1. The Effects of Climate Variability on Buffalo, NY Winters
Robert Hamilton
National Weather Service
Buffalo, NY

2. Climate Variability
…variations in the mean state of the climate on all temporal and spatial scales beyond that of individual weather events. The variability may be due to natural internal processes within the climate system, or to variations in natural or anthropogenic external forcing.
…a fluctuation in climate, which could last for a specified period of time, usually of the order of seasons to years to decades.
…changes in the long-term characteristics of weather.

3. Methodology
CPC’s Oceanic Nino Index (ONI) based on 3 month running mean of Equatorial Pacific SST
Threshold of +/- 0.5C for a Minimum of 5 Consecutive months
Used Winter Values of ONI from 1950 through last winter ( )

4. Methodology…..
NAO Index Based on Difference in MSLP Anomaly between Iceland and Gibraltar.
Used Winter Values of this Index to Present
Unlike ENSO….no real defined ‘Neutral Phase’

5. Methodology….
Buffalo Temperature and Snowfall Departures Since 1950 Were Averaged…Then Grouped With Various ENSO and NAO phases.
The Resulting Temperature and Snowfall Trends Will Be Discussed.

6. ENSO
NAO

7. Mod-Strong El Nino

8. Mod-Strong La Nina

9. El Niño:
Extended Jet Stream
More zonal flow over U.S.
South shift of storm track
Weaker Hudson Bay Low
Fewer arctic outbreaks
La Niña:
Retracted Jet Stream
More meridional flow
Blocking over N. Pac
Stronger Hudson Bay Low
More arctic outbreaks

10. El Nino

11. El Nino

12. Temperature Departure
…For Buffalo…
+1.5 F Average Monthly
Temperature Departure
For All El Nino*
66% of Dec-February
Months Have Had Above
Normal Temperatures…
….The majority of
the Remaining Months
Featured Weak El Ninos
And/Or -NAO’s.
* Dec-Feb

13. Occurrence of Above Normal Temperatures is Related
Weak El Nino Temperature Trends
(Nov through March)
38%
The data shows that the
Occurrence of Above Normal
Temperatures is Related
To the Strength of the
El Nino Episode. - +
62%
Moderate El Nino Temperature Trends
(Nov through March) -
20% +
El Nino Exhibits a
Moderate Statistical
Correlation (.52) to Temperature.
80%
Strong El Nino Temperature Trends
(Nov through March) +
100%

14. Further Evidence That El Nino Strength is Important
Nov Dec Jan Feb Mar
Weak El Nino (-.34 deg F)
Moderate El Nino (1.9 deg F)
Strong El Nino (3.2 deg F)

15. Buffalo Toronto Detroit
Weak El Nino deg F
Moderate El Nino 1.9 deg F
Strong El Nino deg F
(F)
Nov Dec Jan Feb Mar
Toronto
Weak El Nino deg F
Moderate El Nino deg F
Strong El Nino deg F
Nov Dec Jan Feb Mar
Detroit
Weak El Nino deg F
Moderate El Nino deg F
Strong El Nino deg F
Nov Dec Jan Feb Mar

16. Buffalo Temperature Departures During Moderate to Strong El Nino’s
Deg F

17. El Niño:
Extended Jet Stream
More zonal flow over U.S.
South shift of storm track
Weaker Hudson Bay Low
Fewer arctic outbreaks
La Niña:
Retracted Jet Stream
More meridional flow
Blocking over N. Pac
Stronger Hudson Bay Low
More arctic outbreaks

18. Interesting La Nina Statistics
56% of La Nina Winter Months Exhibit Above Normal Temperatures for Buffalo
Above Normal Temperature Departures can be Just as Significant as those from El Nino
La Nina often produces ‘mild winters’ for Buffalo….but helps to provide some of the coldest months.

19. La Nina

20. La Nina

21. Buffalo Temperature Departures During Moderate to Strong La Nina’s

22. (Nov-March) El
Nino El
Nino La
Nina
Deg F La
Nina
Weak
Moderate
Strong

23. (1 inch)

24. ENSO Advantages Drawbacks
Moderate to strong events typically produce Positive Temperature Anomalies
The stronger the ENSO....the higher the confidence level
Weak ENSO events reveal no statistical correlations/trends.
Statistical Correlations using ALL ENSO events are not significant.
Very weak correlations to snowfall. Slightly higher correlations found with La Nina.

25. ENSO
NAO

26. What is the North Atlantic Oscillation?
Difference of normalized sea level pressure between Iceland and the Azores.
Highly variable occurrence with little variation in mean structure from month to month.
Corresponding index fluctuates from month to month and week to week. El Nino can persist for 2-3 years.
NAO is most noticeable during the winter (November - April).

27. The Two Phases of NAO
Positive NAO
Negative NAO

28. Positive NAO
A stronger than usual Subtropical High and a deeper than normal Icelandic Low.
Strong North Atlantic Jet Drains Arctic Air Away from N.America
Eastern U.S. receives “mild and wet” winter conditions.**
** M. Visbeck Feb 2000 (Columbia University)
J. Hurrell (NCAR)

29. Positive NAO

30. Negative NAO Weak Subtropical High and Weak Icelandic Polar Low.
Arctic Air Pools Over Nrn Canada and Settles Southward Due to Reduced North Atlantic Flow.
U.S. East Coast receives more cold air outbreaks and hence snowy weather conditions.**
** M. Visbeck Feb 2000 (Columbia University)
J. Hurrell (NCAR)

31. Negative NAO

32. - NAO + NAO Looking at 500mb…..
The Positive NAO 500mb Chart Features a Strong
Zonal Flow….while the Negative NAO Chart Shows
Increased Amplitude with a Greenland Block in Place.

33. 925 mb Temps
+ NAO
-NAO
Colder Boundary Layer Conditions During a Negatively Phased
NAO with Temperatures Averaging About 5 deg Celsius Lower.

34. NAO Advantages Drawbacks
Moderate Temperature Correlation For Significant Events
Strongest Temperature Correlations Found Over the Western Great Lakes
Most Significant Snow Correlations Found in the Lake Effect Snowbelt areas (Buffalo!)
Very weak month to month temperature correlation
Only a ‘hint’ of a month to month correlation found for snow (less than 0.30).
Only weak correlation for snow found away from the LES Belts.

35. What Are The Combined Effects?
ENSO
NAO

36. ENSO and NAO Do They Have a Combined Effect?
Moderate
Correlation
ENSO
+ NAO
Weak
Correlation
NAO
Essentially
No Correlation
ENSO

37. ENSO and NAO Do They Have a Combined Effect?
La Nina
+2.34
El Nino
+2.3
El Nino
+1.4
La Nina
+0.94
ENSO Component Only
ENSO and +NAO Components

38. The cooling effects of a –NAO are clearly visible
El Nino
+1.4
La Nina
+0.94
El Nino 0.3
La Nina
-.82
ENSO Component Only
ENSO and –NAO Component
The cooling effects of a –NAO are clearly visible

39. Moderate to Strong El Nino Pattern
El Nino, +NAO
+45m
+70m
El Nino, -NAO
500 mb Anomalies During
Moderate to Strong El Nino Pattern
EL Nino Alone
EL Nino and +NAO
EL Nino and -NAO

40. Warmest Averages Found During El Nino / + NAO
925 mb Temp Anomalies During
Moderate to Strong El Nino Pattern
EL Nino Alone
EL Nino and +NAO
EL Nino and –NAO
Warmest Averages Found
During El Nino / + NAO

41. El Nino/Positive NAO
Polar
Jet
Sub-Tropical
Jet

42. Broader Southwest Flow Trof Based Further East
La Nina with
Positive NAO
La Nina with
Negative NAO
Higher Heights and
Broader Southwest Flow
Trof Based Further East

43. This begs the
Question……
When does it get
Cold in Buffalo?

44. Average Temperature Departures in Degrees F
- NAO
+ NAO
Strong La Nina
0.76
2.26
Moderate La Nina
0.16
2.38
Weak La Nina
-2.06
2.32
Neutral ENSO
-0.73
1.44
Weak El Nino
0.61
0.74
Moderate El Nino
0.18
3.03
Strong El Nino
2.04
3.23
18 of the top 20 warmest
-NAO
0.46
+NAO
2.32
-0.73
1.50
1.11
3.13
Average Temperature Departures in Degrees F

46. Winter 1976-77 Neutral ENSO Strongly Negative NAO
January 500mb Composite
Neutral ENSO…Negative NAO
Winter
Neutral ENSO
Strongly Negative NAO
Jan 500mb Hgt Anomaly Comp.
Neutral ENSO…Negative NAO

47. 925mb Temp Anomaly During a Combined Neutral ENSO and Negative NAO

48. What about Snowfall??

49. Unfortunately, ENSO and the NAO do not correlate well to snowfall
Nov
Dec
Jan
Feb
Mar
Total
La Nina
10.8
26.3
24.2
16.2
15.7
93.2
Neutral
10.9
28.9
25.9
17.9
10.7
94.2
El Nino
12.8
16.3
25.5
18.7
13.4
86.7

50. Average Snowfall from Past 50 Years in Buffalo
Nov
Dec
Jan
Feb
Mar
Total
La Nina
10.8
26.3
24.2
16.2
15.7
93.2
Neutral
10.9
28.9
25.9
17.9
10.7
94.2
El Nino
12.8
16.3
25.5
18.7
13.4
86.7
While snowfall during December El Nino events averages 36% below normal….
The 5 month winter average is only 7% below normal.
Statistically….No Correlation Can Be Drawn Between ENSO and Snowfall.
This was also found by a BGM NWS study for SE NY and NE PA,
also by a BUF Student Intern Study on the Great Lakes Region.
Only weak correlations have been found between La Nina and snowfall with
Even less impressive statistics for El Nino.

51. Buffalo Temperature Departures During Moderate to Strong El Nino’s
Deg F

52. No single month* or series total has a departure of more than 16%
Toronto
Nov
Dec
Jan
Feb
Mar
Total
La Nina
3.2
12.6
12.9
10.0
10.6
49.3
Neutral
3.3
9.9
13.4
8.3
45.0
El Nino
4.0
11.8
11.6
8.2
5.7
40.9
No single month* or series total has a departure of more than 16%
from normal, but all sites show a trend to less snowfall during El Nino.
Detroit
Nov
Dec
Jan
Feb
Mar
Total
La Nina
2.6
11.9
10.8
9.4
8.0
42.7
Neutral
2.7
8.1
9.8
10.1
6.8
37.5
El Nino
8.2
11.2
6.7
6.2
34.9

53. Results of Combined ENSO / NAO Events
Gains Generally in Temp Arena Only
Much Improved Temperature Correlations
Certain Combinations Provided Evidence for More Dramatic and Conclusive Temperature Anomalies
Still No Help with Snowfall Prediction (Lake Effect and Number of Synoptic Storms Likely a Contributor to this)

54. Who Benefits? Utility Companies… Particularly Gas Related
Winter Recreational Sites….Ski Resorts
General Public Via CPC

55. What About This Winter??
Mark Rodwell...Researcher for Met Office U.K. has 67% Accuracy Forecasting Predominant Phase of the NAO.
Forecast for This Winter is a POSITIVE NAO.
Given CPC’s Indication of a Weak EL Nino…. What Can Buffalo Expect This Winter?

56. Average Temperature Departures in Degrees F
- NAO
+ NAO
Strong La Nina
0.76
2.26
Moderate La Nina
0.16
2.38
Weak La Nina
-2.06
2.32
Neutral ENSO
-0.73
1.44
Weak El Nino
0.61
0.74
Moderate El Nino
0.18
3.03
Strong El Nino
2.04
3.23
-NAO
0.46
+NAO
2.32
-0.73
1.50
1.11
3.13
Average Temperature Departures in Degrees F

57. Questions?