IntermtntClimateSummaryJune2006

• Title: Intermountain West Climate Summary
• Date: 6/22/2006
• Description: Water Availability Task Force Meeting Presentation
• Basin: Statewide
• Drought Mitigation - Doc Type: Presentation

INTERMOUNTAIN WEST CLIMATE SUMMARY, JUNE 2006

EI Nino Status and Forecast

Source: NOAA Climate Prediction Center, International Research Institute For Climate and Society

According to both the NOAA/CPC sea surface tem-
peratures (SSTs) in the Nino 3.4 region, a critical indi-
cator for the ENSO state, are currently in the average
range, about 0.30 C. Lo\:v level and upper level winds
in the tropical Pacific also averaged close to normal
in the last month or so. These indicators suggest that
ENSO is in a neutral phase.
According to both the NOAA/CPC and the Inter-
national Research Institute for Climate and Society
(IRI), ENSO-neutral conditions are expected to prevail
through the rest of 2006. IRI's "ENSO Update" issued
June 13th says that the western and central equatorial
Pacific have \:varmed to about 0.5 deg C above average
since mid-May 2006, but the surface and sub-surface
temperature anomalies that currently exist in the tropi-
cal Pacific are not particularly large or well structured
to indicate an imminent EI Nino event. The observa-
tions and models suggest that neutral conditions will
be in place at least through mid-2006. Most of a large
set of dynamical and statistical forecast models pre-
dict neutral conditions continuing throughout 2006.
IRI projects the probability of a La Nina or EI Nino
conditions for June-July-August (JJA) is less than the
climatologically expected odds of 25%, and neutral
conditions are favored throughout 2006 starting \:vith
a 80% likelihood for JJA. Historically, EI Nino and La
Nina events tend to develop in the April-June period,
and they reach their maximum strength in December-
February.

Notes
Two graphics in Figure 13a produced by NOAA show the
observed SST (upper) and the observed SST anomalies (low-
er) in the Pacific Ocean. This data is from the TOGA/TAO Ar-
ray of 70 moored buoys spread out over the Pacific Ocean,
centered on the equator. These buoys measure temperature,
currents and winds in the Pacific equatorial band and transmit
data in real-time. NOAA uses these observations to predict
short-term (a few months to one year) climate variations.
Figure 13b shows multiple forecasts for SST in the Nino
3.4 region for nine overlapping 3-month periods from Sep-
tember 2005 to July 2006. "Nino 3.4" refers to the region of
the equatorial Pacific from 1200W to 1700W and SON to 50S,
which is one basis for defining ENSO sea surface tempera-
ture anomalies. Initials at the bottom of the graph represent
groups of three months (e.g. SON = Sept-Nov). The expected
skills of the models, based on historical performance, are not
equal to one another. The skills also generally decrease as
the lead-time increases. Forecasts made at some times of the
year generally have higher skill than forecasts made at other
times of the year. They are better when made between June
and December than between February and May. Differences
among the forecasts of the models reflect both differences in
model design and actual uncertainty in the forecast of the pos-
sible future SST scenario.

Observed Sea Surface Temperature (CO)

20N

30

~

10N

EO

105

205

~60W
1 1
23 24

140W
I 1
25 26

120W 100W
1 I
27 28 29

Observed Sea Surface Temperature Anomalies (CO)

20N

10N

EO

105

205

I
-4

120"W ~ (jaw
1 1_
2 3 4

1
-2

I
-1

I
0.5

Figure 13a. Two graphics showing the observed SST (upper) and the
observed SST anomalies (lower) in the Pacific Ocean. The Nino 3.4 region
encompasses the area between 120oW-170oW and SON-50S. The graphics
represent the 7-day average centered on June 7,2006.

Model Forecasts of ENSO from June 2006

3IRI!

>.
rn
E
o
C
<(
~ 0.5
en
-.;t
M
o
IC
Z

o

-0.5

-1

-1.5

Figure 13b. Forecasts made by dynamical and statistical models for sea
surface temperatures (SST) in the Nino 3.4 region for nine overlapping
3-month periods from June 2006 through April 2007 (released June, 13
2006). Forecasts are courtesy of the International Research Institute (IRI)
for Climate and Society.

On the Web
- For a technical discussion of current EI Nino conditions, visit: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/
enso_advisory/.
- For updated graphics of SST and SST anomalies, visit this site and click on "Weekly SST Anomalies": http://www.cpc.ncep.
noaa. gov /prod ucts/preci piC WI i n k/MJ 0/ enso. shtm I#cu rrent.
- For more information about EI Nino, including the most recent forecasts, visit: http://iri.columbia.edu/climate/ENSO/.

FORECASTS 11 7