Physical Basis For
The Winter 01-02 Forecast
http://www.cpc.ncep.noaa.gov
OPIS 2000
Natio nal Suppl y Sum mit
Seasonal Temperature Variability is Primarily Caused by:
Natural climate variability
- El Nino/Southern Oscillation Phenomena (ENSO)
- Pacific Decadal Oscillation (PDO) - Arctic Oscillation (North Atlantic Oscillation)
Long term trends
Recent Winter Temperature Anomalies (DJFM)
ENSO Neutral Winters Average of
La
Nina
98/99 and 99/00El Nino 97/98
Decade of the 1990’s
Degrees Celsius
El Nino Southern Oscillation El Nino Southern Oscillation
Phenomena
Phenomena
Arctic Oscillation (AO) Arctic Oscillation (AO)
High Index Phase Low Index Phase
AO Index (JFM 1950-1999)
Year
Global Temperatures the Past Three Global Temperatures the Past Three Years Were Primarily a Result of ENSO Years Were Primarily a Result of ENSO
and the Underlying Warm Trend and the Underlying Warm Trend
Observed
Observed Simulated Using Simulated Using Observed Ocean Observed Ocean
Temperatures
Temperatures
Status of the Natural Modes Status of the Natural Modes
Of Climate Variability This Winter Of Climate Variability This Winter
ENSO: Current forecasts indicate this will be near neutral
AO(NAO): Currently no capability to forecast seasonal phase: return to near neutral suggested by trends over the past 13 years
The lack of ENSO related forcing suggests that the coming winter will likely not be as warm as those of the late 90’s and on par with last winter
The unpredictability of the AO introduces large uncertainty
Implications for Winter Forecast:
Winter temperature Anomalies (
Winter temperature Anomalies (
00C) C)
1950s
1960s
1970s
1980s
1990s
Seasonal Forecasts are referenced to a 1961-1990
base period, i.e. a relatively cool period
Probability forecasts indicate changes in the likelihood of the favored category (i.e. above normal, normal, below normal). For example a value of “20” needs to be added to 33% (climatological odds) to arrive at the forecast odds of 53%
change of being above normal.
Forecasts are relative to the 1961-1990 climatology.
“CL” indicates the forecast tools give no guidance, i.e. be prepared.
A
A C L A
A
A
2 0
2 0
0
0 5
5
1 0 1 0
A
C L
5
A
A A A
5
1 0
1 0
2 0
1 0
1 0 5
1 0
0
0 5
1 0
Th is g
rap hic w ill b
e u pd
ate d w ith th e fo
rec ast issu
ed O ct 1
2, 2 000
Climate Outlook Temperature
December-February 2001 January-March 2001
Four Estimate of Trends
OCN- untempered OCN (ENSO-neutral)
Residual “Trend”
Class limits for standardized anomalies *100: upper 33% (45) upper 20% (85)
