1 / 20

Mastering the MOS Forecast: Tips to Beat Model Output Statistics for Accurate Weather Predictions

Learn how to effectively improve weather forecasts by understanding the dynamics of Model Output Statistics (MOS). Discover when MOS performs well, versus when it struggles, such as during outliers or using poor input data. Explore practical strategies to adjust forecasts based on factors like precipitation, temperature gradients, and cloud conditions. Gain insights into common MOS errors and how to recognize patterns, including handling shallow chill problems. Enhance your forecasting skills with tips to leverage analogous thickness methods and consensus MOS for better accuracy.

frey
Télécharger la présentation

Mastering the MOS Forecast: Tips to Beat Model Output Statistics for Accurate Weather Predictions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. HOW TO BEAT MOS • Need to understand how it works • MOS does well when: • Weather is close to climatology (equations lean toward the modal case) • MOS does poor when: • Weather departs from climatology ( the “outliers” of the scatter plot) • Bad model data used as input (GI=GO)

  2. MOS: Equation Development Y1 = mx1 + b1

  3. HOW TO BEAT MOS • Forecast lower than MOS by day if: • It’s precipitating • Overrunning situations • Spatially thin, optically thick cloud (non-climo) • Snow cover • Shallow cold air mass • Sea breeze in hot air mass with cold water • Expected air mass will be record-breaking

  4. MOS ERROR: OVERUNNING 850mb Predictor gives a very poor forecast!

  5. MOS ERROR: SPATIALLY THIN/OPTICALLY THICK CLOUD

  6. MOS ERROR: Shallow Chill

  7. MOS ERROR: Shallow Chill

  8. MOS ERROR: Shallow Chill

  9. MOS ERROR: Shallow Chill

  10. Beating MOS • How to account for shallow chill problem: • Recognize pattern • Look at 2m temps from model (ETA/AVN) • If much colder than MOS, then lower MOS

  11. MOS ERROR: FRONTS Relaxed gradient aloft gets translated to the surface

  12. MOS ERROR: FRONTS Relaxed gradient aloft gets translated to the surface

  13. HOW TO BEAT MOS • Forecast higher than MOS by day if: • Mainly sunny • In warm sector • Especially if in the cooler season and it’s breezy • Expected air mass is record-breaking

  14. HOW TO BEAT MOS • Forecast lower than MOS at night if: • Clear • Calm • Low dew points • Snow cover • (unless its ‘climatological’!)

  15. HOW TO BEAT MOS • Which city is more likely to have the bigger bust in the following situation? • Clear skies, light winds, snow cover • ST. LOUIS vs. INTERNATIONAL FALLS

  16. HOW TO BEAT MOS • Forecast higher than MOS at night if: • Cloudy • Breezy • Not precipitating

  17. MOS ERROR: CYCLONE

  18. HOW TO BEAT MOS • PRECIPITATION • Will tend to miss mesoscale events tied to topography • Lake-effect • Under predicts upslope areas, Over predicts in downslope areas • WIND • A little inflation of sustained winds

  19. HOW TO BEAT MOS • Other considerations: • NGM beyond 48-hours …. Watch out! • Beware if MOS exceeds 850mb ‘rules’ • Lean toward MOS product that makes the most sense: • (i.e. AVNMOS: 65F NGMMOS: 72F and character of day: optically thick/spat. thin overcast) • If unsure, go CONSENSUS MOS ............ wins over long haul! • Analogous thickness methods

  20. HOW TO BEAT MOS • Analogous thickness approach • Use analogous thickness method to “advect” mos errors to forecast location! • If MOS is busting at upstream site and same weather regime is heading to forecast site, then assume error will continue!

More Related