Evaluating the Performance of the National Blend of Models During High Impact Winter Weather in New England

This research project examines the performance of the National Blend of Models (NBM) during high impact winter weather events in New England. The NBM is a state-of-the-art weather forecasting system developed by NOAA that combines multiple numerical weather prediction models as a part of the Weather Ready Nation initiative. The goal of which is simplifying forecasting for National Weather Service (NWS) forecasters, allowing them to devote more time to providing critical decision support services during high impact weather. NBM v4.1 became operational in January 2023, so this evaluation primarily focuses on its performance during high-impact winter weather in New England. Additionally, this project involves a comparative analysis between the current version and its predecessor, NBM v4.0 for the impactful December 2022 Winter Storm that led to a blizzard in the Buffalo, NY region.

To complete this evaluation, data was collected for numerous impactful winter weather events during the 2022-2023 winter season. This includes NBM forecasts and corresponding observations for key variables including temperature, dew point, wind speed, quantitative precipitation forecast (QPF), snowfall, precipitation type, and snow-to-liquid ratio. This analysis was done by examining spatial and temporal forecast errors to identify systematic biases or regional variations. Biases and errors associated with various meteorological setups such as cold air damming, arctic frontal passages, near freezing temperatures, and more were documented. NWS forecasters have gained some understanding through their own forecasting experience of how the NBM performs in certain situations. Through the results of this examination and collaboration with forecasters at NWS Gray, it was determined how forecasters in New England NWS offices could change their approach to utilize the NBM most effectively when making forecasts.

The findings of this project contribute to a better understanding of the NBM’s strengths and weaknesses in providing forecast guidance before high impact winter weather events in New England. This research both provides insights for NWS meteorologists and informs efforts to enhance the accuracy and reliability of the NBM, particularly during extreme weather conditions.