Prognostic Discussion for Long-Lead Seasonal Outlooks 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Mar 16 2023 
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS 
 
In early March 2023, the final La Niña advisory was issued and La Niña has 
ended. ENSO-neutral is now present in the equatorial Pacific ocean and favored 
to continue through the spring and early summer months. Thereafter, El Niño is 
the most likely phase of ENSO from late summer into the autumn months. 
 
The April-May-June (AMJ) 2023 temperature outlook favors above-normal seasonal 
mean temperatures for the north slope of Alaska, parts of the Southwest, 
southern Plains and Southeast and northward to include the Ohio Valley, 
Mid-Atlantic and Northeast. Below-normal temperatures are most likely for 
portions of the Northern Plains and central interior West. 
 
The AMJ 2023 precipitation outlook favors above-normal seasonal total 
precipitation amounts for portions of the Great Lakes, Ohio Valley, 
Mid-Atlantic and Northeast. Below-normal precipitation is most likely for parts 
of the far Pacific Northwest and Southwest. 
 
Equal chances (EC) are indicated for areas where seasonal mean temperatures and 
seasonal total precipitation amounts are favored to be similar to 
climatological probabilities. 
 
BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS 
Note: For Graphical Displays of the Forecast Tools Discussed Below See: 
http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing 
 
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS 
 
La Niña has ended and ENSO-neutral is now present in the equatorial Pacific 
Ocean. Equatorial Pacific Ocean sea surface temperatures (SSTs) continued to 
warm over the past month with negative anomalies in SST only remaining in an 
area near and just east of the Date Line. The most recent weekly value of the 
Nino3.4 SST index is -0.1 degrees C. Further east toward the South American 
coast, positive anomalies in SST have developed with a region of greater than 
+0.5 degrees C departures in the eastern Pacific with the most recent value of 
the Niño1+2 SST index of +1.5 degrees C. Below the surface, the 0 - 300 meter 
depth equatorial temperature anomalies (i.e., integrated heat content) became 
positive in February 2023 and there exists a reservoir of warmer than normal 
water spanning a depth from approximately 75 m to 250 m from 130E to 150W with 
the maximum anomaly ranging from + 4-6 degrees C. 
 
Although the oceanic indicators for La Niña have decreased in the Pacific 
Ocean, there does remain some atmospheric signature and it will likely take 
some time for this response to completely disappear. For example, in the past 
30 day average, suppressed convection remained present near the Date Line along 
the equator and upper-level cyclonic circulations, symmetric about the equator 
in both hemispheres, are evident. Trade winds have decreased in magnitude, but 
this is in part due to a strong MJO event and associated westerly wind 
anomalies crossing the Pacific within the last month. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
Forecasts of the Nino3.4 SST index from the NMME are in general agreement for a 
transition from small negative anomalies to positive departures from normal of 
varying magnitudes ranging from +0.3 to +1.2 degrees C (for the GFDL SPEAR 
model) by late summer 2023. The NMME ensemble mean forecast enters El Nino 
territory (greater than +0.5 degrees C) approximately during July 2023. 
 
The CPC Niño3.4 SST consolidation forecast follows a similar trajectory as the 
NMME models at the start, but hovers near or just below the +0.5 degrees C 
threshold during the late summer and early autumn months. Two statistical 
components of the CPC Nino3.4 SST consolidated forecast, the CA and CCA 
forecasts, predict a much more rapid transition towards El Niño with values of 
the Niño3.4 index near or surpassing +1.0 degrees C by autumn 2023. 
 
The official CPC ENSO outlook favors ENSO-neutral through the JJA season with 
El Niño favored thereafter at an approximate 60% probability through OND 2023. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
Given some likely remaining La Niña atmospheric response at times during April 
2023, typical La Niña impacts are considered to a minor degree very early in 
this set of outlooks (i.e., AMJ 2023). Current anomalous soil moisture and snow 
cover/depth are considered and contributed strongly to the outlook in some 
locations during the AMJ and MJJ seasons. 
 
Dynamical model forecasts from the NMME and C3S multi-model ensemble systems 
are utilized heavily, although precipitation signals  are particularly weak from 
this month's guidance as compared to normal. Moreover, the Calibration, 
Bridging and Merging (CBaM) tool anchored to the NMME forecasts and "bridged" 
to the Niño3.4 index is also significantly utilized. The ENSO-OCN forecast tool 
that targets impacts from ENSO, as predicted by the CPC consolidation SST 
forecast, and long term trends  played a large role in many of the outlooks, 
especially at longer leads. 
 
Consideration and some slight adjustments consistent with potential development 
of El Niño are done in some areas beginning in late summer and autumn 2023, but 
any changes are minor at this stage given the uncertainty in the ENSO forecast 
initialized during this time of the seasonal cycle (i.e., spring predictability 
barrier). 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - AMJ 2023 TO AMJ 2024 
 
TEMPERATURE 
 
The AMJ 2023 temperature outlook favors above-normal seasonal mean temperatures 
from the Southwest eastward to the southern Plains and Southeast as well as 
northward to include the Ohio Valley, mid-Atlantic and Northeast. The greatest 
odds of above-normal temperatures is for Texas and areas along the Gulf coast 
and Eastern Seaboard. There is strong support for warmer than normal 
temperatures in this region from nearly all dynamical model guidance and 
statistical forecast tools as well as long term positive temperature trends . 
Very dry soil moisture conditions and well as above-normal local coastal SSTs, 
further enhance these odds for the southern High Plains and Gulf / Atlantic 
coasts respectively. 
 
Elevated odds of below-normal temperatures are forecast for the Northern Plains 
where abnormally deep snowpack is in place and long term negative temperature 
trends exist. Dynamical model forecast guidance from some participant models of 
the NMME and C3S suite as well as the CBaM hybrid forecast tool support this 
forecast. 
 
A small region of favored below-normal temperatures is highlighted for an area 
in the interior western CONUS. Odds tilting toward below-normal temperatures in 
this area, however, are very modest. The AMJ and MJJ 2023 temperature outlook 
for the western U.S. is challenging due to considerably above normal snowpack 
and soil moisture as a result of recent storminess in February and March, 
offset by forecasts of warmer than normal temperatures predicted by some 
dynamical and statistical forecast guidance. Forecasts from some of the 
statistical forecast tools and dynamical models  indicate high odds for 
above-normal temperatures in the western CONUS from lead 1 onward - perhaps 
linked to a more rapid transition to warmer than average equatorial Pacific 
SSTs and potential consequent atmospheric response. The higher odds for 
above-normal temperatures from these tools seems overdone at the start of this 
month's set of outlooks given the highly anomalous snowpack and soil moisture 
conditions at the start of AMJ 2023. 
 
Although the impact of enhanced surface wetness (either soil moisture to start 
or melting snowpack and consequent elevated soil moisture) is likely to 
diminish relatively quickly as the month of May progresses and in June, the 
season as a whole may still tilt slightly toward below-normal temperatures. The 
monthly temperature outlook for April 2023 favors below-normal temperatures for 
considerable areas in the western U.S. Equal-chances (EC) is forecast for much 
of the remaining area in the western CONUS due to these competing influences. 
There is also support for areas of favored below-normal temperatures in the 
western CONUS from the ECMWF model guidance, the CA forecast tool based on soil 
moisture, and the CBaM hybrid tool. 
 
Negative trends  in sea ice coverage and thickness and so more open water 
earlier than normal for ocean areas along the northwest and northern coast of 
Alaska favors above-normal temperatures for these areas during AMJ 2023. 
 
Elevated odds for below-normal temperatures remains for portions of the 
northern Plains during MJJ 2023, while favored above-normal temperatures 
increase in coverage and probabilities across the western CONUS from MJJ 
through ASO 2023. Weaker and conflicting signals  in the forecast tools increase 
uncertainty for the north-central U.S. and so the area forecast as EC increases 
from the JJA through OND 2023 seasons. 
 
Primarily beginning in SON 2023, the remaining outlooks are largely based on 
the ENSO-OCN forecast tool which is heavily influenced by long-term trends  at 
these leads with some slight adjustments, at this stage, for the potential 
influence of El Niño. For Alaska, increased forecast coverage of favored 
above-normal temperatures is depicted from MJJ through SON 2023. 
 
PRECIPITATION 
 
The AMJ 2023 precipitation outlook favors above-normal seasonal total 
precipitation amounts for portions of the Great Lakes, Ohio Valley, 
Mid-Atlantic and Northeast based on long term positive precipitation trends  as 
defined by OCN, dynamical model guidance from some participant models from the 
NMME and C3S ensemble systems, the CA forecast tool based on anomalous soil 
moisture and potential residual La Niña impacts. 
 
Below-normal precipitation is favored for parts of the far Pacific Northwest 
and the Southwest U.S. where some dynamical model forecast guidance, the CBaM 
hybrid tool, the ENSO-OCN forecast tool and long term negative precipitation 
trends supported the outlook. 
 
It is important to note that signals  from the dynamical model suite for 
precipitation are especially weak for basically all forecast leads for which 
forecast guidance is available, even when considering shoulder seasons within 
the seasonal cycle as well as the transition to ENSO-neutral. 
 
Favored above-normal precipitation in the eastern CONUS is forecast to shift 
eastward and southward with time from MJJ through JJA and then transition 
westward by ASO 2023. This evolution is based on long term positive 
precipitation trends  and to a lesser degree signals  from the NMME and C3S model 
guidance. 
 
Favored below-normal precipitation forecast for the Pacific Northwest shifts to 
include parts of the northern Rockies from MJJ through JAS 2023 - a result of 
the ENSO-OCN forecast tool, long term negative precipitation trends  and some 
dynamical model forecast support. For the Southwest, below-normal precipitation 
is most likely to continue during MJJ 2023, albeit with smaller forecast 
coverage. 
 
Unlike 2022, there are less climate signals  to utilize for prediction of the 
first half of the Southwest summer monsoon. Enhanced wetness across the western 
CONUS from an extremely wet winter may lead to a potentially delayed start and 
less robust monsoon circulation due to perhaps less efficient heating of the 
land and so a weaker thermodynamic induced circulation. The CBaM hybrid 
forecast tool, does favor below-normal precipitation in the Southwest during 
the monsoon season, but there remains considerable uncertainty given the 
evolution of ENSO and how that may or may not influence precipitation in the 
region this summer. 
 
Climate signals  for the state of Alaska for AMJ 2023 are quite weak and 
conflicting amongst the tools when present, so EC is forecast for the entire 
state. However, above-normal precipitation is most likely for parts of northern 
and central Alaska beginning in MJJ 2023 and continuing through the remainder 
of 2023. Model guidance and more open water earlier in the seasonal cycle are 
the basis for these highlighted areas. 
 
Primarily long term precipitation trends  and slight tilts in deference to 
potential EL Niño development are used in making the remainder of the 
precipitation outlooks through AMJ 2024. 
 
FORECASTER: Jon Gottschalck 
 
The Climatic normals are based on conditions between 1991 and 2020, following 
the World Meterological Organization convention of using the most recent 3 
complete decades as the climatic 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. 
 
For a description of of the standard forecast tools - their skill- and the 
forecast format please see our web page at 
http://www.cpc.ncep.noaa.gov/products/predictions/long_range/tools.html 
(Use Lower Cas e Letters) 
Information on the formation of skill of the CAS forecasts may be found at: 
http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Outlook/outlook.shtm 
l 
(use lowercase letters) 
Notes - These climate outlooks are intended for use prior to the start of their 
valid period.  Within any given valid period observations and short and medium 
range forecasts should be consulted. 
 
This set of outlooks will be superseded by the issuance of the new set next 
month on Apr 20 2023 
 
 
1991-2020 base period means were implemented effective with the May 20, 2021 
forecast release. 
$$