90 Day Narrative

FXUS05 KWBC 201231
Prognostic Discussion for Long-Lead Seasonal Outlooks
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Jun 20 2019
The July-August-September (JAS) 2019 temperature outlook indicates that above 
normal seasonal mean temperatures are most likely for the western third of the 
CONUS and all of Alaska. The highest odds for above normal temperatures are 
across Washington and the Alaska Panhandle.  Above normal temperatures are also 
favored for Southern Texas, the Gulf Coast states, and east of the Appalachian 
Mountains. Below normal temperatures are the most likely category from the 
Central and Southern Plains to the Upper Great Lakes. 
Equal Chances (EC; white areas) of below, near, and above normal seasonal mean 
temperatures or seasonal total precipitation amounts are where the likelihoods 
for these three categories are similar to their climatological probabilities. 
Review of subsequent seasonal outlooks and the scientific forecast basis for 
all outlooks are given below.
Note:  For Graphical Displays of the Forecast Tools Discussed Below See:
El Nino conditions continued in the Pacific Ocean during May 2019. Sea surface 
temperatures (SSTs) across much of the equatorial Pacific Ocean remain above 
climatological averages, with anomalies ranging from 0 to +1C from 160E to 
130W.  East of 130W, temperatures are closer to average with smaller scale 
features evident. The latest weekly Nino 3.4 SST anomaly is +0.7 degree C. 
Oceanic heat content, determined from ocean temperature anomalies from the 
surface to a depth of 300 meters along the near equatorial Pacific from the 
Date Line to 100W, has increased to about 0.5C since reaching a local minimum 
during May. Atmospheric conditions, are showing less of a canonical response 
when looking at monthly average wind anomalies.  The drop in oceanic heat 
content and lack of coherent wind response is likely related to stronger 
subseasonal variability related to the Madden-Julian Oscillation (MJO) during 
May and early June. Collectively, these oceanic and atmospheric conditions 
represent a continuation of weak El Nino conditions as of May 2019. Other 
boundary conditions relevant to the seasonal outlook are soil moisture 
anomalies and, in some areas, near-coastal SSTs. Widespread and persistent 
above normal precipitation for most of the CONUS during recent months has 
resulted in positive soil moisture anomalies for many areas of the central and 
eastern CONUS, extending into parts of the Great Basin, with many of these 
areas exceeding the 99th percentile of climatological soil moisture. Sea ice 
coverage for the Arctic is at record low amounts and SSTs are above normal near 
the west coast of Alaska.
The CPC SST Consolidation Nino 3.4 forecast indicates the continuation of an El 
Nino through 2019. The three statistical models all predict at least a weak El 
Nino from autumn 2019 into winter 2019-2020, with the CCA predicting a moderate 
strength El Nino by Dec-Jan-Feb 2019-2020. The CFS dynamical model forecast 
ensemble mean predicts a slow decline in positive Nino 3.4 anomalies, with the 
most recent runs indicating a transition to ENSO neutral conditions during the 
autumn of 2019. The NMME suite of dynamical models shows more spread (implying 
less certainty in the outlooks through the rest of 2019. Most of the models 
indicate either a weak El Nino or ENSO neutral.  Little possibility of a La 
Nina event next winter is indicated by statistical and dynamical model 
forecasts. The probability of a continuation of the current El Nino through the 
2019 summer is 66%, with a 50-55% chance of it continuing into the fall and 
The temperature and precipitation outlooks were based primarily on dynamical 
model guidance from the NMME, IMME, and statistical model guidance which 
includes a statistical forecast of the linear impacts of ENSO combined with 
decadal climate trends based on the CPC SST Consolidation forecast for Nino 
3.4. The potential impacts from a continuation of El Nino conditions were 
considered for the seasonal outlook period through winter 2019-2020. Soil 
moisture conditions were strongly considered for the earliest leads, as well as 
near-coastal SST anomalies. Several statistical and dynamical models, as well 
as hybrid statistical-dynamical models, along with an objective consolidation 
of several forecast tools, were also examined in preparation of the seasonal 
outlooks. Decadal timescale trends were considered for all leads but take a 
primary role in later outlooks, as uncertainty in interannual climate signals 
increases. The potential for an out sized influence from subseasonal 
variability to imprint on the seasonal period was also considered for the early 
leads, as given a weak El Nino, subseasonal modes of variability can have a 
larger than normal influence.
The JAS 2019 through DJF 2019-2020 seasonal mean temperature outlooks utilize 
the predictability of several climate phenomena, including the ongoing El Nino 
event and its potential impacts, anomalous land surface and sea surface 
temperature states, and decadal timescale climate variability or trends. A 
statistical-dynamical hybrid model combining calibrated NMME temperature 
forecasts with statistically bridged impacts from NMME Nino 3.4 forecasts 
(known as calibration, bridging and merging or CBaM) suggest that below-normal 
temperatures are most likely during JAS over much of the central CONUS. Many of 
the dynamical models in the NMME suite indicate below normal temperatures. 
Statistical guidance that emphasizes ENSO and long-term trends indicate that 
near normal temperatures are most likely for much of the same area, while a 
pure ENSO response would favor below normal temperatures potentially across the 
Great Lakes through Aug-Sep-Oct (ASO). Two inputs, summertime ENSO and the 
relation of temperature to soil moisture, offer less predictability in the 
autumn, so the SON and OND outlooks largely reflect the model guidance and 
linear regressions of trend and ENSO. The outlooks beyond OND are largely 
unchanged from the prior months set as the odds for El Nino to continue are 
nearly the same as last month. On the seasonal timescale, during the summer and 
autumn, trends are the dominant mode of variability across Alaska, and trends 
favor above normal temperatures.  The strongest signal is during the months of 
October and November, and the current outlook reflects strong probabilities for 
above normal temperatures during the seasons that include those months.
Beginning with the JAS 2019 precipitation outlook, above normal precipitation 
is forecast for a large region of the CONUS from the interior West to the 
Mississippi Valley. This pattern is suggestive of a northward shift in the 
North American Monsoon, and is supported by model guidance and statistical 
relationships between seasonal precipitation and ENSO.  For JAS 2019, some 
models showed weak signals for below normal precipitation from the Northeast to 
the Mid-Atlantic, though only the Mid-Atlantic portion of that signal is 
consistent with ENSO composites/regressions, so the overall signal was not 
included in the official outlooks. The pattern in the precipitation forecast 
persists for the ASO 2019 season, though during ASO the signal shifts south to 
reflect the potential for moisture to surge northward from the East Pacific, an 
impact typically associated with more tropical cyclone activity. Beyond ASO, 
the signal gradually shifts southward due to the seasonal evolution of 
long-term trends and expected ENSO impacts during the winter of 2019-2020.  
Similar to the temperature outlooks, minimal changes were made to the outlooks 
covering winter 2019-2020 and spring 2020 as no forecasts of major climate 
factors have changed since last month.  The outlooks for next summer were 
modified to reflect trends, including the addition of below normal 
precipitation across the interior Pacific Northwest.
FORECASTER: Matthew Rosencrans
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
(Use Lower Case 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 18 2019
1981-2010 base period means were implemented effective with the May 19, 2011 
forecast release.