Term
| State how divergence and convergence can change the surface pressure: |
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Definition
| The pressure at the surface directly relates to the mass of air in the vertical column above the surface. The surface pressure measures the net effect of the convergence and divergence |
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Term
| What mechanism is believed to be the primary cause of the development of high-and low pressure areas? |
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Definition
| Excess or net divergence aloft for lows. Excess or net convergence aloft for highs |
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Term
| What process creates the chimney effect? What happens to the mass in the column of air? |
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Definition
| Net divergence; it decreases. |
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Term
| What process creates the damper effect? What happens to the mass in the column of air? |
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Definition
| Net convergence; it increases. |
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Term
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Definition
An area of closed counterclockwise circulation occurring on a frontal surface.
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Term
| Explain the difference between stable and unstable waves: |
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Definition
A stable wave has the amplitude decreasing or remaining the same with time and is usually filling or
showing no change in intensity. An unstable wave has the amplitude increasing with time and is usually deepening.
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Term
| Where does an amplifying short wave extract energy during the baroclinic process? |
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Definition
| From the north/south temperature gradient produced by differential heating. |
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Term
| What causes upper-level short wave amplification? |
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Definition
| Large energy transfer (by means of thermal advection) from the temperature gradient to the wave. |
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Term
| How do short waves convert energy into low-level circulations? |
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Definition
| By converting potential energy (transferred from the temperature gradient to the short wave) to kinetic energy. The short wave uses the potential energy to develop the low-level circulation (kinetic energy). |
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Term
| What can be said about baroclinic instability and the development of midlatitude synoptic-scale systems? |
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Definition
It’s the primary mechanism responsible for the development of midlatitude synoptic-scale systems.
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Term
| What’s the relationship between the thermal wave and the contour wave during the baroclinic process? |
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Definition
The thermal wave and contour wave are out-of-phase.
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Term
| Where is cyclogenesis favored in reference to the long-wave pattern? |
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Definition
| At and just downstream from a long-wave trough axis. |
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Term
| What’s the significance and orientation of a negatively tilted trough? |
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Definition
They cause stronger divergence and, therefore, support stronger cyclogenesis.
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Term
| Under what kind of windflow aloft does cyclogenesis typically occur? |
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Definition
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Term
| Explain Petterssen’s rule: |
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Definition
Cyclogenesis occurs when and where an area of upper-level divergence (PVA) becomes superimposed over a low-level frontal zone across which the thermal advection is weak.
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Term
| What causes the surface low to deepen during the self-development process? |
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Definition
Divergence over the surface low.
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Term
| How does boundary layer convergence contribute to the self-development process? |
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Definition
By acting as a breaking mechanism.
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Term
| During the wave initiation stage, what’s associated with the short-wave trough that causes a wave to form on a front? |
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Definition
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Term
| During the wave intensification stage, what causes the upper-level short-wave trough to deepen? What product supports this? |
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Definition
Cold-air advection; 500-mb product.
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Term
| During what stage of low development does an occlusion occur? |
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Definition
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Term
| In what stage of development does a low that’s nearly vertically stacked and is continuing to deepen occur? |
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Definition
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Term
| The winds _____ with height through a warm front. |
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Definition
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Term
| The winds _____ with height through a cold front. |
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Definition
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Term
| The surface winds _____ with passage of a warm front. |
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Definition
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Term
| The surface winds are usually _______ behind both warm and cold fronts. (Greatest or weakest?) |
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Definition
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Term
| Lapse rate through the frontal zone _______ sharply and the dew-point curve ______ sharply. |
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Definition
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Term
| What conveyor belt is a set of streamlines that originates at low levels in the moist tropical air mass? |
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Definition
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Term
| What conveyor belt originates in the low levels and is associated with subsidence well ahead of the low center? |
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Definition
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Term
| Which conveyor belt originates at the upper levels? |
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Definition
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Term
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Definition
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Term
| Warm air replacing cold air: |
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Definition
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Term
| Cold front aloft; warm front on surface: |
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Definition
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Term
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Definition
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Term
| Warm front aloft; cold front on surface: |
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Definition
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Term
| Cold air replacing warm air: |
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Definition
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Term
| Cold air is parallel to the front: |
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Definition
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Term
Name the five factors that determine the type and intensity of frontal weather: |
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Definition
The slope of the front, the water vapor content, stability of the air masses, speed of the front, the relative motion of air masses at the front.
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Term
| Why does weather associated with a frontal passage differ from one place to another along the same front? |
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Definition
Because air mass modifications and mixing create variations in characteristics within the air mass.
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Term
| Classify the frontal system associated with it as active or inactive: Slope 1/40 to 1/80 |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Net windflow is up the frontal slope |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Net windflow is down the frontal slope |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Katafront |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Anafront |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Line of thunderstorms 100 miles ahead of front |
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Thunderstorms and rain in immediate vicinity of front only |
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Definition
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Term
Classify the frontal system associated with it as active or inactive: Sharp temperature gradient with front
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Definition
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Term
| Classify the frontal system associated with it as active or inactive: Dew point and winds are best indicators of frontal passage |
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Definition
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Term
| At what speeds do warm fronts generally move? |
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Definition
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Term
| How does the width of the warm frontal band of weather differ from that of either the inactive or active cold fronts? |
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Definition
Weather occurs up to a several hundred mile wide band ahead of the surface warm front; even the active cold frontal band of weather is much narrower.
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Term
| Describe the situation in which thunderstorms develop with a warm front: |
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Definition
If the overrunning air is unstable, embedded thunderstorms are likely with the warm front.
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Term
| Define the term stationary front: |
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Definition
A front moving less than 5 knots steadily in any direction.
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Term
| Weather associated with a stationary front is similar to the weather found with what other type of front? |
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Definition
It basically resembles warm front weather, but is in a somewhat narrower band.
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Term
| With the approach of a warm front, what change should occur to the pressure, wind, temperature, and dew point? |
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Definition
Pressure falls rapidly or unsteadily, wind velocity increases, temperature and dew point remain constant or rise slowly.
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Term
| On the 850-mb product, what’s the relationship between the warm front and the isotherms? |
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Definition
| The isotherms will be packed ahead of the front and parallel to it. |
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Term
| Which regions of the United States have the most frontal occlusions? |
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Definition
The North—both the northwest and northeast portions.
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Term
| In what season of the year are occluded fronts most common in the United States? |
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Definition
During the winter months.
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Term
If the air behind the cold front is colder than the air ahead of the warm front, what type of
occlusion will occur? |
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Definition
| A cold frontal occlusion. |
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Term
| What type of occlusion occurs when the air behind the cold front is warmer than the air ahead of the warm front? |
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Definition
| A warm frontal occlusion. |
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Term
| Where are the embedded thunderstorms with a cold frontal occlusion normally located? |
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Definition
| The embedded thunderstorms occur with the passage of the surface occluded front. |
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Term
| Which type of occluded front normally has the wider cloud system? |
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Definition
| A warm frontal occlusion. |
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Term
| What type of clouds and weather normally precede a cold occlusion? |
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Definition
Warm frontal clouds and precipitation.
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Term
| With a cold occlusion passage, what will the pressure do? |
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Definition
| Rise rapidly following passage. |
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Term
| As the occlusion process dissipates the warm front, what happens to the thickness gradient associated with the surface front? |
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Definition
| Thickness gradient decreases. |
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Term
| If a pilot descends vertically through a cold-type occlusion to pass through both fronts, how will the wind switch? |
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Definition
| The winds will first back, and then veer. |
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Term
| In a well-developed warm occlusion, what’s the relationship between the cold front portion and the warm front? |
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Definition
| The cold front will be aloft ahead of the warm front. |
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Term
| If showers and thunderstorms occur, where will they usually be located in relation to the front? |
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Definition
| Ahead of and with the upper cold front portion. |
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Term
| Name the four characteristics that are usually occurring with warm-type occlusions: |
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Definition
Increased cloudiness as the upper front approaches.
Greatest clearing of clouds following upper front passage.
Steady rise of pressure following surface front.
Surface temperature rises following surface front passage. |
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Term
| If a pilot descends vertically through a warm-type occlusion to pass through both fronts, how does the wind direction change? |
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Definition
| First it will veer, and then back. |
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Term
| Why are cols favored areas for frontogenesis? |
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Definition
| Because the horizontal motions of the atmosphere in these areas contribute to sharp horizontal temperature gradients. |
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Term
| What will a sharpening of the cyclonic turning do to a front? |
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Definition
| Assists in maintaining or frontogenesizing the front. |
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Term
| How do diabatics support frontogenesis? |
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Definition
By heating the warm air or cooling the cold air.
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Term
| How do diabatics support frontolysis? |
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Definition
By cooling the warm air or heating the cold air.
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Term
| Name the three ways to measure frontal intensity by means of density contrast: |
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Definition
| Thickness gradient, temperature gradient, and lapse rate. |
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Term
| What’s indicated by a negative lapse rate with a cold front in the vicinity? |
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Definition
This indicates that the cold front is strong.
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Term
| What are two other ways to identify the strength of a front outside of density differences? |
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Definition
| Turbulence and wind shear. |
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Term
| Classify the intensity of fronts having the following characteristics: Temperature gradient 15°F/100 miles and thermal wind shear 65 knots |
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Definition
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Term
| Classify the intensity of fronts having the following characteristics: Temperature gradient 8°F/100 miles and thermal wind shear 30 knots |
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Definition
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Term
| Classify the intensity of fronts having the following characteristics: Temperature gradient 25°F/100 miles and thermal wind shear 85 knots |
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Definition
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