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As of the May 19th, 2017, release, Week 3-4 outlooks precipitation outlooks are experimental, whereas the temperature outlooks are operational. Both are issued Friday between 3pm & 4pm Eastern Time.
HOME> Outlook Maps> Week 3-4 Outlooks

Week 3-4 Outlooks
Valid: 01 Sep 2018 to 14 Sep 2018
Updated: 17 Aug 2018

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Temperature Probability

Week 3-4 Outlooks - Temperature Probability
Precipitation Probability

Week 3-4 Outlooks - Precipitation Probability

Click HERE for information about how to read Week 3-4 outlook maps

Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EDT Fri Aug 17 2018

Week 3-4 Forecast Discussion Valid Sat Sep 01 2018-Fri Sep 14 2018

ENSO-neutral conditions currently are present across the equatorial Pacific Ocean. Equatorial sea surface temperatures (SSTs) are near average across most of the central and eastern equatorial Pacific Ocean. Most models indicate a 60% chance of an El Nino forming between September and November. The GEFS RMM index forecast depicts continued West Pacific enhanced convection early, but suggests the reemergence of a coherent subseasonal signal near the Maritime Continent during Week-2. The Week 3-4 temperature and precipitation outlooks rely primarily on dynamical model forecasts from the NCEP CFS, the ECMWF, and the JMA operational ensemble prediction systems, as well as forecasts from the Subseasonal Experiment (SubX), a multi-model ensemble (MME) of experimental ensemble prediction systems. Consideration is also given to the possible evolution of the predicted circulation pattern for Week-2.

Dynamical model guidance from the CFS, ECMWF and JMA is broadly consistent, depicting troughs over the Bering Sea, and the eastern CONUS, while ridging is forecast over the western CONUS. The CFS, ECMWF and JMA ensemble means favor near- to above-normal 500-hPa heights over the CONUS and near-normal 500-hPa heights over Hawaii.

Riding and above-normal 500-hPa heights lead to enhanced probabilities of above-normal temperatures over the northwestern CONUS, extending southward across Nevada, Utah, and Colorado as well as along the Gulf Coast, and over the Northeast. Below-normal temperatures are favored over southeastern Arizona and southwestern New Mexico associated with the enhanced monsoon rains. Below-normal temperatures are also favored over parts of the Middle Mississippi Valley, the Ohio Valley, the Tennessee Valley, the Middle Atlantic, and the Southeast, consistent with dynamical model guidance from SubX. For Alaska, increased chances of above-normal temperatures are forecast across the state with the highest probabilities for above-normal temperatures across western parts of the state due to anomalously warm sea surface temperatures (SSTs) in the Bering Sea.

The various model guidance is in fairly good agreement on the precipitation outlook for the Week 3-4 period. Above-normal precipitation is favored across the southeastern CONUS, and over the monsoon region of the Southwest, although the models are split about how far east the enhanced precipitation will spread. Below-normal precipitation is favored for the Pacific Northwest across the Northern Great Basin to the Northern Rockies, consistent with dynamical model predicted Week 3-4 precipitation amounts. Above-normal precipitation is likely in western Alaska and the Aleutians due to troughing over the Bering Sea.

Sea surface temperatures in the vicinity of Hawaii remain weak above-normal, and the bulk of dynamical model guidance, including the experimental SubX models, depict enhanced chances for above-normal temperatures, especially over the southeastern islands. Dynamical model precipitation forecasts generally favor above-normal rainfall over Hawaiian Islands.

Temperature Precipitation
Hilo A70 A60
Kahului A65 A60
Honolulu A55 A60
Lihue A55 A60

Forecaster: Luke He

The next week 3-4 outlook will be issued on Friday, Aug 24, 2018

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

An ASCII (w/ HTML markup tags) text version of the written forecast is available.

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Page last modified: Nov 08 2017
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