Challenges of Winter Weather Forecasting Along the East Coast Sara Croke sara@weatherornot.com Sullivan Brown sully@weatherornot.com @WeatherorNotInc /WeatherOrNotInc 913.722.3955 Weather Basics Moisture + Lift 1
Surface Lows L Satellite Water Vapor Imagery http://weather.cod.edu/satrad/ Can view stability, moisture and lift 2
Satellite Water Vapor Imagery Most lift occurs downstream from troughs of low pressure up to the nearest ridge. Moisture is shown by the whites and blues. Trough of Low Pressure Ridge of High Pressure Radar K 2 N 0 e D D 6 dd = Not as simple as it looks! Ground Clutter Light rain Ground Clutter Rain Same color can mean different things depending on the size of raindrops, time of year, and the temperature structure of the atmosphere. Bugs, birds, smoke, and even the ground can look like precipitation! 3
Dual Pol Professional meteorologists use dual pol products to help differentiate between precipitation types February 5, 2016 Boston Radar Base Reflectivity and Correlation Coefficient Weather Symbols Liquid Drizzle Frozen Light Snow Light Rain Moderate Snow Moderate Rain Heavy Snow Heavy Rain Thundersnow Thunderstorms with rain Sleet Freezing Rain S 4
Anatomy of an Observation BDL Location Click Here Station Plot Explanation Surface Observations http://weather.rap.ucar.edu/surface/ Meteorologists analyze moisture, temperature, pressure, fronts, ridges, troughs etc. 5
Real Time Weather Resources Northeast Surface Plots http://weather.rap.ucar.edu/surface/displaysfc.php?region=alb&enddate=20160509&endtime= 1&duration=0 Any US Surface Plot http://weather.rap.ucar.edu/surface/ Excellent Real time Wx Data http://weather.rap.ucar.edu/ Environment Canada WX Data http://weather.gc.ca/canada_e.html RWIS Data Road Weather Information System Allows for real time observations of road temperatures and atmospheric conditions. 6
850 MB Temp Decision Tree 0 degrees C 0 to 3 degrees C 3 degrees C Rds <32 Rds >32 Rds <32 Rds >32 Rds <32 Rds >32 Snow that sticks Initial Snow Melts Mix that sticks Initial Mix Melts Freezing Rain If heavy or cold air coming in If light and no cold air coming in If heavy or cold air coming in If light and no cold air coming in If cold air coming in If no cold air coming in Snow may begin to stick Slush or just wet Mix may begin to stick Slush or just wet May become freezing rain Plain Rain Liquid to snow ratio? Normal liquid to snow ratio in Hartford, CT is 10:1 (0.10 * 10) = 1.0 of snow (0.25 * 10) = 2.5 of snow If it s colder (near 20F), a higher ratio is needed (15:1) (0.10 * 15) = 1.5 of snow (0.25 * 15) = 3.75 of snow Sleet accumulates at roughly 3.1 (cuts into accumulations) (0.05 * 3) = 0.15 of sleet (0.20 * 3) = 0.60 of sleet (Click Here for YOUR area ratios) 7
Forecasting East Coast Weather Most common winter weather producer: Nor Easters Kocin, P. J., and L. W. Ucellini, 2004: Northeast Snowstorms Vol 1. Overview. American Meteorological Society, 53 54 pp. Forecasting East Coast Weather Determining Snow Gradients Blizzard Timing and Impacts Ice Storms Effects of High Tide during Nor Easters 8
Northeast Snow Gradients Caused by localized areas of strong lift Fronts and Instability In some cases, 0 12 of snow can occur across short distances. February 5, 2016 Methuen, MA Shrewsbury, MA 9
February 5, 2016 Band of moderate to heavy snow through New England Heavy, wet snow caused afternoon rush problems Downed trees, power outages, fatalities February 5, 2016 Deepening system and strong front in mid levels (850mb/~4000 ) enhanced lift Heaviest snow fell under mid level front North (cool side) sees minimal lift, lesser snow accumulations Snow Gradients Concord, NH 4.3 Greenfield, MA 4.5 Ashland, NH 1.0 Andover, MA 8.5 Petersham, MA 7.0 Laconia, NH 5.0 Distance 42 Mi. Distance 22 Mi. Distance 14 Mi. 10
February 4 th 1pm http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=19&parm=pmsl# Developing mid level front (4000 ) 21 Burlington, VT 46 Cape Cod, MA Very mild prior to event Cold air slowly arriving from NW February 4 th 1pm Surface Plot Surface Reanalysis Data 11
February 5 th 7am http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=19&parm=pmsl# Strong midlevel front across southern New England February 5 th 7am Deepening system off of coast Northwest wind pulling cold air into region Warm temps = Lower snow ratio 6:1 L Surface Reanalysis Data 12
February 5 th 1pm http://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=19&parm=pmsl# Front departing; dry, cold air arriving February 5 th 1pm Low Moving NE Snow Departing NW SE L Surface Reanalysis Data 13
Light and Fine Snow Very Light Snow/Flurries Heavy Snow February 5, 7:03am Boston Radar: Base reflectivity shown February 5, 2:03pm Snow Gradients: What to Look/Listen For Cold air in place ahead of event Strong mid level front (temperature differences) To find mid level fronts (850mb analysis): Click Here Check surface plot for snow enhancement possibilities as well To find surface fronts: Click Here Rapid precip shut off (previous slide) 14
Blizzards Qualifications: Snow/blowing snow ¼ mile visibility 3+ hrs and Sustained winds or frequent gusts 35 mph Blizzard of 2016 New York City Maximum Amounts Allentown, PA 31.9 Kennedy Airport, NY 30.5 Washington D.C. 29.3 Newark, NJ 28.1 Central Park, NY 26.8 Philadelphia, PA 22.4 Union City, NJ 15
Blizzard of 2016 Deepening (intensifying) low pressure to the south coupled with high pressure to the north. This creates a strong pressure gradient and strong winds. Credit: Paul J Kocin Nov. 1983 For more information: Click Here Abundant moisture wrapped into the low pressure system. Blizzard of 2016 7am 1/22 7am 1/22 H L Snow Surface Plots Surface Reanalysis Data 16
Blizzard of 2016 1am 1/23 1am 1/23 H L Snow Snow+ Wind 20 mph (likely higher) Surface Plots Surface Reanalysis Data Blizzard of 2016 7am 1/23 7am 1/23 L H Snow Snow + Wind 20mph (likely higher) Surface Plots Surface Reanalysis Data 17
Blizzard of 2016 7pm 1/23 7pm 1/23 L H Snow Snow + Wind 20mph (likely higher) Surface Plots Surface Reanalysis Data Blizzard of 2016 1am 1/24 1am 1/24 L H Snow Snow + Wind 20mph (likely higher) Surface Plots Surface Reanalysis Data 18
Blizzard of 2016 Blizzard: What to Look/Listen For Strong High to the north, cold air in place Low pressure likely strengthening Big pressure difference over short distance Strong Atlantic moisture getting wrapped into the storm 19
Typical East Coast Ice Storm Setups Arctic Front W/ High Pressure Cold Air Damming Cold Air Trapping Cold Air Damming With Cyclone A Synoptic Weather Pattern and Sounding Based Climatology of Freezing Precipitation in the United States East of the Rocky Mountains Robert M. Rauber, Larry S. Olthoff, Mohan K. Ramamurthy, Dianne Miller, and Kenneth E. Kunkel Journal of Applied Meteorology 2001 40:10, 1724 1747 December 11 12, 2008 Ice Storm Westminster, MA Worcester, MA Cold Air Damming With a Cyclone Event 20
December 11 12, 2008 Ice Storm Hardest hit: Interior New England Ice: 1/2 1 Iso. 1.5 500,000 without power Massive debris removal December 11 12, 2008 Ice Storm Dry and cool northeast winds at surface kept cold in place for major freezing rain event. Strong surge of moisture/rain over the top of surface cold. Cold Air Damming With Cyclone Surface temperatures were marginal 29 32, but a cooling effect caused by falling precipitation at the surface allowed for major event. Most icing occurred overnight. 21
December 11 th 7am Cold Air Damming Mid level Surface L Moisture Surface Plots December 11 th 7am Surface Reanalysis Data 22
December 11 th 7pm Cold Air Damming Mid level Surface L Moist Moisture Surface Plots December 11 th 7pm Cold dry air streaming southward Warm side all rain Front stalling Surface Reanalysis Data 23
December 12 th 7am Mid level Surface L Moisture Surface Plots December 12 th 7am Front still stalled Cold air dammed most of MA, NH, VT, ME Cooling effect of rain built ice Valleys stay coolest longest L? Surface Reanalysis Data 24
Ice Storm: What to Look/Listen For Strong High to north allowing cold to set in Surface front between cold and warm for Low to ride along. Developing system pulling warm, moist Atlantic air north over surface cold. Valley effects For more information: Click Here High Tide Impacts During Nor Easters Strong winds and low pressure drive water levels up. Strong wind + low pressure + high tide = Maximum Storm Surge For more info: http://www.nws.noaa.gov/om/hurricane/resources/surge_intro.pdf 25
High Tide Impacts During Nor Easters Scituate, MA January 2015 Scituate, MA January 2014 Basic Ops Decision Tree Snow Gradient Blizzard Ice Storm Weak Front & Instability Low snow amounts Wide Convergence Zone Consistent Snow Depths Routine Ops Strong Mid Level Front & Instability High snow amounts Narrow Convergence Zone Steep Snow Gradient Plan B: heavy snow, short warning Weak High Pressure North + Weak Low + Little Moisture Non Extreme Event Strong High Pressure North Strong Low + Excessive Moisture Steep Pressure Gradient Blizzard Conditions Additional Plan: destructive winds, debris removal, brutal plowing conditions Weak High Pressure +Limited moisture + Air >32 No Icing Strong High Pressure Dry/Cool NE Surface Winds Moisture pulled in from Atlantic Rain overtops surface cold Icing likely Plan: Debris removal, power outages, borderline RWIS 26
Challenges of Winter Weather Forecasting Along the East Coast Sara Croke sara@weatherornot.com Sullivan Brown sully@weatherornot.com @WeatherorNotInc /WeatherOrNotInc 913.722.3955 Cold Fronts T = 20 Td = 20 Colder Air T=25 Warmer Air T = 65 Td = 40 Cold front 27
Warm Fronts (Warm Air Advection) T = 20 Td = 20 Warmer Air T = 45 Td = 40 Colder Air T=25 Warm front 28