frh guidance msg

• To: g.carter(rec), d.smith.dan(rec), k.mielke(rec),
• Subject: frh guidance msg
• From: M.ROBINSON
• Date: Mon, 21 Jun 1993 10:06:41 -0600

Posted: Wed, Jun 16, 1993   5:07 PM EDT              Msg: BGJD-5754-7540
CC:     m.glackin(rec), r.przywarty(rec)
Subj:   frh guidance msg              
The following message was transmitted over AFOS at approximately 2PM EDT
this afternoon.  This message gives information on the interpretation of 
the NGM FOUS/FRH relative humidity/temperature data.  Russ Treadon, who
works in Development Division in Geoff DiMego's group, provided input  
and is the contact person for technical questions.  Russ has prepared an NMC 
Office Note #394, which will be mailed this week, on the NMC eta model post
processor in which details of direct model output data from the Eta are
described.  (We have also asked NMC to prepare a TPB on this subject.)
----------
Regarding the US Air Force generated snow cover analysis problem, Ken
Mitchell at NMC's Development Division has informed me that a decision
will be made later today on whether this analysis will be turned off.
We will send an NTIM informing users of the status.  Ken said the analysis
has gotten better, and the decision may be to continue to let it run
for a while and closely monitor it.  Ken has been working closely with
Alaska Region (Joel Curtis) and they will have input into the final decision.
Will let you and the field know what the final word is.

Call me if you have questions...Mary Newton (formerly Mary Robinson)
  
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ZCZC WSHPNSNMC ALL
TTAA00 KWSH DDHHMM

NATIONAL TECHNICAL INFORMATION MESSAGE 93-23
NATIONAL WEATHER SERVICE HEADQUARTERS
2:00 PM EDT WED JUN 16 1993

TO:         NWS OFFICES, CARSWELL AFB, CANADA/AES, FAA/WEATHER
            MESSAGE SWITCHING CENTER, and FAMILY OF SERVICES
            USERS (DOMESTIC DATA SERVICE and AFOS GRAPHICS
            SERVICE)

FROM:       MARY M. GLACKIN
            CHIEF, SERVICES DEVELOPMENT BRANCH

SUBJECT:    INFORMATION ON THE GENERATION OF ETA-BASED DIRECT     
            MODEL OUTPUT GUIDANCE (FOUS/FRH DATA) 

REFERENCES:  (1) "The NMC Eta Model Post Processor:  A            
                  Documentation", Russell Treadon, June 1993      
 
            (2)  "FOUS Messages from RAFS", TPB #351, April 1985 


(INFORMATION FOR THIS MESSAGE HAS BEEN PROVIDED BY RUSS TREADON
OF THE DEVELOPMENT DIVISION OF NMC)

Eta-based direct model output guidance, i.e. FOUS Relative
Humidity/Temperature guidance (FOUS60-78 KWBC/AFOS category FRH),
is generated in a manner similar to that used for the NGM.  In
the NGM, the direct model output guidance is obtained from the
sigma layers used in the model.  (See Reference 2 and/or the
green card dated 9/18/92 that gives the interpretation of both
the NGM direct model output guidance and the Model Output
Statistics (MOS) message).  In the Eta model, a different
vertical structure, the Eta coordinate system, is used.  Thus, to
get a product comparable to the NGM product, the Eta post-
processor interpolates from the appropriate Eta model layers to
the approximate mid-point pressure of the corresponding NGM sigma
layer.  This interpolation in the Eta post-processor is done for
the temperatures in the first (T1), third (T3), and fifth (T5)
sigma layers, the wind components in the first sigma layer
(DDFF), and the relative humidity in the first sigma layer (R1). 
The Eta-based relative humidities R2 and R3 correspond to a layer
mean from approximately 35 mb above the surface to 500 mb and
approximately 500 mb to the tropopause, respectively.  

The 700 mb vertical velocity used in the Eta FOUS (VVV) is an
INSTANTANEOUS value rather than a time-averaged value as was done
for the LFM FOUS.  

The Eta lifted index (LI) is based on the six lowest layers. 
There are six 30 mb deep layers above the model surface.  The
definitions of other variables in the Eta FOUS 60-78 bulletins
(PTT, PS, and HH) coincide with those used in the NGM FOUS
messages.

If you have questions or would like additional information on the
Eta-based direct model output guidance, please call Russ Treadon
at (301)-763-8469.  We plan to release a Technical Procedures
Bulletin (TPB) on this subject in the near future.  Meanwhile,
Reference 1 is being mailed this week to all NMC Office Note
subscribers.  NWS offices may contact their Regional Scientific
Services Division (SSD) for a copy or relevant sections.  

If you would like to receive a copy of Reference 2 and/or the
green card mentioned above, please call Mary Newton or Chris Alex
at (301) 713-0462.

SENT - W/OM23

Posted: Thu, Jun 17, 1993   3:08 PM EDT              Msg: FGJD-5756-3760
        g.hufford(rec), 
        j.partain(rec), r.livingston(rec), l.miller.ucar(rec), 
        j.schaefer(rec), 
        t.whittaker(rec)
CC:     e.kalnay(rec), j.curtis(rec)
Subj:   snow cover analysis-part 2                    
The following message, regarding the Air Force generated snow cover analysis
used in the Eta and NGM models, was transmitted over AFOS this afternoon.
This is a follow up from a previous message I sent on last week which
identified the problem of a low level cold bias in output from the Eta and
the NGM.  Ken Mitchell in coordination with Joel Curtis in Alaska Region have
worked very hard over the past several days to provide feedback to the Air
Force regarding their apparent bias in the snow cover analysis.  Based on
an improvement in the analysis, NMC made the decision to continue the use
of the analysis operationally.  Daily monitoring, however, by NMC will
continue and a re-assessment will be done within a 2-week period.
-----------------------------------------------------------------------
ZCZC WSHPNSNMC ALL
TTAA00 KWSH DDHHMM

NATIONAL TECHNICAL INFORMATION MESSAGE 93-24
NATIONAL WEATHER SERVICE HEADQUARTERS
2:00 PM EDT THU JUN 17 1993

TO:         ALL USERS OF THE NGM AND ETA MODELS:
            NWS OFFICES, CARSWELL AFB, CANADA/AES, FAA/WEATHER
            MESSAGE SWITCHING CENTER, and FAMILY OF SERVICES
            USERS (DOMESTIC DATA SERVICE and AFOS GRAPHICS
            SERVICE)

FROM:       MARY M. GLACKIN
            CHIEF, SERVICES DEVELOPMENT BRANCH

SUBJECT:    PROBLEM WITH THE SNOW COVER ANALYSIS USED IN THE ETA
            AND NESTED GRID MODELS

REFERENCE:  NTIM 93-22, SAME SUBJECT, Dated June 11, 1993

(INFORMATION FOR THIS ANNOUNCEMENT HAS BEEN PROVIDED BY
KEN MITCHELL OF THE DEVELOPMENT DIVISION OF NMC)

As mentioned in the Reference NTIM, a problem with the daily snow
cover analysis used in both the NGM and the Eta models was
identified last week.  The problem was an overanalysis of snow
cover over all of Alaska, northern Nevada, central Idaho, western
Washington, western Oregon, and the western 1/6th of Canada. The
effect of this problem was a low level cold bias in both the NGM
and Eta Forecast for the areas mentioned.  

Based on feedback from NMC, in consultation with the Alaskan
Region, the Air Force snow analysis has IMPROVED thus removing
the low level cold bias that was prevalent over the last five
days.  NMC has decided to continue using the analysis
operationally as input to the NGM and Eta models.  Daily
monitoring (by NMC) of quality of the Air Force snow analysis
will continue, followed within a week or two with a re-
assessment.  

Again, thanks for the input from the Alaska Region regarding this
problem.  Additional follow-up status message will be issued as
required.  

If you have any questions, call Ken Mitchell at (301)-763-8161.

SENT - W/OM23