Subject: NAM-WRF Eval Comments

From: private sector #2

Date: Thu, 01 Jun 2006 04:44:22 -0400

To: David Michaud \<David.Michaud@noaa.gov\>

Dave,

Sorry for the delay. The holiday played havoc on getting people\'s
thoughts. Below are comments by the staff who focused on the NAM-WRF
daily in operational forecasting needs.

The NAM-WRF seems to be doing much better now that we are in the more
convective season. The NAM-WRF is picking out more smaller scale type
features and shows the convective nature of showers and thunderstorms in
the warm season even better than the ETA. I still think the NAM-WRF will
have problems with larger scale type development and the evolution of
warm air advection situations that are on a larger scale. So, it looks
as if we will have to compare and not average the NAM-WRF and GFS.

I think the weaknesses of the NAM-WRF will be made up by the GFS. Where
the GFS has trouble handling smaller scale development we can rely more
heavily on the NAM-WRF. Comparing the WRF to the ETA I believe during
the warm season the NAM-WRF will be just as good and in many cases
better. As we head into the colder season I think the WRF will either do
just as good as the ETA or perhaps not quite so good. We did not have a
good chance to see how the NAM-WRF handles good synoptic scale storm
systems during the cold season like coastal development.

What little we did see was not impressive and in most cases we had to
rely more heavily on the GFS. I will be very interested in seeing how
the NAM-WRF does with smaller scale snow and ice situations. Based on
what little we saw of the NAM-WRF during large synoptic scale storm
systems I believe the model will have trouble with coastal development
and perhaps handling of cut off lows. But it probably won\'t be too far
off from what we have seen in the ETA version of the NAM.

Finally, the last submitted comment from forecasters about the NAM-WRF
was focused on short range convection forecasts. This is a comment about
the convection over PA Tuesday night:

Although the 18z nam-wrf suggested tstms would develop over us or very
nearby before the 6z time step, the 00z run missed the whole thing.
Considering areas just east of us seemed to get more than 3 inches of
rain, that\'s unacceptible.

\> \>

Private Sector #2 previously wrote:

\>\> \>\> Hello,

\>\> \>\>

\>\> \>\> Some comments on NAM-WRF data:

\>\> \>\>

\>\> \>\> April 12

\>\> \>\> On 4/5 at 12z, there was significant disagreement between the
NAM and WRF on the 500 mb height field over the eastern US at 84 hours
(00z on the 9th). The NAM was more progressive with a southern-branch
feature, placing it close to the southeast coast of the US. The WRF had
it hanging back, very much separate from the feature swinging through
the northeast at the same time. A look at the 500 mb height verification
for 00z 4/9 indicates that the reality was closer to the NAM, and that
the WRF did not handle the situation very well on the 12z run from 4/5.

\>\> \>\>

\>\> \>\> April 13

\>\> \>\> Has same problems as NAM in being too dry with shower or
t-storm development in the southern states with general return flow
development and convection. Sometimes it is even drier than the MAM. It
seems to overdevelop more than the NAM on surface low development near
Florida.

\>\> \>\>

\>\> \>\> April 13

\>\> \>\> NAM-WRF did better than NAM with small convection cell/cells
over PA and Northeast in April 13th 12z forecast due to shortwave
passing over region. NAM nothing, NAM-WRF printout. Convection depected
well under this shortwave in NAM-WRF - much better than NAM

\>\> \>\>

\>\> \>\> April 26

\>\> \>\> Yesterday (April 25), a band of rain streaked from Ohio to the
Middle Atlantic Coast in just a few hours following a cold frontal
passage. The rapid spread and then ending of the precipitation was
symptomatic of jet streak influence. The GFS yesterday morning portayed
this very well, but it seemed the NAM_WRF model was a little weak on the
development. I have also noticed with some overrunning patterns that the
model is a little slower than actual starting times along the Middle
Atlantic Coast.

\>\> \>\>

\>\> \>\>

\>\> \>\> Hope the comments are helpful,