Transcript Chapter 30
Chapter 30 WEATHER FORECASTING & SEVERE WEATHER Severe Wx BFRB Pages 125-129 Wx Forecasting Pages 130-132 FORECASTING Station Models • Used on weather maps to show the current weather conditions for a particular location • They are easy to read and understand • ESRT’S Page 13 Bottom • The circle at the center shows the amount of cloud cover • The “flag pole” coming out of the circle shows the direction that the wind is coming from • Each “flag” shows approximate wind speed. A half flag shows an approx. 5 knot wind, and a whole flag shows an approx. 10 knot wind • *Add up the amount for all of the flags to get the total wind speed • Air pressure is shown by using the last 3 digits of the pressure in millibars (coded) – Ex. 1018.6mb = 186 on the station model • To determine the air pressure from the numbers on the station model, use the following rule: (aka to decode) – If the first number is 5 or less, put a 10 in front of it – If the first number is 6 or higher, put a 9 in front of it – Put the decimal point between the last two numbers • Ex. 892 for air pressure on the station model • The first number (8) is greater than 5, so I will put a 9 in front of it (becomes 9892) • Then I put the decimal between the last two numbers (becomes 989.2mb) • The correct air pressure is 989.2mb from the number 892 on the station model • **Remember, surface air pressure is usually between 960mb – 1050mb • If your answer is not in this range, then it is wrong. Check your work! Encode this weather data: Cross River – Cloudy, 61°F, 58° DP, 8.0 mile visibility, 30.35 inches falling, wind speed 9 mph, from SW. 61 280 8 \ 58 0 Decode this Station Model!!! 88 ¼ 862 -11\ 86 .35 SEVERE WEATHER Thunderstorms • small area storms formed by the strong upward movement of warm, moist air • usually occurs ahead of a cold front as the colder, denser air shoves the warmer air upward • This forms the cumulonimbus clouds that produce thunderstorms • These storms are accompanied by heavy rain, thunder, lightning, sometimes hail, and can also produce tornadoes • All thunderstorms produce lightning • Lightning is the discharge of huge amounts of static electricity (think of walking across a carpet in your socks and then touching something-ZAP) • Lightning can travel from the cloud to the ground, cloud to cloud, or even from the ground to a cloud! • Thunder is the result of the air quickly expanding from the heat of the lightning bolt (causes a sound wave) • You cannot have lightning without thunder and vise versa!! Supercell Thunderstorm formations – will form SEVERE storms and tornadoes! THIS IS ONE BIG STORM SYSTEM! Tornadoes • Form from very powerful thunderstorms (cumulonimbus clouds) • These are funnel shaped columns of spiraling winds that extend down to the ground from the base of a cloud • The winds move into a tornado (low pressure), and can reach a maximum of 318 mph! • The actual funnel is made by water droplets (clouds) and dust • Tornadoes are especially dangerous because it is so difficult to predict where they will form • Damage is usually along a narrow path where the tornado traveled • They usually last less than one hour • Most fatalities are caused by flying debris • Tornadoes are rated on the Fujita scale (F0 – F6) • An F6 is very rare, and can have wind speeds up to 318 mph NEW YORK TORNADOES! Tornadoes will pick up dust and debris from the ground when they “touch down” – this creates a wider swirl at the bottom of the tornado Hurricanes • Huge tropical low pressure systems that get their energy from the tremendous amount of warm ocean water that is evaporated and condenses inside the storm • Hurricanes MUST form over open warm ocean water (WARM WATER = FUEL) • VIF - Since this is where it gets its energy from, hurricanes weaken as they pass over land or colder water • Since hurricanes are extreme low pressure storms, the winds blow into the storm, and it spins counter-clockwise (to the left) • The lowest air pressures on Earth have been recorded inside the eye of hurricanes • Hurricanes are associated with very high winds and heavy rains • Storm surge is the term used for the water that a hurricane blows onto the shore, causing severe flooding – Spring Tides = more severe flooding – Neap Tides = less severe flooding • Most fatalities are caused by drowning in the storm surge (many foolish people do not evacuate areas when told to do so)!! • A “tropical storm” is designated a “hurricane” when its winds reach 74 mph and vice versa. • Hurricanes are classified as Category 1 – Category 5 (strongest) • All hurricanes are named in each ocean in alphabetical order, alternating male and female names • Pacific, Atlantic and Indian Oceans all have their own names for their Hurricane Seasons!!! The Eyewall of a Hurricane Airforce Meteo planes fly through Eyewalls of Hurricanes to collect data to help meteorologists determine where a Hurricane will travel to Hurricane damage can range from broken windows to complete demolition of buildings. Until Katrina, Andrew was the costliest hurricane to date for the USA with a price tag of over $20 BILLION! Katrina is now estimated to have a $200 BILLION price tag!!!