January History Great Flood of 1937 70% of Louisville was submerged 3.3 billion in damages Crest - 85.4 ft. (Flood Stage – 55 ft.) 15 inches of rain in 12 days

Chapter 1: Monitoring the Weather (Basics) One of the Deepest Extratropical Cyclones Ever Recorded

Difference between Weather and Climate Weather is the state of the atmosphere at some place and time Described with quantitative variables Temperature, humidity, cloudiness, precipitation, wind speed, wind direction Meteorology is the study of the atmosphere and the processes that cause weather Climate is weather conditions at some locality averaged over a specified time period Climate is an average of the weather, figured over the last 30-years and updated every decade A locale’s climate also includes weather extremes

Look at Climatological Information

Sources of Weather Information Television The Weather Channel and local newscasts Radio NOAA Weather Radio Continuous broadcasts repeated every 4 - 6 minutes Interrupted with warnings and watches The Internet (Ag Weather) What about now? Survey of Farmers at the 2013 National Farm Machinery Show

Early Days in Ag Weather Green Thumb – Brought on demand market, futures, and weather information. 100 farmers in 2 counties as a pilot project. Viewed on televisions by accessing county computers using a telephone line Keypad allowed farmers the option to choose what they wanted to view. AGTEXT - Worked with KET to distribute closed captioning information to anyone across Kentucky. Forecasts were updated real time. Netscape in the 1990s, before the World Wide Web became established

Retrieving Weather Information & Maps Weather info received via TV, radio, or the Internet includes Weather maps National Regional Satellite/radar images Data on current/past conditions Weather forecasts Short-term 24 – 48 hours Long-term Up to 7 days or longer

GOES-R Much higher resolution Can scan areas for severe weather every 30 seconds Also detects lightning strikes Not fully operational until November. 22,300 miles high

Two Types of Pressure Systems High Pressure Systems, or “Anticyclones” Low Pressure “Cyclones”

Pressure Systems Cont. High and low refer to air pressure Highs Lows High pressure area is relatively high compared to surrounding air Low pressure area is relatively low compared to surrounding air Highs Fair weather Clockwise rotation of sinking air (in Northern Hemisphere) Generally track toward the east and southeast Lows Stormy weather Counterclockwise rotation of rising air (in Northern Hemisphere) Generally track toward the east and northeast Lows tracking across the northern U.S. or southern Canada produce less moisture than lows tracking across the southern U.S. Weather to the west and north – usually cold Weather to the south and east – usually warm

(High and Low Pressure Centers) Pressure Systems Cont. (High and Low Pressure Centers) Arrows indicate surface horizontal winds

(What’s the weather like?) Pressure Systems Cont. (What’s the weather like?) 1. Tallahassee, FL 2. Greenville, NC 3. Duluth, MN 4. Scranton, PA Wind Direction? Cloudy/Wet, Clear/Dry?

Air Masses Huge volume of air covering thousands of square kilometers Horizontally relatively uniform in characteristics Temperature Humidity Gathers characteristics from its source region Cold, dry air masses form at higher latitudes over continents Cold, humid air masses form at higher latitudes over maritime surfaces Warm, dry air masses form over continents in subtropical regions Warm, humid air masses form near the equator or in the subtropics over maritime surfaces

Air Masses Across North America Old Saying in the Ohio Valley: “Don’t like the weather today? It will change tomorrow!”

Fronts “Transition Zones between Air Masses” Warm Front Warm Air Rising Cold Front

Fronts – Boundary Between Air Masses Cold Front Generally, a narrow band of precipitation along or just ahead of the surface front, where precipitation is brief (couple of minutes to a few hours) Precipitation can be severe Boundary between advancing cold air and retreating warm air Plotted on a map as a blue line with triangles pointed in the direction of motion Sharp Temperature Change

Fronts – Boundary Between Air Masses 2. Warm Front Generally, a wide band of precipitation along or just ahead of the surface warm front, where precipitation can be persistent (12-24 hours) Precipitation is generally light to moderate Boundary between advancing warm air and retreating cold air Plotted on a map as a red line with semi-circles pointed in the direction of motion

Fronts – Boundary Between Air Masses Right - A cyclone with the warm and cold fronts extending outward from the low pressure center. Showers generally form along the warm front, while more severe weather can occur along the cold front. Left - Shows how the warm and cold fronts act as boundaries between different air masses. Notice how the wind directions are different on either side of the fronts, and that the flow is counterclockwise and convergent.

Ways to Locate a Front on a Surface Weather Map Precipitation Cloud Cover Wind Shift Temperature Difference Dew Point Difference

Other Types of Frontal Boundaries Stationary – a non-moving front where winds on either side blow in opposite directions. Can become a cold or warm front based on advection. 2. Occluded – when the air behind the cold front overtakes the air ahead of the warm front

Characteristics of Air Masses & Fronts Wind directions are different on the two sides of a front Some fronts have no clouds or precipitation. Passage indicated by wind shift, and temperature/humidity changes In summer, temperature can be nearly the same on both sides of a cold front Difference will be humidity Fronts are anchored to lows on a weather map. Counterclockwise flow brings contrasting air masses together to form fronts Thunderstorms/severe weather often occur in the warm, humid air mass located between the cold and warm front

Describing the State of the Atmosphere What do Forecasters Tell Us? Maximum Temperature Usually occurs in early to mid-afternoon Minimum temperature Usually occurs around sunrise Dewpoint (frost point) The temperature at which air must be cooled at constant pressure to become saturated with water vapor and for dew (or frost) to form Higher Dewpoint = More Moisture Relative humidity A percentage; the ratio of the actual concentration of the water vapor component of air compared to the concentration the air would have if saturated with water vapor Relative humidity will change throughout the day as the temperature varies Generally highest around sunrise and lowest when warmest Precipitation amounts General rule – 10” of snow = 1” of precipitation

Example: More about RH and Dew Point Dew Point Temp F Human Perception R. Humidity 75 + Extremely uncomfortable, oppressive 62% 70-74 Very Humid, quite uncomfortable 52-60% 65-69 Somewhat uncomfortable for most people 44-52% 60-64 OK for most 37-46% 55-59 Comfortable 31-41% 50-54 Very comfortable 31-37% 49 or lower Feels like the western US 30% None Danger Emergency Livestock Cold Stress?

Describing the State of the Atmosphere Cont. What do Forecasters Tell Us? Air Pressure And its tendency (rising or falling) Falling may indicate approaching cold front Wind direction and speed Wind direction is the direction wind is blowing from Example; a west wind is blowing from the west, toward the east Sky cover Fraction of the sky covered in clouds NWS Weather watch – issued when hazardous weather is considered possible NWS Weather warning – issued when hazardous weather is imminent or actually taking place

Weather Satellite Imagery Two major types of satellite orbits Geostationary High orbits 36,000 km (22,300 miles) high Orbits planet at same rate as Earth’s rotation and in same eastward direction Currently 2 of these provide a complete view of much of N. America and adjacent oceans to latitudes of about 60 degrees Positioned over equator at 750 W longitude, 1350 W longitude Low angle in polar regions Polar orbiting Low orbits 800-1000 km (~500-600 miles) high (Much more detailed info) Provides overlapping north-south strips of images Passes over the same point twice every 24 hours

Orbits of Each Type of Satellite Geostationary Satellite Polar Orbiting Satellite

Weather Satellite Imagery Visible Black and white photograph of the planet Only available during daylight hours Highly reflective surfaces appear bright white and less reflective surfaces are darker

Weather Satellite Imagery Infrared Available anytime, not just during daylight Provides temperature comparison of features within image Colder = Bright Warmer = Dark Lower Altitude= Gray Higher altitude =Bright colors

Weather Satellite Imagery Water vapor imagery Enables tracking of plumes of moisture Shades of white = increasing moisture Upper-level clouds appear milky to bright white

Weather Radar Complements satellite surveillance Doppler radar detects movement Excellent tool to forecast tornadoes

Understanding UTC Time Weather observations are taken across the world based on a standard time. In doing so, a 24 hour clock is used, similar to military time. UTC (Coordinated Universal Time or Universal Time Coordinated) Also called “Z Time” To get local time in the United States, you have to subtract a certain number of hours based on time zone. Daylight Savings Time does make a difference

Understanding UTC Time UTC Time = 1200 UTC Daylight Savings Time? (Not until March 8th) No -5 Hours for EST = 7 AM 18 UTC = 18Z = ? 00 UTC = 0Z = ? 06 UTC = 6Z = ?