Subseasonal prediction of the state and evolution of the North Pacific jet stream Journal Article uri icon

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abstract

  • The state and evolution of the North Pacific jet (NPJ) stream strongly; influences the character of the downstream synoptic-scale flow pattern; over North America. This study employs data from nine models within the; Subseasonal-to-Seasonal Reforecast Database hosted by the European; Centre for Medium-Range Weather Forecasts to examine the subseasonal (2; weeks–1 month) predictability of the NPJ through the lens of an NPJ; phase diagram. The NPJ phase diagram provides a visual representation of; the state and evolution of the NPJ with respect to the two leading modes; of NPJ variability. The first mode of NPJ variability corresponds to a; zonal extension or retraction of the climatological jet-exit region,; whereas the second mode corresponds to a poleward or equatorward shift; of the climatological jet-exit region. The analysis reveals that; ensemble forecasts of the prevailing NPJ regime, as determined from the; NPJ phase diagram, are skillful into week 3 of the forecast period.; Forecasts initialized during a jet retraction, or verifying during a jet; retraction and equatorward shift, feature the largest forecast errors; during weeks 1–2 of the forecast period for all models. Beyond week 2,; the verifying NPJ regime characterized by the largest forecast error; varies by model and is related to forecast frequency biases in the; prediction of each NPJ regime at subseasonal time scales. Examination of; the worst-performing 21-day forecasts from each model demonstrates that; the worst-performing forecasts are uniformly associated with; development, maintenance, and decay of upper-tropospheric ridges over; the high-latitude North Pacific.

publication date

  • April 18, 2021

has restriction

  • hybrid

Date in CU Experts

  • April 19, 2021 6:35 AM

Full Author List

  • Winters A

author count

  • 1

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