN IN "PARTIAL" CYCLING MODE.
WITH PARTIAL CYCLING...SOIL PARAMETERS /TEMPERATURE/MOISTURE/
..TURBULENT KINETIC ENERGY...AND CLOUD WATER/ICE AT THE START OF
EACH EDAS CYCLE ARE OBTAINED FROM THE PERVIOUS EDAS CYCLE INSTEAD
OF THE GDAS. ACCOMPANYING THIS CHANGE IS AN INCREASE IN THE
NUMBER OF SOIL LAYERS IN THE ETA MODEL LAND-SURFACE PACKAGE FROM
TWO TO FOUR.

4/ THE COMPUTATION OF THE MASTER LENGTH SCALE FOR VERTICAL
TURBULENT TRANSPORT IN THE ETA MODEL HAS BEEN MODIFIED.

B/ CHANGES TO MODEL OUTPUT

1/ ALL OUTPUT FILES PACKED IN OFFICE NOTE 84 FORMAT HAVE BEEN
DROPPED.

2/ A NEW 32-KM LAMBERT CONFORMAL GRID /AWIPS GRID 221/ WILL BE
OUTPUT WHICH COVERS NEARLY THE ENTIRE COMPUTATIONAL DOMAIN OF THE
32-KM ETA MODEL GRID

3/ THE AVAILABILITY AND TIMELINESS OF ALL OTHER GRIB / BUFR /
ICWF OUTPUT WILL BE UNAFFECTED BY THIS IMPLEMENTATION.

FURTHER DETAILS ON THIS IMPLEMENTATION CAN BE FOUND IN THE NWS
TECHNICAL PROCEDURES BULLETIN #447..."CHANGES TO THE NCEP
OPERATIONAL "EARLY" ETA ANALYSIS AND FORECAST SYSTEM"...LOCATED
ON THE WORLD WIDE WEB AT HTTP://WWW.NWS.NOAA.GOV/OM/447.HTM
/LOWER CASE/.

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