Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Mar 16 2023 
 
 
30-DAY OUTLOOK DISCUSSION FOR APRIL 2023 
 
The La Niña event has ended as of March, 2023. Sea surface temperature (SST) 
anomalies have tended towards positive across most of the equatorial Pacific 
Ocean in recent weeks, and the most recent Niño 3.4 region anomaly is 
approaching zero degrees Celsius. The East Pacific is particularly warm with an 
anomaly of +1.5 C in the Niño 1+2 region. Easterly equatorial wind anomalies 
over the Pacific Ocean have weakened in the last month and are confined to a 
small area of the central Pacific. Upper-level westerly wind anomalies 
continued over the eastern equatorial Pacific. Positive subsurface temperature 
anomalies observed in the western and central equatorial Pacific Ocean have 
expanded eastward, while extending towards the surface in the eastern Pacific 
Ocean. Negative subsurface temperature anomalies near the surface of the 
central Pacific Ocean have weakened. Although ENSO-neutral conditions are 
predicted in the official ENSO outlook to continue through the Northern 
Hemisphere spring, a rapid warming of the Niño 3.4 region SST anomaly is 
forecast by most statistical and dynamical models , with an increasing chance of 
an El Niño from summer into autumn. Consolidated dynamical model forecasts from 
the North America Multi-Model Ensemble (NMME) predict positive SST anomalies in 
the Niño 3.4 region, bordering on El Niño conditions near the 0.5 degree C 
threshold, from summer through autumn. The Madden-Julian Oscillation (MJO) 
strengthened significantly in the beginning of March with convective activity 
currently over the Western Hemisphere. Dynamical model forecasts of the 
Real-time Multivariate MJO (RMM) index indicate a weakening MJO signal 
propagating eastward into the Indian Ocean towards the end of March. 
 
The ECMWF dynamical model forecasts for the beginning of April indicate likely 
below-normal temperatures for much of the western contiguous U.S. (CONUS) and 
parts of the northern Great Plains. Anomalous snowpack and snow cover over 
parts of the West play a role in the temperature outlook for April. In addition 
to surface boundary conditions, near-coastal sea surface temperature anomalies 
were considered. Linear regression forecasts based on the RMM index indicate a 
potential for below-normal temperatures across much of the CONUS at the 
beginning of April, followed by warming, particularly in the East. The 
temperature and precipitation outlooks for April are based primarily on a 
skill-weighted consolidation of dynamical model forecasts from the North 
America Multi-Model Ensemble (NMME). Statistical tools, such as the Canonical 
Correlation Analysis (CCA), Constructed Analog (CA), and a linear regression 
model based on the CPC SST Consolidation forecast of the Nino 3.4 index and 
decadal trends  were considered, but played a lesser role given the uncertainty 
of ENSO-related signals  given the rapid transition in the ENSO state. In 
addition, skill-based consolidations of statistical and dynamical tools for 
temperature and precipitation were consulted. 
 
The April Monthly Outlook favors below-normal temperatures for southwestern 
Alaska, as indicated by the NMME consolidation tool, with negative SST 
anomalies along the coast contributing to cooler temperatures. Above-normal 
temperatures are favored for northeastern Alaska, supported by the NMME 
consolidation tool, as well as the statistical forecast tool consolidation. The 
probability of below-normal temperatures is enhanced in the Pacific Northwest, 
Northern Rockies, and parts of the Great Basin, supported by recent CFSv2 and 
ECMWF dynamical model forecasts for April, and consistent with areas of 
anomalous snow cover and deep snowpack. Negative SST anomalies near the Pacific 
coast contribute to an increased likelihood of below-normal temperatures for 
the coasts of California, Oregon and Washington. Above-normal temperatures are 
favored from parts of the Southwest eastward across the Southern Plains, and 
from the Gulf Coast region northward across the eastern CONUS, as indicated by 
the NMME model forecasts. Strong positive SST anomalies along the Gulf Coast 
increase the likelihood of above-normal temperatures. Conflicting signals  in 
the temperature forecast tools lead to equal chances of below, near and 
above-normal temperatures in the April outlook over a large area of the 
north-central CONUS. 
 
Above-normal precipitation is favored for parts of the west coast of Alaska, as 
indicated in the precipitation consolidation of dynamical and statistical tools 
and the CFSv2 model forecasts. Below-normal precipitation is slightly favored 
for parts of the south coast of Alaska, as predicted by the NMME precipitation 
anomaly forecast. Below-normal precipitation is favored for a large area of the 
western CONUS from California and southern Oregon to the Central and Southern 
Rockies, as predicted by most dynamical and statistical model forecasts and 
consistent with decadal precipitation trends  for April. Above-normal 
precipitation is favored from the western Gulf Coast region northward into 
parts of Oklahoma and Arkansas, as predicted by the dynamical and statistical 
model forecast consolidation. Above-normal precipitation is also favored for 
parts of the Midwest and Great Lakes region, supported by recent dynamical 
model forecasts such as the CFSv2 and ECMWF, and consistent with decadal 
precipitation trends  for April. 
 
FORECASTER: Dan Collins 
 
The climatic normals are based on conditions between 1991 and 2020, following 
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies 
for temperature and precipitation based on these new normals better represent 
shorter term climatic anomalies than the forecasts based on older normals. 
 
An updated monthly outlook... for Apr will be issued on Fri March 31 2023 
 
These outlooks are based on departures from the 1991-2020 base period. 
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