IMAGe Brown Bag- Subseasonal Predictions of Eastern US hot days from the mid-latitude Pacific

01/29/2016 - 12:00pm to 1:00pm
Mesa Lab - Damon Room

Karen McKinnon
NCAR/ASP

Anomalously hot weather has an adverse effect on human health and agriculture that could be diminished with advance warning, yet the current generation of seasonal forecast models has minimal skill in predicting hot summer weather in the mid-latitudes. The identification of statistical relationships between slowly-varying boundary conditions and hot weather may, however, allow for skillful long-lead predictions of specific types of extreme events. In this talk, I will first present a method based on clustering weather station measurements of daily maximum temperature to identify regions of the US that tend to experience hot days synchronously, and introduce a metric to quantify heat extremes across the regions. Focusing on the eastern half of the US and building upon previous work suggesting a relationship between monthly precipitation deficits and hot weather, I will demonstrate that these deficits indeed provide for skillful predictability of hot days at lead times out to 45 days. Skill is measured by Relative Operating Characteristic scores due to their applicability to both binary and unusual events. Next, I will identify a mid-latitude Pacific sea surface temperature anomaly pattern, termed the Pacific Extreme Pattern (PEP), that evolves in a predictable manner during the 50 days preceding hot weather in the Eastern US. The similarity between an observed SST anomaly and PEP is a skillful predictor of hot days at lead times up to 50 days. Furthermore, PEP is associated with low precipitation over the Eastern US, suggesting that the two predictors are interrelated. Further work is required to determine the nature of the ocean-atmosphere interactions that lead to the coevolution of PEP with the atmospheric anomalies that lead to extended periods of low precipitation and subsequent hot days.

Friday, January 29, 2016
12:00-1:00 pm
Mesa Lab, Damon Room
(Please bring your lunch)