Weather Forecasting Exam 1

Term
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What is the mixing ratio?
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Terms in this set (142)
What is the mixing ratio?
Mass of water vapor to the mass of dry air
What is the saturation mixing ratio?
Mixing ratio if the air was saturated; dependent on temperature
As temperature increases, what happens to the mixing ratio?
Mixing ratio increases
What is relative humidity related to?
It is relative to temperature
What is vapor pressure?
Pressure exerted by water vapor
What is saturation vapor pressure?
Maximum amount of vapor pressure at a given temperature; dependent on temperature
What is relative humidity?
Amount of water vapor compared to the capacity of the air
What is dew point temperature?
Temperature at which air must cool for saturation to occur (assuming pressure remains constant); lower the temperature or increase moisture to reach saturation
What is the equation to find dew point temperature?
Td = T - ((100-RH)/5)
Is relative humidity or dew point temperature a better indicator of atmospheric moisture?
Dew point temperature because it allows us to make a forecast; air temperature can't cool below the dew point
What is wet bulb temperature?Temperature the air would be if cooled adiabatically through evaporation to the dew point temperatureHow does atmospheric density change with height?It decreases with heigh due to gravity; greatest near the surfaceWhat is the height of isobars dependent on?Temperature; warmer temperatures = higher height lines for a given pressureWhat does the upper atmosphere consist of (pressure levels)?200 mb (summer), 250 mb (fall and spring), 300 mb (winter)What is the height of the atmosphere (in meters and feet)?10,000 m - 13,000 m (33,000 ft - 43,000 ft)What is the upper atmosphere used to identify? (3)Identify longwave patterns (troughs and ridges), jet stream, jet streaksWhy is divergence important in the upper atmosphere?It is important because it is located above the level of non-divergence (500 mb)What is a trough?An elongated area of lower Geopotential heights in the upper atmosphere; decrease in thickness (lower heights) due to colder mean layer temperaturesWhat is a ridge?An elongated area of higher heights in the upper atmosphere; increase in thickness (higher heights) due to warmer mean layer temperaturesWhat is the jet stream?An area of fast moving winds in the upper atmosphereWhat do horizontal temperature differences influence?Horizontal pressure differencesHow do isobars tilt in regard to warm air?UpwardHow do isobars tilt in regard to cooler air?DownwardHow does PGF change with height?It increases due to the tilts of the isobarsHow does geostrophic winds change with height?IncreasesWhat are some characteristics of the jet streams? (3)- westerly winds aloft - winds are dependent on the horizontal temperature gradient - strongest winds aloft are located near the strongest horizontal gradient (strongest PGF) - jet stream is a response to the horizontal temperature gradientWhat is the jet streak?A localized region of enhanced winds speeds located within the jet stream due to a strong thermal gradientHow does the jet streak move in regard to the jet stream?Tends to move faster than the jet stream, but slower than the winds moving through the jet streakWhat are the four quadrants of convergence and divergence of the jet streak?- top left: convergence - bottom left: divergence - top right: divergence - bottom right: convergenceDescribe the flow of a parcel through a jet streak (test question)- as parcel travels through the jet streak, the flow transitions from geostrophic to ageostrophic at times due to the PGF and the delayed response of the Coriolis (PGF is an immediate response, Coriolis is a delayed response) - as a parcel enters the jet streak, the PGF increases causing the parcel to move toward the lower heights; at this point the parcel is in ageostrophic flow (PGF is stronger than Coriolis and eventually Coriolis force will balance out the PGF and the parcel will return to geostrophic flow) - as a parcel exits the jet streak, PGF decreases causing the parcel to move toward the higher heights; at this point the parcel is in ageostrophic flow (Coriolis force is stronger than the PGF and eventually Coriolis will balance out the PGF and the parcel will return to geostrophic flow)Diagram of jet streak (KNOW!!!)What are the two different types of vorticity?relative and planetaryWhat is relative vorticity?Based on wind flow and wind speed (curvature and shear)What is planetary vorticity?Due to Earth's rotation (Coriolis parameter)What is absolute vorticity?the combination of relative and planetary vorticityWhat direction does positive relative vorticity spin?counterclockwise; cyclonic (trough with curvature and faster winds to the south for shear)What direction does negative relative vorticity spin?clockwise; anticyclonic (ridge with curvature and faster winds to the north for shear)What is the direct (natural) circulation for a jet streak?- Cold air is sinking and warm air is rising (weak static stability leads to more instability) - Thermal gradient is destroyed - Warm air is forced to rise (cool) - Cold air is forced to sink (warm)What is the indirect (unnatural) circulation for a jet streak?- Warm air is sinking and cold air is rising (strong static stability leads to less instability) - Thermal gradient is enhanced - Warm is forced to sink (warm) - Cold air is forced to rise (cool)What must happen to keep a jet streak going?The temperature gradient must be enhancedWhat are some characteristics for positively tilted trough? (3)- trough axis is oriented from the northeast-southwest - weak temperature gradient - these are usually at the beginning of a mid-latitude cycloneWhat are some characteristics for a negatively-tilted trough? (6)- trough axis is oriented from northwest-southeast - stronger temperature gradient - greater chance of severe weather - slower moving - much more well-developed warm front associated with this tilt - cold front is reinforcedWhat pressure levels is the middle atmosphere?500 mb (6,000 meters or 18,000 ft)What features can be identified in the middle atmosphere? (4)- general flow of the atmosphere (mid-level troughs and ridges) - cyclonic/ positive vorticity advection (CVA/PVA) - anticyclonic/ negative vorticity advection (AVA/NVA) - shortwavesAt what pressure level is the level of non-divergence located550 mbHow does a mid-level trough deepen? (4)- moving toward a long wave trough axis - jet max is located behind the trough axis - low-level cold air advection is occuring - heights are deepening (greater cold air advection)How does mid-level troughs filling occur? (4)- moving away from a long wave trough axis - jet max is located ahead of the trough axis - low-level warm air advection is occurring - trough contains zonal flow near the rearHow does a mid-level ridge intensify? (3)- moving toward a long wave ridge axis - jet max is located behind the ridge axis - low-level warm air advection is occuringHow does a mid-level ridge weaken? (4)- moving toward a long wave trough axis - jet max is located ahead of the ridge axis - low-level cold air advection is occurring - ridge contains zonal flow near the rearWhat happens to a parcel as it enters a vorticity field?It begins to spinWhat happens when there is increased spin of a parcel?Horizontal convergence and vertical stretching downward (sinking air)What happens to a parcel as it exits a vorticity field?The parcel's spin decreasesWhat happens when there is decreasing vorticity of a parcel?Horizontal divergence and vertical compression upward (rising air)What is cyclonic vorticity advection/ positive voritcity advection?Higher vorticity values are being adverted into an area with lower vorticity valuesWhat is anticyclonic vorticity advection/ negative vorticity advection?Lower vorticity values are being adverted into an area with vorticity valuesWhere are shortwaves identified?500 mb, but easier to identify at 700 mbWhat is a shortwave?An area of lower heights embedded within the large-scale flowWhat are shortwaves related to?Thermal advection; associated with colder temperatures (height lines drop)What type of satellite can help identify shortwaves?Mid-level water vaporHow are shortwaves located?By identifying: - cyclonic wind shift in the atmospheric flow - thermal trough upstream - highest 500 mb vorticity is usually collocated with the location of a shortwaveIs upward motion located ahead or behind shortwaves?Ahead; upward motion can contribute to rain and thunderstormsWhat pressure level is the mid-lower atmosphere?700 mb; about 3,000 meters or 10,000 ftWhat is the 700 mb level used to identify?- shortwaves - depth of warm and cold air advection - depth of moisture advection - inversionsAt 700 mb, do weather systems have on open or closed patternOpen, broad patternWhat pressure level are fronts found poleward?700 mbWhat percent of the 700 mb wind speeds do surface lows move?70%Between how many feet do most clouds in frontal systems form?5,000 - 15,000 ftRelative humidity values of what percent or what dewpoint depression tend to produce overcast conditions?70% relative humidity or dewpoint depressions 5 degrees Celsius or lessWhat is relative humidity a good measure of? (2)Synoptic-scale lift and moisture700 mb helps to identify what?Upward vertical velocities (UVV) after looking at vorticity and thermal advectionWhat two types of advection is upward vertical velocities a combination of?Thermal and vorticity advectionIf there is warm air advection in the low-levels (850 mb) and PVA in the mid-levels (500 mb), what happens to the value of omega and upward vertical velocity? Does this lead to rising or sinking motion?Negative omega and negative UVV; rising airIf there is cold air advection in the low-levels (850 mb) and NVA in the mid-levels (500 mb), what happens to the value of omega and upward vertical velocity? Does this lead to rising or sinking motion?Positive omega and positive UVV; sinking motionWhen is significant upward motion expected? (Hint: what value should UVV be less than)When UVVs are -3 mb/s or lessdWhat is the convective temperature?The temperature that air reaches to rise on its own with no lifting mechanismWith convective forecasts, at what temperature will convection be inhibited?14 degrees Celsius or greaterWhat does a dewpoint depression of 5 degrees Celsius at 700 or 850 mb indicated?Deep layer moisture (heavy rain likely if a lifting mechanism is availableAt what pressure level is the planetary boundary typically located?800-850 mbWhat is a subsidence inversion and at what pressure level is this usually found?An inversion caused by warming from above (typically seen in the Mexican Plateau)What is a radiation inversion and where is it usually found?An inversion caused by the cooling of the Earth's surface; found near the surfaceAre shortwaves easier to identify at 500 mb or 700 mb?700 mbAt what pressure level is considered the lower atmosphere?850 mb (1,500 meters or 5,000 ft)What is the lower atmosphere used to identify? (5)- shortwaves - warm and cold advection - moisture advection - frontal boundaries - low-level jetWhat are two characteristics for frontal identification at 850 mb?- packing of height lines on the cold side of a front - 850 mb front should be displaced behind the surface frontWhat are 3 characteristics of frontal boundaries at 850 mb?- focuses convection - large scale cap removal due to the atmosphere mixing - location for developing extra tropical mid latitude cyclonesWhat type of advection is very prominent at 850 mb?Thermal advectionWhat is warm air advection?Upward motion and atmospheric expansionWhat is cold air advection?Downward motion and atmospheric compressionWhat is the low-level jet at 850 mb associated with? (3)- mid latitude cyclone warm sector - exit region of the upper-level jet - nocturnal cooling of the rocky mountainsWhat does METAR stand for?Meteorological Terminal Air Report; international standard code for hourly observations and special observationsWhat does ASOS stand for?Automated Surface Observing SystemsWhat does AWOS stand for?Automated Weather Observing SystemsHow often do ASOS stations report data?Hourly intervalsHow often does AWOS stations report data?20 minutes intervalsLabel what each part of a surface observation isWhat does a surface chart often contain? (5)- surface station models - isobars (lines of equal pressure) - high pressure centers - low pressure centers - frontal positionWhat should you be aware of when analyzing a surface chart? (3)- frontal zones (areas of convergence) - surface moisture - location of high and low pressure centersWhat conditions should you look for in a tropical cyclone? (2)- how shear is changing at 850 mb and 200 mb - look to see of winds are going in the same directionWhat conditions are necessary for a tropical cyclone to develop? (7)- 5 degrees of latitude away from the equator - sea surface temperatures at least 26.5 degrees Celsius - low vertical wind shear (less than 20 knots) - lack of dry air (Saharan air layer ) - moisture - unstable conditions (low-level convergence and upper-level divergence) - disturbance presentWhat should be looked at when forecasting a tropical cyclone? (3)- shear - cyclonic flow above low pressure system - tropical cyclones following the trade windsWhat is important for tropical development? (4)- easterly wave - stalled/ stationary front (aids in low-level convergence) - upper-level low (typically cold and dry; strong vertical gradient with cold air aloft) - ITCZWhy do strengthening hurricanes cause more damage at landfall than a weakening hurricane at the same intensity?Deeper convection; increased mixing of strong winds aloft down to the surfaceWhy don't well-developed major hurricanes regain their intensity once they make landfall and then move over open water again?- inner low pressure loses energy (weaken) - the stronger outer band of convection blocks the inner low pressure from gaining heat (sea surface temperature)What are the frictional effects of tropical systems? (2)- friction will cause the storm to turn - slowerWhat quadrant of a tropical cyclone is the most destructive/ most intense?Front right quadrantWhich quadrant has the strongest winds, possibility of tornadoes, and storm surge?Front right quadrantWhat are weaker tropical cyclones steered by?Low-level windsWhat are stronger storms influenced by?Mid and upper-level windsWhat circulation pattern is useful in helping to forecast hurricanes?MJO (Madden Julian OscillationReview Metar decoding and MOS decodingWhat type of conditions are associated with a baratropic environment?Lack of advection and frontsWhat type of conditions are associated with a baroclinic environment?Advection and fronts; unstable atmosphereWhat can affect the temperature of the region? (7)- terrain - latitude and longitude - daylength - elevation - urban vs. rural areas - bodies of water - other local effects (ex. Sea breezes)What should be the first step in making a temperature forecast?Look at a surface chartFor temperature forecasting, what should you look for on surface charts? (6)- airmass types - thermal advection - cloud cover - high and low pressure - fronts - moistureWhat is the importance of cloud cover?Clouds limit the amount of heating during the day and limit the amount of cooling at nightWhat is the importance of low-level moisture for temperature forecasting? (4)- evaporation, melting, and sublimation are cooling processes - condensation, freezing, and deposition are warming processes - water vapor is a greenhouse gas (nighttime temps won't cool as rapidly) - water has a higher heat capacity than dry airIs evaporation a warming or cooling process?CoolingIs melting a warming or cooling process?CoolingIs sublimation a warming or cooling process?CoolingIs condensation a warming or cooling process?WarmingIs freezing a warming or cooling process?WarmingIs deposition a warming or cooling process?WarmingWhat is the second step in creating a temperature forecast?Verifying model dataTrue or false: Models are only as accurate as the data used in the modelTrueWhen making a temperature forecast, what should you compare when verifying model data? (5)- surface observations - skew-t charts - analysis charts - precipitation - surface high and low centersWhat model should you use for long-range forecasting with temperatures?European modelWhat is the third step in making a temperature forecast?Looking at 850/ 700 mb charts depending on locationWhen making a temperature forecast, what should you look for in regard to to 850/ 700 mb level?thermal advectionWhere is the strongest thermal advection typically located?The top of the planetary boundary layer due to less frictionHow can analyzing temperatures of the planetary boundary layer help in temperature forecasting?Help to determine the highest possible temperature for the dayWhere is the planetary boundary layer for both sea level and high elevations?Sea level: 850 mb (5,000 ft) High elevations: 700 mb (10,000 ft)What happens to air id mixing is present within the planetary boundary layer?Air from the PBL will be forced to sink and warm adiabaticallyHow do fronts affect temperature forecasting? (3)- fronts can cause highs to occur during the night and lows to occur during the day - inaccurately forecasting the timing of a front can lead to a busted forecast - type and strength of the front can dramatically impact the weatherHow does terrain affect temperature forecasting? (3)- mountain ranges are heavily impacted by winds - varying wind directions can lead to a wide variety of weather (downslope winds warm adiabatically and upslope winds cool adiabatically and lead to clouds/ precipitation if moisture is present) - the difference between windward and leeward side of mountain rangesHow does precipitation affect temperature forecasting? (2)- unexpected precipitation can lead to cooler temperatures due to evaporational cooling - impacts are dependent upon the amount, duration, and the timing of the precipitationWhen temperature forecasting, what should be taken into consideration? (8)- WWA/CAA - daylength - albedo - dew point - wind speeds and direction - latent heat - mesoscale processes - impacts of nearby stormWhat is the fourth step when creating a temperature forecast?Looking at MOS dataWhat is the fifth step in making a temperature forecast?Actually making the forecastIn general, what should a temperature forecast include? (7)High temperature, low temperature, wind speed, wind direction, cloud cover, humidity, and probability of precipitationWhat may be included for regional and seasonal forecasts contain? (2)Wind chill and heat indexWhat is the sixth and final step in making a temperature forecast?Check your forecast