Synoptic Patterns Associated with the 6-8 January 2017 South Texas Cold Air Outbreak Event

WAYLON COLLINS NOAA/NWS/SR/WFO CORPUS CHRISTI 27 JANUARY 2018 Outline

 Eastern U.S. (east of Rockies) Cold Air Outbreak (CAO) events of short duration (≤ 5 days) precursor patterns  Large Scale Meteorological Patterns (LSMP) associated with eastern CAO event onset  Analysis of 6-8 January 2017 CAO event in context of precursor patterns and LSMP.  1-4 January 2018 CAO event and the Stratospheric Polar Cold Air Outbreak Definition and Development

Cold Air Outbreak (CAO) Event Departure of cold air mass into a warmer region (Kolstad 2010)

Typical North American wintertime CAO event development process Two stage process (Grotjahn et al. 2016) 1. Formation of an air mass/surface over 2. Rapid horizontal transport of the air mass to lower latitudes (enabled by a lower level circulation associated with a large scale meteorological pattern)

Cold air partially offset by adiabatic warming in response to 100-300mb descent (Walsh et al 2001)

Kolstad, E. W., Breiteig T., and A. A. Scaife, 2010: The association between stratospheric weak events and cold air outbreaks in the , Q. J. R. Meteorol. Soc., 136: 886-893. Grotjahn R., Black R., Leung, R. et al., 2016: North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends, Clim Dyn,. 46: 1151. Walsh, J. E., A. S. Philips, D. H. Portis, and W. L. Chapman, 2001: Extreme cold outbreaks in the United States and Europe, 1948–99. J. Climate, 14, 2642–2658 Eastern North American (NA) Cold Air Outbreak (CAO) Precursor Patterns Grotjahn (2016)  Anomalously high MSLP coincident with polar air mass  Negative Phase of the North Atlantic Oscillation Teleconnection Pattern  Positive Phase of the Pacific North American Teleconnection Pattern  Anomalously weak stratospheric polar vortex Teleconnection: Correlation between geopotential heights (on a specific pressure surface) at widely separated points on earth (Wallace and Gutzler, 1981)

Grotjahn, R., Black, R., Leung, R. et al., 2016: North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends, Clim Dyn,. 46: 1151. Wallace, J. M., and D. S. Gutzler (1981), Teleconnections in the geopotential height field during the Northern Hemispheric winter, Mon. Weather Rev., 109, 784-812. Formation of Polar Air Mass over Western Canada

The following formation process based on a composite study of 93 Northwest Canadian Arctic air mass formations by Turner and Gyakum (2011): First Stage: Snow falls into unsaturated layer in the lee of the Rockies  Subliminal cooling/moistening subcloud layer  Mid-tropospheric cooling via cloud-top radiation emissions Second Stage: Cessation of snow and associated drying of air column  Clear sky surface radiation (augmented by high emissivity of fresh snow)  Surface temperature falls rapidly (dataset maximum 18oC day-1) Third Stage: Near surface ice crystals and ice fog develops (when near surface temperature falls below the frost point.) Near end of formation: Cold air damming with cold pool/anticyclone at the lee of the Rockies, lower pressure over Gulf of Alaska, strong baroclinic zone oriented NW-SE along the Rockies.

Turner J. K., and J. R. Gyakum, 2011: The Development of Arctic Air Masses in Northwest Canada and Their Behavior in a Warming Climate, Journal of Climate, 24: 4618-4633 Eastern N.A. CAO Precursor Patterns: Negative Phase of North Atlantic Oscillation

North Atlantic Oscillation (NAO) “…meridional oscillation in atmospheric mass with near the and the high…” (Hurrell and Van Loon, 1997) A measure of strength of the North Atlantic Oceanic within the 40oN- 60oN latitude belt (Greatbatch 2000) NAO Index: Normalized pressure difference between Stykkisholmur, Iceland and Lisbon, Portugal (Hurrell 1996) According to Hurrell (1996), the NAO accounted for 31% of variance in northern hemispheric (north of 20oN) surface temperatures in winter for the 1935-1994 period

Greatbatch, R. J., 2000: The North Atlantic Oscillation, Stochastic Environ. Res. Risk Assess., 14(4), 213–242, doi:10.1007/s004770000047 Hurrell, J. W., 1996: Influence of variations in extratropical wintertime teleconnections on Northern Hemisphere temperature, Geophysical Research Letters, 23(6), 665-668 Hurrell, J. W., and H. van Loon, 1997: Decadal variations in climate associated with the North Atlantic Oscillation. , 36, 301-326. Eastern N.A. CAO Precursor Patterns: Negative Phase of North Atlantic Oscillation

Positive NAO: Stronger westerlies over North Atlantic Northward displacement of tracks Polar air more likely to remain over Canada/Fewer Cold Air Outbreaks

Negative NAO: Weaker westerlies over North Atlantic Southward displacement of storm tracks Polar air less likely to remain over Canada/more Cold Air Outbreaks

Woollings, T. J., A. Hannachi, B. Hoskins, and A. Turner, 2010b: A regime view of the North Atlantic Oscillation and its response anthropogenic forcing. J. Climate, 23, 1291–1307 Climate Prediction Center, 2005: North Atlantic Oscillation Correlation with Surface Temperature Departures, DOC/NOAA/NWS/NCEP/CPC. URL http://www.cpc.ncep.noaa.gov/data/teledoc/nao_tmap.shtml (accessed 17 November 2017) Eastern N.A. CAO Precursor Patterns: Positive Phase of Pacific North American Teleconnection Pattern

Pacific North American Teleconnection Pattern (PNA) “…the strongest teleconnection pattern of low-frequency variability of the in winter in response to changes in the sea surface temperature” (AMS Glossary) A measure of the strength of the mid-latitude East Asian PNA Index: Combination of normalized 500-mb geopotential height anomalies at four locations (Wallace and Gutzler, 1981; Cellitti et al 2006): PNA = 0.25 [z(20oN, 160oW) – z(45oN, 165oW) + z(55oN, 155oW) – z(30oN, 85oW)] PNA = 0.25 [z(near Hawaii) – z(North Pacific Ocean) + z(Alberta) – z(U.S. Gulf Coast Region)]

Cellitti, M. P., J. E. Walsh, R. M. Rauber, and D. H. Portis, 2006: Extreme cold air outbreaks over the United States, the polar vortex, and the large-scale circulation, J. Geophys. Res., 111, D02114, doi:10.1029/2005JD006273. Wallace, J. M., and D. S. Gutzler , 1981: Teleconnections in the geopotential height field during the Northern Hemispheric winter, Mon. Weather Rev., 109, 784-812. Eastern N.A. CAO Precursor Patterns: Positive Phase of Pacific/North American

Climate Prediction Center, 2005: Pacific / North American Pattern, DOC/NOAA/NWS/NCEP/CPC. URL http://http://www.cpc.ncep.noaa.gov/data/teledoc/pna_map.shtml (accessed 24 January 2018) Ge, Y., G. Gong, and A. Frei, 2009: Physical mechanisms linking the winter Pacific–North American teleconnection pattern to spring North American snow depth. J. Climate, 22, 5135–5148 Eastern N.A. CAO Precursor Patterns: Anomalously weak stratospheric polar vortex/sudden stratospheric warming

Sudden Stratospheric Warming (SSW) Definition (AMS Glossary): A rise in temperature of the in the polar region in late winter resulting from enhanced propagation of energy from the by planetary- scale waves Definition (Charlton and Polvani, 2007): Zonal mean zonal winds at 60oN and 10-mb become easterly during the winter Process: 1. Persistent propagation of tropospheric planetary waves into the stratosphere 2. Wave breaking and subsequent drag exerted on stratospheric zonal flow 3. Geostrophic balance violation creating a poleward air mass movement 4. Convergence, sinking and adiabatic warming of air at high latitudes If wave-breaking is severe, stratospheric zonal flow reversal occurs resulting in sudden stratospheric warming (e.g. Kolstad et al 2010)

Charlton, A. J., and L. M. Polvani, 2007: A new look at stratospheric sudden warmings. Part I: and modeling benchmarks. J. Climate, 20, 449–469 Kolstad EW, Breiteig T, Scaife AA, 2010: The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere. Q. J. R. Meteorol. Soc., 136: 886-893. Eastern N.A. CAO Precursor Patterns: Anomalously weak stratospheric (not tropospheric) polar vortex/sudden stratospheric warming

Waugh, D. W., Sobel, A. H., and L. M. Polvani, 2017: What is the Polar Vortex and how does it Influence Weather? Bull. Am. Meteorol. Soc., 98: 37-44. Eastern N.A. CAO Precursor Patterns: Anomalously weak stratospheric polar vortex/sudden stratospheric warming

Butler,A., D. Seidel, S. Hardiman, N. Butchart, T. Birner, and A. Match, 2015: Defining sudden stratospheric warmings. Bull.Amer.Meteor.Soc., 96, 1913–1928 Eastern N.A. CAO Precursor Patterns: Anomalously weak stratospheric polar vortex/sudden stratospheric warming

Statistically significant negative temperature anomalies over the Eastern CONUS

Mitchell D. M., Gray L. J., Anstey J., Baldwin M. P., and Andrew J. Charlton-Perez, 2013: The Influence of Stratospheric Vortex Displacements and Splits on Surface Climate, Journal of Climate, 26: 2668-2682. Eastern NA Cold Air Outbreak (CAO) Large Scale Meteorological Patterns (LSMP)

Eastern United States (east of the Rockies) Cold Air Outbreak Onset South/Southeastward advection of polar air mass in association with one or more of the following Large Scale Meteorological Pattern (LSMP) features (Grotjahn et al. 2016): 1. Southward extension (for CAO events affecting Texas) or propagation (for CAO events affecting the East Coast) of high MSLP from Canada 2. Surface over the eastern United States 3. Anomalously low 500-mb geopotential heights over the Great Lake region 4. Southeast movement of an upper level shortwave from Canada

Grotjahn, R., Black, R., Leung, R. et al., 2016: North American extreme temperature events and related large scale meteorological patterns: a review of statistical methods, dynamics, modeling, and trends, Clim Dyn,. 46: 1151. Large Scale Meteorological Patterns (LSMP) associated with eastern CAO event onset: Anomalously low 500-mb geopotential heights over the Great Lake region

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Strong 500-mb negative anomalies over the Great Lakes region during CAO onset Day-2 Day 0

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Day+10

Cellitti, M. P., J. E. Walsh, R. M. Rauber, and D. H. Portis (2006), Extreme cold air outbreaks over the United States, the polar vortex, and the large-scale circulation, J. Geophys. Res., 111, D02114, doi:10.1029/2005JD006273. Large Scale Meteorological Patterns (LSMP) associated with eastern CAO event onset: Southeast movement of upper level shortwave from Canada

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Colle B. A., C. F. Mass, 1995: The Structure and Evolution of Cold Surges East of the Rocky Mountains, Mon Wea Rev., 123: 2577-2610 Large Scale Meteorological Patterns (LSMP) associated with eastern CAO event onset: Southward extension (or propagation) of surface high pressure from Canada H

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Day-10 Day-6 H

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Colle B. A., C. F. Mass, 1995: The Structure and Evolution of Cold Surges East of the Rocky Mountains, Mon Wea Rev., 123: 2577-2610 Walsh, J. E., A. S. Phillips, D. H. Portis, and W. L. Chapman (2001), Extreme cold outbreaks in the United States and Europe, 1948–99, J. Clim., 14, 2642–2658. 6-8 January 2017 South Texas CAO event Precursor Patterns and LSMP

Precursor Patterns Associated with the 6-8 January 2017 South Texas CAO event  High MSLP coincident with Polar Air Mass  Negative Phase of the NAO teleconnection pattern  Weak Stratospheric Polar Vortex Large Scale Meteorological Patterns (LSMP) Associated with the 6-8 January 2017 South Texas CAO event  Southward propagation of surface high pressure from Canada  Low 500-mb geopotential heights over the Great Lake Region  Southeast Movement of Upper Level Shortwave from Canada 6-8 January 2017 South Texas CAO event Precursor Patterns: High MSLP over Western Canada linked to Polar air mass

CWJX 311200Z AUTO 25014KT M07/M10 CWJX 011200Z AUTO 03008KT M14/M17 CWJX 021200Z AUTO 23002KT M27/M30 RMK AO1 SOG 03 8014 PK WND RMK AO1 SOG 03 1017 SLP182 RMK AO1 SOG 03 1009 SLP305 25017/1152 SLP041 T10691103 T11401170 T12661300

CWJX Leader Airport CWJX Leader Airport CWJX Leader Airport Saskatchewan Canada Saskatchewan Canada Saskatchewan Canada ASOS -109.5014, 50.9094 x ASOS -109.5014, 50.9094 x ASOS -109.5014, 50.9094 x 12/31/2016 1200 UTC MSLP/Fronts 1/1/2017 1200 UTC MSLP/Fronts 1/2/2017 1200 UTC MSLP/Fronts

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12/31/2016 1200 UTC 300-mb wind 1/1/2017 1200 UTC 300-mb wind 1/2/2017 1200 UTC 300-mb wind 6-8 January 2017 South Texas CAO event Precursor Patterns: Negative Phase of NAO

Negative NAO develops 3 days before 3 January 2017 CAO event onset 6-8 January 2017 South Texas CAO event Precursor Patterns: Weak Stratospheric Polar Vortex

Split in Stratospheric Polar Vortex Late October 2016

Weak Stratospheric Polar Vortex November 2016 6-8 January 2017 South Texas CAO event Large Scale Meteorological Pattern: Southward Extension/Propagation of Surface High Pressure from Canada

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31 December 2016 1200 UTC 1 January 2017 1200 UTC 2 January 2017 1200 UTC 3 January 2017 1200 UTC

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4 January 2017 1200 UTC 5 January 2017 1200 UTC 6 January 2017 1200 UTC 7 January 2017 1200 UTC 6-8 January 2017 South Texas CAO event Large Scale Meteorological Pattern: Low Geopotential Heights over the Great Lakes Region and Southeast Movement of Upper Level Shortwave from Canada

31 December 2016 1200 UTC 1 January 2017 1200 UTC 2 January 2017 1200 UTC 3 January 2017 1200 UTC

4 January 2017 1200 UTC 5 January 2017 1200 UTC 6 January 2017 1200 UTC 7 January 2017 1200 UTC 1-4 January 2018 South Texas CAO event Precursor Pattern: Weak Stratospheric Polar Vortex

Displacement in Stratospheric Polar Vortex Mid December 2017

Weak Stratospheric Polar Vortex December 2017 Data to assess current and forecast North Atlantic Oscillation (NAO) Previous, Current and Forecasts http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml

GFS Outlooks (Example) Ensemble Mean Outlooks (Example) Data to assess current and forecast Pacific North American (PNA) Pattern Previous, Current and Forecasts http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/pna.shtml GFS Outlooks (Example) Ensemble Mean Outlooks (Example) Data to assess current and forecast strength of Stratospheric Polar Vortex

Current and Previous Analysis: NASA site at URL https://ozonewatch.gsfc.nasa.gov/meteorology/wind_2017_MERRA2_NH.html First click the current pair of years on the right (e.g “2017/2018”), then click “10” under “pressure (hPa)” for the 60N zonal wind section. The resultant image will depict the zonal mean zonal wind at 60N latitude and 10-mb relative to the climatological mean. Previous/Current Analysis and Forecasts: 1. The image generated from the NASA site mentioned above. A 7-day forecast is superimposed on this image. 2. Freie Berlin site at URL http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/ Click on the most recent date under “Stratospheric Diagnostics” (e.g. “27 December 2017”), then click “fluxes” to the right of “Zonal mean wind and fluxes 60N” (near the bottom of the webpage.) Examine the 60N “10hPa Zonal Wind” plot; the black line at the end of the plot is a 10-day forecast based on the ECMWF Data to assess current and forecast strength of Stratospheric Polar Vortex 1. Current/Previous Analysis and 7-Day Forecast: NASA site at URL https://ozonewatch.gsfc.nasa.gov/meteorology/wind_2017_MERRA2_NH.html

2. Current/Previous Analysis and 10-Day Forecast: Freie Berlin site at URL 2 http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics 1 10-day forecast

7-day forecast Summary

 Cold Air Outbreak (CAO): Departure of Cold air mass into warmer region  CAO event two (2) step process: (1) Development of polar air mass coincident with anomalously high surface anticyclone followed by (2) rapid horizonal transport to lower latitudes enabled by circulations associated with LSMP  CAO precursor patterns: Polar air mass associated with high MSLP region, negative (positive) phase of the NAO (PNA), weak stratospheric polar vortex  LSMP associated with CAO onset: Extension/propagation of anticyclone from NW Canada, upper level shortwave from NW Canada, surface low pressure system over the eastern U.S., anomalously low geopotential heights over the Great Lake region  Several of the precursor and large scale meteorological patterns occurred in association with the 6-8 January 2017 CAO event. A weak stratospheric vortex preceded the 1-4 January 2018 CAO event.  Data is available to access sign of the NAO/PNA, and stratospheric vortex strength. THE END