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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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    0.5mn Jul 2021

Tools Used (see Discussion for explanation)
HOME> Outlook Maps>Seasonal Forecast Discussion
Prognostic Discussion for Long-Lead Seasonal Outlooks 
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Jun 17 2021


ENSO-neutral conditions are present across the equatorial Pacific Ocean, as
represented in current oceanic and atmospheric observations. The official CPC
ENSO forecast indicates that ENSO-neutral conditions are likely to persist
through the fall. Looking further ahead, El Nino is the least likely scenario
through the upcoming winter.

The July-August-September (JAS) 2021 temperature outlook favors above normal
temperatures for Alaska, the western half of the CONUS, the eastern quarter of
the CONUS, and the Northern Plains, with the largest probabilities (greater
than 60 percent) forecast across the Northeast. The JAS 2021 precipitation
outlook depicts enhanced probabilities of below normal precipitation amounts
across the Pacific Northwest, Rockies, and parts of the High Plains.
Above-normal precipitation is more likely from the Eastern Seaboard to the
Lower Mississippi Valley and parts of the Southern Plains. Above normal
precipitation amounts are slightly favored for parts of northwestern Alaska.
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.

Note: For Graphical Displays of the Forecast Tools Discussed Below See:


The coupled oceanic and atmospheric observations reflect ENSO-neutral
conditions. During the past four weeks, sea surface temperatures (SSTs)
returned to near average across most of the equatorial Pacific Ocean. In the
last two months, positive subsurface temperature anomalies extended across most
of the Pacific Ocean. However, recently, negative anomalies have emerged in the
Central Pacific at 50-200m depth. Beginning in mid-March, integrated
upper-ocean heat anomalies have been positive. Since early May, these positive
anomalies have weakened to near zero. During the past 30 days, suppressed
convection was located south of the Equator near the Date Line and over parts
of Indonesia. Enhanced convection was evident over the far western Pacific
Ocean. The RMM index recently emerged over Africa with enhanced convection
noted over the tropical Atlantic. A weakening of this signal is anticipated and
models are predicting a potential new intraseasonal feature over the Western
Hemisphere by late June.


A majority of the models in the IRI/CPC plume predict ENSO-neutral to continue
through the fall 2021. By the late fall and winter, La Nina chances increase to
near 50 percent, reflecting the historical tendency for a second winter of La
Nina following the first, and also the predictions from the North American
Multi-Model Ensemble. However, these cooler conditions are predicted to exist
for a short duration (3 overlapping seasons) and these predictions are still
over 6 months into the future. In summary, ENSO-neutral is favored through the
Northern Hemisphere summer (greater than 60 percent chance for the JAS season)
and fall (50 percent chance for the SON season). El Nino is the least likely
scenario (less than 10 percent chance) through the upcoming winter.


Dynamical model forecasts from the NMME and Copernicus (C3S) multi-model
ensemble systems are used extensively for the first six leads when they are
available, as was the objective, historical skill weighted consolidation, that
combines both dynamical and statistical forecast tools.

Additionally, the official ENSO forecast depicts probabilities of El Nino that
are significantly less than climatological probabilities through the upcoming
winter. This anticipated lack of an El Nino signal played a role in the
construction of these outlooks. Anomalously wet (dry) soil moisture conditions
was also a factor in the temperature outlook across the Southern Plains and
Lower Mississippi Valley (northern Great Plains) during summer and early fall.
At later leads, decadal trends in temperature and precipitation were
increasingly relied upon in creating the seasonal outlooks.



Above normal temperatures are favored throughout a majority of the forecast
domain during JAS, except for parts of the Southern and Central Plains and the
Lower and Middle Mississippi Valley, where equal chances (EC) of below, near,
or above normal temperatures are forecast. This EC area is due to weaker
signals among temperature tools coupled with abnormally wet soil moisture
conditions across most of this region and represents a reduction in above
normal temperature probabilities relative to last month's outlook.
Probabilities of above normal temperatures are increased relative to last month
across the Northern Plains due, in part, to continued dry soils. Chances of
above normal temperatures are also increased for the Northeast due to excellent
agreement among both dynamical and statistical guidance. Above normal
temperatures are favored throughout Alaska during JAS, but with a reduction of
probabilities across the Panhandle compared to last month where dynamical model
support is the weakest.

From ASO through SON, above normal temperatures are favored across the entire
CONUS as soil moisture impacts begin to diminish. Thereafter, the forecast
pattern increasingly begins to reflect trends with above normal temperatures
favored across the southern and eastern CONUS through the fall, winter, and
next spring. Probabilities of above normal temperatures peak in the Southeast
during the winter, consistent with an anticipated absence of El Nino, and again
later next Spring, as trends play a greater role. Conversely, below normal
temperatures are slightly favored for the Northern Plains late this upcoming
winter into early spring consistent with recent trends and corresponding to a
strong cold signal from ENSO composites. Elevated chances of above normal
temperatures return to the entire West Coast by late next Spring consistent
with trends . Forecast uncertainty is generally high across much of Alaska,
where warm trends conflict with colder ENSO composites and dynamical model
guidance to varying degrees. EC is forecast across much of southern Alaska from
late fall through early spring where disagreements among these conflicting
tools are at its greatest. Otherwise above normal temperatures are generally
forecast for northern Alaska where the trend signal is the strongest.


Model guidance remains consistent from previous months depicting elevated
probabilities of below normal precipitation for the Pacific Northwest, Rockies,
and northern to central High Plains during JAS. However, the strength of the
signal diminishes considerably farther to the south, resulting in a forecast of
EC across much of the Southwest Monsoon Region. Farther to the east, above
normal precipitation is favored from the Southern Plains to the Northeast. The
highest confidence for above normal precipitation is across the Lower
Mississippi Valley, consistent with the strongest signal among dynamical model
guidance, and for parts of the Mid-Atlantic States and the Northeast, where
statistical tools depict the strongest signal. A small region of elevated
probabilities of above normal precipitation is also indicated for parts of
northwestern Alaska, consistent with CPC's skill weighted consolidation tool.
EC is indicated for the rest of the forecast domain as signals for the various
dynamical and statistical tools are too weak or conflicting to issue a forecast
with a sufficient degree of confidence.

As we progress further into late summer and into the fall, dynamical and
statistical guidance converge on a drier solution for the Southwest Monsoon
Region. This dry signal is consistent with the anticipated absence of El Nino
conditions and, consequently, the potential inhibition of tropical activity in
the Pacific. Looking further ahead the dry signal expands eastward to encompass
the entire Southern Tier from coast to coast by late fall through most of the
winter, consistent with absence of El Nino. Thereafter, a region of elevated
probabilities of above normal precipitation is indicated for parts of the
Mississippi and Ohio valleys late winter into early spring consistent with
trends. This region of favored above normal precipitation expands southward to
the Southern Plains and eastward to parts of the East Coast during the spring
consistent with trends and ENSO composites. Trends also favor dryness for parts
of the western CONUS as we progress deeper in the Spring into next summer. As
was the cas e with temperature, uncertainty in the precipitation forecast across
much of Alaska is quite high and EC is indicated across much of the state for
all forecast leads. However above normal precipitation is favored for parts of
the South Coast late in the summer into early fall consistent with ENSO
composites and the C3S. Above normal precipitation is also favored for northern
Alaska beginning in the fall through early spring due to trends and for eastern
Alaska during the winter due to a wet ENSO signal. Trends and ENSO composites
also lead to favored wetter than normal conditions for parts of eastern Alaska
next summer.

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
(Use Lower Cas e Letters)
Information on the formation of skill of the CAS forecasts may be found at:
(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 Jul 15 2021

1991-2020 base period means were implemented effective with the May 19, 2011
forecast release.

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