980602: Eta Model Changes

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 980602: Eta Model Changes
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Tue, 2 Jun 1998 10:54:25 -0600 (MDT)

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NATIONAL TECHNICAL IMPLEMENTATION MESSAGES 98-10
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
915 AM EDT TUE JUN 2 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

SUBJECT:  CHANGES TO THE NATIONAL CENTERS FOR ENVIRONMENTAL
          PREDICTION /NCEP/ OPERATIONAL "ETA" MODEL SYSTEM...
          EFFECTIVE JUNE 3 1998

AT 1500 UNIVERSAL COORDINATED TIME /UTC/ 03 JUNE 1998 A SERIES OF
CHANGES TO THE OPERATIONAL MESO ETA MODEL SUITE AT NCEP WILL BE
IMPLEMENTED. IN THE DESCRIPTION BELOW...ETA-32 REFERS TO THE 32KM
GRID/45 LEVEL ETA MODEL...WHILE ETA-29 REFERS TO THE CURRENT 29KM
GRID/50 LEVEL ETA MODEL RUNNING IN THE MESO RUN SLOT. 

A BRIEF DESCRIPTION OF THESE CHANGES FOLLOWS. YOU CAN ACCESS
TECHNICAL PROCEDURES BULLETIN /TPB/ NUMBER 447 AT
HTTP://TGSV5.NWS.NOAA.GOV/OM/TPB/447.HTM  /USING LOWER
CASE/...WHICH DESCRIBES THE ETA-32...3-DIMENSIONAL VARIABLE
ANALYSIS /3DVAR/ AND ETA DATA ASSIMILATION SYSTEM /EDAS/ CYCLING
THAT WERE IMPLEMENTED 9 FEBRUARY IN THE 0000 UTC AND 1200 UTC
EARLY RUN SLOT.

A/ OFF-TIME ETA-32 FORECASTS

1/ THE 0300 UTC RUN OF THE ETA-29 /SO-CALLED "MESO" ETA/ WILL BE
REPLACED BY A 0300 UTC RUN OF THE ETA-32. THIS FORECAST WILL BE
THE SAME LENGTH AS THE ETA-29 FORECAST /33 HOURS/. THE 0300 UTC
ETA-32 RUN WILL BE INITIALIZED BY A 3-HOUR ASSIMILATION STARTING
AT 0000 UTC...AS IS NOW DONE FOR THE ETA-29 BUT WILL USE A 3DVAR
AND WILL START FROM AN EDAS FIRST GUESS INSTEAD OF THE GLOBAL
DATA ASSIMILATION SYSTEM /GDAS/.

2/ THE 1500 UTC RUN OF THE ETA-29 /SO-CALLED "MESO" ETA/ WILL BE
REPLACED BY AN 1800 UTC RUN OF THE ETA-32. FORECAST LENGTH WILL
BE 30 HOURS WITH THE 1800 UTC ANALYSIS PRODUCED BY A 6-HOUR EDAS
RUN FROM 1200 UTC TO 1800 UTC. 

3/ FORECAST PRODUCTS DISTRIBUTED FROM THE 0300 UTC ETA-32 RUN
WILL BE IDENTICAL TO THOSE PRODUCTS DISTRIBUTED FROM THE ETA-29
WITH THE ONLY EXCEPTION THAT DURING HURRICANE SEASON THEIR
AVAILABILITY MAY BE DELAYED.  THE 1800 UTC ETA-32 FORECAST WILL
CREATE FORECAST OUTPUT IDENTICAL TO THAT PRODUCED BY THE 1500 UTC
ETA-29 RUN EXCEPT THAT IT WILL BE AVAILABLE 2 TO 3 HOURS LATER. 
THERE WILL BE NO FILENAME CHANGES ON THE OFFICE OF SYSTEMS
OPERATIONS SERVER.  CONSEQUENTLY...THE 'MESO' RUN FILE NAMES WILL
CONTINUE TO HAVE THEIR CYCLE-TIME MISLABELED AS T00Z /ACTUALLY
THE 0300 UTC RUN/ AND T12Z /ACTUALLY THE 1800 UTC RUN/.

B/ ANALYSIS CHANGES

1/ IN THE 9 FEBRUARY 1998 ETA IMPLEMENTATION...THE EDAS WAS
MODIFIED TO RUN IN "PARTIAL" CYCLING MODE...IN WHICH SOIL
PARAMETERS /TEMPERATURE AND MOISTURE/...TURBULENT KINETIC ENERGY
/TKE/...AND CLOUD WATER/ICE AT THE START OF EACH EDAS CYCLE IS
INITIALIZED FROM THE PREVIOUS EDAS CYCLE...WHILE ATMOSPHERIC
VARIABLES /TEMPERATURE...MOISTURE...WIND/ ARE OBTAINED FROM THE
GDAS. WITH THIS IMPLEMENTATION THE EDAS WILL RUN IN FULL CYCLING
MODE...WITH THE ATMOSPHERIC VARIABLES CYCLED FROM THE PREVIOUS
EDAS IN ADDITION TO SOIL...TKE...AND CLOUD PARAMETERS.

2/ THE USE OF OPTIMUM INTERPOLATION IN THE MESO ETA ANALYSES HAS
BEEN REPLACED EVERYWHERE BY THE USE OF A 3DVAR.

IF YOU HAVE FURTHER QUESTIONS...YOU MAY CONTACT

DR. GEOFFREY DIMEGO OR
ERIC ROGERS
NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION
REGIONAL AND AND MESOSCALE MODELLING BRANCH  - W/NP22
5200 AUTH ROAD
CAMP SPRINGS MD 20746-4304
TELEPHONE 301-763-8000
EXTENSION 7221 FOR DIMEGO
EXTENSION 7227 FOR ROGERS

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