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 Feb 21 2020

Week 3-4 Forecast Discussion Valid Sat Mar 07 2020-Fri Mar 20 2020

ENSO-neutral conditions currently are present across the equatorial Pacific Ocean. Equatorial sea surface temperatures (SSTs) are near-to-above average across the Pacific Ocean. Enhanced convection in the tropics has organized and strengthened over the western Pacific over the past week.The GEFS and ECMWF both indicate that interference with the eastward moving signal is likely to continue through the next two weeks, leading to a disorganized signal on the RMM index. The Week 3-4 Outlook is based primarily on dynamical model forecasts, including the NCEP CFS, ECMWF, and JMA ensemble prediction systems, as well as the Subseasonal Experiment (SubX), a multi-model ensemble (MME) of both operational and experimental ensemble prediction systems. Statistical forecasts, including a multivariate linear regression (MLR) of lagged temperature and precipitation forecasts to currently observed MJO and ENSO indices, are also consulted. Decadal timescale temperature trends are also a source of predictability in both dynamical and statistical forecast tools.

Dynamical model guidance from the various models is broadly consistent, depicting pronounced ridging over the North Pacific, particularly south of the Aleutians, with below-average heights over the Arctic and extending over Greenland and to some extent over Canada. This pattern suggests that the CONUS would be vulnerable to cold air intrusions. All three dynamical model systems depict a weakness in the height field over the Southwest, which may provide a conduit for Pacific flow into the U.S., particularly across California.

Above-normal temperatures are forecast across Alaska as ridging builds to the south. Below-normal temperatures are favored across much of the northern tier of the CONUS, with a southward extension to the Central Plains due to the potential for cold air intrusions from Canada. Dynamical models also favor increased chances for below-normal temperatures across New England. Above-normal temperatures are also slightly favored over California due to a long-term warming trend. Above-normal heights favor above-normal temperatures for the Florida Peninsula.

The area of highest confidence in the precipitation outlook is Alaska, where dynamical models strongly favor enhanced precipitation across the western half of the State and along the North Slope. Below-median precipitation is forecast for the Alaska Panhandle and parts of the southern Coastal Alaska as well as the Pacific Northwest, while Pacific moisture may result in enhanced precipitation for Arizona and southern Utah. Further east, the possibility for cold continental airmass intrusions into the central U.S. favor below-median precipitation for the Plains, Great Lakes, and New England. Near- to above-median precipitation is more likely for parts of the Southeast, supported by the CFS/ECMWF/JMA Correlation and Equal Weighted tools as well as the Autoblend tool.

SST anomalies remain above-normal in the vicinity of Hawaii, although the magnitude of the anomalies has been gradually decreasing. Dynamical model forecasts, including the Subseasonal Experiment (Sub-X) suite, support above-normal temperatures across Hawaii. Dynamical models generally favor enhanced precipitation.

Temperature Precipitation

FCST FCST

Hilo A55 A60

Kahului A55 A60

Honolulu A55 A60

Lihue A55 A60

Forecaster: Luke He

The next week 3-4 outlook will be issued on Friday, Feb 28, 2020

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