#OREGON VORTEX MANUAL#

Above-normal temperatures are favored across all of Alaska with anticipated southerly flow.

#OREGON VORTEX MANUAL#

While the manual blend of dynamical and statistical model guidance keeps fairly low probabilities for the Northwest, an experimental subsampling of the highest skill ensemble model forecasts provides a substantially warmer solution for the Northwest, meriting an increase in above-normal temperature probabilities. Equal chances for below- and above-normal temperatures are maintained for the southwestern CONUS and central Rockies, where near-normal heights are favored by the dynamical model guidance. Elsewhere, several tools indicate a potential for periods of cooler conditions for the Northeast, leading to slightly reduced probabilities of above-normal temperatures. Experimental Weeks 3-4 heatwave tools based on dynamical model guidance indicate a potential for periods of late season extreme heat across the Southern Plains during the outlook period. This pattern is broadly consistent with the MLR-based height anomaly forecast, leading to a fairly straightforward temperature forecast.Ĭonsistent with the idea of anomalous ridging over the east-central CONUS, above-average temperatures are favored for the entire CONUS east of the Rockies, with the highest probabilities existing across the south-central Plains. The upstream pattern during the Weeks 3-4 period favors troughing over the Bering Sea, with above-average heights across the Northwest Pacific, which would promote enhanced southerly flow into southern Alaska. The anticipated 500-hPa height anomaly pattern is fairly consistent among the dynamical models, showing a shift from the forecast Week-2 pattern, which favors ridging over western North America and shallow troughing over the east, towards increasing ridging over the east-central CONUS and a weakness across the Southwest. This Weeks 3-4 outlook is based on a combination of operational and experimental dynamical model guidance and statistical guidance that is reflective of the ENSO base state. Statistical guidance for the Weeks 3-4 period based on tropical teleconnections is therefore most similar to composite forecasts based on past cold ENSO events, with ENSO and long term trends comprising the main contributors to the Multivariate Linear Regression (MLR) tool. Recent observations reflect a similar pattern, with a weak MJO projection due to destructive interference with ENSO over the Pacific following enhanced activity across the Indian Ocean and Maritime Continent through late August. While the Madden-Julian Oscillation (MJO) was active throughout the summer as well, destructive interference with the strong La Niña base state limited the ability for organized enhanced convective envelopes to cross the Pacific to the Western Hemisphere. The tropical pattern continues to be dominated by La Niña conditions over the Pacific, which were unusually strong throughout the Boreal summer months.

Week 3-4 Forecast Discussion Valid Sat Oct 01 2022-Fri Oct 14 2022

NWS Climate Prediction Center College Park MD Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks

Oregon vortex