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What are air masses?
- •Air Mass Classification
- based upon temperature and humidity
- •P =
- •T =
- •A =
- •m =
- •c =
What are theie two-letter abbreviations?
- cA=Continental Artic
- cP=Continental Polar
- mP=Maritime Polar
- cT=Continental Tropical
- mT=Maritime Tropical
What are the five different air masses and how do they difffer from one another?
- Symbol Properties Tem Satmix DewPoint Ratio %
- cA Verycold -30 0.15 -38 0.09 60
- Very dry
- cP Cold,Dry 12 1.45 11 1.38 95
- mP Cool,moist 39 4.76 36 4.40 92
- cT warm,dry 75 18.51 61 11.33 61
- mT Warm,moist 75 18.51 72 16.70 90
Where do air masses form?
cA and cP
- Continental polar (cP) or continental arctic (cA) air masses are cold, dry,
- and stable.
- These air masses originate over northern Canada and
- Alaska as a result of radiational cooling. They move southward, east of Rockies
- into the Plains, then eastward. Continental polar or continental arctic air
- masses are marked by surface high pressure, cold temperatures, and low dew
How are air masses modified?
- Air masses can be modified significantly as they pass over regions with
- different characteristics. When air masses are modified, they are renamed
- according to their new characteristics.
- Where do air masses form?
- Maritime polar (mP) air masses are cool, moist, and unstable.
- Some maritime polar air masses originate as continental
- polar air masses over Asia and move westward over the Pacific, collecting warmth
- and moisture from the ocean. Some mP air masses originate from the North
- Atlantic and move southwestward toward the Northeast States. The latter air mass
- generally is colder and drier than the mP off of the Pacific.
Where do air masses form?
- Maritime tropical (mT) air masses are warm, moist, and usually unstable.
- Some maritime tropical air masses originate in the
- subtropical Pacific Ocean, where it is warm and air must travel a long distance
- over water. These rarely extend north or east of southern California. Some
- maritime tropical air masses originate over the Gulf of Mexico and Caribbean
- Sea. They can be associated with fog and low clouds as they moves northward. In
- the spring and summer, this air mass accounts for the thunderstorms in the Great
- Plains and elsewhere.
Where do air masses form?
- Continental tropical (cT) air masses are hot, dry, unstable at low levels
- and generally stable aloft (upper-level ridge)
- Continental tropical air masses originate in northern
- Mexico. They are characterized by clear skies and negligible rainfall. If one
- moves into the Great Plains and stagnates, a severe drought can
What air masses can Influence Fresno CA?
cA and cP
What is a pineapple express?
- The "Pineapple Express" is when we have a weather system that has its origins
- from the Hawaiian tropics
- Warm extreme moisture from Hawaii=a lot of rain to the valley
- It doesn't affect us all the time
What is a front?
A front is defined by the transition zone or boundary between two air masses with different characteristics including: temperature, wind direction, density and dew point.
- Similar to the warm front, a cold front is the leading edge of colder air coming in to replace warmer air.These cold fronts tend to move from northwest to southeast bringing cooler temperatures and dryer air.
- The movement of cold air into an area can be quite noticeable as temperatures can drop more than 15 degrees in a short amount of time.
- The symbol on a weather map for a cold front is a solid line (usually shown in blue) with triangles pointing in the direction of movement and pointing towards the warmer air.
- -Cold fronts have a tendency to move faster than all other types of fronts
- -are associated with some of the most violent weather
- -tend to maintain their intensity for very long distances
- -cirrus clouds often proceed a cold front
- -violent thunderstorms along and ahead of the front can result due to the drop in temperature caused by the cold front
- -often followed by a broad band of clouds behind the front
- -can also be associated with squall lines or mini thunderstorms located parallel or ahead of the front
- -usually bring cooler temperatures, clearing skies and a drastic change in the direction of the wind
- -steep slope (of air)
- A warm front is the leading edge of a warmer air mass coming in to replace a cooler one.
- The general direction in which warm fronts move in North America is from the southwest to the northeast.
- Since the air temperature increases as a warm front moves in, the air mass is able to hold more moisture and thus brings warmer and more humid characteristics with it.
- The symbol for a warm front as shown on a weather map or a weather channel is a solid line (most often red) with semi-circles pointing in the direction of its movement and towards the cooler air mass.
- -tends to move slowly
- -produces less violent weather (light to moderate continuous rain)
- -proceeded by cirrus clouds, then altostratus or altocumulus, stratus and in some cases fog (sometimes referred to as the “lowering of the ceiling”)
- -brings about clear skies that follow
- -gentle slopes (of air)
- This is a unique front in that it can be produced from either a cold air mass or a warm air mass. Just as the name implies, a stationary front occurs when an air mass stops moving, returning to a cold front or warm front once it is set in motion again.
- Since the front is the boundary between two different air masses, it is represented on a map by alternating solid blue and red lines.
- On the lines, there are blue triangles pointing towards the warmer air and red semi-circles pointing towards the colder air. Since the air masses involved are of different temperatures, there is a significant change in temperature and/or wind direction when crossing from one side of the front to the other.
- -similar to warm fronts, but even more inactive
- -most often, the winds on either side of the front are parallel to each other
- The main requirement for an occluded front to occur is that a cold front must catch up to a warm front and overtake it.
- To the north of this warm front, we also need a third component of cold air in place before the fronts start moving. On a map, an occluded front is shown by a solid line (usually purple) with alternating triangles and semi-circles, all pointing in the direction of travel.
- As the cold front rotates around and overtakes the warm front, two types of occlusions can be formed.
- In North America, the most common type of occlusion is called a “cold-front occlusion” which occurs when the air behind an occluded front is colder that the air ahead of it. In this case, the colder air behind the front undercuts the cool air in front of it.
- The other type of occlusion is called a warm occlusion and occurs when the air behind the front is warmer than the air ahead of it.
- Similar to a warm front, the slightly warmer air behind the front is lifted up over top of the cold air.
- -changes from higher to lower temperatures
- -lower dew point temperatures (indication of drier air)
- -changes in wind direction
- -indicative of dissipating storms (mature storms)
- A dry line is a boundary that separates a moist air mass from a dry air mass. Also called a "Dew Point Front", sharp changes in dew point temperature can be observed across a dry line. Dry lines are most commonly found just east of the Rocky Mountains, separating a warm moist air mass to the east from a hot dry air mass to the west.
- -Warm,dry air eight more than moist air so it forces the mosit air to rise.
What are mid-latitude cyclones?
- A cyclone is an area of low pressure around which the winds flow counterclockwise in the northern hemisphere. Winds associated with midlatitude cyclones transport heat and moisture from the tropics to higher latitudes and these air masses typically clash in the middle latitudes, often producing clouds and precipitation. The purpose of this activity is to introduce the characteristics of cyclones, the associated air masses and fronts, and finally how to locate the center of a cyclone from wind observations.
Whare do mid-latitude cyclones usually form and where do they not?
- •Lee-side lows -turn out in the coast
- Typical paths of winter mid-latitude cyclones
- Typical paths of winter mid-latitude
- anticyclones – cold air during winter
- -Golf of Alaska
- -East side of the rockies, colorado
- •Hatteras low (nor’easters)-
- These are the
- MOST INTENSE systems and they form along the thermal boundary between the warm
- Gulf Stream and the cold Atlantic coast. They can bring flooding rains along
- the coast and several feet of snow further inland as they use the ocean as a
- vast source of the moisture.
- Explosive cyclogenesis or “bomb”-All low-pressure systems have some form of cyclogenesis during its life cycle. What we are seeing with the next approaching system is the same as cyclogenesis, but put in fast forward. Bomb” or “Explosive” cyclogenesis is a term used for when a low-pressure system rapidly deepens. The strict definition is a system center drops 24 millibars in 24 hours or lessAlberta Clipper-they often trck quickely from canda to usa paa over great lakes, cold air ,snow events fast. 24mb with in 24 hrs.
How do they form? (wave cyclone)
Solid lines are height contours.
- Mid-latitude cyclone-forms and moves along polar front in wavelike manner.
- Wavelength of wave number 1 is as
- wide as the United States.
- Dashed lines show the position of longwave troughs.
- Most of the time we have 4 wavelinght that we can identify. Cold air at the pols
- 5=move fast
- 3= move backward
What weather events can be created form mid-latitude cyclones?
It is possible for mid-latitude cyclones to bring winter weather to areas as far south as Florida depending on where the storm develops. Mid-latitude cyclones usually track in a northeast direction up the East Coast of the United States dumping heavy amounts of precipitation to the Southeast and New England states. This track allows continuous moisture to feed in from the ocean and enhance the precipitation in the cyclone.
How do upper-air winds affects mid-latitude cyclones?
- Because of the sharp difference between polar and temperate air masses, the tropopause on the top of the polar front makes a sharp turn where warmer air roll over colder one. It forms a vortex that is taken eastward by the Coriolis effect of the earth's rotation. We call that the jet streams.
- Because mid-latitude cyclones are born from the lesser pressure of the warm air rising over the cold one, this is where most low pressures (cyclones) are born. And they follow the trade winds at an average speed of 20 knots, eastward.
What is a jetstreak and how does it affect mid-latitude cyclones?
- and exit regions associated with divergence and convergence, right exit allows
- localized extent
- -It could add or subtract
- -Jet streaks can form inside a jetstrem.
What is a Blizzard?
- blizzard means that the following conditions are expected to prevail for a
- period of 3 hours or longer:
- 1.Sustained wind or frequent gusts to 35 miles an hour or
- greater; and
- 2.Considerable falling and/or blowing snow (i.e., reducing visibility
- frequently to less than 1/4 mile)
- Blizzard Warning
- for winter storms with when these conditions are expected to prevail for a
- minimum of 3 hours, but could last longer.
Where are the blizzard most commonly found?
- Blizzards are found all over the world, except near
- the equator. They are common in Europe. Blizzards are most common in Russia and
- surrounding countries. Strong blizzards are occasional in Europe. Also,
- northern Asia has strong and weak blizzards. North America has blizzards as
- well; most are in Canada and Greenland. Blizzards usually happen in the
- northeast and in mountainous terrain in the U.S. The northeastern United States
- has another, “old fashioned” name for a blizzard. They call it a nor’easter. It
- got this name because it happens in the northeast part of the U. S.
- zone – North, South Dakota and Minnesota; 1 to
- 2 per year
what are some of the problems that blizzards might cause for people who have to deal with them?
- Many blizzard-related deaths involve people who die of hypothermia in their
- cars, on the street or in wilderness areas. Sadly, most of these deaths could
- have been avoided with proper preparation. Blizzards also cause countless cases
- of frostbite, as well as damage to unsupported structures and homes.
What is an Alberta Clipper?
2.Waves in jetstream trigger development of a cyclone
3.Cyclone moves south
- 1.Develop after cold air is present (for a
- period of time)
- 4.New arctic front moves south toward low
- 5.Merges with cyclone as before, creates
- 6.Alberta Clippers, less snow (2 to 5
- inches), but low in density (dry), easily blown by winds (hazardous)
- 7.Wind chills down to -50oF to -60oF(-45oC
how does an Alberta Clipper differ from a blizzard taht froms along the Rockies?
- Blizzards along the Rockies
- -Overrunning warm, moist air lonft
- -Increase in elevation
- -It was to be from before it passes the rockies
- Alberta Clipper
- -Develop after cold air is present
What are the concerns that one should consider when one is in a blizzard?
- Have extra blankets on hand and make sure that each member of your household
- has a warm coat, gloves or mittens, hat, and water-resistant boots.
- Store flashlights, matches and firewood, in case of a power failure. Gather
- extras if a winter storm is on its way.
Think about the safety ideas and consider which ones seem to be very obvious and which make a great deal of sense
- WINTER STORM AUTOMOBILE SURVIVAL
- • Mobile phone, charger, batteries -
- • Blankets/sleeping bags/extra clothes –
- heat preservation
- • Flashlight with extra batteries /
- first-aid kit / knife
- • High-calorie, non-perishable food
- • Large empty can to use as emergency
- Tissues and paper towels for sanitary purposes
- • Small can and waterproof matches, and
- candles to melt snow for drinking water and to keep warm.
- • Sack of sand or cat litter for traction
- / shovel / windshield scraper and brush
- • Tool kit
- • Tow rope
- • Battery booster cables
- • Water container
- • Compass and road maps, or personal
- Keep your gas tank near full to avoid ice
- in the tank and fuel lines. Avoid traveling alone. Let someone know your
- timetable and primary and alternate routes.
- STAY WITH YOUR VEHICLE!