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 26 2024

Week 3-4 Forecast Discussion Valid Sat May 11 2024-Fri May 24 2024

El Niño conditions are currently present with above average sea surface temperatures (SSTs) across the central and east-central tropical Pacific Ocean. Low-level wind anomalies were easterly in small regions over the western tropical Pacific Ocean and upper-level wind anomalies were easterly over the eastern equatorial Pacific. The Madden Julian Oscillation (MJO) remained weak and incoherent during mid-April, according to the Real-time Multivariate MJO (RMM) index. Both the GEFS and ECMWF favor a strengthening MJO over the Maritime Continent during the next two weeks. The Week 3-4 Temperature and Precipitation Outlooks are based primarily on operational dynamical model guidance including the GEFSv12, CFSv2, ECMWF, and JMA, in addition impacts of the El Niño Southern Oscillation (ENSO), and the predicted evolution of the pattern from the Week-2 forecast.

Dynamical model 500-hPa height anomaly forecasts during week 3-4 show a fairly consistent evolution from Week-2 forecasts. A blend of the CFSv2, ECMWF, JMA, and GEFSv12 500-hPa height pattern forecasts, plus a small contribution from the Multivariate Linear Regression (MLR) height forecast based on the RMM index, ENSO, and decadal trends, predicts a weak trough over the Aleutians. Anomalous troughs are also forecast over the eastern CONUS and southwestern California. Anomalous ridging is predicted over the northwestern CONUS extending northwestward into Alaska. Near normal 500-hPa heights are forecast over Hawaii.

The Week 3-4 temperature forecast continues to tilt toward above normal temperatures across the north-central CONUS, extending from the Pacific Northwest and northern California to the Upper Great Lakes due to predicted positive 500-hPa height anomalies and mid-level ridging over the region. Probabilities are highest over parts of the Northern Rockies. Conversely, chances for below normal temperatures are increased over parts of the southwestern CONUS, under predicted below normal 500-hPa heights and troughing. Most dynamical temperature forecast tools also favor above normal temperatures over Florida and portions of the Northeast. Below normal temperatures are likely over parts of the Mid-Atlantic and the Ohio Valley, consistent with the Analogue tool. Elevated probabilities of above normal temperatures are indicated over eastern and central Mainland Alaska as well as Southwest Alaska under predicted ridging, while near to below normal temperatures are favored over western Alaska.

The Week 3-4 Precipitation Outlook favors above median precipitation over parts of the south-central CONUS. A majority of the dynamical guidance favors a tilt toward drier than average conditions for the Pacific Northwest, northern California, the Ohio Valley and the Great Lakes region. Odds tilt towards above median precipitation for southwestern Alaska due to increased southerly onshore flow, while below median precipitation is favored over Southeast Alaska, consistent with most of the dynamical precipitation forecast tools.

Slightly above normal temperatures are forecast over Hawaii during the Week 3-4 outlook period. Dynamical model guidance also indicates elevated probabilities of above median precipitation for Kauai, Oahu and Maui, while EC is forecast for the Big Island.

Temperature Precipitation

FCST FCST

Hilo A55 EC

Kahului A55 A60

Honolulu A55 A60

Lihue A55 A60

Forecaster: Luke He

The next week 3-4 outlook will be issued on Friday, May 03, 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