An Anomaly-Based Analysis of High Impact Wind Events in the Anchorage Area

Although not frequent, strong orographically induced winds propagated via the Chugach Mountains and Turnagain Arm in Southcentral Alaska can pose a significant risk to life and property in the greater Anchorage region. The threat of high impact winds is magnified by the challenge that they present to forecasters due to their complexity. This study attempted to improve the operational forecasting of orographic wind events by using standardized anomalies as a prognostic tool combined with more traditional stability indicators to estimate peak gust intensity in Anchorage.

After initially building a database of high impact winds in the Anchorage region, overall synoptic composites of these events were created. This process was followed by the calculation of standardized anomaly values for a variety of fields, after which the contribution of each parameter was examined from a physical point of view. Eventually, it was determined that dynamic forcing could largely be tied to the standardized anomaly values of local pressure gradients and the 850mb cross-barrier flow. More traditional parameters usually tied to mountain wave generation like the Froude Number and Scorer Parameter were also examined.

Following the weighting of each value relative to its theorized physical contribution, an overall categorical index of wind impacts in Anchorage was developed by combining the “dynamic” and “wave” parameters into an overall score. Ideally, this index will be used in an operational setting at the WFO in the near future as a means of communicating potential wind risks to the public well in advance of an event.

This project was completed as part of the NOAA Ernest F. Hollings Undergraduate Scholarship Program.