Weather Weather is the current atmospheric conditions, such as air temperature, wind speed, wind direction, cloud cover, precipitation, relative humidity, air pressure, etc. 8.10B: global patterns of atmospheric movement influence local weather using maps that show high, low pressures and fronts 8.10C identify the role of oceans in the formation of weather systems such as hurricanes
Extreme weather! If the ocean creates more stability, why do we have hurricanes and other severe storms? Question to ponder do you think that weather has gotten more extreme in recent years? What is this usually attributed to?
What a Hurricane Needs to Develop
Hurricane Ingredients Warm tropical water - at least 80 F High Humidity Light wind Low Pressure Area Form between 5 and 20 latitude
Hurricane Formation As water evaporates from warm ocean waters, the warm, moist air (less dense) rises in the atmosphere, leaving less air near the surface, and forming a low pressure area Hurricane Formation
Hurricane Formation As more ocean water evaporates and fuels the hurricane, the low pressure at the surface will get stronger and it will spin faster, leading to higher sustained wind speeds How Hurricanes Form
Hurricanes need warm water to form so they form near the equator, but not on it. Why?
Answer: Hurricanes turn to the right away from the equator because of the Coriolis Effect caused by Earth s rotation. http://www.guardian.co.uk/world/interactive/2008/jan/28/hurricanes
Hurricanes, typhoons and cyclones oh my! Hurricanes, cyclones, and typhoons are all the same weather phenomenon; we just use different names for these storms in different places. Called a Hurricane in the Atlantic and Northeast Pacific Typhoon in the Northwest Pacific Cyclones occur in the South Pacific and Indian Ocean. If the right conditions persist long enough, violent winds, incredible waves, torrential rains, and floods are created.
When hurricanes reach land:
Hurricanes weaken as they move over land They lose their source of heat and moisture Hurricane Weakening Friction over land also reduces the circulation of surface winds, weakening a hurricane
History Connection: Famous Hurricanes Off the Texas coast Galveston: 1900 Known as "the Galveston Hurricane," the deadliest hurricane disaster in U.S. history occurred on September 8. More than 8,000 people died More than half of all the homes and buildings were destroyed.
Other massive storms: Monsoons Monsoons are the season during which the southwest wind blows, commonly causes heavy rains. Monsoons are due to seasonal changes in sea and land breezes It almost always refers to the Asian monsoon (the name for wind), a large region extending from India to Southeast Asia
Another weather phenomenon - El Niño and La Nina
El Nino and La Nina The children of the ocean What are the phases of ENSO (el Niño southern oscillation) is a periodic change in the atmosphere-ocean system in the equatorial Pacific It has two phases el Niño and la Nina
El Nino Starts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South America It is a change in the weather that is characterized by above average ocean temperatures in the Pacific Ocean
El Nino This changes where the convection current occurs Causing rain where it usually doesn't occur and drought where it usually rains The result is more rain in California and SE United States. (Including Texas)
La Nina High pressure develops over the eastern Pacific and low pressure over western Pacific. The results? 1. Southern US gets less rain, while northern US gets more snow that year. 2. Warm water gathers in western Pacific and more hurricanes occur in North Atlantic. 3. For Texas, this means that it is warmer and dryer that the average prediction Note La Nina is the OPPOSITE of el Nino!
Highlight the differences on your notes
El Nino and La Nina Explained Watch videos: http://education.nationalgeographic.com/education/activity/the-oceanand-weather-el-nino-and-lanina/?ar_a=1 http://www.kspr.com/weather/whatis-el-nino/21051524_22912504
Weather Patterns why all of this happens Changes in the weather patterns occur as the earth tries to equalize the temperature. The equalization comes from Global Wind Currents Global Ocean Currents
An air mass is a large body of air that has similar temperature and moisture properties
There are two ways to identify air masses. You can identify air masses by the amount of : moisture temperature
Using Moisture to identify air masses: Continental (c) - Located over large land masses - DRY Maritime (m) - Located over the oceans - HUMID
Using temperature to identify air masses: Polar (P) - Cooler Tropical (T) - Warmer
Moisture and temperature are then combined to describe the air mass (pick 2) ct cp Dry cold mt Humid warm Humid cold mp Dry warm
30 o Latitude Tropic of Capricorn Put together on a map:
A front is the front edge of the boundary between air masses that have different characteristics. Fronts There are 4 different types of fronts Cold Front Warm Front Stationary Front Occluded Front
Cold Front The cold dense air behind a cold front pushes the warmer air up forming cumulus clouds A cold front usually moves fast and causes showers and thunderstorms
Warm Front Front Animations The warm air behind a warm fronts pushes over the cooler air ahead of it forming stratus clouds A warm front causes steady rain, drizzle and fog. The clouds are slow to build, and the rain lasts longer
What makes a thunderstorm? Imagine that a mass of air is sitting on top of Canada. Like the ground below, the air becomes chilled, in winter, it is downright cold.
Opposing Front - Warm Now consider another mass of air that forms over the sun-baked lands of Mexico. This air is warm!
On the move Air, being a gas, doesn t just sit around, it moves. As the air masses move, they bring the weather with it. So when that Canadian air mass moves south, it drops the temperatures of the areas that it passes over. And the same with that warm front, it raises the temperatures of land it passes over.
Cold Front Rapid Climb Since cold air is heavier than warm air, it stays near the ground. So as the cold front moves into a warmer region, it rapidly lifts the surrounding warm air. It acts like a wedge, sending warm, moist air up.
Cold Front Rapid Climb As the warm, humid air gets pushed up, it cools This quick cooling produces condensation and precipitation. This is the ideal setting for a thunderstorm. The upward push creates rapid and violent air currents. The quick cooling condenses water vapor and produces quick intense cloud bursts.
Stationary Front A stationary front occurs when a front stops moving The air is unsteady and sometimes causes rain, and showers
Stationary Front Going Nowhere As the name implies, a stationary front doesn t move (for a while). If the stationary front produces rain, then the rain continues to fall until the front does finally move. This type of front can lead to flooding (just as we saw 3 summers ago).
Occluded Front An occluded front occurs when two cooler air masses merge, forcing warmer air to rise between them Weather similar to a warm front
Occluded Front Has a mass of air that gets carried up. The most common occluded front occurs during a winter storm Warm air gets occluded as it rises above the boundary between a cool and cold air masses.
Other winds - Have you ever noticed? Have you ever noticed that your flight to a location can be longer than the return flight (or vice versa) For example, a flight from Seattle to Boston can be 30 min faster than a flight from Boston to Seattle. Why?
The jet stream is a river of fast moving air high in the atmosphere that flows from west to east and controls other weather patterns Blows from west to east at about 200 to 400 km/hr Airplanes are aided by jet streams when traveling east (with the jet stream)
BETWEEN
Pressure Systems - High High Pressure: higher density air sinks and pressure gets higher winds go clockwise good weather few clouds no rain
Pressure Systems - Low Low Pressure: low density air rises, then cools. Water vapor condenses winds go counterclockwise usually means stormy weather lots of clouds rain is more common
Pressure Systems Label these in your notes!
Weather Maps Weather maps are a combination of analyzed data This data is visually represented In order to communicate world wide, standard symbols have been created You will learn some basic symbols and terms
Weather Map Symbols: Fronts and Pressures Cold Front - Warm Front Stationary Front Occluded Front - High Pressure Low Pressure Make sure you have these in your notes!
Weather Map Symbols: Isobars 1. Isobars are lines on a map that connect areas of equal atmospheric pressure 2. The highest wind speeds are found where the isobars on a weather map are spaced closest together
Weather Map Symbols: Cloud cover and wind (c)
Wind Direction Winds are named for the direction that they come FROM
D. Wind symbols Westerly Wind Wind speed is 65 kts, direction is west
Wind Symbols: Speed Calm Less than 5kts 5 kts 10 kts 50 kts
Now You Try It 45kts 15kts 20kts 30kts 25kts 40kts 35kts
Two types of wind representation: With modern systems, color is now used, although the symbol and number system is still used
Interpreting Weather Maps HW Link is on teacher website
We will start this today and complete next class Weather Map Stations Lab