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Overview of upgrade scheduled for December 2017. Note that this was originally scheduled for October 2017, but has been pushed back due to technical issues.

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KPDX Wind Verification

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Bill Schneider, modified 6 Years ago.

KPDX Wind Verification

Youngling Posts: 8 Join Date: 9/24/12 Recent Posts

I stumbled across this accidentally... Looking at URMA time series for u and v wind at Portland, Oregon (KPDX) it appears that the URMA analysis is actually substantially degraded over the background field (unless I am misinterpreting the plot). A quick check of other nearby stations indicates that, while not as bad as KPDX, the analysis is adding little if any improvement over the background field at least at the METAR stations.  I thought this may be due to mesonet observations damping down the wind speeds in the analysis. However, when I checked on the RTMA viewer there are no mesonet stations shown in the wind speed analysis field. I know I use to be able to display all the METAR and mesonet stations on the display and the mesowest stations were often shown as rejected.  It appears that only the METAR stations are used now. Is this correct (or am I doing something wrong)? I also noted that at the one buoy location (46050) shown on the map in our CWA, both the analysis and background field winds are very close to the observations. It would be nice to add the other buoys in our marine waters to this plot (buoy 46029, 46089).

 

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SL
Steven Levine, modified 6 Years ago.

RE: KPDX Wind Verification

Youngling Posts: 174 Join Date: 11/13/14 Recent Posts
Hi Bill,

The time series graphs you posted are of u and v components of wind, rather than of wind speed itself.  However you are correct in noting that in both cases for KPDX the analysis value is closer to zero than the background.  Keep in mind that since we are dealing with u and v, negative values are possible here.  For buoy 46050, you only posted a time series of the v component of wind.

The individual u/v wind variables work a little differently than the wind speed analysis.  For u and v, the analysis actually computes stream function and velocity potential and derived u and v from that.
There is a separate, wind-speed only variable that is analyzed much more like temperature, moisture, etc.  What you see on the NBM viewer is the speed-only analysis.  Wind direction is derived from the u and v analyses.

Perhaps it would be helpful if we got rid of the separate u and v graphs on the time-series site and kept only the wind speed values, this would match with what is available on the NBM viewer.  I can certainly see how keeping the speed and direction and u/v plots all up there can be confusing.

As far as obs used, there is still an issue of lower-wind speeds available from mesonets that often bring down the analysis wind speed.  

The values listed on the viewer shots you provide are of grid point values, not observation values.  My understanding is that this is the default of the viewer.  If you click on the + box in the upper-left panel, you'll see a drop-down menu where you need to un-check 'Gridbox values' and check 'URMA obs.'  See attached shot of obs used for the cycle you specify (8/27 17Z).  KPDX is the 9.9 kts entry (it reported 10 but there are conversion issues).  You can see many other obs which were used that all report much less than that.  The white and yellow obs were used, the red ones were not.  In the lower-left, you can see that the obs are generally lowering the wind speed values around Portland.

In our next version, generally fewer mesonet wind obs will be used.  I remind everyone that you can request that any ob be flagged for wind (or any other variable) by using the form available in VLab.

Adding those other buoys to the time-series site should not be a problem.

Steve

On Tue, Aug 28, 2018 at 12:07 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:

I stumbled across this accidentally... Looking at URMA time series for u and v wind at Portland, Oregon (KPDX) it appears that the URMA analysis is actually substantially degraded over the background field (unless I am misinterpreting the plot). A quick check of other nearby stations indicates that, while not as bad as KPDX, the analysis is adding little if any improvement over the background field at least at the METAR stations.  I thought this may be due to mesonet observations damping down the wind speeds in the analysis. However, when I checked on the RTMA viewer there are no mesonet stations shown in the wind speed analysis field. I know I use to be able to display all the METAR and mesonet stations on the display and the mesowest stations were often shown as rejected.  It appears that only the METAR stations are used now. Is this correct (or am I doing something wrong)? I also noted that at the one buoy location (46050) shown on the map in our CWA, both the analysis and background field winds are very close to the observations. It would be nice to add the other buoys in our marine waters to this plot (buoy 46029, 46089).

 


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Bill Schneider RTMA/URMA Discussion Group Virtual Lab Forum https://vlab.noaa.gov/web/715073/discussions-forums-/-/message_boards/view_message/4717808VLab.Notifications@noaa.gov

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