Transcript File
Basic Meteorology Earthstorm 2009 ©Oklahoma Climatological Survey The Pre-Game Show • • • • • • • Big picture vs. local detail: What do you need? What really drives our weather? The CEOs of weather A few sidetracks Air masses and fronts Severe Wx Ingredients Other Ingredients! Our Methods are At Odds … • Meteorologist in Oklahoma: – Big picture first, then drill down to local. You can’t make an accurate forecast without understanding the big picture. (We call this the forecast funnel) • Teachers in Oklahoma: – Local first! What is my immediate threat? I will worry about later, tomorrow, the next day, etc.! • Unfortunately, weather folks have been slow to provide information that is “friendly” to nonmeteorologists. Fun with Flashlights Less Intense More Intense Less Intense Sun’s Incoming Rays Polar Regions Equatorial (Tropical) Regions Polar Regions This imbalance in the planet’s heating drives our “big-picture” weather The atmosphere is constantly trying to “even things out” by sending warm air to the poles and cold air to the equator. Exactly how does that happen? Vertical View of Air Top View of Air Circulation Let’s get sidetracked … • Meteorologists are weird: – We love maps – We live in a different time zone – We play with balloons We Love Maps! • ALWAYS READ THE MAP LEGEND • Are these actual observations or are they forecasts? – When were the observations made? – When is the forecast valid? – What was the forecast lead time? • Who created the map? Map Times • Most maps from commercial providers have clear, familiar times – Gov’t maps: another story • Z, GMT & UTC time: they’re all the same • Subtract five hours for CDT, six hours for CST – Ex.: 0354Z ( or “UTC”, or “GMT”) on the 11th is really 2254 CDT (10:54 pm CDT) on the 10th. What’s in a weather map? • State variables tell us a little bit about the state of the atmosphere: – – – – Temperature Moisture (relative humidity, dew point) Wind speed and direction Pressure / height • Almost all “station plot” type maps have each of these elements. A Surface Plot (OK Mesonet) with ‘decoder ring’ A Station Plot • The wind barbs fly into the wind. – – – – Long sticks = 10 mph Short sticks = 5 mph Pennant = 50 mph NE of station: “wind gusting to” in mph • NW of station: Tair (air temperature) • SW of station: Tdew (dewpoint temperature) • SE of station: Rainfall (if any) “a mental picture of air motion” This is the only part we really care about! The Troposphere (this is where the weather happens) 200 mb About 40,000 ft. 300 mb About 30,000 ft. 500 mb Meteorologists are big fans of 500mb About 18,000 ft. 700 mb About 10,000 ft. 850 mb 1000 mb About 5,000 ft. About sea level Radiosonde (wx balloon) locations Wx is shorthand for weather. Each 3-letter station launches two balloons daily: 0Z and 12Z So, what times of day does the Norman balloon fly? What a Difference 6 Months Makes! January July Date Elevation Why did the 1000-500mb thickness expand from 5419m to 5824m? The Troposphere (this is where the weather happens) 200 mb Summer 300 mb 500 mb Winter About 40,000 ft. About 30,000 ft. Meteorologists are big fans of 500mb About 18,000 ft. 700 mb About 10,000 ft. 850 mb 1000 mb About 5,000 ft. About sea level TROUGH TROUGH RIDGE A 500 mb map shows the state of the atmosphere “half way up” Looking Down at the North Pole Key Points: • The global connectivity • The alternating pattern: ridgetrough-ridgetrough • This ties in with the heat imbalance Troughs are associated with cooling, Ridges with warming Ridge Ridge Trough A global composite water vapor image. ©Oklahoma Climatological Survey The CEOs of Weather • Ridges and Troughs play a prominent role in determining the big picture of the day’s weather. – They do not dictate the details at the surface! • Troughs are associated with disturbed weather: – Winder, cloudier, colder, possibly precip • Ridges are associated with more tranquil weather: – Calmer, sunnier, warmer, rarely precip TROUGH TROUGH RIDGE A 500 mb map shows the state of the atmosphere “half way up” Low (Cyclone) versus Wave