ntim - CHANGE TO ETA FREEZING LVL GUIDANCE

• To: G.CARTER(REC), R.LIVINGSTON(REC), D.SMITH.DAN(REC),
• Subject: ntim - CHANGE TO ETA FREEZING LVL GUIDANCE
• From: C.ALEX
• Date: Fri, 11 Jun 1993 08:30:24 -0600

Posted: Fri, Jun 11, 1993   8:50 AM EDT              Msg: AGJD-5747-6265
        K.MIELKE(REC), 
        G.HUFFORD(REC), J.PARTAIN(REC)
CC:     L.MILLER.UCAR(REC)
Subj:   ntim - CHANGE TO ETA FREEZING LVL GUIDANCE    
I sent the following Nat'l Tech. Info. Msg. on AFOS etc. last evening - thanks 
to Dan Baumgardt and the Western Region forecasters for getting to the bottom 
of this.
---------------------------------------------------------------------------
WSHPNSNMC
NOUS41 KWBC 102210

NATIONAL TECHNICAL INFORMATION MESSAGE 93-21
NATIONAL WEATHER SERVICE HEADQUARTERS
615 PM EDT THU JUN 10 1993

TO:         NWS OFFICES, CARSWELL AFB, FAA/WEATHER MESSAGE
            SWITCHING CENTER, ISPAN

FROM:       MARY M. GLACKIN
            CHIEF, SERVICES DEVELOPMENT BRANCH

SUBJECT:    ETA FREEZING LEVEL GUIDANCE - FOH40 - 43

(INFORMATION FOR THIS ANNOUNCEMENT HAS BEEN PROVIDED BY
RUSS TREADON OF THE DEVELOPMENT DIVISION OF NMC AND DAN BAUMGARDT
OF THE SCIENTIFIC SERVICES DIVISION OF WESTERN REGION
HEADQUARTERS...EDITED FROM A WESTERN REGION ADMINISTRATIVE
MESSAGE SENT OUT 6/10/93 AT 2048 UTC)

A number of forecasters in the Western Region have noted a
problem (cold bias) with the freezing level guidance from the Eta
model (AFOS PILs NMCFOH40-43;  WMO headers FOUS40-43 KWBC). 
Western Region Headquarters reported this to NMC, and the problem
has been identified, and will be corrected with the 0000 UTC
cycle 6/11/93).

The model executable file for the creation of this product has
been changed to now give freezing level above mean sea level
(MSL).  The equation had subtracted the Eta model station height
from the calculated freezing level - this will no longer be done.
Since the Eta model topography is a step-type function, the
actual station elevation could be hundreds of meters from the
model station elevation used, thus producing the error.

Thanks for all the helpful input from the field concerning this
matter.  If the change does not occur on the 0000 UTC run, NMC
has stated it will occur with the 1200 UTC model run.

If you have any questions, call Russ Treadon at (301)-763-8005.

SENT - W/OM23