HomeMy WebLinkAboutHandout 10-13-15Typical BI Nino jet stream patterns across the U.S. during the winter include a more
persistent than usual storm track entering the Southwest U.S. bringing wetter than
normal conditions. The Northwest U.S. is then removed from the storm track, resulting
in a drier than normal winter season.
Winter Temperature and Precipitation Outlook
Temperature
Climate Prediction
Center Outlooks
Produced August 2D, 2015
for Dec -Jan -Feb 2015116
Numbers Indicate percent
chance of temperature
in warmest one -third and
of precipitation in wettest
one -third
CPC 11 http:llwww cpc.
noep.naaa.gov/products/
predi cti onsll on grange!
Precipitation
The official NOAA outlooks for Dec - Jan -Feb temperature and precipitation
for the West reflect the development of a strong El Nino during this period.
Above normal temperatures and below normal precipitation are anticipated
in the Pacific Northwest and northern Rockies. There is a 50% chance that
winter precipitation totals will be in the top 33% of historic values across far
southern California, Arizona, and New Mexico. The forecast is less confident
moving northward. These outlooks are likely to change as we track the progress
of El Nino and other climate variables in the coming months. This El Nino
event is forecast to rival previous strong El Nino events, such as 1982183
and 1997198. During those events, above normal precipitation extended
northward into northern California, the Great Basin, and the coastal Pacific
Northwest. However, no two years are identical even when a strong El Nino
is present. There are other sources of variability and :uncertainty that can
impact this winter's weather. These include background warming of the ocean
and atmosphere, unique ocean temperature patterns, and other atmospheric
patterns besides El Nino.
IM :�
El Nino and the West
A strong El Nino is predicted during winter
2015116.
El Nino is a warming of the Pacific Ocean
that occurs along the equator between
South America and the Date Line and can
influence the storm track over the West. El
Nino conditions do not "cause" individual
storms but rather influence their frequency
and characteristics.
El Nino is typically associated with wetter
than normal conditions along the southern
third of California eastward following the
U.S.- Mexico border and drier than normal
conditions in the Inland Northwest and
northern Rockies.
El Nino is not usually a good predictor
of winter precipitation for northern
California and the northern Great Basin,
though model simulations suggest a very
strong EI Nino may drive above normal
precipitation in this area and further north.
Past Strong El NiAo Events
Above: El Nino events with an Oceanic
Nino Index (ONI), an indicator based
on equatorial SSTs, peaking at > =1.5.
Below: 92% of 26 dynamical and
statistical climate models favor a strong
El Nino, with most peaking during the
late fall or early winter of 2015116.
El Nino Strength 201SI16
Potential Ell Niho Event Intensity
4%: Moderate
I go El ho
Nn�/ Meawnd.. diwb w+perYisMCYmHw7anc� +bhn+ol
1
1957/1958
1.7
2
7
1965/1966
1.8
3
197211973
2.0
4
1982119113
2.1
5
1991/1992
1.6
6
199711998
2.3
7 (TBD)
2015/2016
2.3 (predicted)
Above: El Nino events with an Oceanic
Nino Index (ONI), an indicator based
on equatorial SSTs, peaking at > =1.5.
Below: 92% of 26 dynamical and
statistical climate models favor a strong
El Nino, with most peaking during the
late fall or early winter of 2015116.
El Nino Strength 201SI16
Potential Ell Niho Event Intensity
4%: Moderate
I go El ho
Nn�/ Meawnd.. diwb w+perYisMCYmHw7anc� +bhn+ol
California Precipitation During Prior "Strong" El Nil3o Events
j057168 'ki 166 1972173 200%
wet
1 100%
Normal
%1982183 %19191192 1997198 Dry
25%
Image courtesy of NWS Sacramento Data: PRISM, OSU
Above: Precipitation total by Water Year (Oct 1- Sep 30). Of the 6 strong El Nihos on
record, only half produced statewide above normal precipitation: 1957158, 1982183, and
1997/98. Flooding in California can occur in both El Nino and non-El Niho years. Most
of the state's largest floods occured during non-El Nino conditions, such as in the winter
of 1996197, a neutral year. Extreme rainfall and flooding in CA is often associated with
surges of subtropical moisture into the region that are known as atmospheric rivers
(ARs). Research suggests ARs are less frequent in the eastern Pacific during El Nino,
though the relationship between El Nino and ARs is the subject of active investigation.
Current Sea Surface Temperature (SST) Anomalies
ON
40°
o°
4a°
ao°
Blob' —
..._.... -- ------ ...r...... ....
El Nino area
s Aug 23-Sep 2 2015
ap a0 °E 1201 160°W 120V W1W 04
Left: Over the past 2 years,
much above normal SSTs were
observed across the northeastern
Pacific and along the U.S. West
Coast. Scientists are referring to
this area as "The Blob."
Data: NOAAIESRUPSD
Images: Ben Hatchett, NV SCO
4.5 -2 0 2 4.5
Degrees C, Base Period: 1981 -2010
The Blob (above) formed under the persistent upper level ridge that has been present
over the eastern Pacific during much of the last 4 winters. Under the ridge, ocean waters
were warmed by the sun, reduced upwelling, and less wave mixing. The Blob's influence
on winter 2015116 is not well understood, though it is expected to play some role.
Past Strong El Nino SSTAnomalies
WN ,i..
40 °N �° ^ •.•
� h
I -
ao °s December 1982
09 1Z0 E - 1401W 120 eo as
80 °N
a° - -
40'8 J-11
eo °s Dec :em ber 1997 —
0 601E 12VE 180W 1 20 Gid} °W e°
Each El Nino event has
different characteristics that can
affect the way it impacts the
western US. Both the 1982183
(left, top) and 1997198 (left,
bottom) had SST anomalies
peak offshore of South America,
but other El Niho events
(2004105, not shown) have
peaked towards the central
equatorial Pacific. Past very
strong El Niho events shown
to left did not have a "blob%
like feature, so there is not a
good analog for this scenario.
Timing and characteristics of
precipitation during El Nifio
events may vary as well; CA's
8- Station Index saw well above
normal precipitation in Oct/Feb/
Mar of 1982183, but only during
Jan -Feb of 1997198.
El Nifio and California Drought
California just experienced 4 years
of drought. Recovery from drought
in California is a multi- faceted issue.
Storm location is important as most of
California's major reservoirs are located
in the northern part of the state where
the relationship between El Nino and
precipitation is generally weak. A healthy
Sierra Nevada snowpack is important
for drought recovery as well. Intensity
of precipitation also affects groundwater
replenishment and runoff into reservoirs; El
Nino does not provide insight to this.
Looking towards Red
Slate Peak and the
upper Convict Greek
watershed in the High
Sierra. Runoff from this
area provides water
resources to eastem
Sierra communities and
to Los Angeles via the
Los Angeles Aqueduct.
Photo: Ben Hatchett
March 2010
Western Region Partners
Western Regional Climate Center
wrcc.dri.edu
National Integrated Drought Information
System (NIDIS)
drought.gov
Western Region Climate Services Director
ncdc.noaa.gov /resd
Western Governors' Association
westgov.org
Western States Water Council
westgov.org /wswc
NOAAIESRL Physical Sciences Division
esri.noaa.gov /psd
NOAA Climate Prediction Center
www.cpc.ncep.noaa.gov
National Centers for Environmental
Information (NCEQ
wvvw.ncdc.noaa.gov
USDAINRCS National Water and Climate
Center - www.wec,nres.usda.gov
National Interagency Fire Center
www,nifc.gov
DOI WaterSIVART
www.usbr.gov/WaterSMART
Western Water Assessment
wwa.colorado.edu
Climate Assessment for the Southwest
climas.arizona.edu
California Nevada Applications Program
meteora.ucsd.edu /cnap
Climate Impacts Research Consortium
pnwchmate.org /resources
NWS River Forecast centers
water.weather.gov/ahps/rfcJrfc.php
NOAA Fisheries Service
www.nmfs.noaa.gov/
NWS Western Region Forecast Offices
www.wrh.naaa.gov/
State Climatologists
stateclimate.org