Presentation on theme: "The Effects of Climate Variability on Buffalo, NY Winters"— Presentation transcript:
1 The Effects of Climate Variability on Buffalo, NY Winters Robert HamiltonNational Weather ServiceBuffalo, 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 MethodologyCPC’s Oceanic Nino Index (ONI) based on 3 month running mean of Equatorial Pacific SSTThreshold of +/- 0.5C for a Minimum of 5 Consecutive monthsUsed 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 PresentUnlike 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.
9 El Niño:Extended Jet StreamMore zonal flow over U.S.South shift of storm trackWeaker Hudson Bay LowFewer arctic outbreaksLa Niña:Retracted Jet StreamMore meridional flowBlocking over N. PacStronger Hudson Bay LowMore arctic outbreaks
12 Temperature Departure …For Buffalo…+1.5 F Average MonthlyTemperature DepartureFor All El Nino*66% of Dec-FebruaryMonths Have Had AboveNormal Temperatures…….The majority ofthe Remaining MonthsFeatured Weak El NinosAnd/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 theOccurrence of Above NormalTemperatures is RelatedTo the Strength of theEl Nino Episode.-+62%Moderate El Nino Temperature Trends(Nov through March)-20%+El Nino Exhibits aModerate StatisticalCorrelation (.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 MarWeak 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 FModerate El Nino 1.9 deg FStrong El Nino deg F(F)Nov Dec Jan Feb MarTorontoWeak El Nino deg FModerate El Nino deg FStrong El Nino deg FNov Dec Jan Feb MarDetroitWeak El Nino deg FModerate El Nino deg FStrong El Nino deg FNov Dec Jan Feb Mar
16 Buffalo Temperature Departures During Moderate to Strong El Nino’s Deg F
17 El Niño:Extended Jet StreamMore zonal flow over U.S.South shift of storm trackWeaker Hudson Bay LowFewer arctic outbreaksLa Niña:Retracted Jet StreamMore meridional flowBlocking over N. PacStronger Hudson Bay LowMore arctic outbreaks
18 Interesting La Nina Statistics 56% of La Nina Winter Months Exhibit Above Normal Temperatures for BuffaloAbove Normal Temperature Departures can be Just as Significant as those from El NinoLa Nina often produces ‘mild winters’ for Buffalo….but helps to provide some of the coldest months.
24 ENSO Advantages Drawbacks Moderate to strong events typically produce Positive Temperature AnomaliesThe stronger the ENSO....the higher the confidence levelWeak 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.
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).
28 Positive NAOA stronger than usual Subtropical High and a deeper than normal Icelandic Low.Strong North Atlantic Jet Drains Arctic Air Away from N.AmericaEastern U.S. receives “mild and wet” winter conditions.**** M. Visbeck Feb 2000 (Columbia University)J. Hurrell (NCAR)
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)
32 - NAO + NAO Looking at 500mb….. The Positive NAO 500mb Chart Features a StrongZonal Flow….while the Negative NAO Chart ShowsIncreased Amplitude with a Greenland Block in Place.
33 925 mb Temps+ NAO-NAOColder Boundary Layer Conditions During a Negatively PhasedNAO with Temperatures Averaging About 5 deg Celsius Lower.
34 NAO Advantages Drawbacks Moderate Temperature Correlation For Significant EventsStrongest Temperature Correlations Found Over the Western Great LakesMost Significant Snow Correlations Found in the Lake Effect Snowbelt areas (Buffalo!)Very weak month to month temperature correlationOnly 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.
42 Broader Southwest Flow Trof Based Further East La Nina withPositive NAOLa Nina withNegative NAOHigher Heights andBroader Southwest FlowTrof Based Further East
43 This begs theQuestion……When does it getCold in Buffalo?
44 Average Temperature Departures in Degrees F - NAO+ NAOStrong La Nina0.762.26Moderate La Nina0.162.38Weak La Nina-2.062.32Neutral ENSO-0.731.44Weak El Nino0.610.74Moderate El Nino0.183.03Strong El Nino2.043.2318 of the top 20 warmest-NAO0.46+NAO2.32-0.731.501.113.13Average Temperature Departures in Degrees F
49 Unfortunately, ENSO and the NAO do not correlate well to snowfall NovDecJanFebMarTotalLa Nina10.826.3188.8.131.523.2Neutral10.928.925.917.910.794.2El Nino12.816.325.518.713.486.7
50 Average Snowfall from Past 50 Years in Buffalo NovDecJanFebMarTotalLa Nina10.826.3184.108.40.2063.2Neutral10.928.925.917.910.794.2El Nino12.816.325.518.713.486.7While 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 withEven 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% TorontoNovDecJanFebMarTotalLa Nina3.212.612.910.010.649.3Neutral3.39.913.48.345.0El Nino4.011.8220.127.116.110.9No 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.DetroitNovDecJanFebMarTotalLa Nina2.611.910.89.48.042.7Neutral18.104.22.1680.16.837.5El Nino22.214.171.124.234.9
53 Results of Combined ENSO / NAO Events Gains Generally in Temp Arena OnlyMuch Improved Temperature CorrelationsCertain Combinations Provided Evidence for More Dramatic and Conclusive Temperature AnomaliesStill 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 ResortsGeneral 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+ NAOStrong La Nina0.762.26Moderate La Nina0.162.38Weak La Nina-2.062.32Neutral ENSO-0.731.44Weak El Nino0.610.74Moderate El Nino0.183.03Strong El Nino2.043.23-NAO0.46+NAO2.32-0.731.501.113.13Average Temperature Departures in Degrees F