APWA Meeting John Gordon, NWS Louisville

Transcription

1 APWA Meeting John Gordon, NWS Louisville Weather Forecasting, it s a rough job

2 NWS Operations Advanced Weather Interactive Processing System (AWIPS)? Assess all data: model, observed, satellite, radar, etc.? Compose graphical weather forecasts? Issue all watches, warnings, and statements WATCHES & WARNINGS weather.gov/louisville weather.gov/lexington weather.gov/bowlinggreen

3 Point And Click Forecasts Point and click forecasts provide the highest detailed forecast. Available on our internet home page. Simply click on the map to get a forecast for that point Available at: Hourly Weather Graphs

4 Graphical images from the NWS, your tax dollars at work Max Temps We manipulate graphics of various weather elements, from which software generates text forecasts Prob. Of Precip Graphics are sent to the National Digital Forecast Database and displayed on our website Surface Winds weather.gov/louisville National Digital Forecast Database

5 GRAPHICAL FORECASTS Adding Detail to Local Forecasts Create a grided display or relative humidity and wind over Bluegrass Army Depot.

6 Climate Prediction Center products This map and the one on the next slide show the temperature and precipitation forecasts from the Climate Prediction Center for this winter. Temperatures in the central and eastern tropical Pacific Ocean are expected to become cooler than normal this winter which corresponds to a La Nina. Historically, La Nina influenced winters trend toward dryness in the southern tier of states and wetter than normal weather across the Pacific Northwest. An anticipated warmer than normal winter across the Desert Southwest reflects the ongoing drought and a forecast of less then normal winter precipitation. Seasonal Precipitation Outlook for Dec, Jan and Feb.

7 Collaboration with the Media and EMA The Warning Triad Winter Storm Outlooks A first heads up covered in the extended section of the forecast ie days 3 through 5 Issued when there is sufficient confidence that a major winter storm may create a hazard to public safety. Confidence at this early stage should be greater than 30 percent. This information is covered in the extended section of the hazardous weather outlook. Our local website.and your gateway to all our forecasts climate and river data as well as graphics...is: Weather.gov/louisville Weather.gov/paducah Weather.gov/lexington Weather.gov/jacksonky

8 Winter Storm Watch A watch is issued if the threat of severe winter weather is high (expect warning criteria) Greater than 50% This watch covers the 2 nd and 3 rd periods of a forecast. May cover the 4 th period if confidence is high. Snow or ice amounts are projected for the first time. Winter Storm Warning Issued when we expect significant accumulations of snow, sleet, freezing rain or mixed precipitation. We issue warnings when travel outdoors and on highways are expected to become dangerous. Heavy snow criteria 4 inches of snow or more in a 12 hour period or 6 inches of snow within a 24 hour period. Ice storm warning Ice accumulations expected to exceed ¼ inch or more on exposed surfaces. Damage to tree limbs begins around this point. Blizzard warning very rare across Lower Ohio Valley Sustained winds or frequent gusts of 35 mph or more and reduced visibilities of ¼ mile or less for a 3 hour period

9 Snow advisory criteria across Kentucky. 2 to 4 3 to 5 1 to 4 1 to 4 2 to 4 Winter Weather Advisory Criteria Issued when any combination of snow, sleet or freezing rain is expected to create a hazard but not pose a significant threat to life or property. Snow advisory Snow accumulations of 1 to 4 inches. Freezing rain advisory Ice accumulation are expected to create travel hazards but not reach ¼ inch accumulations on exposed surfaces.

10 Heavy snow warning criteria across Kentucky. > 4 > 5 > 4 > 4 > 4 Kentucky s Vast Topography

11 Other winter weather hazards Wind chill warning Issued when the wind chill is expected to fall to -25 degrees or lower.with at least a 10 mph wind. A wind chill advisory will cover situations where wind chills range between -10 and -24 degrees. High wind warning/advisory High wind warning issued when sustained winds of 40 mph are expected for at least an hour s time or for a non-thunderstorm related wind gust of 58 mph. Advisory criteria is satisfied when sustained winds of 30 mph or gust of 45 mph or greater are expected. Dense fog advisory Widespread dense fog expected to reduce visibilities to less than ½ mile.

12 NOAA Weather Radio

13 Number of Days with at Least One Inch of Snowfall Location Normal Last Winter Bowling Green 3 3 Covington 7 4 Jackson 7 5 Lexington 5 2 Louisville 4 1 Paducah 4 1 Kentucky s Snowiest Months Month Year Snowfall Location December Louisville (Cherokee Park) January LaGrange (Oldham County) February " Benham (Harlan County)

14 January 6, 2002 Tight Snow Gradient

15 HPC Products and Services-Winter Weather Desk Low Tracks Graphic The displayed model and ensemble low positions show the uncertainty of the low positions- the black line represents the HPC preferred track HPC Products and Services Winter Weather Desk Probabilistic Snow Forecasts are issued for 4, 8 and 12 inches, and icing for 0.25 inches

16 An graphical example of a snow amount associated with a winter storm warning across southern Kentucky. In this example, the 4 in. of snow illustrated over Bowling Green is forecast to fall within a 6 hour period. Assessing Societal Impacts Timing of Storm (Day of Week / Time of day) Seasonality Type of Snow Post Storm Conditions

17 Derived Winter Weather Impact Graphics Probability of one inch per hour snowfall 00z Friday April Where was the most snow in the country on New Years Eve 1963/64?

18 HAZARDOUS WEATHER OUTLOOK Issued to 7 days, including short term (Day 1), extended (Days 2-7) Concise, generally non-technical information conveying the potential for significant weather hazards in forecast period Emphasis placed in Day 1 and possibly Days 2 and 3; beyond Day 3, more generalized info given about potential hazards Hazards that normally will be discussed: Severe thunderstorm potential in Days 1-3 (and beyond if appropriate) Non-severe storm potential in Day 1 (and beyond as appropriate) Heavy rain and/or flood potential Winter storm outlooks Winter storm watches, warnings, and advisories ERIE NY-GENESEE NY- INCLUDING THE CITIES OF...BUFFALO NY...BATAVIA NY...Lake Effect Snow Warning For This Afternoon And Tonight... A General Snowfall Will Develop This Morning And Produce Accumulations of 2 to 3 Inches By Nightfall. This Snowfall Will Be Accompanied by a Band of Heavier Lake Effect Snow That Will Develop to The North of Buffalo Early This The Afternoon. This Band of Heavy Lake Effect Snow Is Expected to Slowly Drift to The South Across Genesee And North Central Erie County Later This Afternoon And Evening...Where Accumulations of up to 6 Inches Are Possible by Nightfall. The Steadiest And Heaviest Snow For The Buffalo Metropolitan Area Is Expected to Fall Between 2 and 6 PM. Commuters During This Evenings Rush Hour Will Likely Experience Very Difficult Driving Conditions. Snowfall Rates of an Inch or Two an Hour, Combined with a Heavy Volume of Traffic, Could Clog Many of the Major Arteries Around The Metropolitan Area. Motorists Should Be Prepared For a Slow and Difficult Evening commute.

19 Important Processes for Producing Heavy Snow As with warm season weather we need to consider three critical factors for the production of heavy precipitation. Lift Moisture Instability Winter storms are typically are accompanied by strong dynamics which produce synoptic-scale lift. So, the forecaster must diagnose/forecast if Lift will become focused ( km) scale Moisture will be deep enough to produce ice crystals in a region where the temperature is between 13 to -17 C (dendrite formation zone) increase snow to liquid equivalent ratios Instability will be generated to contract and enhance the upward vertical motions over a mesoscale area (possibly linear bands) HPC Winter Weather Desk Forecast Process Climatology of Snow to Liquid Ratios

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21 The snowfall graph to the right shows the tremendous amount of snow that fell during the month of March 1960 especially across southern Kentucky. The official snowfall total for Bowling Green was 32 inches. This made March 1960 the snowiest month ever! A large portion of southern Kentucky s excessive March snowfall came During the period ranging from the 7 th to the 11 th of March. Bowling Green officially received 27 inches during this period although due to melting and snow compaction, quite a bit less was measured on the ground at any one time.

22 This graph illustrates the snow totals from the mid-january snowstorm of This event gave Louisville almost 17 inches over a 24 hour period. Lightning was observed during the peak of this storm, which gave over 20 inches to some locations northeast of Louisville. Deep snow cover contributed to our state s lowest temperature ever Recorded (-37 degrees). This was set in Shelbyville on January 19 th, The winter of was especially severe due to the persistent cold air masses and snowcover across the state. Measurable snow fell in Kentucky on 19 of the 31 days of January. The worst came on January when a severe blizzard caused KSP to close nearly every road in Kentucky and the National Guard was called into action. Many schools in Kentucky were closed for nearly the entire month of January. The entire state had snowcover through all of February. By the end of the winter, snowfall totals ranged from 31 at Scottsville (Allen County) to 84 at LaGrange (Oldham County). Williamstown (Grant County) reported at least one inch of snow on the ground for 74 days of the season.

23 Recent Major Storms February 15-16, 2003: Ice storm in central Kentucky Frankfort and Lexington hardest hit. 125,000 citizens without power for five days. One fatality in Anderson County. $26.3 million damage. February 3-6, 1998: Major snowstorm in the central and east. 10 to 25 inches of snowfall. The snow was extremely wet, leading to significant damage. Some areas went without power for 2 weeks. Numerous buildings collapsed. Much of the eastern 2/3 of the state was declared a disaster area. $10 million damage. Five fatalities made this our deadliest winter storm since at least 1950, when records begin, tied with the Superstorm of March 1993 when up to 30 of snow fell in the Kentucky Appalachians. Wind Chill Chart

24 Hypothermia Condition where the core body temperature decreases to a level at which normal muscle and brain functions are impaired. There are many factors that can influence susceptibility to hypothermia, including prolonged exposure to cold temperatures. Hypothermia may cause: Drowsiness Unconsciousness Lower heart and breathing rates Severe hypothermia may cause death For those who survive hypothermia, one could suffer from lifelong kidney, liver, and pancreas problems. Kentucky s Biggest Plunge! The temperature at Bradfordsville (Marion County) fell 82 degrees in 24 hours, from 52 degrees January 23, 1963, to -30 the next day.

25 Trivia About how many people die each year in the United States from hypothermia? A)300 B)700 C)850 D)1000 A) 300 B)700 C)850 D)1,000 The answer is

26 Did You Know Between ,555 deaths were attributed to hypothermia. Infants and the elderly are at the greatest risk for cold related illnesses. The answer is A) 3,000-4,000 B)6,000-7,000 C)9,000-10,000 D)12,000-13,000

27 Climatology of Freezing Precipitation Climatology of frequency of freezing precipitation (ZR/ZL) in hours per years (30 years of data)

28 Example Soundings

29 Improve communication to public We re here to listen to your needs We use your data!

30 Black Ice Transparent coating of ice on a roadway surface. While not truly black, it allows the usually black asphalt to be seen through it. Deposited by freezing rain, mist, or fog It often has a dull appearance rather than the expected gloss. Can be hazardous when driving or walking. Black Ice Picture

31 WEBSITE FORECASTS Questions, Comments, Suggestions?