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1W051O Vol2

Weather Journeyman

QuestionAnswer
What are the three states of matter? Solid, liquid, and gaseous
changes of state A solid becomes a liquid Fusion.
changes of state A gas becomes a solid. Deposition.
changes of state A liquid becomes a gas. Vaporization.
changes of state A solid becomes a gas. Sublimation.
changes of state A liquid becomes a solid. Freezing.
changes of state A gas becomes a liquid. Condensation.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Vaporization. Take.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Condensation. Release.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Freezing. Release.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Fusion. Take.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Sublimation. Take.
determine whether H2O would take heat from the atmosphere or release heat to the atmosphere: Deposition. Release.
What two effects cause differences in saturation vapor pressure (es) in terms of CCN growth? Explain these effects assuming that the environment and air surrounding the droplet are saturated Solute;if droplet has vapor pressure less than enviro droplet grows due evap. Curvature;Small droplets tightly curved have larger saturation vapor pressure than bigger droplets less curved-if the droplet has larger es than enviro, becomes smaller due evap
Would you expect greater collision-coalescence of a droplet to occur with stratus clouds or cumulonimbus clouds? Why? Cumulonimbus clouds. The residence time in cloud would be increased as updrafts in the cloud would increase distance and coalescence time of the droplet
A large array of droplet sizes would be indicative of what? Variable droplet fall velocities
What is the most effective means of cooling water vapor until it condenses? Adiabatic cooling
A cold front has a slope of 1/50 (1 mile rise over 50 mile run). A second cold front has a slope of 1\100. Which front has the potential to produce more clouds? (Assume each has the same stability and atmospheric moisture present.) Why? 1/50;of the two, this front has the steeper slope, stronger lifting capabilities, and the adiabatic cooling process increases faster
Our station has winds of 270º at 25 knots and winds 20 miles to the east of your station are 270º at 10 knots. Based solely on the wind flow, where might clouds develop and why? To the east of your station due to low-level speed convergence occurring there.
Your base has a north/south-oriented mountain range to east. The winds at all levels from west. Satellite shows clouds on west side of mountains but no clouds apparent to east side of the mountains. What might be a logical explanation for this situation? With westerly winds, orographic lift and adiabatic cooling would produce the clouds on the windward side. However, as the wind continues to flow down the leeward side of the mountains, adiabatic warming would occur and dissipate the clouds.
What are four general tools for forecasting clouds? Any four of the following: climatology, model and centralized guidance, forecast relative humidity values, extrapolation and weather radar.
What is a general tool for forecasting clouds that is derived from decades of observational data and is a time-proven method? Climatology.
What general tool for forecasting clouds is generated from model data and provides guidance on relative cloud amount and height range out to 48 hours? Forecast relative humidity values.
What general tool for cloud forecasting is being used when you simply advect clouds from their current location downstream? Extrapolation.
Which general tool for forecasting clouds should NOT be used without other supporting products? Weather radar.
What is the main difference and added consideration when forecasting cumuliform clouds versus stratiform clouds? Atmospheric stability.
At what level do clouds form when mechanical lift is the predominant factor? Lifting condensation level.
What is the lifting condensation level? The level in the atmosphere where condensation occurs with a parcel of air due to adiabatic cooling.
What causes thunderstorm tops to penetrate into dry layers at higher levels? Strong instability.
What is a method to forecast bases of clouds caused by active surface convection using a surface weather parameter? Dew point depression method.
With what type of atmosphere are stratus clouds associated? A stable atmosphere.
Where do the bases of the stratus clouds form? Where the RH reaches or exceeds 65 percent.
Where are the tops of the stratus in relation to the RH? Where it decreases below 65 percent.
Given the same synoptic situation, at what height would stratus clouds form? They tend to recur frequently at the same altitude, less than 1,000 feet.
How does wind affect the formation of stratus clouds? The wind may allow fog or it may blow the stratus cloud away, depending on its strength.
In the following statement, what is incorrect? Cyclonically curved contours create clouds and precipitation only if there is sufficient moisture associated with a surface system. It is not necessary for the system to show on the surface.
In a cold air mass, when do showers and cumuliform clouds occur? Only when the air is moving in a cyclonically curved path.
As a warm front approaches your station, when can you expect the cirrus cloud to reach you? After the 500mb ridge has passed.
indicate whether rain should be observed and, if so, indicate whether it should be continuous or intermittent (if possible). Dew point spread of 4C at 850 and 700mb No precipitation
indicate whether rain should be observed and, if so, indicate whether it should be continuous or intermittent (if possible). Dew point spread of 2C at 850 and 700mb. Yes, but the type is not predictable.
indicate whether rain should be observed and, if so, indicate whether it should be continuous or intermittent (if possible). Cloud top temperature –10C in an unstable cloud. No precipitation.
indicate whether rain should be observed and, if so, indicate whether it should be continuous or intermittent (if possible). Cloud top temperature –17C in an unstable cloud. Yes, shower type precipitation
indicate whether rain should be observed and, if so, indicate whether it should be continuous or intermittent (if possible). Cloud top temperature –15C in a stable cloud. Yes, continuous type precipitation.
The snow or rain zone is frequently determined by what parameter scale? Small scale.
Generally, what front is connected with the snow or rain zone? Polar front
With a flat, fast westerly flow aloft, in which direction does the snow or rain zone spread? Eastward.
Indicate using a “C” those processes that create fog or use a “D” for those that dissipate fog: Addition of moisture. C
Indicate using a “C” those processes that create fog or use a “D” for those that dissipate fog: Removal of moisture. D
Indicate using a “C” those processes that create fog or use a “D” for those that dissipate fog: Cooling of air. C
Indicate using a “C” those processes that create fog or use a “D” for those that dissipate fog: Warming of air. D
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Evaporation from falling precipitation. C, addition of moisture
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Combustion of hydrocarbon fuels, such as gasoline. C, addition of moisture
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Contact warming of the air near the ground D, warming of air
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Orographic, frontal, or turbulent lifting of the air. C, cooling of air.
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Advection over warmer surface D, warming of air
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Evaporation from a wet surface C, addition of moisture
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Advection over colder surface. C, cooling of air.
Indicate, using “C” the parameters that may create fog and “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Subsidence, down slope motion, or turbulent transfer downward of the air. D, warming of air
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Nocturnal radiation. C, cooling of air.
Indicate, using a “C,” the parameters that may create fog and use a “D” to indicate those that may dissipate fog. Identify how it creates or dissipates fog by listing the process involved: Turbulent mixing with warmer air aloft. D, removal of moisture/warming of air.
What is the most common type of fog in the Northern Hemisphere? Radiation fog
What factors determine the rate at which an air mass cools due to nocturnal radiation? The initial temperature and the rate and duration of net long-wave radiation transfer.
Which type of fog is advection fog that forms in warm moist air that is cooled to saturation as it moves across cold water? Sea fog.
What type of fog forms in higher elevations and builds downward? Upslope fog.
What type of fog is usually limited to areas near human habitation? Ice fog.
This restriction develops in layers in a stable atmosphere usually of fairly large depth. The visibility is usually between 3 & 6 miles. To predict this restriction, must locate a source of pollution and predict the stagnation of an air mass in your area. Haze.
This restriction is a localized phenomenon that depends on the wind direction to determine areas of restriction. There must be a strong inversion and light winds. To predict its occurrence, must locate the source and know the wind direction. Smoke.
This restriction varies with the wind speed and type of restriction. The visibility may be restricted completely or only partially, depending on local conditions. Windblown restrictions.
What is the intensity of snow showers occurring at you station with a prevailing visibility of fiveeighths of a mile? Light.
Which general tool for forecasting winds can provide information on surface frictional effects? Topography.
What general tool should you use to forecast winds if the synoptic situation is stagnant and not changing? Trends.
Which general tool for forecasting winds are graphical in nature, based on the WRF model and provide wind forecasts for three hour intervals? Meteograms.
What would the approximate low-level wind speed be if open-cell cumulus in the shape of an elongated doughnut was present? 11 to 20 knots.
predict the speed of the surface wind Time 2300L, strong inversion, gradient wind of 30 knots, and 5,000-foot wind of 50 knots 12 to 21 knots.
predict the speed of the surface wind Time 1100L, weak inversion, gradient wind of 30 knots, 5,000 foot wind of 60 knots. Temperature needed to break the inversion of 72, current temperature is 71. What will the winds be at 1200 LST? 30 knots with gusts to 48 knots.
predict the speed of the surface wind Time 2300L, no inversion, gradient wind of 30 knots, and a 5,000 foot wind of 50 knots. 30 knots with gusts to 40 knots.
predict the speed of the surface wind Time 1100L, no inversion, gradient wind of 30 knots, and 5,000 foot wind of 50 knots. 30 knots with gusts to 40 knots.
What is the usual way to forecast frontal winds? Through extrapolation of current conditions with modifications based on expected changes
Name the four categories of tertiary circulations Local heating, local cooling, adjacent heating and cooling, and forced circulations.
What is the nocturnal wind that flows into valleys and to what category of tertiary circulation does it belong? Mountain breeze; local cooling.
Identify the wind caused by warming the air near the mountain slopes and to what category of tertiary circulation does it belong? Valley breeze, local heating
In which tertiary circulation are land and sea breezes? Adjacent heating/cooling.
The Mistral and Bora belong to which category of wind? Fall winds
What category of wind is the fall wind? Forced circulation.
Cap, rotor, and lenticular clouds are characteristic of which forced-circulation wind? Foehn winds.
Explain the relationship between temperature and molecular activity in an object The molecules in a warm body are more active than in a cold body
Determine what happens to thermal energy between two objects of different temperature Thermal energy is transferred from the warm body to the cold body.
Name the three temperature scales primarily used in meteorology and give the freezing and boiling point for each. Celsius scale where freezing is 0° and boiling is 100°; Fahrenheit scale where freezing is 32° and boiling is 212°; and Kelvin or absolute scale where freezing is 273° and boiling is 373°.
temperature conversions: 45°F to degrees Celsius. 7.20°C
temperature conversions: 24°C to degrees Fahrenheit. 75.2°F.
temperature conversions: 30°C to degrees Kelvin 303°K.
temperature conversions: 425°K to degrees Fahrenheit 305.6°F.
measures of humidity: Indicates an equal exchange of water vapor between the air and a moisture source. Saturation vapor pressure
measures of humidity: Affected by temperature. Water vapor pressure. Vapor pressure Saturation vapor pressure. Relative humidity
measures of humidity: Ratio of actual water vapor to amount of water vapor that a quantity of air can hold. Relative humidity
measures of humidity: Partial pressure of the atmosphere due to the presence of moisture. Water vapor pressure
measures of humidity: Ratio of mass of water vapor to mass of dry air. Mixing ratio. Absolute humidity.
measures of humidity: These two measures of atmospheric moisture are the same. Mixing ratio. Absolute humidity.
measures of humidity: Ratio of mass of water vapor to mass of natural air. Specific humidity
What tool provides a summary of monthly and annual climatic data for a station? OCDS.
What tool can be used to collate temperature forecasts from several sources or products? Temperature forecasting checklist.
Is temperature a conservative property in an air mass? No, it is nonconservative.
Clouds affect the temperature by reducing what? Insolation and terrestrial radiation.
How does cloud cover affect temperatures during the day and at night? It means a lower temperature in day and higher at night.
How does a stable lapse rate affect heating? Heating occurs more rapidly.
How do strong winds affect heating? There is less heating due to greater mixing.
How does condensation affect surface temperatures? The surface heats only a little bit.
What conditions describe a heat wave? A heat wave varies from place to place but it generally refers to very high unpleasant temperatures and humidities
How does a heat wave develop? The long-wave trough stagnates over the Rockies and a long-wave ridge is over the eastern US. The jet is in Canada and the surface pressure is higher than normal in the eastern US.
What is a cold wave? A cold wave in the U S is a net decrease of 20F or more in 24 hours with the temperature falling below a preset minimum.
How does a cold wave develop? A very cold continental polar air mass in Canada moves southward near the surface beneath a strong ridge over the western US and a strong trough in the eastern US.
What sources can you obtain forecasted sea-level pressure values from? Centralized charts, numerical bulletins, and meteograms
Which product can provide you with a graphical indication of a frontal passage in the sea-level pressure? Meteogram.
Why is an altimeter necessary? It indicates the height of an aircraft with respect to MSL.
How does pressure create an error in altimeter readings? The altimeter is based on standard atmosphere. Pressure variances from standard result in altimeter errors.
How does temperature create an error in altimeter readings? The altimeter is based on the standard atmosphere. When the temperature differs from the temperature expected in a standard atmosphere, the altimeter is in error.
What is the D-value? D = true altitude - standard altitude
What is the D-value for 9,000 feet if the height of the 700mb level is 10,240 feet? D = +460 feet
Compute the pressure altitude: Altimeter:29.84 Field Elevation +150 Forecasted PA = +230ft
Compute the pressure altitude: Altimeter:29.96 Field Elevation +460 Forecasted PA = +420ft
Compute the pressure altitude: Altimeter:30.05 Field Elevation +105 Forecasted PA = -25ft
Compute the pressure altitude: Altimeter:29.72 Field Elevation +890 Forecasted PA = +1090ft
Compute the pressure altitude: Altimeter:29.92 Field Elevation +30 Forecasted PA = +30ft
What is density altitude? The altitude that a given density is found in the standard atmosphere
What elements are used in computing density altitude? Pressure and virtual temperature at an altitude or location under consideration.
Where should turbulence be anticipated? In thunderstorms, areas of strong temperature advection, areas of considerable horizontal directional and/or speed shear, and areas of considerable vertical shear, particularly below strong stable layers
From which agencies are centralized turbulence products available? AFWA and NWS Aviation Weather Center.
What source of turbulence reports should you review after checking all forecast products? Pilot reports (PIREPS).
What category of aircraft does a turbulence forecast normally specify? Category II.
What six factors increase the effects of turbulence for a fixed-wing aircraft? Non-level flight, increased airspeed, increased wing surface area, increased altitude/decreased air density, and decreased wind sweep angle.
What four factors increase the effects of turbulence for a rotary-wing aircraft? Increased airspeed, decreased weight of the aircraft, decreased lift velocity and increased arc of the rotor blade.
Describe the regions where turbulence should be expected in the mountain wave and the intensity of each region The most turbulent regions in the mountain wave are in the rotor and cap clouds. The cap cloud has downdrafts of 5,000 ft per minute and the rotor cloud has both updrafts and downdrafts of 5,000 ft per minute. Lenticular clouds are also turbulent.
Define CAT. CAT is all turbulence not associated with convective activity.
At what altitude does most CAT occur? 30,000 to 40,000 ft.
How thick is the average layer of CAT? 2,000 ft.
How long is the average length of CAT in the direction of the wind? 50 miles over land and 100 miles over water.
Where does CAT occur in relationship to the jet stream? Below and to the cyclonic side over land but on the anticyclonic side over water.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm): 30KT Moderate.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):95KT Extreme.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):75KT Severe.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):20KT Light if any.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):60KT Severe.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):49KT Moderate.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):55KT Severe.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):35KT Moderate.
Predict the intensity of CAT for the conditions Horizontal shear (knots/90nm):40KT Moderate.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 3KT Light.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 18KT Extreme.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 12KT Severe.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 7KT Moderate.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 6KT Moderate.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 15KT Extreme.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 8KT Moderate.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 14KT Severe.
Predict the intensity of CAT for the conditions Vertical shear(knots/1,000 ft): 22KT Extreme.
What causes wake turbulence? It is the result of flow around an aircraft wingtip.
How long can surface winds keep a vortex of turbulence over a runway? Indefinitely.
To avoid wake turbulence, when should an aircraft lift off if it is following another aircraft? It should lift off before the aircraft ahead of it.
What is in-flight icing? The accretion of supercooled liquid water (SLW) on the airframe of aircraft.
Name the three types of aircraft icing. Rime icing, clear icing, & mixed icing
Describe the Rime ice type of aircraft icing. Formed when SLW drops are small,such as lgt DZ or moisture n stratified clouds, liquid remaining after initial impact w/aircraft freezes quickly b4 liquid has time to spread over surface. small frozen drops trap air between them giving rough milky opaque
Describe the Clear ice type of aircraft icing. If after initial impact the remaining liquid from the SLW drop flows out over aircraft’s surface & gradually freezes, it forms smooth sheet of ice. Large drops, as found in rain or in cumuliform clouds, create this.is hard and glossy, heavy and tenacious.
Describe the Mixed ice type of aircraft icing. A combination of clear and rime ice. When supercooled drops vary in size or are mixed with snow or ice particles, a combination of clear and rime ice can form and form rapidly.
What determines the intensity of in-flight icing? Icing intensity is determined by the rate of accumulation and its impact on deicing and anti-icing equipment
List the four intensities used to categorize in-flight icing. Trace, light, moderate, and severe.
What is the greatest impact caused by in-flight icing? It destroys the airfoil effect
Describe tail stall. tail sfc of AC normally ice faster than wing. tail acts as horztal stab. balances tendency of nose to pitch dwn by generating downward lift on tail of AC. When tail stalls from ice accum, downward force is less/removed, & nose of AC can severely pitch dwn
Describe how icing disrupts the airfoil properties of an aircraft’s wings. Icing distorts the shape of airframe surfaces, which destroys the smooth flow of air, increasing drag while decreasing the ability of the airfoil to lift.
In what capacity does the weather journeyman assist pilots in developing an ice-avoidance flight plan? By informing pilots of any potential icing areas along their planned route of flight.
Describe some of the anti-icing and deicing equipment used on aircraft. Anti-icing equipment consists of carburetor heat, prop heat, fuel vent heat, windshield heat, and fluid deicers. Deicing equipment consists of three major types: boots, weeping wing systems and heated wings.
What are the two AFWA produced graphic products that forecast icing? High and low-level hazard charts.
What types of icing can the Military Weather Advisory (MWA) alert you to the possibility of? Moderate or severe icing.
Indicate the icing intensity, probability, and type for the data: Icing location is 200 miles ahead of a warm front, temperature of –18C, 5C point spread, unstable clouds, and neutral advection 10 percent probability of light rime icing.
Indicate the icing intensity, probability, and type for the data: Icing location is 50 miles behind a cold front with flight altitude temperature of –9C, 2C dew point spread, unstable clouds, and neutral advection. 75 percent probability of moderate rime icing
Indicate the icing intensity, probability, and type for the data: In freezing rain. 100 percent probability of severe clear icing
Indicate the icing intensity, probability, and type for the data: In unstable clouds with temperature –9C, 3C dew point spread, and strong cold advection. 80 percent probability of light mixed icing.
Where does the greatest icing occur in thunderstorms? In the updrafts where the temperature is between 0C and –20C.
Where does the greatest icing occur in frontal zones? In the updrafts where the temperature is between 0C and –20C and in freezing precipitation.
Define “wind shear.” The change in the vector wind field in any direction in space
How would an aircraft be affected when flying from a tailwind to a headwind during landing? The indicated airspeed increases and the aircraft rises above the glideslope.
How would an aircraft be affected when flying from a headwind to a tailwind during landing? The indicated airspeed decreases and the aircraft drops below the glideslope.
Low-level shear may persist for six hours or more due to the small slope and slow movement. Warm frontal boundaries.
Occurs at night and causes very little threat to flying safety. Land breezes.
Causes one of the most dangerous LLWS conditions Thunderstorm gust front.
Wind shear associated with this condition usually lasts for only one to two hours due to large slope. Cold frontal boundaries
Most intense shear can be expected in the mid to late afternoon. Sea breezes.
Moves faster than the generating storm. Thunderstorm gust front.
Chinook, Santa Ana, and Foehn are examples of this shear producing phenomenon. Gusty surface winds.
Characterized by light surface winds and strong winds just above the surface inversion. Low-level jet (LLJ).
Indicate whether LLWS should be expected: An approaching cold front has a temperature difference across the front of 18F per 75nm. Yes
Indicate whether LLWS should be expected: The sustained surface wind is 12 knots and the gradient wind speed is 30 knots. No
Indicate whether LLWS should be expected: The sustained surface wind is 8 knots and the absolute value of the vector difference between the gradient wind and the surface wind is 40 knots. Yes
Indicate whether LLWS should be expected: You expect a low-level jet to form at 2,500 ft AGL No
Indicate whether LLWS should be expected: A thunderstorm is situated 6nm north of your station Yes
Indicate whether LLWS should be expected: A cold front moving at 35 knots has just passed your station. No
What are the moist and dry adiabatic lapse rates in C? The moist adiabatic lapse rate is 6C per 1,000 meters. The dry adiabatic lapse rate is 10C per 1,000 meters.
How is stability determined? By comparing the temperature of a rising air parcel to that of its surrounding environment
What is the stability of the atmosphere if an air parcel rises from the surface and remains colder than the environmental lapse rate? Absolutely stable.
What is the stability of the atmosphere if the environmental lapse rate is less than the moist adiabatic lapse rate? Absolutely stable.
What effect does cold air advection at the surface and warm air advection in the upper levels of the atmosphere have on atmospheric stability? Increase stability.
What is the stability of the atmosphere if an unsaturated air parcel rises at the same lapse rate as the environment? Neutral.
What is the stability of the atmosphere if an air parcel rises from the surface and remains warmer than the environmental lapse rate? Absolutely unstable.
What is the stability of the atmosphere if the environmental lapse rate is greater than the dry adiabatic lapse rate? Absolute instability.
What condition exists if a rising saturated parcel of air has a lapse rate less than the dry adiabatic rate but greater than the moist adiabatic rate? Conditional instability.
What is the stability of the atmosphere if a saturated air parcel rises and decreases temperature at a rate of 4.5 for every 1,000 meters? Absolutely stable.
When during a day does maximum instability usually occur? During the hottest part of the day.
What region of the CONUS has the most thunderstorm activity? Southeast United States
Where are severe thunderstorms most prevalent in the CONUS? From the Continental Divide to the Appalachian Mountains and from the Gulf of Mexico to Canada. The greatest occurrence of severe activity is along “Tornado Alley.”
What months in the CONUS appear to be the best for the occurrence of tornadic activity? March through June
What are the two air-mass boundaries in the CONUS that are conducive to forming severe weather? cP and mT, mT and cT.
How does CONUS seasonal activity shift? With the position of the PFJ. From the Gulf Coast states in late winter, to the Southern Plains states in early spring, to the Central Plains in Midwest states in late spring, and finally, to the Northern Plains and Great Lakes region in the summer.
What are the categories for non-severe and severe thunderstorms? Non-severe: winds up to 49 knots and hail up to 3/4 inches. Severe: winds equal to or greater than 50 knots and hail equal to or greater than 3/4 inches
During the weather briefing, how should you brief an aircrew that has isolated thunderstorms projected along its route? Brief the crew to consider all thunderstorms in flight as severe. Also brief that hail, severe turbulence and icing, heavy precipitation, lightning, and wind shear are to be expected in and near thunderstorms
What are the five conditions necessary for the formation of severe thunderstorms, tornadoes, and their associated phenomena? The thermal air structure must be conditionally unstable. Large quantities of moisture must be available. Strong mid-level winds are required. There must be a lifting mechanism. The height of the WBZ must be favorable.
Explain the parcel theory. If lapse rate of surrounding air mass exceeds rate of cooling by an ascending parcel, the parcel becomes warmer than its environment & rises due to positive buoyancy. Conversely, parcel sinks if it is colder than the environment due to negative buoyancy
Why can air-mass thunderstorms result in local heavy rain? Because weak winds aloft result in little cell movement
What type of thunderstorm is often confused with a frontal passage? The squall line thunderstorm
When does climatology support prime activity of the dryline? Spring and early summer.
When do the most violent thunderstorms occur with a dryline? When the dryline is associated with an upper-level atmospheric disturbance along with intersections between the dryline and other boundaries.
What are the stages of non-severe thunderstorm development? Cumulus, mature, and dissipating
What non-severe thunderstorm stage is the most violent? Mature stage.
How does a hailstone form and become larger? Hail forms in the shear zone between the updrafts and downdrafts near the freezing level in a convective cloud. The developing hailstone grows rapidly due to the accretion of super-cooled water droplets on ice crystals.
What causes a meso-high to form at the base of a downdraft? The meso-high results from the increased density of subsiding evaporatively cooled air striking the surface.
Why is the presence of strong mid-level winds essential to developing severe thunderstorms? Because they can carry precipitation downstream to fall ahead of the updraft; keeping the updraft unobstructed.
What is “discrete propagation?” New cells forming on the inflow flank (while older cells decay) causing the thunderstorm complex appear to move to the right of the mid-level winds.
How do strong winds aloft contribute to supercell severe thunderstorm development? They act as an exhaust mechanism, enhancing the updraft.
What is the Magnus effect? When the updraft shifts to the right (lower pressure) due to pressure imbalances
What term refers to the supercell downdraft associated with the gust front? The forward flank downdraft (FFD).
What downdrafts are associated with the RFD? Downbursts and microbursts
What are the characteristics of the right cell of a splitting cell? Cyclonic rotation; deviates approximately 30 to the right and slows down; potential tornado producer.
What time of day has the greatest frequency of tornado occurrences? Between 1200 and 2100 hours local time
What is the highest wind speed ever measured in a tornado? 313 miles per hour or 272 knots.
What area of the US has the greatest frequency of tornado occurrences? In an area bounded by 600 miles east of the Rockies to 100 miles west of the Appalachians.
What is the average length of a tornado path? 20 to 40 miles.
Where is the most common place for tornadoes to first appear in relation to the low-level moist area? At the windward border of the moist tongue near the 55F isodrosotherm.
What kind of air mass is normally associated with the dryline synoptic pattern? Type I air mass.
What is recommended as a first estimation of the location of the dryline? The 55F isodrosotherm.
What dew-point temperature difference should be present across a dryline? Greater than 10oF degrees.
Where do the most violent thunderstorms occur with dryline activity? At intersection points between the dryline and another boundary.
What type of weather pattern is the most predominant severe weather producer in the CONUS? The type B – frontal pattern.
Where does the most violent weather activity occur with a type B pattern? Where a squall line intersects a warm front or an outflow boundary.
What can lead to enhancement of frontal activity with a type C pattern? A major short-wave trough embedded in the westerly wind flow.
Why is hail very common with a type D pattern? Due to the low freezing level.
What are the two most frequent axes for NWF events? The first extends from eastern North Dakota east-southeast to southwestern Pennsylvania. The second axis extends from the Texas panhandle into Iowa
What is the average 500mb wind flow angle for an NWF event? 280.
What is the average Showalter index, the total totals index, and the surface-based lifted index associated with NWF activity? Less than –3C, greater than 54, and less than –6C, respectively.
What is a derecho? A rapidly moving extratropical convective system known to produce widespread significant straight-line wind damage via a family of downburst clusters.
What are the two most distinctive, common physical characteristics of a derecho? The radar configuration and the rapid rate of propagation in a direction slightly to the right of the mean wind vector.
What is an absolute requirement for the maintenance or life span of a derecho? High values of low-level moisture which results in very high levels of conditional instability.
What upper-level feature is involved in all derecho events? A 500mb short-wave trough.
What characterizes an MCC? Cloud shield temperatures at least as cold as –32C. Horizontal cloud tops extent to at least 100,000km2 (about 70 percent of the size of the state of Iowa). An interior cloud top region of temperatures colder than –52C and covering at least 50,000km2.
What are the stages in the lifecycle of a MCC? The genesis stage, the development stage, the mature stage, and the dissipation stage.
What are the standard indices for an MCC event? A surface-based lifted index less than –8, a total totals index greater than 54, a lifted index less than –4, and a K-value greater than 30.
Why is it extremely important to identify the upper-level difluence zone over an MCC genesis region? It generates an area of mass outflow and divergence into the top of the MCC that helps sustain the low-level convergence and the resultant mass inflow from the boundary layer through 700mb.
Define a Haboob? An intense sandstorm or dust storm resulting from a convective downdraft or downburst.
What are the two primary forecast concerns when forecasting a haboob? Visibility and wind speed.
What is the max wind speed you would forecast for a haboob moving at 30 knots? 58.5 knots.
How does dust appear on visible satellite imagery? Diffuse with a medium to light gray shade.
What are the only two agencies authorized to issue warnings on tropical cyclones? The Tropical Prediction Center and the Joint Typhoon Warning Center.
How would the surface pressure react with the approach and passage of a tropical cyclone? The pressure falls very rapidly 3 hours before the storm arrives and rises at an equal rate after passage.
What are the most significant clouds associated with a mature tropical cyclone? Heavy cumulus and cumulonimbus clouds that spiral inward toward the edge of the storm’s eye.
What cloud type is often the first clue to the arrival of a storm system? Cirrus that is becoming denser.
What is the first sign of an approaching cyclone? The sea swell.
What determines the size and speed of the sea swell? The velocity of the winds, the size of the water surface the winds are flowing over, and the slope and terrain of the ocean floor.
Define storm surge. An abnormal rise of the sea along a shore and is the result of storm winds. It’s measured as the difference between the actual sea-surface elevation and the elevation expected without a storm.
Sometimes the worst flooding associated with a tropical storm may occur several hours away from the time of the storm’s greatest intensity. Why? An interaction between the tide and the storm surge.
What is the most important factor in determining the storm surge? The relationship of the maximum wind to the coast. Essentially, if the maximum wind is perpendicular to the coast, the storm surge will be higher than if the maximum wind is parallel to the coast.
Where should you forecast heavy snow in relation to the 500mb vorticity center track? 6.5 to 7.0 downstream and 2.5 to the left.
Where would you forecast heavy snow in relation to the path of the surface low? 5 downstream and 2.5 to the left.
Where would you forecast heavy snow in relation to the 1,000-to–500mb thickness ridge? Within the contour interval of 5,310 and 5,370 meters.
What type of temperature advection in the lower levels increases the potential of heavy snow? Warm advection increases the potential.
Where does heavy snow fall that’s associated with a non-occluded low? What is the snowfall rate? It lies to the left of the surface low oriented parallel to the track of the low. The southern edge of the maximum snowfall is located about 60 nautical miles to the left of the low approximately 100–200 nautical miles wide
What are the winds, temperatures, and visibilities associated with a baroclinic deep occluding low? Blizzard: winds  40 knots, temperatures  20F; Severe blizzard: winds  50 knots, temperatures  10F. Visibilities are drastically reduced in both instances.
When does the heavy snowfall end that is associated with an inverted trough? All snowfall usually ends with the passage of the 700mb trough.
Indicate whether rain or snow should be forecast: Surface temperature 20F. Snow.
Indicate whether rain or snow should be forecast: Surface dew point of 5C. Rain.
Indicate whether rain or snow should be forecast: 850mb temperature of –4C. Snow.
Indicate whether rain or snow should be forecast: Freezing level at 2,000 feet. Rain.
Indicate whether rain or snow should be forecast: Freezing level 10mb above the surface. Snow.
Indicate whether rain or snow should be forecast: Entire sounding below freezing Snow.
What wind speed do strong nonconvective winds exceed? 34 knots.
What knowledge is beneficial to weather journeymen in better understanding their role as forecasters of nonconvective winds? (a) They must know how strong nonconvective winds impact their customers. (b) They must know the meteorological techniques used by their weather unit for forecasting nonconvective winds
In terms of nonconvective wind forecasting, describe a ROT It is a meteorological technique that has been proven successful in forecasting nonconvective wind speeds
Explain how flowcharts assist forecasting nonconvective winds A flowchart assists journeymen forecasters by taking them through a planned sequence of activity and decision making steps to arrive at a forecasting solution for nonconvective winds
What are wind boxes? Geographical areas that often experience wind speeds in excess of 35 knots.
During which months does the summer shamal typically occur? June through September.
Explain the synoptic conditions associated with a shamal during the summer? Surface high pressure in place over the northern portion of the Saudi Arabian Peninsula with the monsoon trough draped over the southern portion of the peninsula.
What are the three main soils in the desert? Clay, silt, and sand.
How long can a post-frontal dust storm last? Up to five days.
mb level with associated height in meters: 1500m 850mb
mb level with associated height in meters: 3100m 700mb
mb level with associated height in meters: 5500m 500mb
mb level with associated height in meters: 9300m 300mb
How are CAA and WAA identified on the vertical wind profile of a Skew-T? Backing or veering of the winds with height
How are isotherms identified on a Skew-T? Straight equally spaced lines that slope from the lower left to the upper right of the diagram.
What is the thickness of the 850–500mb layer when the 850mb level is at 1510m and the 500mb level is at 5520m? 4010m.
If we have a sample of air with a T of –12C and a w of 2g/kg, what would the (Tv) be? –11.67C.
What is potential temperature? The temperature an air sample would have if its pressure were increased to 1,000mb in a dry adiabatic process
What is wet-bulb temperature? It is the lowest temperature to which a parcel of air can be cooled by evaporating water into it at a constant pressure
What is wet-bulb potential temperature? It is the wet bulb temperature a parcel of air would have if it were brought moist adiabatically to the 1,000mb level
Define equivalent temperature. Equivalent temperature is the temperature a parcel of air would have if it were cooled both dry and moist adiabatically until all of its moisture was condensed from it.
What is equivalent potential temperature? It is the temperature a parcel of air would assume if, having reached its equivalent temperature, it was warmed by adiabatic compression to 1,000mb.
What is virtual temperature? The temperature at which a parcel of dry air would have the same density as a parcel of moist air at a given pressure.
What is the LCL? The level at which a parcel of air, when lifted, will cool dry adiabatically until condensation occurs.
The intersection of what two lines comprises the LCL? The mixing ratio line and the dry adiabat.
What is the CCL? The theoretical level where condensation in an ascending parcel is reached because of convection
What determines the method of finding the CCL? How you are going to use it.
What is the MCL? The MCL is the lowest height in a layer, mixed by turbulence, at which saturation occurs after complete mixing of the atmosphere
What is the MCL used for? Forecasting cloud bases in areas of strong mechanical mixing
What is Tc? The temperature that the surface air must reach to initiate convective currents that will extend high enough for the air to become saturated.
What is Tcml? A method to compute the TC when the moisture content is highly variable in the lower levels near the surface.
What is the LFC? The height at which a parcel of air , which is lifted, first becomes warmer (less dense) than the environment.
What is indicated when the TW will not cross the temperature curve when extended upward? No LFC exists.
What kind of lapse rate is associated with an inversion? Negative.
What kind of inversion is surface based? Radiational.
What is the difference between a subsidence inversion and a frontal inversion? The dew point associated with a subsidence inversion rapidly decreases at the base of the inversion. The dew point associated with a frontal inversion increases.
What is CAPE? The buoyancy that a parcel of air has as compared to its environment.
What happens when the CAPE goes above 2,500 J/kg? Hail potential increases dramatically.
What comprises the TT index? Vertical totals and cross totals.
What are the two main parameters we look at for the TT index? Temperature and moisture.
What makes up the SWEAT index? Temp and dew point at both 500 and 850mbs plus wind speeds and directional shear
What does the SWEAT index evaluate? The potential of thunderstorms to produce tornadoes.
What moisture parameters are incorporated in the K Index? 850mb dew point and 700mb dewpoint depression.
Where would the K index be least effective: Patrick AFB, Scott AFB, Peterson AFB or Ft. Lewis? Peterson AFB.
What does a negative SSI indicate? Unstable and buoyant lower levels of the atmosphere.
Below 10,000 ft, what is the hail distribution between areas in the storm and areas beneath the overhang of the cloud? Equally divided.
Between 10,000 and 20,000 ft, what is the hail distribution? 40 percent in the clear air, 60 percent in the storm, and 85 percent under the overhang.
Above 20,000 ft, what is the hail distribution in the storm and in the clear air beneath the anvil or overhang of the cloud? 80 percent in storm with 20 percent in the clear air or overhang.
Do you forecast hail if the CCL is at 830mb, the freezing level is at 700mb, and the EL is at 150mb? 130/680 = .19 Yes.
Do you forecast hail if the CCL is at 795mb, the freezing level is at 590mb, and the EL is at 210mb? 205/585 = .35 No.
What is an important point to remember about hail and aircraft? Aircraft may encounter hail at any altitude in or near thunderstorms.
What is the first step in forecasting hail? Determine the CCL.
If a sounding on a Skew-T has an inversion, what point on the inversion do you use to calculate T1? The warmest part of the inversion
What layer closely approximates the direction of maximum gusts at the surface? Between 10,000 and 14,000 feet.
What is important to remember in using the T2 method? Indicates the maximum gusts expected and that the thunderstorm must pass over the forecast point and moderate to heavy rain must occur, except in a Type IV sounding.
What is the better indicator of a frontal zone, the temperature or dewpoint curve? Dewpoint curve
What are the best sources for identifying frontal inversions? A combination of temperature and dewpoint curves coupled with the vertical wind distribution
Do wind speeds usually increase or decrease with a wind shift? Increase.
What determines the severity when forecasting turbulence in convective clouds? The temperature difference between the moist adiabat and the free-air temperature curve.
From the surface to 9,000 feet, what do we use to forecast the maximum surface temperature? The convective temperature.
When is the best time to apply forecast sounding? Max heating.
In the low levels what parameter is most favorable for destabilization? Moisture.
What parameter is most conducive to destabilization at 700mb? Dry-air advection
Is cold air advection or weak warm air advection favorable for destabilization at 500mb? Cold-air advection, occasionally weak warm air advection.
Created by: adgaston