Tornadoes, Air Masses, Global Air Currents
Texas is known to have lots of tornadoes. Texas, Oklahoma, Kansas, Nebraska, Iowa, and South Dakota are the states that make up the Tornado Alley. These central plains are where the tornadoes occur. Dallas Texas is a part of it. The cold dry air from Canada meets the warm moist air from the Gulf of Mexico and the warm dry air from Mexico. The warm moist air is the warm front and the cold dry air is the cold front. When the different temperature and humidity meet, it forms a tornado. Tornadoes are thunderstorms caused by the cold and the warm fronts.Weather changes when a new air mass moves over your area. An air mass is a large body of air that has a certain temperature and amount of humidity. Air masses form in different regions on land and water. This determines the amount of moisture it carries. The temperature is determined from where it comes from. Like the tornado alley diagram above, the cold dry air is from the pole over land. The warm moist air is from the equator over sea. The warm dry air is from the equator but over land.
This hot and cold air meeting follows the global air currents, the sun shines directly on the equator, making the area the hottest and the less dense hot air rises to the poles and the cold air is more dense so it sinks to the equator. The global air currents cause global winds. Winds blow steadily across the Earth in paths that are thousands of kilometers long. The winds steer weather in certain directions. The jet stream is an example of a high-altitude wind that steer weather systems from west to east over north America.
Tornadoes usually occur in the spring and the summer.
Dallas has an average of 4 tornadoes per year and have had 221 tornadoes since 1950.
^Tornado in Dallas area Rowlett, 12/26/15
Hurricanes and Global Ocean Currents
Hurricanes don't occur in Dallas because it is not near the sea or ocean. Hurricanes only form in warm oceans near the equator. Water evaporates to give energy to the hurricane. Hurricanes occur monthly in the fall. Hurricanes cause storm surges, making water flood into coasts. But Dallas is not near the coast so hurricanes never occur here. Global ocean currents are like air currents but in water. They can affect land because it distributes heat around the glob since the majority of the sunlight is absorbed by the ocean. Ocean currents, like air currents, are hot and cold water currents moving. The cold currents move towards the equator and the hot currents move north. The cold currents are more dense so they are usually very low and the hot currents are high. the canary current is from the northern hemisphere and it moves from the pole to the equator. It is a cold current because it is from the pole.
Dallas Climate
Climate is an average of weather over a period of time. It is different from weather. Climate is usually in annual terms.
Annual Averages-
High: 77.1°F
Low: 51.5°F
Average: 64.3°F
Precipitation: 40.97 in.
Humidity: 82% Morning/49% Afternoon
Wind Speed: 10.7 mph
Highest High Temperature Month: August- 96°F
Lowest High Temperature Month: January- 57°F
Highest Low Temperature Month: July and August- 71°F
Lowest Low Temperature Month: January- 30°F
Land and Sea Breezes
Land and sea breezes also don't occur in Dallas, it occurs in shores where it has the sea and the land. Shore breezes are caused by the uneven heating and cooling of the land and water, convection. For a sea breeze, the sun heats both the land and the water, but the land heats up faster. The air above the land becomes warmer than the air above the water. The cooler and denser air that is over the water moves in toward the land and the warmer and less denser air rises. The air that moves in from the sea and heads towards the land is a sea breeze. For a land breeze, the sun sets cooling off the land and water. The land cools off faster than the water. The warmer and less dense air above the water rises and the cooler more dense air that is over land moves in to take its place. The air that moves out from the land and heads towards the sea is a sea breeze.
Global Air Currents cont', Types of Winds
Polar easterlies- dry, cold winds that blow from the high pressured areas of the polar highs at the north and souh poles to the low pressured areas within the westerlies.
Prevailing westerlies- winds in the middile latitudes. Blow from high pressure areas towards the poles. They blow from west to east.
Tropical easterlies- prevailing wind belts from 0-30 degrees latitude, aka Trade Winds
The doldrums- Very low pressure area where the prevailing winds are the calmest. It is caused by the constant heating of the sun because it is located on the equator (belt extends 5 degrees north and south of the equator)
Types of Heat Transfers
Conduction- process of which heat is transmitted through collisions between neighboring molecules.
Ex: A stove and a frying pan.
Convection- heat transfer by fluid like air and water when the heated fluid is caused to move away from the heat source, carrying heat with it.
Ex: Hot and cold air or water, weather!
Radiation- transfer of heat in the forms of waves; electromagnetic radiation.
Ex: The sun radiating the Earth.
Fronts/Weather Map
Cold front- If cold air is coming, it is a cold front.
Causes thunderstorms, followed by cooler temperature.*
Warm front- If warm air is coming in, it is a warm front.
Causes rain showers, followed by precipitation.*
Collision of two fronts=Precipitation
Stationary front- A pair of air masses that is not strong enough to replace the other. Boundary between two different fronts. Doesn't move, light continuous rain.*
Occluded front- Warm air trapped between two cold fronts.
Causes light rain.
*How to tell what direction a front is moving: whatever direction the spikes or the semicircles are pointed, that is the direction of movement. Stationary fronts don't move, and that is why there are semicircles and spikes pointing in different directions.
High pressure system- Cool temperature, clear sky
Air pressure can tell us about what kind of weather to expect
Low pressure system- warmer weather, storm and rain
A cold front is on Dallas and it is moving south. A thunderstorm or rain might follow and cool temperature will also follow. A stationary front is around El Paso but it won't affect Dallas. High pressure systems are on the northwest and the Atlantic ocean. Low pressure systems are in the north and El Paso. The cold fronts around Kansas could move south towards Texas but looking at the forecast, it probably won't.
Weather Forecast Dallas, TX
What causes weather? Convection and movements of air masses.
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