Climate Prediction Center - Week 3-4 Outlook

Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EST Fri Dec 02 2022

Week 3-4 Forecast Discussion Valid Sat Dec 17 2022-Fri Dec 30 2022

Dynamical model guidance broadly agrees on an amplified wave-like pattern in the anomalous 500-hPa height field that features a ridge over the North Pacific Ocean followed by a trough over CONUS and a ridge centered west of Greenland. Some features of this wave train resemble a negative Arctic Oscillation (AO) teleconnection pattern, which is forecast to remain in a negative phase for the next two weeks leading up to the forecast period. Across the guidance for the anomalous 500-hPa height field there are also indications of a negative North Atlantic Oscillation (NAO) as well as a negative Pacific North American (PNA) teleconnection pattern, though the latter is trending neutral. In addition to these teleconnection signals, this forecast is influenced by the climate signals from the persisting La Niña conditions in the Tropical Pacific Ocean.

A blend of dynamical and statistical guidance favor colder than normal temperatures across much of northern CONUS with a maxima in the North Central Plains. It is worth noting that the aforementioned anomalous troughing could usher in significantly cold air during the outlook period. The CFSv2 forecast indicates the strongest departures from average for a broad region of CONUS while the GEFSv12 keeps the coldest anomalies contained to the Northern Plains and the ECMWF has moderate below average anomalies across the northern tier of CONUS. The guidance disagrees on the westward and southward extent of cold temperatures. As noted, CFSv2 favors a colder 14-day averaged outlook across nearly all of CONUS including the West Coast and Southeast. ECMWF also indicates a colder than average outlook for much of CONUS but tilts toward a warmer than average outlook for the West Coast and Southwest. GEFSv12 agrees with ECMWF on a colder outlook for the North Central Plains and Tennessee Valley but is bullish with a warmer than average outlook for the Southern Plains, the Southwest and across the Rocky Mountains to the West Coast. Given the disagreement across model guidance, Equal Chances is forecast for the West Coast and southern tier of CONUS. Blended guidance has the strongest signals for above average temperatures along the North Slope in Alaska and a below average outlook along the Panhandle. However it should be noted that temperature guidance was mixed across the tools with some experimental tools indicating a warmer outlook state-wide for Alaska.

Blended guidance of dynamical and statistical models favors an above average precipitation outlook for the Northwest region as well as the Great Lakes region. Below average rainfall is forecast across the Southwest extending from southern California to Louisiana. Equal Chances for above or below precipitation is indicated for the East Coast where model probabilities are low and mixed. Above average rainfall is forecast for the northern and eastern most regions of Alaska.^M

The SubX multi-model ensemble forecast for Hawaii indicates strong probabilities of above-average temperatures and above-average rainfall for all islands.

Temperature Precipitation

FCST FCST

Hilo A80 A60

Kahului A80 A60

Honolulu A70 A60

Lihue A70 A60

Forecaster: Emerson LaJoie

The next week 3-4 outlook will be issued on Friday, Dec 09, 2022

These outlooks are based on departures from the 1991-2020 base period

These are two category outlooks and differ from official current three category outlooks currently used for the monthly and seasonal forecasts.

The shading on the temperature map depicts the most favored category, either above-normal (A) or below-normal (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

The shading on the precipitation map depicts the most favored category, either above-median (A) or below-median (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

In areas where the likelihoods of 2-week mean temperatures and accumulated precipitation amounts are similar to climatological probabilities, equal chances (EC) is indicated.

As of May 19, 2017, the temperature outlook is operational, while the precipitation outlook is still experimental