http://www.meted.ucar.edu/metedbb/forums/show/15.page JForum - http://www.jforum.net
Stephen]]> http://www.meted.ucar.edu/metedbb/posts/preList/79/231.page http://www.meted.ucar.edu/metedbb/posts/preList/79/231.page GMT Details and a case example illustrating the differences are presented on COMET web pages linked from the Operational Models Matrix. The differences are large and noteworthy - you will notice a significant improvement!
Go to http://www.meted.ucar.edu/nwp/pcu2 then scroll down to the Assimilation System section toward the bottom of the page and click on "Updates" under RTMA.

If you notice anything about the RTMA you would like to discuss, any examples of problems you have seen or something it handled very well, or any questions about the changes, please post here and, if you can, attach an image showing what you are talking about.

Stephen]]> http://www.meted.ucar.edu/metedbb/posts/preList/76/227.page http://www.meted.ucar.edu/metedbb/posts/preList/76/227.page GMT
I am still not happy with some of the RTMA data across our higher elevations. When I examined the RTMA Max Temperature information for 3/11/08, I noticed the MaxT for Snowshoe (highest point in our forecast area) on that date was portrayed as 44 degrees. However, the actual MaxT for that location was actually 37 degrees.

The RTMA MaxT information across the lowlands seemed reasonable.

Has anyone else seen these issues?

Jeffrey Hovis ]]> http://www.meted.ucar.edu/metedbb/posts/preList/75/221.page http://www.meted.ucar.edu/metedbb/posts/preList/75/221.page GMT
Where the downscaled terrain is below the 13-km RUC terrain, the temperature is now allowed to be up to 10 deg C colder than the 13-km RUC 2-m temperature, based on multiplying the elevation difference by the low-level lapse rate, though it is still not allowed to be colder than the 13-km RUC 2-m dewpoint. Previously, the lapse rate was truncated at isothermal, preventing the downscaled temperature at lower elevation from being colder than the RUC 2-m temperature. However, the dewpoint is still not allowed to be less than the 13-km RUC 2-m dewpoint.

When the downscaled terrain is above the 13-km RUC terrain, the temperature is now allowed to be warmer than the 13-km RUC 2-m temperature, based on the colder of: 1) multiplying the elevation difference by the low-level lapse rate, or, 2) the free atmosphere temperature difference in the RUC between the downscaled terrain and the lowest RUC model layer. Previously, procedure (2) was used except the result was truncated to not allow a warmer temperature than the 13-km RUC 2-m temperature. Also, the dewpoint calculation was changed so that the downscaled dewpoint now uses the 2-meter mixing ratio from the 13-km RUC based on the pressure at the downscaled terrain height.

Stephen]]> http://www.meted.ucar.edu/metedbb/posts/preList/71/216.page http://www.meted.ucar.edu/metedbb/posts/preList/71/216.page GMT http://www.meted.ucar.edu/metedbb/posts/preList/70/214.page http://www.meted.ucar.edu/metedbb/posts/preList/70/214.page GMT
What is the process to relay a systematically bad ob from the observation. Looks like we have a bad MADIS observation showing up over the Escambia County Florida/Baldwin County line. Can't recollect the ID number off hand.

Stephen Miller
Mobile AL]]> http://www.meted.ucar.edu/metedbb/posts/preList/66/205.page http://www.meted.ucar.edu/metedbb/posts/preList/66/205.page GMT
This forum is for discussing how well or poorly the analyses compares with various observations or conceptual sense of observed phenemona, how the analysis is constructed, how it can be used in preparing short term forecasts or in verifying previous forecasts, how it can be used in assessing the current or recent forecasts, how or whether the analysis error size estimate could be used to identify areas where forecasters should focus attention or avoid spending a lot of effort fine-tuning a forecast, and any other such topics as you would like to discuss. Please don't wait for me to post something - this is your discussion forum and what you see may be of interest to others, and others may have useful feedback to help you.

Some background on RTMA:

The RTMA analyses are presently all univariate (no variable influences another). Temperature, dew point, and wind analyses are based on a 2-d var Gridpoint Statistical Analysis (GSI) on the National Digital Forecast Database (NDFD) grid using a first guess from the RUC interpolated down to the NDFD resolution and terrain, along with mesonet observations from all types of mesonets across the country. The hourly precipitation estimates come from the multisensor Stage II analyses (not quality-controlled by the River Forecast Centers - quality controlled data is available too late for RTMA) mosaic produced at NCEP remapped from the HRAP grid, and the sky cover estimate comes from the NESDIS Effective Cloud Amount, which is based on a GOES field of view (larger than NDFD grid box but smaller than a human's visible celestial dome in clear, unobstructed situations) and cannot distinguish between translucent overcast and opaque scattered to broken clouds.

NCEP has been producing the RTMA and sending it over the SBN for many months, and AWIPS has been able to ingest it since OB7.2. However, this original version has too little correction to the RUC first guess. After significant tuning to the GSI and some other adjustments, an improved version is scheduled for implementation tentatively on June 26, 2007. The precipitation and sky cover products are not affected by this change. Concomitantly, COMET will be releasing training on how the RTMA is produced and examples describing the capabilities and limitations of this new version. A link to that training will be posted on this forum.

Even with the June 2007 implementation, a variety of significant changes will still be under development, with one focus on observation quality control and another on allowing the state of the atmosphere itself (e.g., isentropes and streamlines) to affect the shape of an observation's influence on the analysis. The latter would be easy to accomplish if calculation time were unlimited but is a challenge to make fast enough for the short-fuse RTMA.

The RTMA is presently available only over the CONUS. Plans are to implement it over Alaska later in 2007 and subsequently for Hawaii, Guam, and Puerto Rico. The first guess for these will have to be based on the NAM, except GFS for Guam, because these are outside of the RUC domain.]]> http://www.meted.ucar.edu/metedbb/posts/preList/60/197.page http://www.meted.ucar.edu/metedbb/posts/preList/60/197.page GMT