A review of 2005-06 Extreme Events

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A review of 2005-06 Extreme Events
Klaus Weickmann, ESRL/PSD

• Background and variables used
• Extreme sea surface temperatures
• Focus on 850 mb temperature anomalies
• also Dartmouth Flood Monitor
• 1968-2006 and Oct 2005-Sept 2006
• gt 2 sigma anoms lt -2 sigma anoms
• Northern Hemisphere time series of area
• Global map of days with extreme temps
• Extreme cases (1998, 2002, 2003, 2005, 2006)
• Speculation on Synoptics
• USA monthly temp and precip xtremes

Special thanks to Cathy Smith, Don Hooper, Klaus
Wolter, Alex McColl, Barry McInnes
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May-Sep 1998, 2002, 2003, 2005, 2006 composites
on right
SSTA
H
H
L
L
L
H
H
200uv
OLRA
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Temperature 850 hPa
Annual mean standard deviation 1968-2006
Annual mean 1968-2006
Note full seasonal cycle of standard deviation
used in analysis that follows
4
98
850 temperature Oct 68 Sep 06 91-day running
mean
06
03
05
lt -2 s
02
gt 2 s
area 20-90N
Jan 77
Pinatubo
82-83
Mean 2.46 2.06
5
Oct 1968 to Sep 2006
days gt 2 s
Shading 2-4, 4-6, gt6
days lt -2 s
orography not blocked out
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11 Sep
850 temperature Oct 05 Sep 06 daily plus
91-day running mean
15-16 Aug
lt -2 s
gt 2 s
21 Jul 8.7
area 20-90N
11 Jul 2
7
3.5C!
Oct 1968 to Sep 2006
850 mb temperature anomalies (degrees
C) Shading 0.5-1.0, 1.0-2.0, 2.0-3.0
850 mb temperature normalized anomalies Shading 0
.5-1.0, 1.0-1.5
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Oct 2005 to Sep 2006
days gt 2 s
Shading 5-10, 10-15, gt15
days lt -2 s
orography not blocked out
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98
850 temperature Oct 68 Sep 06 91-day running
mean
06
03
05
lt -2 s
02
gt 2 s
area 20-90N
Jan 77
Pinatubo
82-83
Mean 2.46 2.06
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Percent of days out of 91 with 850 hPa
normalized temperature anomalies greater than 2
sigma Shading levels 8-16, 16-32, 32-48, gt48
Jun 13 Sep 11, 1998
May 20 Aug 18, 2002
Jul 14 Oct 3, 2005
Aug 3 Nov 3, 2003
Jul 12 Oct 10, 2006
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Daily dates with maxima in area gt 2 sigma
during Jul 12 Oct 10 2006
USA west coast heat wave
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Speculation on Synoptics Two areas of tropical
forcing due to extreme SSTs in warm pool
region MJO-like behavior faster time scale and
consolidation of anomalies, esp.
summer/fall? Leads to more transient
split flows with stronger westerly winds in
tropics subtropics Favors extreme ridging
events and subtropical jets spiraling into
mid-latitudes Reflecting increased heat
transport due warm tropical SSTs?
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Summary and Conclusions

• Expanded gt 29C SSTs in warm pool region,
  especially since July 2001
• 2005-06 continues recent string of extreme
  temperatures during summer/fall, and more general
  trend of increasing warm extremes
• gt 2 sigma more often, over larger area and
  especially at warm time of year
• Synoptic discussion of Nov-Dec 2005 (USA west
  coast precip), April 2006 (CA precip) and June
  2006 (USA east coast precip) extreme events _at_
  http//www.cdc.noaa.gov/MJO/Forecasts/climate_disc
  ussions.html

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Possible impact of assimilation model errors on
results?