Complete List of Terms and Definitions for Synoptic Exam

Terms Definitions
negative tilt *strong/rapid cyclone development
*strong vorticity advection
*maximum intensity of surface cyclone
What are geostrophic winds? Winds aloft
What is θe? Equivalent potential temperature. Describes temperature and moisture. High θe means warm and moist.
radiation inversion temperature warms throughout the atmosphere; cool ground; occurs overnight
What does the intertropical convergence zone move with? The seasons
What does the prefix "kata" mean? Downslope wind
quasigeostrophic flow balance between pressure gradient and coriolis at any latitude other than 45
vorticity Fluids to spin.
Counter clockwise is POSITIVE,
Clockwise is NEGATIVE.
What is TTAA format? Temperature, dewpoint depression, height of pressure level, wind speed and direction of mandatory levels.
Where is the strongest lift located? 500 mb
What does RUC stand for? Rapid update cycle
Geostrophic wind shear is to horizontal temperature gradients as geostrophic wind is to what? Horizontal height gradients.
What is the strength of the winds aloft in a katafront? Stronger
free lifting lower density air will vertically rise upward
What humidity measuring device is used on a radiosonde balloon? Electrical hygrometer
What humidity measuring device is not very accurate? Hair hygrometer
Is remote sensing or in-situ more efficient? Remote sensing
What do shortwaves of vorticity represent? Smaller, concentrated, vorticity maxima that move through longwave features, which often feature broader areas of weaker vorticity. A shortwave wave trough that enters the base of a longwave trough will deepen the longwave trough and increase its vorticity.
What does the geostrophic wind assumption not make use of? Friction force, acceleration, curvature of the contours, wind speed and direction, and will not work at equator (coriolis force=0).
What does low equivalent potential temperature mean? Cold and dry air
open wave well defined low with at least one closed isobar; a trailing cold front to the SW and a leading warm front to the NE
What is the final chart of "contoured" observed weather data known as? An analysis
Where are the clouds the darkest? At the lower level
What does ARINC stand for? Aeronautical Radio, Inc., Annapolis, Maryland
What is the average pressure for the jet to be in the atmosphere? 250 mb
What is PPBB format? Wind speed and direction for significant levels.
What does a radiosonde measure? Temperature, humidity, winds, and pressure up to about 30 km.
When are radiosondes launched in the United States? 00z and 12z
What is the typical rawinsonde output type? Skew-T log-P diagram
What is the WRF model? Weather Researching and Forecasting model. Model is run at 4 km for entire US in experimental mode. Will supposedly provide inproved forecasts. Can produce output that looks like a radar.
What is diffluent flow? ugeo wind component decreases in the downstream direction. Winds are spreading out.
What is geostrophic vorticity? When high accuracy is not needed. ς_g=g/f ∇^2z
What is the comma head structure produced by? The warm conveyor belt.
CCL (convective condensation level) level lifted to by buoyancy from strong surface heating
What is a front? A transition zone between two air masses of different densities (temperatures)
What type of air mass is continental polar (cP)? Cold and dry
What is consensus? If both models agree, can be more confident in forecast.
How is water vapor imagery useful? Useful for monitoring synoptic features. 300-500 mb layer, the less water vapor there is in the atmosphere, the further down you are seeing in the troposphere, as low as 800 mb, but you can never see low level moisture. Can note mesoscale regions of moistening/drying and also provides clues to vertical motion. Air over an area that becomes increasingly dry is sinking and air over an area that becomes increasingly moist is rising. Can examine finer scale details (8 km) that are not present or inaccurate in numerical products (12 km).
What is the earth-oriented spacecraft? Providing efficient duty cycles for imaging and sounding, yielding both high spatial resolution and high signal-to-noise ratios.
What is a rawinsonde? An instrument used to obtain the vertical distribution of temperature, pressure, humidity, and winds.
What is a Persistence Forecast? Tomorrow's weather will be like today's.
Imperfect numerical weather predictions may result from what? Flaws in the computer models, errors that creep in along the model's boundaries, sparseness of data, inadequate representation of many pertinent processes and interactions due to inadequate model resolution, and inherently chaotic behavior that occurs within the atmosphere.
What wind shear is along the streamline? Stretching and shrinking and divergence.
What is vorticity using natural coordinates? Natural coordinates are set up relative to the flow. s is the coordinate along the streamline and n is the coordinate normal to the streamline. ς=V/r-∂V/∂n where V/r is the curvature term and -∂V/∂n is the shear term.
When is vorticity maximized? For regions of strong shear and sharp curvature. A sharply curved trough, with strong winds through the base of the trough and weak winds poleward of the base.
What is potential vorticity? The ratio of the absolute vorticity to the static stability. PV is conserved (its value remains the same) for flow that is frictionless and adiabatic. As very stable air descends from the stratosphere, it will enter an environment that is less stable, requiring an increase in vorticity in order for PV to remain conserved. PV=-g ((ς_θ+f))/(∂p/∂θ) where (ςθ+f) is absolute vorticity and ∂p/∂θ is static stability
What does the ageostrophic wind represent? The amount of deviation from geostrophic balance that appears in the real wind. In association with all the processes that can lead to deviations from geostrophic motion as discussed before.
What is frontolysis (FLYS)? The dissolution of fronts due to 3 things: horizontal deformation of the flow (shear and confluence terms), vertical deformation of the flow (tilting), and unequal (differential) diabatic heating.
Where do cyclones and anticyclones tend to propagate? Cyclones generally propagate to the east and northeast from genetic regions, while anticyclones propagate to the east and southeast after forming.
In ASOS, how do we measure wind speed? Cup anemometer. Photointerrupter device (beam of light) on shaft counts the number of pulses in a given time.
What imagery do we use a lot in Synoptic? Water vapor imagery
What is rawinsonde drift? It refers to the transport of a rawinsonde balloon and instrument package away from its launch site by the wind. It is associated with both the horizontal displacement of the rawinsonde and the time delay due to its relatively slow ascent.
What should a forecast show? "Skill" meaning it should be better than persistence or climatology.
What is ACARS data? It represents a way of sending out data from in-flight aircraft- engine performance data, flight plan information, crew/dispatch messages, fuel loading, meteorological data. Available variables: latitude, longitude, altitude, time, temperature, wind direction and speed, measures of turbulence, dewpoint and icing info (a few aircraft). 140,000 wind and temperature observations per day, 100,000 of which are over continental US, coming from more than 4000 aircraft; more data during the day than night. Has been QC'd, very high quality, and no averaging is performed. Resolution: above 23,000 ft- every 5-6 minutes, below 18,000 ft- 1000-2000 ft in the vertical, and on ascent- could be up to 300 ft for first minute.
What is warm air advection? Wind is carrying warm air our way.
What are the four scales of motion? Global scale, synoptic scale, mesoscale, and microscale
What are the three boundary layers in the atmosphere? Tropopause, stratopause, and mesopause
What is relative humidity? How close is the air to being saturated.
What is the inertial-convective wind a function of? Geostrophic wind shear and the vertical motion
What would happen if there was no ageostrophic wind? The weather would never change.
What are circular regions of vorticity more typically associated with? Low height centers and shortwave troughs.
What is the inertial advective component of the ageostrophic wind? Due to changes in speed and/or direction downstream. E.g. changes in speed downstream as in the vicinity of a jet streak. It is significant if the geostrophic wind changes speed and/or direction downstream (i.e. going along the flow).
Where are the winds supergeostrophic (more than geostrophic)? In a ridge, the acceleration is opposite the flow, acting to slow it down.
How is geostrophic wind and geostrophic speed related to height? Geostrophic wind is along the height contours and the speed is proportional to the height gradient.
What is the physical interpretation of frontogenetical circulation? Represents the rate of increase (decrease) of the magnitude of the 3-D temperature gradient with time following a parcel (Lagrangian).
How does the computer make a model? Observations are fed into the equations. The equations are formulated to predict new values of temperature, moisture, etc for a given future time. Now we have new values we can insert into the equations to solve for the next five minutes. Repeat this process until a desired time is reached (12, 24, 36, 48 hours). Computer will then analyze the data on the grid and produce a map.
What are the cons to automation? There is no backup when equipment fails. Lack of detailed remarks on sky conditions and present weather. Expensive to have both observer and ASOS in same location (but good for employment of meteorologists.)
What is the formula for range folding? R_max=c/2PRF PRF is the pulse repetition frequency, how often a pulse is sent out, and c is the speed of light 3*10^8 ms^-2
What are the wavelengths for the different satellite images? Visible: 1km, Shortwave infrared: 4 km, Water Vapor: GOES west8 km and GOES east 4 km, Longwave infrared: 4 km, and Low level water vapor/ split window infrared (dirty window): 4km.
What is the fifth key to meteorology? Pressure in the atmosphere decreases with increasing height.
How is the geostropic wind calculated? Only from the height field, with no reference to the observed wind.
How can we tell if "weather" is happening on a weather map? Wherever we see strong ageostrophic motions.
In the northern hemisphere, the thermal wind "blows" parallel to what? The mean isotherms such that with your back to the thermal wind, cold air lies on the left and warm air lies on the right.
What does the confluence term do? There is cold advection to the north and warm advection to the south. It is important around fronts, troughs, outflow boundaries. ∂v/∂y'<0, ∂θ/∂y'<0, (∂θ/∂y') (∂v/∂y')=C>0
What are some facts about the forward-sloping warm conveyor belt: katatfront type cold front? The surface front is typically poorly defined- mostly through dew points and relative humidity. Many times there is an upper-level, so-called "split front" or "cold front aloft", which represents the leading edge of overrunning dry air. The CFA can be hundreds of km downstream from the surface front. Since dry, mid-level air is overrunning moist, low-level air convective instability is typically associated with the CFA- leading to convective precipitation along the leading edge of the upper-level front. There is a shallow moist zone upstream from the CFA. Many katafronts are associated with a "dry" cold frontal passage or just a narrow line of precipitation at or near the surface front.
What is a katatfront type cold front associated with? A forward sloping warm conveyor belt.
What are many old occluded systems that finally merge with the great semi-permanent low pressure systems on the weather map called in the North Atlantic and in the Pacific? Icelandic low in the North Atlantic and Alention low in the Pacific.
What can you find in the infrared imagery? Air streams and the conveyor belt.
What do air masses and fronts have? They have both horizontal and vertical extent and we call them frontal surface or a frontal zone.
How does an electrical resistance thermometers work? It measures resistance of a wire whose resistance increases as temperature increases. Used in ASOS.
What is the Michigan Automated Weather Network? A group of 47 stations throughout Michigan and da UP. Designed for agricultural benefits. This measures temperature/dewpoint/ relative humidity, pressure, wind speed/direction, solar radiation, soil temperature/moisture, leaf wetness, and precipitation (non-frozen).
What is the third key to meteorology? The rotation of the earth destroys this simple wind pattern, twisting winds and producing great wind spirals known as high and low pressure areas.
In ASOS, what do we use to identify the type of precipitation? A precipitation identification sensor. Identifies precipitation as rain, snow, or precipitation undetermined. Will only report if fall rates are .01 inch per hour or greater. Categorizes as light, moderate, or heavy. Pulsed infrared is sent from the transmitter in one arm to the receiver in the other. The sensor is really only a precipitation indicator, as observations of weather such as haze are made by readings from a combination of sensors. Sometimes gets confused- sleet reported as rain, hail as rain, blowing snow as snow or rain. 1 meter between transmitter and receiver. Rain vs. snow discrimination based on fall speed. Rapid interruption of beam=rain, slower interruption of beam=snow, and another sensor decides if freezing rain is occurring.
What does the angle help us to determine geostrophic advection? Positive advection when α > 90°, negative advection when α < 90°, and advection is maximized when α=0° or 180°.
What are the characteristics of an anafront? There is a sudden, large drop in temperature with frontal passage, there is a high, slight decrease in relative humidity with frontal passage, the clouds clear slowly with frontal passage, the precipitation is moderate to heavy rain with frontal passage; steady postfrontal rain, and the wind veers sharply, followed by decrease in speed behind front.
What type of flow and moisture profile does a katafront have? A downslope flow that warms dry adiabatically and is moist at lower levels then dries out in the sounding.
Where do cyclones become stronger in January and why does this occur? The East coast of the U.S. because east coast storms undergo more deepening than Rocky Mountain storms. This underlies the importance of the East coast baroclinic zone aided by the warm Gulf Stream waters and the influence of the strong oceanic heat fluxes in winter.
What are some real life examples of anafront and katafront characteristics? A cold front can change its characteristics with time- it is not always an ana- or kata- front. Many times the northern part of the cold front moves east and has strong front-normal winds aloft leading to katafront characteristics. However, the southern tail of the cold front moves southeast with weaker front-normal winds aloft, thereby leading to anafront type conditions (with "overrunning" and stratiform precipitation in the cold air).
What are the two things that make up the evolution of the pattern? Divergence aloft that exceeds surface convergence and warm air advection aloft.
What is sounding data and what does it helps us with? They are observed profiles from radiosondes, can also be output from models for the predicted state of the atmosphere in the vertical for any location, and can provide forecasting info for severe weather and precipitation type especially.
When (if) the computer does a better job of predicting precipitation than a human does, what will the role of a forecaster be? To interpret the models and also discuss probabilities and confidence in various events
What are the cons of visible imagery? It is tough to distinguish clouds from snow-covered ground. A field of clouds smaller than the resolution will show up as a uniform gray area. Thin clouds will not show up very brightly, especially up against a highly reflective surface.
What is data transmission formats for direct broadcast users? Allows users access to the entire data set at reasonable costs, with potential for growth over time.
When are the soundings for the ACARS data created? Soundings can be created on ascent and descent. Have greater resolution and accuracy than a satellite based sounding and data are semi-proprietary (not freely available to us). ACARS data goes into the weather models. We can get the data only when the aircraft is taking off or landing.
In ASOS, what do we use to detect cloud heights? Senses and reports cloud heights (to nearest 100 ft), vertical visibility, and sky coverage. Even though it only looks straight up, over time it gives a reasonable picture of cloud cover because cloud systems drift across the sky. 30 minute sample is used, weighted to last 10 minutes. Sky coverage is based on the number of cloud base readings made- may be inaccurate under rapidly changing conditions. Only measures up to 12,000 ft, can report no more than 3 different cloud height levels at a time. Cloud coverage is inaccurate if a cloud parks itself over the instrument. Cannot detect cloud type. Reports cloud bases lower than reality if precipitation or obscurations (fog, haze) are present. For cloud bases less than 2,000 ft, vertical visibility (VV) reports are issued in 100 ft increments.
What is DCP and what does it stand for? It stands for Data Collection Package. It is the data from each sensor is passed over fiberoptic cabling to the DCP and transmitted to the ACU.
How does a cold front aloft (CFA) work? As the CFA moves east it occludes with the upward-sloping region of high equivalent potential temperature air ahead of the drytrough. CFA is associated with frontogenesis at the "nose" of the colder (and drier) air aloft. Also, beneath CFA nose the rate at which the pressure falls decreases due to the advection of cold air aloft. This produces an ageostrophic wind, convergence and upward vertical motion. Ahead of the CFA there is convectively unstable air.
What type of imagery is not in the atmospheric window? Water vapor imagery. It senses at the wavelength where water vapor absorbs and emits.
Why is it useful to look at FGEN over several different levels? Because looking at FGEN as an average over a chosen layer will often "wash out" the strongest FGEN present within the layer.