Predictive Skill of Temperature and Precipitation Forecast Deviations from Climatology in the Boulder, Colorado Flood and the August 2013 Central US Drought

Mid-September 2013 rainfall along the Front Range of the Rocky Mountains produced catastrophic flooding in cities like Boulder and Longmont, Colorado. Model forecasts of this event in the days leading up to the flooding rain projected large amounts (3+ inches) of rainfall near these cities. The National Operational Model Archive & Distribution System (NOMADS) contains archived temperature and precipitation data and the National Climatic Data Center (NCDC) contains archived climatology data that date back to 1981. This combined data is typically used to create maps showing seasonal outlooks and drought monitors, and can also be used to show where a certain location is deviating substantially from their climatology over a certain time period.

The overarching goal of this project is to use the Global Forecast System (GFS) and North American Mesoscale Model (NAM) along with climatological data to indicate regions in the US where the forecast precipitation amounts and temperatures approach record levels. Using climatological data for numerous US cities from 1981-2010, forecasted extreme precipitation events and temperatures can be mapped to show locations in the US that will deviate significantly from their climatological average over a 3-day, 7-day and 10-day forecast period using the NAM and GFS models. This presentation will focus on the algorithms used to define extreme events as well as highlight a mapping technique used to notify the public of the forecasted extreme events. The main emphasis of this presentation will be to showcase model forecasts for the mid-September extreme rainfall in Colorado as well as the central US drought in August.