NOTE: This is PART 1 of the presentation and contains only slides 1 thru 21 of the complete PowerPoint presentation saved as HTML.
INTELLIGENT USE OF THE AVN/MRF
Understanding the performance of an operational model is critical to being able to forecast the sensible weather
Why models have forecast problems
The T126 version of the Avn does not have sufficient resolution to adequately depict the rain shadow east of the Cascades. A forecaster needs to know the climatology of precipitation during certain flow regimes.
The way the physics are approximated can lead to model errors, for example
AVN/MRF APPROXIMATED PHYSICS
A NUMBER OF AVN/MRF PERFORMANCE CHARACTERISTICS HAVE CHANGED IN THE PAST YEAR.
LATEST AVN/MRF CHANGES
AVN/MRF Still Often Has Problems Handling Upslope Events
About 75% of the AVN Rainfall Over the OK Panhandle Was Grid-scale Precipitation (Not Convection).
Another Case: AVN Wraps Low Too Far North And West. Both Surface and 500 mb Lows Are Too Deep.
Aviation Model handling of 500 mb trough
BIAS COMPARISON OF 12-36 HR MRF AND EARLY ETA FORECASTS
The MRF and MRFX spin-up precipitation bombs and tropical systems erroneously at all time ranges.
MRF PRECIPITATION Convective - dashed Gridscale - solid green (inches -Vs- time) BEFORE 7/21 AFTER 7/21
MRF RELATIVE HUMIDITY (pressure -Vs- time) BEFORE 7/21 AFTER 7/21
MRF THETA-E (pressure -Vs- time) BEFORE 7/21 AFTER 7/21
After the change
During Oct-Feb 1999, the AVN/MRF now had a bias of
During OCT-JAN 1999 4 INCH OR GREATER ISOHYETS
SINCE THE CHANGES IN JUNE AND JULY, THE ETA BIAS FOR HEAVY AMOUNTS HAS DECREASED SIGNIFICANTLY
Email: norman.junker@noaa.gov
Download complete PowerPoint presentation source