Meteorology Final Exam

yes girl you got this

nowcasting forecasting

present - 6 hours from now

short-range forecasting

1 - 3 days

long-range forecasting

5 - 10 days

extended range forecasting

up to 90 days

folklore forecasting

sayings to predict weather, some are accurate while others are not

persistence forecasting

what happened yesterday will likely happen today, works best in North Pole and in tropics

climatology forecasting

long-term average of weather conditions used to predict weather for the day, fairly accurate

trend forecasting

uses short-term trend of temp/precip based on observations of nearby locations, assumes speed and direction of weather systems will not change, accuracy of method drops dramatically with time

analogue forecasting

find a date in the past where weather looks the same as it does today, relies heavily on forecaster experience, works best with severe and winter weather events

numerical weather prediction forecasting (NWP)

forecasts pressure, temp, wind, humidity, clouds, and precip using equations consisting of pressure variations, gravity, friction, how heat and moisture are transferred, and how water vapor changes state, accuracy drops dramatically after day 4

the forecasting process

observations (what’s happening to the W and NW?), analysis (storm systems, temp, pressure, dew point), prediction (look at models, ask what would make this event not happen?), post-processing (evaluate your accuracy)

station model plots

temp (upper left #), dew point (lower left #), sky cover (fill of circle), pressure (upper right #), wind speed and direction (half stick equals 5 knots, stick equals 10 knots, triangle equals 50 knots)

comma weather symbol

drizzlet

three commas weather symbol

moderate drizzle

arrow up and zig zag down weather symbol

thunderstorm

period weather symbol

rain

three periods weather symbol

moderate rain

)( weather symbol

funnel cloud

asterisk weather symbol

snow

three asterisks weather symbol

moderate snow

ordinary (air mass) thunderstorms

most common, form in areas with weak wind shear, self-extinguishing (fall apart with colder, downdraft air), short lifetimes (almost always one hour or less)

growth stage of thunderstorms

• first stage

• rising air parcels cool and condense, forming a cumulus cloud

• rising air continues to cool and condense, making cloud taller

• latent heat release changing from vapor to liquid

• keeps rising air warmer than surrounding air

• cloud continues to grow as long as updrafts continue

mature stage of a thunderstorm

• second stage

• as cooler and drier air helps to evaporate water droplets, heavy air descends

• downdraft happens - the exhaling process of wind/cool air from a cloud

• thunderstorm is now inhaling and exhaling air, feeding itself

• storm most intense during this stage

• takes on an anvil shape and may grow up to 40,000 ft

overshooting top

strong updrafts push cumulonimbus clouds into the stratosphere past the tropopause, indicator of a very strong storm that may have rotation at the surface underneath the top

decaying stage of a thunderstorm

• third stage

• updrafts weaken and downdrafts dominate

• normally occurs thirty minutes after the storm develops

multicell thunderstorms

clusters of thunderstorms that form in different growth stages in the same area, have stronger winds than ordinary thunderstorms, last longer and often more severe than ordinary thunderstorms

multicell: squall-line thunderstorms

organized line of thunderstorms with most intense rainfall at the leading edge, form along or ahead of a cold front, intense storms, most moisture comes from the south so the southernmost part of the storm is usually the strongest

bow echo

when a portion of a squall-line’s leading edge curves out ahead of the rest of the line, produces damaging winds

supercell thunderstorms

thunderstorm with a rotating updraft (mesocyclone, most organized and long-lived thunderstorm, (2+ hours and 100+ mi), come in HP and LP varieties, all are severe

flanking line

updraft/food supply for mesocyclone

rear-flank downdraft

rear portion of the mesocyclone’s downdraft

inflow

“suck-zone”, influx of moisture-rich air into a mesocyclone

mesoscale convective systems (MCS)

large grouping of multiple storms that move together and last for hours

circular MCS

covers many states, can produce severe winds and hail, heavy rain producers, low chance of tornadoes

linear MCS

very strong winds, can produce isolated and quick tornadoes

gust fronts

leading edge of cold air coming from a large, severe thunderstorm

microbursts

a localized column of sinking air that produces damaging straight-line winds at the surface, can be confused with tornadic damage

derechos

a widespread, long-lived, violent windstorm associated with a fast moving band of severe thunderstorms that usually take a bow echo form

• usually associated with a warm airmass

• occurs most often in July

thunder and lightning

have to exist together

thunder

the heating and expansion of the air creating a shock wave

if thunder is heard 15 seconds after lightning strike, how far away is the storm?

3 miles, storms move at 5 seconds per mile

thunder sounds like

a crack followed by a bang when you are close to a storm, a rumble when you are far away

lightning

happens because negative charges are found near the base of a cloud, positive charges higher up in the cloud and at the ground, the buildup of negative charges at the base eventually overcomes the insulation of the air and electricity is created

stepped leader

initial spark of lightning that leaves the cloud base, as it approaches the ground, a positive charge starts upward and meets the negative charges

return stroke

the upward flow of current that we see as lightning

heat lightning

distant lightning that illuminates the sky but is too far away for thunder to be heard

tornado

a rapidly rotating column of air that reaches the ground

• has a diameter of 50-100 yds

• path length: 2-4 mi

• lifespan: 5-10 min

• wind speed: 80-300 mph

waterspouts

similar to tornadoes but over water and with much slower wind speeds (30-40 mph)

landspouts

similar to tornadoes but from from the ground up because of low-level circulation

funnel cloud

a cloud of condensed water droplets associated with a rotating column of air, extends from the base of a cloud (usually cumulonimbus), but don’t reach the ground

dust-whirl stage of a tornado

• first stage

• dust swirls upwards from the ground and grows toward the funnel cloud

• damage usually minimal in this stage

organizing stage of a tornado

• downward extension of funnel cloud and connection with dust whirl on ground

• damage light in this stage

mature stage of a tornado

• tornado is on the ground

• strong winds and a howling noise

• damage most severe during this stage

decaying stage

• rotation slows and stops

• tornado is stretched into a thin funnel-shaped rope as storm moves away

what time do tornadoes occur most often?

in the late afternoon due to daytime heating and the atmosphere being more unstable

suction vortices

mini-tornadoes within the tornado that have stronger winds and produce significant damage

doppler radars detect

wind (velocity) and precipitation (reflectivity)

red on a doppler radar indicates that wind

is blowing away from the radar

green on a doppler radar indicates that wind

is blowing towards the radar

enhanced Fujita scale

measures tornado damage on a scale from EF-0 to EF-5

warning signs for tornadoes

strong, persistent rotation, circling dust and debris, hail preceding rapid quiet, a loud roar with heavy rain

Doppler radar is helpful for measuring precipitation, but not wind

false

A forecast of an extended period of dry weather would be made for a region beneath

an upper-level ridge

​Suppose that where you live, the middle of January is typically several degrees warmer than the rest of the month. If you forecast this "January thaw" for the middle of next January, you would have made a

climatological forecast

​A weather forecast that predicts that the future weather will be the same as the present weather is called

persistence forecast

The ASOS system is designed to provide nearly continuous information about wind, temperature, pressure, cloud-base height, and runway visibility at various airports.

true

Sinking air warms, yet the downdrafts in a thunderstorm are usually cold.

true

Supercell thunderstorms are different from ordinary thunderstorms in that supercell thunderstorms​

have a tilted, rotating updraft

squall lines generally do not form

behind a cold front

Each year, U.S. fire departments respond to more than ____ fires started by lightning in the United States.

20,000

To be rated a severe thunderstorm by the National Weather Service, the storm has to have at least one of the following: large hail with a diameter of at least an inch, surface wind gusts of 40 knots or greater, or produces a tornado

false - wind speeds must be 50 knots or greater

The greatest frequency of hailstorms in the United States is

over the great plains

Is this statement true or false: "Lightning never strikes twice in the same place"?​

false

Tornadoes that form ahead of an advancing cold front tend to move from the ____.​

​southwest toward the northeast

The tornado alley of the United States ____.

stretches from central Texas to Nebraska

​With the Doppler radar, a radar transmitter sends out ____, and when they strike an object, some are reflected and scattered back to the antenna.

microwave pulses

The Central Plains region is susceptible to tornadoes because ____.​

warm, humid surface air is overlain by cooler, drier air aloft