Prognostic Discussion for Long-Lead Seasonal Outlooks 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Sep 21 2023 
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS 
 
El Niño conditions are present, as represented in current oceanic and 
atmospheric observations. A continuation of El Niño is extremely likely this 
Fall and Winter, with over a 95 percent chance through January-February-March 
(JFM) 2024. Additionally, a strong El Niño is likely by late Fall and early 
Winter, with approximately a 70 percent chance of occurrence during the 
November-December-January (NDJ) 2023-24 season. 
 
The October-November-December (OND) 2023 temperature outlook favors above 
normal temperatures for Alaska, the western third of the Contiguous United 
States (CONUS), the Northeast, Great Lakes, parts of the Southern Plains, 
Florida, and the immediate Gulf and East Coasts. The largest probabilities 
(greater than 60 percent) of above normal temperatures are forecast across the 
North Slope of Alaska. Above normal temperatures are also likely (probabilities 
greater than 50 percent) for parts of the Pacific Northwest and northern New 
England. The OND 2023 precipitation outlook depicts enhanced probabilities of 
above normal precipitation amounts across the Southeast, Southern Plains, and 
parts of the mid-Atlantic states as well as northern and western Alaska. The 
greatest chances of above normal precipitation (above 50 percent probability) 
are indicated for parts of northern Florida and southern Georgia. Equal chances 
(EC) are forecast for areas where probabilities for each category of seasonal 
mean temperatures and seasonal accumulated precipitation amounts are expected 
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 
 
The coupled oceanic and atmospheric observations reflect El Niño conditions. In 
August, sea surface temperatures (SSTs) were above average across the 
equatorial Pacific Ocean with strengthening positive anomalies noted in the 
central and east-central Pacific. In the last week, the Niño index values 
ranged from +1.1°C to +2.6°C. Area-averaged subsurface temperature anomalies 
increased compared to July in association with anomalous warmth in the central 
and eastern equatorial Pacific Ocean. Tropical atmospheric anomalies were also 
consistent with El Niño. Over the east-central Pacific, low-level winds were 
anomalously westerly, while upper-level winds were anomalously easterly. 
Convection was slightly enhanced around the International Date Line, stretching 
into the eastern Pacific, just north of the equator. Convection was mostly 
suppressed around Indonesia. The equatorial Southern Oscillation Index (SOI) 
and the traditional station-based SOI were both significantly negative. 
Collectively, the coupled ocean-atmosphere system reflected El Niño. 
 
The Real-time Multivariate Madden Julian Oscillation (RMM) index currently 
indicates incoherent intraseasonal activity, with the Madden Julian Oscillation 
(MJO) signal retreating westward to the Indian Ocean at a low amplitude during 
the past week. Dynamical model RMM forecasts generally favor the resumption of 
an eastward propagating MJO signal over the Maritime Continent, but remain 
divided in regards to its eventual amplitude with large ensemble spread. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
The most recent International Research Institute for Climate and Society (IRI) 
plume indicates El Niño will persist through the Northern Hemisphere winter 
2023-24. Despite nearly the same ensemble mean amplitude as last month, the 
shorter forecast horizon means that the odds of a "strong" El Niño (≥1.5°C for 
the November-January seasonal average in Niño-3.4) have increased to 71%. In 
summary, El Niño is anticipated to continue through the Northern Hemisphere 
winter (with a greater than 95% chance through JFM 2024). 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
Dynamical model forecasts from the North American Multi-Model Ensemble (NMME), 
the Coupled Forecast System model Version 2 (CFSv2), and the Copernicus (C3S) 
multi-model ensemble system were used extensively for the first six leads when 
they are available, as was the objective, historical skill-weighted 
consolidation and Calibration, Bridging, and Merging (CBaM) guidance, that 
combines both dynamical and statistical forecast information. 
 
Additionally, the official ENSO forecast depicts probabilities of El Niño that 
are exceptionally high through the upcoming winter, with a strong event likely. 
This anticipated El Niño signal played a key role in the construction of these 
outlooks. At later leads, decadal trends  in temperature and precipitation were 
increasingly relied upon in creating the seasonal outlooks. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2023 TO OND 2024 
 
TEMPERATURE 
 
One of the major forecast challenges for the upcoming fall and winter is 
managing the competing influences between El Niño and recent trends . Across the 
southern CONUS in particular, El Niño composites tend to favor cooler than 
normal conditions while recent trends  lean warm. Due to these competing 
influences, a large swath of EC is indicated across much of the interior South 
for OND. A slight tilt toward above normal temperatures is indicated along the 
Gulf and East coasts, where warm trends  and above normal SSTs have a greater 
chance to counteract potential El Niño influences. Above normal temperatures 
are favored with greater confidence across the Northeast and parts of the Great 
Lakes, where recent trends  and model guidance from the C3S are warm. 
Probabilities of above normal temperatures exceed 50 percent across parts of 
northern New England where recent trends  are the strongest and SSTs in the 
adjacent Atlantic Ocean are warmer than normal. Recent trends  and dynamical 
models guidance also favor warmth across the western third of the CONUS. The 
greatest probabilities of above normal temperatures (above 50 percent chance) 
are indicated for the Pacific Northwest, where dynamical and statistical inputs 
are in generally good agreement and adjacent SSTs are above normal. Relatively 
weaker probabilities of above normal temperatures (less than 40 percent chance) 
are indicated over the southwestern CONUS, where El Niño influences may 
counteract recent warm trends . Farther to the north and east, EC is indicated 
for the north-central CONUS where guidance from the NMME and recent trends  
yield weak signals . Above normal temperatures are favored throughout Alaska as 
El Niño, trend, and dynamical model guidance all favor milder than normal 
conditions across much of the state. The strongest probabilities of above 
normal temperatures (greater than 60 percent chance) are indicated across the 
North Slope as sea ice extent is currently much below normal across the 
adjacent Arctic Ocean. 
 
From November-December-January (NDJ) through March-April-May (MAM), impacts 
from the ongoing El Niño strengthen as above normal temperatures are favored 
across the northern CONUS and persist across Alaska. EC is indicated across the 
southern CONUS as El Niño favors cooler than normal conditions for most of the 
region while recent trends  favor warm. A small area of enhanced below normal 
temperature probabilities are indicated for parts of the Southwest and southern 
High Plains during JFM and FMA where El Niño composites yield a cold signal and 
recent trends  are relatively weak. After MAM, the forecast pattern increasingly 
reflects trends  with above normal temperatures generally favored across the 
Northeast during Spring and then expanding across the entire eastern third of 
the CONUS by the early Summer. Similarly, an area of elevated above normal 
temperature probabilities across the Northwest during the Spring expands across 
most of the remainder of the western third of the CONUS during the summer 
months. Alaska is generally favored to experience milder than normal conditions 
throughout the spring and summer months. During the late summer and early fall, 
trends favor warmth across all of the forecast domain so above normal 
temperature probabilities are elevated across the entire nation from JAS 
through SON. Trends  weaken later in the Fall across southeastern Alaska and the 
northwestern CONUS where EC is indicated during the OND 2024 season. 
 
PRECIPITATION 
 
Model guidance and El Niño composites are in good agreement in favoring above 
normal precipitation across the southeastern CONUS and along much of the East 
Coast during the OND 2023 season. Thus, above normal precipitation is favored 
for these regions. Probabilities of above normal precipitation exceed 50 
percent across parts of northern Florida and southern Georgia, where ensemble 
guidance from the NMME and C3S yield the strongest wet signals . Elevated 
probabilities of above normal precipitation also expand west to the Southern 
Plains, consistent with combined El Niño/Optimal Climate Normals (OCN) 
composites. Conversely, below normal precipitation is more likely across the 
northwestern CONUS and the Great Lakes region, based primarily on a combination 
of El Niño composites and dynamical model guidance. Above normal precipitation 
is favored across northern and western Alaska due to anticipated El Niño 
influences, recent trends , and dynamical model guidance. Below normal sea ice 
extent in the adjacent Arctic Ocean may also contribute to increased 
precipitation chances across the North Slope. 
 
During the winter months, impacts from El Nino are expected to increase, and 
above normal precipitation is favored for most of the Southern Tier of the 
CONUS from NDJ to February-March-April (FMA). Additionally, above normal 
precipitation is favored along much of the Eastern Seaboard during the core of 
the winter as an East Coast storm track is generally favored during El Niño 
winters. Conversely, below normal precipitation is more likely across much of 
the Northern Tier, particularly for the northwestern CONUS and the Great Lakes 
region. Uncertainty is high across the West Coast as El Niño tends to favor wet 
along much of the California coast while trends  favor dry. Given the increased 
possibility of a strong El Niño event, a tilt toward above normal precipitation 
is indicated for Southern California. A tilt toward above normal precipitation 
is also indicated across the North Slope of Alaska through FMA, consistent with 
recent trends . Confidence in potential ENSO impacts decreases substantially as 
we head to next Spring and Summer, resulting in increased uncertainty and 
coverage of EC across much of the nation. However, during late Winter and early 
Spring (FMA), guidance from the CFSv2 and other models yields a wet signal 
across the Southern and Central Plains. The wet signal generally progresses 
eastward across the Southeast by early Summer (April-May-June (AMJ)) and then 
to the Mid-Atlantic and Northeast by the middle of the summer (June-July-August 
(JJA)), consistent with trends . As this wet signal progresses eastward and 
northward, the statistical consolidation and trends  become increasingly dry 
over parts of the Central and Southern Plains by late Spring and early Summer. 
As a result, below normal precipitation is slightly favored across these 
regions during May-June-July (MJJ) and JJA. A slight tilt toward below normal 
precipitation is also indicated for parts of the northern High Plains and 
Northern Rockies through August-September-October (ASO), consistent with 
trends. Farther to the north, uncertainty is high for most of Alaska, and EC is 
indicated for most of the state from late Spring through the Summer. As we 
enter the late summer and early fall, a wet trend signal is reflected across 
parts of the Tennessee Valley during July-August-September (JAS), translating 
farther to the south and west across the western Gulf Coast in ASO and Rio 
Grande Valley deeper into next Fall in September-October-November (SON). Above 
normal precipitation is favored for the North Slope of Alaska next Fall due to 
recent trends  and the statistical consolidation also favors above normal 
precipitation for southwestern parts of the state during the same time period. 
Later next Fall and early next Winter (OND), recent trends  depict a tilt toward 
dry for parts of Southeast Alaska and the eastern Great Lakes, and a wet signal 
for parts of the Upper and Middle Mississippi Valley and the Tennessee Valley. 
 
FORECASTER: Scott Handel 
 
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 Oct 19 2023 
 
 
1991-2020 base period means were implemented effective with the May 20, 2021 
forecast release. 
$$