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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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More Outlooks
    0.5mn ASO 2021
    1.5mn SON 2021
    2.5mn OND 2021
    3.5mn NDJ 2021
    4.5mn DJF 2021
    5.5mn JFM 2022
    6.5mn FMA 2022
    7.5mn MAM 2022
    8.5mn AMJ 2022
    9.5mn MJJ 2022
   10.5mn JJA 2022
   11.5mn JAS 2022
   12.5mn ASO 2022
    0.5mn Aug 2021


Tools Used (see Discussion for explanation)
   CCA
   OCN
   CMP
   SMT
   POE
 
HOME> Outlook Maps>Seasonal Forecast Discussion
 
Prognostic Discussion for Long-Lead Seasonal Outlooks 
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Jul 15 2021

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

ENSO-neutral conditions persist across the equatorial Pacific Ocean, as
indicated by current oceanic and atmospheric observations. The CPC/IRI ENSO
consensus forecast predicts that ENSO-neutral conditions are likely to persist
through the next three-month season, while La Nina conditions are more likely
in autumn and winter. By winter there is approximately an equal chance of weak
La Nina conditions, moderate-to-strong La Nina conditions, or ENSO-neutral
conditions. El Nino is the least likely scenario through winter.

The August-September-October (ASO) 2021 temperature outlook favors above normal
temperatures for the western half of the CONUS, the Midwest, and the eastern
quarter of the CONUS, with the largest probabilities exceeding 60 percent over
parts of the Great Basin and Central Rockies as well as the Northeast. The ASO
2021 precipitation outlook predicts enhanced probabilities of below normal
precipitation across much of the western half of the CONUS, excluding parts of
the Pacific Northwest, as well as the Northern Plains and western Great Lakes
region. Above normal precipitation is likely for the central and eastern Gulf
Coast region and from the Apppalachians to the Atlantic Coast, excluding the
Florida Peninsula. Above normal precipitation is slightly favored for the
southern coast, eastern interior, and North Slope of Mainland Alaska, as well
as the northern Alaska Panhandle. Equal chances (EC) are indicated for areas
where probabilities for each category of seasonal mean temperatures and
seasonal accumulated precipitation 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 ENSO-neutral
conditions. Sea surface temperatures (SSTs) are near climatological averages
across most of the equatorial Pacific Ocean. Positive subsurface temperature
anomalies persisted across most of the Pacific Ocean, while negative
temperature anomalies emerged at depths of 50 to 200 meters in the eastern
equatorial Pacific Ocean. Integrated upper-ocean heat anomalies, that have been
positive since March, are now near zero. Convection is suppressed near the Date
Line and enhanced near the Maritime Continent, while low-level easterlies and
upper-level westerlies are near climatological averages over much of the
equatorial Pacific Ocean.

PROGNOSTIC DISCUSSION OF SST FORECASTS

Dynamical models of the NMME predict weak Nino 3.4 SST anomalies between zero
and -0.5 C in the next three months, followed by larger anomalies below -0.5 C,
the threshold for potential La Nina conditions, later in autumn and through
winter. Statistical models generally predict ENSO-neutral conditions, with Nino
3.4 SST anomalies between -0.5 and +0.5 C over the same period. The CPC SST
Consolidation, a skill weighted combination of dynamical and statistical
models, tracks more closely to the dynamical model forecasts with the
probability of La Nina increasing through autumn into winter. The Copernicus
(C3S) international, multi-model ensemble system, in contrast to the NMME,
predicts a greater persistence of weak negative Nino 3.4 SST anomalies through
autumn, reflecting ENSO-neutral conditions. The official CPC/IRI consensus ENSO
outlook calls for greater than a 50 percent probability of La Nina through five
overlapping seasons from SON 2021 through JFM 2022, consistent with the
historical tendency for a second winter of La Nina following the first La Nina
winter, and predictions from the North American Multi-Model Ensemble.

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

Dynamical model forecasts from the North American Multi-Model Ensemble (NMME)
and Copernicus (C3S) multi-model ensemble systems are used extensively for the
first six leads when they are available. The ENSO-OCN statistical forecast tool
was used for the OND 2021 through FMA 2022 seasons to determine expected
climate impacts of likely La Nina conditions, as predicted by the CPC ENSO
outlook and CPC SST consolidation forecast, in addition to decadal climate
trends. The objective, skill weighted consolidation, that combines both
dynamical and statistical forecast tools, was used for all leads.

Anomalously wet soil moisture conditions across the Southern Plains and Lower
Mississippi Valley and anomalous dry soil moisture conditions across the
western CONUS and Northern Plains were factors in the temperature outlook for
late summer and early fall. At longer leads, decadal climate trends in
temperature and precipitation, as represented by the OCN tool, are the primary
climate signal in the seasonal outlooks.

PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2021 TO ASO 2022

TEMPERATURE

Above normal temperatures are likely throughout a majority of the forecast
domain during ASO, 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 corresponds to weaker
signals in the dynamical model temperature forecasts, as well as areas with
persistent abnormally wet soil moisture conditions. A reduction in above normal
temperature probabilities for this area relative to last month's outlook is
seen for both ASO and SON. Probabilities of above normal temperatures are
increased relative to last month’s outlook across the Northern Rockies and
Northern Plains, as indicated by the NMME dynamical model forecasts and due in
part to continued dry soil moisture conditions. Above normal temperatures are
likely for most of Alaska in ASO, with an expanded area of EC for southeastern
Mainland Alaska and the Panhandle, as indicated by dynamical model forecasts.

For SON, above normal temperatures are favored across the entire CONUS,
corresponding to dynamical model forecasts and the decreased impact of
anomalous soil moisture conditions. For OND 2021 through MAM 2022, the seasonal
outlook represents the enhanced likelihood of La Nina. Positive decadal
temperature trends across most of the domain are moderated by the impacts of
temperature variability due to La Nina. Areas of EC expand across southern
Alaska and the northern tier of the CONUS in OND 2021 through MAM 2022,
including the Pacific Northwest, Northern and Central Plains, and western Great
Lakes regions. Below normal temperatures are more likely for parts of the
Pacific Northwest in DJF through FMA 2022, and across the northern tier into
parts of the Northern Plains in FMA. Below normal temperatures are also favored
for parts of southeastern Mainland Alaska and the Alaska Panhandle in JFM and
FMA 2022, due to potential La Nina impacts.

For AMJ 2022 and thereafter, the forecast pattern primarily reflects decadal
trends with above normal temperatures favored for much of the West and across
the southern and eastern CONUS through next spring and summer. Probabilities of
above normal temperatures peak in the summer of next year across the West and
along the Atlantic coast, consistent with the seasonal influence of decadal
climate trends . Decadal trends favor above normal temperatures for northwestern
areas of Alaska next spring, related to long term changes in sea ice cover
during this season, and across the state by summer of 2022.

PRECIPITATION

Dynamical model forecasts from the NMME support slightly elevated probabilities
of below normal precipitation for much of the West into the Northern Plains and
western Great Lakes region, excluding parts of the Pacific Northwest, in the
ASO seasonal outlook. Dynamical model forecasts favor above normal
precipitation in ASO for much of the central and eastern Gulf Coast region,
excluding the Florida Peninsula, and from the Appalachians eastward to the
Atlantic coast. Probabilities for above normal precipitation are enhanced for
eastern areas of the Alaska Mainland, consistent with decadal trends , the SST
constructed analog forecast, and dynamical model forecasts from the NMME and
C3S. Enhanced probabilities for below normal precipitation persist for much of
the Southwest and across the Great Plains in SON, while enhanced probabilities
of above normal precipitation continue for the Mid-Atlantic, as supported by
the NMME. Below normal precipitation for the Southwest in early autumn is
consistent with the increasing possibility of La Nina conditions, and the
potential inhibition of tropical activity in the eastern Pacific. Beginning in
the OND seasonal outlook, the precipitation pattern begins to evolve to reflect
the increasing likelihood of La Nina. Below normal precipitation is generally
favored across southern regions of the CONUS from Southern California to the
Southeast by winter. Above normal precipitation is more likely for parts of the
Pacific Northwest for NDJ and DJF and for southeastern Mainland Alaska in DJF
and JFM 2022.

From next winter into next spring and summer the precipitation pattern forecast
increasingly reflects decadal precipitation trends . Enhanced probabilities of
below normal precipitation persist for much of the Southwest through MAM 2022,
while probabilities of above normal precipitation are enhanced for parts of the
Mississippi and Ohio Valleys from JFM through AMJ 2022 and for parts of the
Mid-Atlantic in AMJ through ASO 2022. Decadal trends are the primary signal for
above normal precipitation for the North Slope of Alaska in NDJ 2021 through
FMA 2022 and for parts of eastern interior Alaska in JJA through ASO 2022.

FORECASTER: Dan Collins

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 Aug 19 2021


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

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Page last modified: January 17, 2006
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