Past IEM Features tagged: hrrr
Some weather prediction computer models are run at a spatial scale that is able to begin to resolve individual thunderstorms. The primary such model in the US is the High Resolution Rapid Refresh (HRRR). The featured map displays a simulated depiction of RADAR reflectivity valid this afternoon at 6 PM. While the HRRR model does not explicitly predict RADAR reflectivity, it does predict many of the hydrometer particles that cause returns on weather RADAR. So with a bit of model output post-processing and assumptions, a simulated depiction of forecasted RADAR reflectivity can be made. The forecast shown for today predicts strong thunderstorms in western Iowa at this time.
The showers and thunderstorms that pushed into western Iowa yesterday and made it to Des Moines was a bit unexpected. One of the main high resolution and short term forecast models run by NCEP/NWS is called HRRR. This model is run every hour producing a 15 hour forecast. The featured map presents the percentage of these runs (15 in total) that had simulated reflectivity above 30 dBz (stronger showers) for 6 PM yesterday evening. The inset map shows the actual RADAR data at that time. Only the last few model runs that afternoon picked up on the showers in west central Iowa and the coverage was under predicted.
Tags: hrrr forecast
The HRRR model is a recently developed weather prediction system run by NOAA that forecasts weather out for 15 hours and run 24 times per day (each hour). For any given time, there are 15 previous forecasts made for that time. On Tuesday, successive HRRR runs were predicting storm development in western Iowa just northeast of Council Bluffs. The featured map displays the frequency of where the forecasted storm development would be at 4 PM. The higher percentages imply more insistence that the model believed storm development would occur at that location. The inset image shows the actual RADAR presentation at 4 PM and sure enough, the HRRR was mostly correct with the initial development! Please note that a smoother was applied to the data to aid in this comparison.