Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EDT Fri Jul 05 2024
Week 3-4 Forecast Discussion Valid Sat Jul 20 2024-Fri Aug 02 2024
The Madden-Julian Oscillation (MJO) signal appears to be weak at the start of July, based on the real-time multivariate MJO (RMM) index, with low frequency subsidence in the Eastern Pacific more prevalent in tropical atmospheric conditions. Velocity potential forecasts show some eastward propagation on subseasonal timescales. However, MJO forecasts remain somewhat incoherent and uncertain. ENSO-neutral conditions are established in overall Pacific climate conditions. While the positive sea surface temperature (SST) anomaly has decreased below the +0.5 degrees Celsius threshold for El Niño conditions in the Niño 3.4 region, the SST anomalies remain above zero in the east-central Pacific. Although subsurface negative temperature anomalies in the Eastern Pacific have weakened, the tropics may be showing signs of the beginning of a transition towards La Niña conditions with negative equatorial SST anomalies and anomalous easterlies in the Eastern Pacific Ocean. Because specific extratropical teleconnections to the mid-latitudes are unclear, the Week 3-4 Outlook relied primarily on dynamical model tools for the patterns of temperature and precipitation over the forecast domain.
Dynamical model forecasts from the ECMWF, GEFS, CFS and JMA ensembles are in good agreement on the overall predicted circulation and climate patterns for North America in the Week 3-4 period. A persistent positive 500-hPa height anomaly and ridge are predicted near and south of the Aleutians by all available ensemble means and the manual blend. Troughing is favored to the north and downstream of this ridge, which would favor onshore flow from the Bering Sea across much of Alaska. Positive 500-hPa height anomalies and ridging are predicted across the Contiguous U.S. (CONUS) by the manual blend and all ensemble means.
Below-normal temperatures are favored across the Aleutians and much of Mainland Alaska, under enhanced northerly or onshore flow, as predicted by most dynamical models. Above-normal temperatures are favored for parts of the North Slope of Alaska, following the manual blend of calibrated model temperature forecasts. Above-normal temperatures are likely across the CONUS under positive 500-hPa height anomalies, with probabilities exceeding 60 percent in most areas. Probabilities exceed 70 percent in some areas of the northwestern CONUS, and exceed 80 percent in parts of the Northern Rockies. There is an enhanced likelihood of extreme heat extending from week 2 into week 3 in these areas. Soil moisture feedback, related to recent or predicted precipitation, leads to a moderation of probabilities favoring above-normal temperatures in the Southwest Monsoon region and parts of Texas, Oklahoma, and the Lower Mississippi Valley. Above-normal temperatures are favored for all of Hawaii, as indicated by the manual blend of calibrated dynamical model forecasts.
Above-median precipitation is favored across Alaska, with the exception of the southern Alaska Panhandle, ahead of troughing over the Bering Sea. Below-median precipitation is favored for the Pacific Northwest across the northern tier into the Northern and Central Plains, under the predicted ridge. Most dynamical models predict an enhanced Southwest Monsoon and above-median precipitation in this region in the Week 3-4 Outlook period. Above-median precipitation is favored from eastern Texas across the Southeast, consistent with most dynamical model forecasts. Above-median precipitation is slightly favored for the northern Great Lakes region and Northeast, consistent with the ECMWF calibrated precipitation forecast. Above-median precipitation is favored for the southeastern Hawaiian Islands, consistent with the manual blend of dynamical model forecasts.
| Temperature | Precipitation |
| FCST | FCST |
| Hilo | A55 | A55 |
| Kahului | A55 | A55 |
| Honolulu | A55 | EC |
| Lihue | A55 | EC |
Forecaster: Dan Collins
The next week 3-4 outlook will be issued on Friday, Jul 12, 2024
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