WX 301 FINAL || 100% Errorless Answers.
NUMERICAL correct answers WEATHER PREDICTION
1. Explain why the true state of the atmosphere can never be known exactly and can only be
approximated by assimilating all available data correct answers +Not all aspects of the
atmosphere are observed equally.
+Coverage is intermittent in both space and time
+Instruments, themselves, have error.
2. Explain the fundamental difference between ensemble forecast models and deterministic
forecast models correct answers +Deterministic forecasts start with an initial state and generate a
single forecast
+Ensembles utilize multiple forecasts for the same time period
Deterministic Models correct answers GFS: Global Forecast System
NAM: North America Mesoscale model
RAP: Rapid Refresh Model
3. Determine the analysis time, valid time, forecast length given numerical model output. correct
answers GFS/NAM: Runs four times per day (00, 06, 12, and 18 UTC) out to 16 days.
RAP: (0- to 12-hr) forecast
Ensembles correct answers GEFS: Global Ensemble Forecast System
SREF: Short-Range Ensemble Forecast
WINTER correct answers WEATHER
1. Identify the favored regions around a low pressure system the formation of snow and other
types of frozen precipitation correct answers Snow frequently to northwest of Low and north of
warm front
2. Describe how the temperature must change with height to produce rain, snow, sleet, or
freezing. correct answers - Thickness of less than 5400m--snow.
- Thickness of greater than 5400m--rain.
3. Define critical thickness correct answers +Thickness is useful in determining if an air mass is
cold enough to produce snow
+The thickness at which the air is cold enough to snow is referred to as the "critical thickness"
4. Analyze a 1000-500mb thickness chart to determine the likelihood of rain versus snow.
(Recall that the 540 dam line only identifies where snow first becomes possible, the lower the
, thickness values the greater the likelihood of snow.) correct answers +5220m or less - almost
definitely snow
+5400m = rain/snow mix or sleet/freezing rain
+5520m or greater - almost definitely rain
5. Define what is meant by ground icing "hold-over" times. correct answers Hold-over time:
Length of time deicing fluid will prevent ice build-up on an aircraft.
6. Explain why equivalent liquid water precipitation rate is important in aviation winter weather
decision-making and how it affects hold-over times. correct answers We have no effective means
of determining precipitation rates in real time
ICING correct answers AIRCRAFT PERFORMANCE
1. Identify the fundamental cause of icing correct answers Flying through liquid water droplets
(clouds or precipitation) at temperatures below freezing
2. Identify the temperatures favorable for rime, clear and mixed icing correct answers Rime-
freeze rapidly causing trapped air(-15c)
Clear-larger drops with little trapped air(-5-0c)
Mixed- mixed drop size (-5 to -15c)
3. Describe the impacts of icing on aircraft performance (stall speed, fuel consumption, service
ceiling, stall angle, etc) correct answers Decrease on all performance.
4. Describe the effects exposure time on ice buildup. correct answers Most significant icing
degradation occurs in the first few minutes of build up
5. Describe the relationship between wing size and performance degradation due to icing correct
answers Smaller wings therefore tend to accrete more ice than larger wings
6. Identify the most critical aerodynamic factor in icing accumulation correct answers -Small
amounts of ice can increase the stall speed by 15 kts
-Icing on wings can disrupt flow over the ailerons
7. Describe super-cooled large droplets (SLDs) and runback icing as well the hazards they pose
correct answers -Small droplets freeze more rapidly
-Super-cooled Large Droplets (SLDs) freeze more slowly and tend to run back
SLD > 0.04 mm
ICING correct answers METEOROLOGICAL CONDITIONS
1. Identify the favored areas for icing near mountains correct answers +Near mountains
(orographic lift)
+Cumulus congestus and Thunderstorms (strong updrafts—vertical motion)
+Areas of sleet
NUMERICAL correct answers WEATHER PREDICTION
1. Explain why the true state of the atmosphere can never be known exactly and can only be
approximated by assimilating all available data correct answers +Not all aspects of the
atmosphere are observed equally.
+Coverage is intermittent in both space and time
+Instruments, themselves, have error.
2. Explain the fundamental difference between ensemble forecast models and deterministic
forecast models correct answers +Deterministic forecasts start with an initial state and generate a
single forecast
+Ensembles utilize multiple forecasts for the same time period
Deterministic Models correct answers GFS: Global Forecast System
NAM: North America Mesoscale model
RAP: Rapid Refresh Model
3. Determine the analysis time, valid time, forecast length given numerical model output. correct
answers GFS/NAM: Runs four times per day (00, 06, 12, and 18 UTC) out to 16 days.
RAP: (0- to 12-hr) forecast
Ensembles correct answers GEFS: Global Ensemble Forecast System
SREF: Short-Range Ensemble Forecast
WINTER correct answers WEATHER
1. Identify the favored regions around a low pressure system the formation of snow and other
types of frozen precipitation correct answers Snow frequently to northwest of Low and north of
warm front
2. Describe how the temperature must change with height to produce rain, snow, sleet, or
freezing. correct answers - Thickness of less than 5400m--snow.
- Thickness of greater than 5400m--rain.
3. Define critical thickness correct answers +Thickness is useful in determining if an air mass is
cold enough to produce snow
+The thickness at which the air is cold enough to snow is referred to as the "critical thickness"
4. Analyze a 1000-500mb thickness chart to determine the likelihood of rain versus snow.
(Recall that the 540 dam line only identifies where snow first becomes possible, the lower the
, thickness values the greater the likelihood of snow.) correct answers +5220m or less - almost
definitely snow
+5400m = rain/snow mix or sleet/freezing rain
+5520m or greater - almost definitely rain
5. Define what is meant by ground icing "hold-over" times. correct answers Hold-over time:
Length of time deicing fluid will prevent ice build-up on an aircraft.
6. Explain why equivalent liquid water precipitation rate is important in aviation winter weather
decision-making and how it affects hold-over times. correct answers We have no effective means
of determining precipitation rates in real time
ICING correct answers AIRCRAFT PERFORMANCE
1. Identify the fundamental cause of icing correct answers Flying through liquid water droplets
(clouds or precipitation) at temperatures below freezing
2. Identify the temperatures favorable for rime, clear and mixed icing correct answers Rime-
freeze rapidly causing trapped air(-15c)
Clear-larger drops with little trapped air(-5-0c)
Mixed- mixed drop size (-5 to -15c)
3. Describe the impacts of icing on aircraft performance (stall speed, fuel consumption, service
ceiling, stall angle, etc) correct answers Decrease on all performance.
4. Describe the effects exposure time on ice buildup. correct answers Most significant icing
degradation occurs in the first few minutes of build up
5. Describe the relationship between wing size and performance degradation due to icing correct
answers Smaller wings therefore tend to accrete more ice than larger wings
6. Identify the most critical aerodynamic factor in icing accumulation correct answers -Small
amounts of ice can increase the stall speed by 15 kts
-Icing on wings can disrupt flow over the ailerons
7. Describe super-cooled large droplets (SLDs) and runback icing as well the hazards they pose
correct answers -Small droplets freeze more rapidly
-Super-cooled Large Droplets (SLDs) freeze more slowly and tend to run back
SLD > 0.04 mm
ICING correct answers METEOROLOGICAL CONDITIONS
1. Identify the favored areas for icing near mountains correct answers +Near mountains
(orographic lift)
+Cumulus congestus and Thunderstorms (strong updrafts—vertical motion)
+Areas of sleet
