Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EST Fri Mar 24 2023
Week 3-4 Forecast Discussion Valid Sat Apr 08 2023-Fri Apr 21 2023
While Tropical Pacific sea surface temperatures (SSTs) have eased within the threshold for neutral El Niño Southern Oscillation (ENSO) conditions, the overlying atmospheric circulation still exhibits some La Niña features. After a record amplitude Madden Julian Oscillation (MJO) event, observed Realtime Multivariate MJO (RMM) indices indicate weaker but still moderate convection over the Indian Ocean (RMM Phase 2). RMM forecasts consistently weaken the MJO-related convection in the next few days as it moves over the Maritime Continent, but it is possible that the RMM diagnostic is misrepresenting the MJO signal due interference from the residual La Niña signal. Forecasts of the 200-hPa velocity potential suggest a continued eastward propagation of the MJO envelope until at least the beginning of April. However, as we move into the spring seasons, the tropical sources of predictability tend to have a weaker impact on North American temperature and precipitation outlooks. Extratropical teleconnections, including the North Atlantic Oscillation, are forecast to be near-neutral by the end of Week-2. As such, the influence of these climate signals on the Week 3-4 Outlook is less dominant and may add to uncertainty within the forecast tools.
The dynamical model guidance is split on the anomalous 500-hPa circulation pattern over the Contiguous United States (CONUS). The CFS and JMA solutions favor a weak east-west dipole with positive height anomalies for western CONUS and negative height anomalies in the Northeast. ECMWF and GEFS place the positive height anomalies more centrally across the Midwest and Mississippi Valley. As a result of the disagreement, blends of the dynamical models result in weak signals throughout much of the CONUS for the Week 3-4 period. Model agreement is stronger over the Aleutian Islands where anomalous ridging is forecast.
As a result of the aforementioned model uncertainties, the Week 3-4 Temperature Outlook map is largely dominated by Equal Chances (EC) of above or below normal temperatures. In many regions throughout the CONUS, temperature signals were either weak or in disagreement amongst the models. Across the Northern Plains and northern New England, both dynamical and statistical models consistently tilt probabilities toward below normal temperatures. A slight tilt toward below normal temperatures is also forecast for northern Utah. While the anomalous overlying circulation doesn’t necessarily favor below normal temperatures, the significantly above normal snowpack and potential snowmelt may keep temperatures anomalously cold. Above normal temperatures are consistently indicated for the Southeast among the dynamical model guidance. The anomalous ridging over the Aleutian Islands and the resulting northerly flow favors below normal temperatures for much of southern and central Alaska.
For the Week 3-4 Precipitation Outlook, dynamical guidance favors above normal precipitation from the Southwest toward the Florida Panhandle, potentially arising from anomalously warm SSTs in the Gulf of Mexico. Conditions tilt slightly toward anomalously dry over the Northeast. Elsewhere across the CONUS, EC of above or below median precipitation is forecast due to weak and conflicting model signals. Offshore flow across the Gulf of Alaska favors below normal precipitation while probabilities are shifted above normal for the Northern Slope.
For Hawaii, elevated probabilities of above normal temperatures are indicated as result of anomalous warm SSTs and strong model consensus across the SubX multi-model suite. Dynamical model guidance also favors above normal precipitation with strongest probabilities for Lihue.
| Temperature | Precipitation |
| FCST | FCST |
| Hilo | A70 | A55 |
| Kahului | A70 | A60 |
| Honolulu | A70 | A60 |
| Lihue | A70 | A70 |
Forecaster: Laura Ciasto
The next week 3-4 outlook will be issued on Friday, Mar 31, 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