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 Mar 17 2023

Week 3-4 Forecast Discussion Valid Sat Apr 01 2023-Fri Apr 14 2023

The Week 3-4 Outlook has entered the Spring season which typically means that predictability is lower than other times of the year. The outlook this week tries to reconcile mixed dynamical and statistical guidance, the transition from La Niña to neutral conditions in the tropical Pacific, and the spread among model members in forecasting the Madden Julian Oscillation (MJO) at the start of this outlook period. Some MJO forecast guidance shows a weakly emerging MJO into phase 7 at the start of the weeks 3-4 outlook. Forecasts of the Pacific North America pattern (PNA) shows it slightly negative also at the start of the weeks 3-4 outlook. The combination of climatic states and dynamical and statistical tools are the primary guidance for the weeks 3-4 outlook issued this week. Because the guidance is mixed, a manual blend of the 500-hPa heights shows a very weak signal, with only small anomalies depicted across the CONUS and Alaska. Thus, overall forecast confidence is low.

Among the widely varying forecasts, dynamical model guidance agrees the most on below-average temperatures for the Northwest, Northern Plains, and southern Alaska. The largest departures from average occur in the ECMWF for the Northern Plains where anomalies are forecast to be on average -2 to -4 degrees (C) below normal. Various statistical guidance also forecast probabilities of below-normal temperatures for the Northern Plains during the first two weeks of April, on average, however this same guidance disagrees on the probabilities further south. Given that a slight majority of dynamical and statistical guidance forecast above-average temperatures in the Southeast, the highest probabilities for warmer than average conditions is forecast for the area from east Texas to the Carolinas. Elsewhere, Equal Chances is forecast to reflect both weaker probabilities as well as mixed forecast guidance.

Dynamical guidance broadly agrees on wetter than average conditions for the Mississippi Valley and north to the New England seaboard, as well as along the Alaska Panhandle and the Northwest. Equal Chances in the Southwest and Central Plains reflects both weaker probabilities and mixed guidance for the area. Dynamical guidance agrees on dryer than average conditions for the Northern Plains. Forecast guidance for Alaska overall agrees on dryer than average conditions for the Aleutians while wetter than average conditions are forecast for the Panhandle. For the rest of Alaska, guidance was mixed with weak signals. Some operational and experimental statistical tools that have performed well recently indicate a tilt toward above-average rainfall for the main state of Alaska, however Equal Chances is forecast for this area given the mix of guidance from various tools.

For Hawaii, the multi-model ensemble from the experimental SubX database forecast above normal temperature probabilities of over 70% for all the islands and an 80% probability for above-average temperatures for Kahului. Above normal precipitation is also forecast for all the islands at a 60% probability with Honolulu favored to see wetter than average conditions at a 70% probability.

Temperature Precipitation

FCST FCST

Hilo A70 A60

Kahului A80 A60

Honolulu A70 A70

Lihue A70 A60

Forecaster: Emerson LaJoie

The next week 3-4 outlook will be issued on Friday, Mar 24, 2023

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