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    Inversion Forecast


    Discussion Last Updated: 02-21-2019 1:31:19 pm MST

    Update 02/21/2019: The active weather pattern continues to suppress the odds for the development of inversions--especially long-lived events that accrue high levels of pollution. However, with snow on the ground of many low-lying areas across the state, all that is needed is the return of high pressure for an extended period. Thankfully, that scenario is not forecast to occur in the next month but is still in the cold-season cards should the jet stream shift. That said, we find ourselves at the back-end of the inversion season as we wrap up February meaning each day without high pressure in our forecast is one more day closer to not needing to worry about a late-season event unfolding. So far, this year has been mostly mild and inversion-free. Despite the plethora of snow coverage, the necessary long-lived high pressure remained elusive across the region. Great news for our lungs!

    This product is being developed by researchers at the Utah Climate Center. Using output from the National Center for Environmental Prediction’s (NCEP) Climate Forecast System (CFSv2), this technique projects surface inversion probability for persistent inversion events—defined as events lasting longer than 4 days—with a demonstrated “skill” over a span of ~ 30 days. A surface inversion probability of 35% or greater suggests a statistically significant likelihood of an extended event. It should also be noted that inversion forecasts, in and of themselves, are not air quality projections. The projection is valid for a radius of roughly 200 miles around Salt Lake City.

    Image Interpretation: The blue bar graph shows the calculated Surface Inversion Probabilities. Values above the horizontal yellow line (~35% on the right axis) have a statistical significance of manifesting as persistent (> 4 days) inversion events. The solid black line above the SIP chart shows the ensemble average of 200mb geopotential heights for the most recent 16 CFSv2 forecasts. The individual dotted lines are individual model runs. The vertical red and yellow lines identify the initialization (+0) and 30 day (+30) locations. SIP values lying within this 30 day window have a statistically significant confidence interval. Values before the initialization data are obtained from NCEP reanalysis data.

    For more information on the methodology and origins of this product, see the following publication here.