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

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Presentation on theme: "The Effects of Climate Variability on Buffalo, NY Winters Robert Hamilton National Weather Service Buffalo, NY."— Presentation transcript:

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

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

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

15 Nov Dec Jan Feb Mar Buffalo Weak El Nino deg F Moderate El Nino 1.9 deg F Strong El Nino 3.2 deg F Toronto Weak El Nino -1.1 deg F Moderate El Nino 0.6 deg F Strong El Nino 2.4 deg F Detroit Weak El Nino -0.1 deg F Moderate El Nino 1.6 deg F Strong El Nino 2.8 deg F

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

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

22 WeakModerateStrong Deg F (Nov-March) La Nina El Nino La Nina El Nino

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 NAONegative 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 1995 (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 1995 (NCAR)

31 Negative NAO

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

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

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 ENSO NAO What Are The Combined Effects?

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

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

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

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

40 El NinoEl Nino, +NAO 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 La Nina with Negative NAO La Nina with Positive NAO Higher Heights and Broader Southwest Flow Trof Based Further East

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

44 - NAO - NAO + NAO + NAO Strong La Nina Moderate La Nina Weak La Nina Neutral ENSO Weak El Nino Moderate El Nino Strong El Nino NAO -NAO NAO Average Temperature Departures in Degrees F 18 of the top 20 warmest

45

46 January 500mb Composite Neutral ENSO…Negative NAO Jan 500mb Hgt Anomaly Comp. Neutral ENSO…Negative NAO Winter Neutral ENSO Strongly 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 Neutral El Nino

50 Nov Dec Jan Feb Mar Total La Nina Neutral El Nino Average Snowfall from Past 50 Years in Buffalo 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 Toronto Nov Nov Dec Dec Jan Jan Feb Feb Mar Mar Total Total La Nina Neutral El Nino Detroit Nov Nov Dec Dec Jan Jan Feb Feb Mar Mar Total Total La Nina Neutral El Nino 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.

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 - NAO - NAO + NAO + NAO Strong La Nina Moderate La Nina Weak La Nina Neutral ENSO Weak El Nino Moderate El Nino Strong El Nino NAO -NAO NAO Average Temperature Departures in Degrees F

57 Questions?


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