90 Day Narrative

460 
FXUS05 KWBC 211231
PMD90D
Prognostic Discussion for Long-Lead Seasonal Outlooks
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Mar 21 2019
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
The April-May-June (AMJ) 2019 temperature outlook favors above normal seasonal 
mean temperatures for Alaska, the Pacific Northwest and from southern Texas 
northward to the eastern Great Lakes and eastward to the East Coast. 
Probabilities exceed 50% for Alaska, areas in the Pacific Northwest, 
mid-Atlantic and Northeast. Below normal temperatures are favored at modest 
odds for the northern and central Great Plains. 
The AMJ 2019 precipitation outlook indicates enhanced odds of above normal 
seasonal total precipitation amounts for much of interior Alaska and for a 
region extending from the central Great Basin eastward and southward to the 
Gulf of Mexico and Atlantic seaboard. Below normal precipitation is favored for 
the Alaska Panhandle and parts of the Pacific Northwest. All precipitation 
probabilities are modest and do not reach 50% probability.
Equal Chances (EC; white areas) of below, near, and above normal seasonal mean 
temperatures or seasonal total precipitation amounts are where odds for these 
three categories are similar to their climatological probabilities. Review of 
subsequent season outlooks and the scientific forecast basis for all outlooks 
are given below.
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
Weak El Nino conditions remained in place in the Pacific Ocean during March 
2019. Sea surface temperatures (SSTs) along the equatorial Pacific Ocean remain 
above +0.5 degrees C with many areas above +1.0 degrees C for the most recent 
4-week average and the latest Nino3.4 value is +1.0 degrees C. Oceanic heat 
content (ocean temperature anomalies from the surface to a depth of 300 m along 
the equatorial Pacific) has rapidly once again increased over the past two 
months. Atmospheric conditions continue to respond to the anomalous SST forcing 
with enhanced convection now more consistently observed along the equator near 
the Date Line and just to the west and east. Modest westerly wind anomalies 
along the equator and an upper-level anticyclonic circulation north of the 
equator in the central Pacific are also now present. Collectively, these 
combined oceanic and atmospheric conditions represent a continuation of weak El 
Nino conditions as designated in early February 2019. 
A review of other boundary conditions relevant to the seasonal outlook are soil 
moisture anomalies, current snowpack and in some areas near coastal SSTs. 
Widespread and persistent above normal precipitation for most of the CONUS 
during the winter months and especially during February and March has resulted 
in very high positive soil moisture anomalies for parts of California, but 
especially for many areas of the central and eastern CONUS. Moreover, the 
exceptionally anomalous and persistent cold that impacted much of the western 
and north central CONUS in February into March, combined with a persistent 
storm track, rapidly increased snowpack for the northern Plains, western Great 
Lakes and much of the West. The lack of sea ice in waters bordering much of 
western Alaska have remained free of or have below normal sea ice coverage and 
thickness.
PROGNOSTIC DISCUSSION OF SST FORECASTS
The CPC SST Consolidation forecast for Nino3.4 depicts the continuation of a 
weak El Nino. There is considerable spread, however, in its constituent input 
models with the CA favoring ENSO neutral conditions, the CCA and Markov 
statistical models forecasting an increase in Nino3.4 SST during summer 2019 
into the winter of 2019-2020. The dynamical model CFS forecast increases in 
positive value through autumn 2019 to moderate or strong strength (as indicated 
by this measure). The NMME suite of models also shows large spread with some 
solutions depicting a strong event by autumn, some maintaining a borderline 
weak-moderate event to autumn and still others favoring a decrease to ENSO 
neutral conditions by autumn.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
The temperature and precipitation outlooks were based on some consideration and 
potential impact from the ongoing El Nino base state, however, due to the high 
uncertainty of its evolution in coming months as well as a typically weaker 
signal during the warm season, impacts associated with El Nino during the warm 
season were limited. Most recent soil moisture conditions (both contemporaneous 
and lagged as well as local versus remote influences) were considered as well 
as recent snowpack observations and near coastal SST anomalies. Several 
statistical, hybrid and consolidated forecast tools as well as dynamical model 
guidance from the NMME and IMME were also a substantial part of the outlook 
preparation. Long term trends were considered at all leads but especially for 
later outlooks.
PROGNOSTIC DISCUSSION OF OUTLOOKS - AMJ 2019 TO AMJ 2020
TEMPERATURE
The forecast rationale for preparation of the AMJ - JAS 2019 seasonal mean 
temperature outlooks utilized and considered several factors including the 
ongoing El Nino base state (albeit weak) and its potential evolution into and 
through the summer months, strongly anomalous land surface states and dynamical 
model consistency and confidence. Below normal temperatures are favored for a 
region in the northern and central Great Plains during AMJ 2019 and to a lesser 
extent in coverage during MJJ 2019. Lag correlation forecast tools relating 
soil moisture to subsequent future month(s) temperature and soil moisture based 
constructed analogue statistical guidance both support these forecast areas. 
Moreover, although a more minor consideration, long term temperature trends, as 
represented by OCN, also support the potential for below normal temperatures in 
the northern portion of these areas in AMJ and MJJ 2019. Forecast guidance from 
ECMWF among some others also support below normal temperatures, primarily in 
the southern portions of these areas. For JJA and JAS 2019, potential El Nino 
influence and residual land surface state feedback resulted in less coverage 
and lower probabilities for above normal temperatures for parts of the 
Southwest, south-central Great Plains and western Ohio Valley compared to the 
previous set of outlooks. 
From AMJ - JAS 2019, areas where odds for above normal temperatures are 
indicated are supported overwhelmingly by both statistical and dynamical model 
information. This includes Alaska (primarily for AMJ 2019) where the largest 
probabilities are along parts of the west and north coast of the state and is 
linked to the continued downward long term trends in sea ice coverage and 
thickness, more open water earlier in the seasonal cycle and so greater 
potential for warmer temperatures impacting portions of the state.
The outlooks from ASO 2019 through NDJ 2019-2020 depict full or near full 
coverage of the forecast domain for above normal temperatures supported by 
available statistical and dynamical model forecast tools and guidance. These 
outlooks, however, were modified for potential El Nino influences in subtle 
ways (given the high uncertainty of the evolution of ENSO) from the previous 
set of outlooks through this period. Long term temperature trends dominant the 
basis for the remaining temperature outlooks through AMJ 2020.
PRECIPITATION
For AMJ 2019, above normal precipitation is forecast at modest probabilities 
for a large region from the central Great Basin to the Gulf and East coasts, 
while below normal precipitation is most likely for parts of the Alaska 
Panhandle and Pacific Northwest. This general precipitation forecast pattern 
remains, to first order, consistent through JAS 2019. The forecast rationale is 
based on dynamical model forecast guidance from the NMME and IMME constituent 
models and is consistent with a potential El Nino influence over the period 
(primarily for a region stretching from Texas to the northern Rockies and Great 
Basin). For JJA and JAS 2019, there is a substantial change in the forecast for 
the northern Rockies from the previous set of outlooks which were mainly based 
on long term precipitation trends. Above normal precipitation is now forecast 
to extend into this region through JAS 2019 where there are consistent signals 
of enhanced wetness from statistical and dynamical model guidance and is 
consistent with any potential El Nino summer impact. 
For ASO and SON 2019, the focus of elevated odds for above normal precipitation 
shifts over time to the Southwest CONUS. Outlooks from OND 2019 only depict at 
the current time above normal precipitation for areas in Alaska related to long 
term precipitation trends. Other areas where similar type trends may be 
designated at these long forecast leads are somewhat at odds with potential El 
Nino related impacts during the autumn and winter months of 2019-2020. 
FORECASTER: Jon Gottschalck
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 Case 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 Apr 18 2019
1981-2010 base period means were implemented effective with the May 19, 2011 
forecast release.
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