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 EDT Fri Apr 19 2019

Week 3-4 Forecast Discussion Valid Sat May 04 2019-Fri May 17 2019

The MJO has been inactive for the past month. Although some of the forecast models, including the GEFS and ECMWF, suggest that the MJO will re-emerge over the next week, there isn't enough confidence in that forecast to use the MJO as a main predictor for the Week 3-4 time period. Aside from a few stray Kelvin and equatorial Rossby waves, ENSO is the most important mode of tropical variability for today's forecast. The current El Nino state favors anomalous warmth throughout the north-western and north-central CONUS, and anomalous cold over the Southwest. It also favors anomalous rainfall throughout much of California in association with an off-shore trough. These relationships are used in conjunction with the dynamical models to create the final forecast this week.

The CFS, ECMWF, and JMA agree broadly on the forecast over North America - each model has some sort of anomalous trough west of California and in the Gulf of Alaska. Although each model also has an anomalous ridge over the central CONUS, the ridge is centered just north of North Dakota in the CFS and ECMWF, but further east over Pennsylvania in the JMA. The ECMWF also has a stronger anomalous trough northeast of Maine than the other two models, which gives it a slightly colder New England solution (by about 10%) than the CFS and JMA.

The temperature forecast combines these ideas to come up with a broad region favoring anomalous warmth that encompasses Alaska and stretches southeastward through the Plains to the tip of Florida. The axis of highest probabilities (60-70%) stretches from Alaska to northwestern Missouri, which is remarkably consistent between the models. The forecast leans slightly warm over the Northeast (50-55%), despite the ECMWF's colder solution, because so many of the SubX models, as well as the long-term trend, agree with the CFS and JMA.

The models are also in good agreement regarding the precipitation forecast. Generally, the CFS, ECMWF, and JMA agree on anomalously dry conditions over the northeastern CONUS and anomalously wet conditions throughout California, Nevada, and the Pacific Northwest in association with strong troughing over the Pacific. There is also good model agreement regarding anomalously wet conditions throughout the Southern Plains and the Southwest.

Weak anomalous ridging is expected around Hawaii during Weeks 3-4, but SST anomalies are currently negative around the western islands. This results in a forecast of above normal temperatures for the entire state, with probabilities around 55% for the western islands. There is also a 55-60% probability of below average precipitation throughout the state due to the weak ridging and cool waters.

Temperature Precipitation

FCST FCST

Hilo A70 B55

Kahului A60 B55

Honolulu A55 B60

Lihue A55 B60

Forecaster: Kyle MacRitchie

The next week 3-4 outlook will be issued on Friday, Apr 26, 2019

These outlooks are based on departures from the 1981-2010 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