Abstract:

Assessing wind speed is a normal part of checking the weather forecast during colder months as high downslope winds are most dominant during this season. As highlighted by recent wind and wildfire events in the Front Range of Colorado, when downslope wind events occur, winds can cause significant damage to the community. Despite the level of destruction from recent wind events (Marshall Fire), since the 1980’s, anecdotal evidence suggests that NCAR’s Mesa Lab in Boulder, Colorado has recorded fewer intense (>70 mph) wind events along with more mild damage to Boulder homes and infrastructure. Here, we present an analysis aimed at understanding this apparent trend. By reviewing multiple instrumental anemometer records; Colorado, Utah, and Wyoming radiosondes; as well as building codes to account for structural biases, we evaluate potential climate signals. We will show a trend analysis from long radiosonde data records, as well as windroses from anemometer records for general and high wind events.  Trends are computed using sounding data from Lander, Grand Junction, and Salt Lake City, based on an empirical formula from the National Weather Service developed to forecast downslope winds. Finally, we utilize both anemometer and radiosonde data to identify key events in reanalysis products to diagnose trends in synoptic conditions necessary to produce downslope winds.