Climate Prediction Center - Week 3-4 Outlook

Prognostic Discussion for Week 3-4 Temperature and Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EDT Fri Apr 25 2025

Week 3-4 Forecast Discussion Valid Sat May 10 2025-Fri May 23 2025

ENSO-neutral conditions are currently present with equatorial sea surface temperatures (SSTs) near-to-below average in the east-central and central Pacific Ocean. Above-average outgoing longwave radiation (OLR) is observed around the Date Line and western Pacific, while below-average OLR is evident over Indonesia, the Philippines, northern Australia, and the eastern Pacific. The Madden Julian Oscillation (MJO) remains weak with the RMM-based index meandering within the unit circle during mid-April. The GEFS dynamical forecast shows a strengthening MJO propagating east over the Western Hemisphere during the next two weeks, while the ECMWF model maintains a weak MJO into early May. The Weeks 3-4 Temperature and Precipitation Outlooks are based primarily on operational dynamical model guidance, including the GEFSv12, CFSv2, ECMWF, and JMA, as well as the predicted evolution of the pattern from the Week-2 forecast.

Dynamical model 500-hPa height anomaly forecasts during Weeks 3-4 show a fairly consistent evolution from Week-2 forecasts. A blend of the ECMWF and GEFSv12 500-hPa height pattern forecasts, plus a contribution from the Multivariate Linear Regression (MLR) height forecast based on the MJO RMM index, ENSO, and decadal trends, predicts ridging and above average height anomalies across most of the northern tier of the contiguous United States (CONUS), while a trough and below normal 500-hPa height anomalies are forecast over parts of the Southeast. A trough and negative 500-hPa height anomalies are also predicted over the Gulf of Alaska. Near normal 500-hPa heights are predicted over Hawaii.

Enhanced chances for above normal temperatures are predicted for most of the CONUS due to the anticipated mid-level ridging, generally near to above normal 500-hPa height anomalies, and supported by most of the dynamical temperature forecast tools and an experimental manual blend of GEFSv12, CFSv2, JMA, ECMWF, and the MLR tool. Probabilities favoring above normal temperatures reach 60% for parts of Washington, the Northern and Central High Plains, the Northern and Central Rockies, the Northern and Central Great Basin, as well as portions of the Northeast. Equal chances (EC) of above and below normal temperatures are indicated across the California Coast, in part due to uncertainty in dynamical model temperature forecasts. EC are also forecast for parts of the Southern Great Plains due to favored above median precipitation. Near to above normal temperatures are favored over Alaska, consistent with most of the temperature forecast tools.

The Weeks 3-4 Precipitation Outlook favors below median precipitation over the Great Lakes region, under above normal 500-hPa heights. A majority of the dynamical guidance favors a tilt toward above median precipitation over portions of Colorado, New Mexico, Kansas, Oklahoma, and northern Texas. Above median precipitation is also favored over parts of the southern East Coast ahead of a trough predicted over the Southeast. Above normal precipitation chances are elevated over southeastern Mainland Alaska and southeast Alaska, due to a predicted trough over the Gulf of Alaska, and consistent with most precipitation forecast tools.

Above-average SSTs and dynamical model guidance favor above normal temperatures across the Hawaiian islands (Kauai, Oahu, Maui and the Big Island) during Weeks 3-4. Above median precipitation is indicated across the islands by most dynamical precipitation forecast tools.

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, May 02, 2025

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.