Prognostic Discussion for Long-Lead Seasonal Outlooks 
NWS Climate Prediction Center College Park MD 
830 AM EDT Thu Sep 19 2019 
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS 
 
The October-November-December (OND) 2019 temperature outlook favors above 
normal temperatures throughout the entire forecast domain, although 
probabilities vary. The highest regional probabilities for above normal 
temperatures are forecast across parts of the Southwest, the Northeast, and the 
North Slope of Alaska. Probabilities for above normal temperatures are lowest 
from the northern Great Plains and Upper Mississippi Valley to interior 
portions of the east-central Gulf Coast region, and for interior parts of 
southern Alaska. 
 
The OND 2019 precipitation outlook indicates that above normal seasonal total 
precipitation is favored near the Atlantic Coast from Florida to New Jersey, 
much of the west-central and central CONUS, and Alaska (excluding the 
Panhandle). Below normal precipitation is favored over the north-central 
portion of the West Coast. 
 
Equal chances (EC; white areas) of below, near, and above normal are forecast 
in areas where the likelihood of seasonal mean temperatures or seasonal total 
precipitation amounts are expected to be similar to their 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 
 
Oceanic and atmospheric observations across the equatorial Pacific reflected 
ENSO-neutral conditions during August and early September. The 7-day average 
sea surface temperature (SST) observations centered on September 11th are below 
average (-0.5C to -1.5C) over the central and eastern Pacific, and above 
average (+0.5C to +1.5C) over the west-central Pacific. The latest weekly Nino 
3.4 SST anomaly is -0.3 deg C, down from +0.0C one week ago. Subsurface 
temperatures range from -0.5C to greater than -3.0C below average over much of 
the central and eastern equatorial Pacific, to a depth of about 175 meters. 
Outgoing longwave radiation (OLR) anomalies depicted near average convection 
across the equatorial Pacific from August 16th to September 10th, and 
suppressed tropical convection over Indonesia. Trade winds during the past 
month averaged close to normal over the equatorial Pacific. The Madden-Julian 
Oscillation (MJO) remained weak for at least the past 40 days, with other modes 
of subseasonal variability (such as Kelvin waves, equatorial Rossby waves and 
Tropical Cyclones (TC)) influencing convection across the global tropics. 
 
Sea surface temperature anomalies of +2.5 to +3.5 degrees C, or higher, persist 
throughout areas surrounding Alaska. These anomalies and the likelihood for 
another autumn season with significantly delayed sea ice onset were major 
factors in the temperature outlook for Alaska this fall. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
A substantial spread in the dynamical and statistical model forecasts of SSTs 
across the equatorial central and eastern Pacific during the fall and winter 
continues. Statistical model forecasts such as the Canonical Correlation 
Analysis and the Constructed Analog predict a Nino 3.4 SST anomaly at or 
slightly above +0.5 degree C through most of winter 2019-2020, with a very slow 
decline within the upper half of the Neutral category (that is, +0.0C to 
+0.49C) throughout spring. The CPC SST Consolidation and the NMME (North 
American Multi-Model Ensemble) predict only slightly reduced anomalies 
(relative to the tools noted above) throughout the upcoming winter and spring, 
though the forecast anomalies still range within the upper half of Neutral. The 
CPC/IRI consensus forecast indicates that ENSO-neutral conditions are most 
likely through the winter with La Nina the least likely to develop. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
The temperature and precipitation outlooks were based on calibrated NMME 
forecasts, a statistical-dynamical hybrid model combining calibrated NMME 
forecasts with statistically bridged impacts from NMME Nino 3.4 forecasts 
(CBaM), and a new Consolidation (CON) tool which uses the CCA (Canonical 
Correlation Analysis), the CA (Constructed Analog), the NMME, OCN (Optimal 
Climate Normals) and ENSO phase. The CA-SST (Constructed Analog which uses 
tropical Pacific SSTs as input) was also utilized. Due to the expectation that 
ENSO is unlikely to provide a major influence on the mid-latitude circulation 
pattern at least through earlier lead times, decadal climate trends  were 
weighed more heavily during the fall and winter 2019-2020. Decadal climate 
trends became the major tool for temperature and precipitation outlooks at the 
longer leads. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2019 TO OND 2020 
 
TEMPERATURE 
 
Above normal temperatures are favored throughout the forecast domain during 
OND, based on good agreement among the dynamical models  and statistical tools. 
In Alaska, there is not only good agreement among the models and tools, but 
SSTs range from +1.5C to +3.5C above average surrounding most of the state, 
which contributes toward relative warmth in coastal regions. The greatest 
chances for above normal temperatures (in excess of 70%) are across the North 
Slope, where there is a strong historical trend during the past two decades for 
a significant delay in the formation of sea ice over the adjacent waters of the 
Arctic Ocean and Chukchi Sea. 
 
Over the Lower 48 states, probabilities for above normal mean temperatures 
exceed 60% over the Southwest, supported by the calibrated NMME, CBaM, 
historical temperature trends , and the CON tool. Probabilities for above normal 
(upper-tercile) temperatures exceed 50% over parts of the Northeast based on 
the CA-SST tool, trends , the calibrated NMME, the CON, and the CBaM. 
Probabilities for above normal temperatures are tempered across the northern 
Great Plains where more variability is expected during the three month period, 
and where the signal is weaker among dynamical models . In addition, the 
potential for recurving tropical cyclones in the northwest Pacific and their 
effect on the longwave pattern downstream over North America limits confidence 
in the temperature outlook across the north-central CONUS. These tempered 
probabilities for upper-tercile temperatures extend southeastward towards the 
central and eastern Gulf Coast region, as indicated by CCA, the calibrated 
NMME, CBaM, and the CON tool. If ENSO-neutral conditions persist through the 
upcoming winter as expected, subseasonal variability such as the Arctic 
Oscillation (AO) could play a greater role in determining the seasonal mean 
temperature pattern. 
 
During the next few leads (NDJ 2019-20 through FMA 2020), probabilities for 
above normal temperatures are reduced somewhat across much of the domain, with 
an area of EC (Equal Chances) being favored initially over the north-central 
CONUS. This area of EC expands across the Great Lakes and Ohio Valley, reaching 
a maximum spatial extent in JFM 2020 before decreasing in coverage. This area 
of increased uncertainty is highlighted in the calibrated NMME and CBaM tools, 
and to a lesser degree the OCN and new CON. As noted earlier, with ENSO-neutral 
favored to persist through the upcoming winter, the odds of other subseasonal 
factors such as the AO playing a larger role in the temperature pattern may 
result in episodic cold air outbreaks across the north-central states in 
particular. 
 
Temperature outlooks during the spring and summer 2020 were not changed from 
the previous set of outlooks issued last month, since multi-decadal trends  
remain the primary tool. During these seasons, above normal temperatures are 
most likely across Alaska and a majority of the CONUS except for the 
north-central CONUS. By fall 2020, increased chances of above normal expand to 
include all of the forecast domain which follows long-term trends . 
 
PRECIPITATION 
 
The OND 2019 precipitation outlook favors above normal precipitation over 
Alaska (except the Panhandle), much of the west-central and central CONUS, and 
the Middle and Southern Atlantic Coast states. To various degrees, these areas 
are based on the CON, CBaM, trends  (especially in the Carolinas and 
Mid-Atlantic), the CA-SST, and to a lesser extent the calibrated NMME. The 
anticipated delay in sea ice formation just north of Alaska, in addition to 
anomalously warm SSTs surrounding the state, also contribute to the relatively 
wet forecast. The Southern Atlantic region is also vulnerable to tropical 
cyclones, especially during October, as the main formation area returns to the 
Caribbean and Gulf of Mexico. Parts of the Southwest CONUS are also susceptible 
to tropical cyclones in October, and resultant Gulf surges with east Pacific 
tropical storms and hurricanes. Below normal amounts of precipitation are 
favored over north-central portions of the West Coast. This is supported by the 
CON tool, the CA-SST, and the CA. 
 
From NDJ 2019-20 to MAM 2020, odds favor above normal precipitation across much 
of Alaska. For the CONUS, the enhanced odds of above normal precipitation 
across the Middle Atlantic and Southern Atlantic Coast states gives way to EC, 
suggestive of a relatively wet month of October. The broad area of favored 
wetness over the west-central CONUS transitions to the northern CONUS, from 
about central Montana to the Great Lakes region. Increased odds of below normal 
precipitation shift southward with time from Oregon and northern California to 
most of California and Nevada by JFM 2020. Precipitation signals  become very 
weak over the CONUS in FMA and MAM 2020, with EC favored. 
 
At the longer leads, AMJ 2020 through OND 2020, the tilt in the odds towards 
above normal precipitation across parts of the eastern CONUS is consistent with 
long-term trends . Also, the favored area for below normal precipitation, 
beginning with JJA 2020 across parts of the western and north-central CONUS is 
also related to trends . 
 
FORECASTER: Anthony Artusa 
 
The Climatic normals are based on conditions between 1981 and 2010, 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 17 2019 
 
 
1981-2010 base period means were implemented effective with the May 19, 2011 
forecast release. 
$$