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| FORECAST CONCEPTS 2 |
This is a continuation of the forecast concepts test from this link:
http://theweatherprediction.com/fxconcepts/
In this webpage you will find forecasting situations. Each one will be expressed as a multiple choice question. The answer explanation for each question is at the bottom of this webpage.
21. The wind is strong from the west in Miami, Florida. There is a tropical storm in the region. What general direction from Miami is the tropical storm's center of circulation located?
a. North
b. South
c. East
d. West
22. The surface relative humidity changes from 50% to 70% in the course of 3 hours. Which of the following does a forecaster know for certain given only this information?
a. The amount of moisture in the air is increasing
b. Daytime heating is occurring
c. The air is becoming closer to saturation
d. Cold Air Advection is occurring
e. Warm Air Advection is occurring
23. St. Louis, Missouri has a near record high on January 15 and then a near record low on January 18. In this situation the jet stream is most likely to be:
a. Weak
b. Zonal
c. Meridional
d. Retrograding
24. The following four location (Miami, FL; Dallas, TX; Phoenix, AZ and Chicago, IL) have the same 7 am temperature of 70 F and clear skies with light winds are expected at all four cities during the day. Which city would typically have the warmest high temperature for that day?
a. Miami
b. Dallas
c. Phoenix
d. Chicago
25. You are storm chasing in western Oklahoma around noon. The NWS at OKC launches an 18 Z special sounding. The highlights of the sounding are 3,400 Joules per kilogram CAPE, 450 storm relative helicity, 520 SWEAT, surface dewpoint of 68 F, and a cap of 1.5 C. There is also a noticeable dryline bulge in the eastern Texas Panhandle. As a storm chaser, what should you expect and do that afternoon?
a. Storms should not be severe, head for home
b. Nothing is going to happen this afternoon due to a very strong cap, head for home
c. Nothing is going to happen due to the lack of a lifting mechanism, head for home
d. A severe weather outbreak is likely, severe storms are imminent within the next few hours, stay on location and wait for rapid development of cells
e. A severe weather outbreak is likely, but it looks like it is going to occur overnight, take a long lunch at Diary Queen and wait around until the evening
26. You are in Buffalo, NY. Many ingredients are coming together for a "lake-effect snow event". All of the following are contributing factors to heavy lake-effect snow EXCEPT:
a. Inversion at 475 mb
b. Cold polar air with an upstream relative humidity of 30% advecting over lake
c. Average PBL wind of 25 knots with a 20 degree directional change in the wind from the surface to 700 mb
d. Average PBL temperature of 33 F with a dewpoint of 17 in Buffalo
e. Deep layer of polar air advecting over lake
27. Light rain is falling and the surface air temperature is 38 F with a dewpoint of 38 F. The precipitation turns to heavy wet snow for 2 hours. No thermal advection is taking place. What is the most likely surface air temperature during the middle of the heavy wet snow event?
a. 38 F
b. 36 F
c. 34 F
d. 32 F
e. 30 F
28. The location is Atlanta, Georgia. The wind is from the east and then gradually turns to the south during the morning hours. The dewpoint increases during the morning hours. Which frontal passage type most likely occurred during the morning?
a. Warm front
b. Cold front
c. Dry line
d. Stationary front
29. If the barometric pressure has been rising over the last 6 hours, which of the following answer(s) could explain this:
a. Low pressure system moving away from the forecast area
b. High pressure system moving toward the forecast area
c. Cold front has passed and is moving away from the forecast area
d. Warm front has passed and is moving away from the forecast area
e. All of the above
30. In which case(s) below would the answer choice define a storm as a severe thunderstorm using the National Weather Service definition?
a. 50 mile per hour convective wind gusts that results in significant property damage
b. Pea size hail that destroys a large amount of agriculture
c. Vivid lightning that results in deaths
d. Flash flooding that results in deaths
e. All of the above
f. None of the above
31. All of the following tend to make a smog event worse EXCEPT:
a. Strong temperature inversion at the top of the boundary layer
b. Strong wind in the boundary layer
c. Urban setting
d. High relative humidity and warm temperature
e. High pressure subsidence
32. All of the following help contribute to flash flooding during heavy rain EXCEPT:
a. Frozen top soil
b. Snow melt
c. Urbanization
d. Dense vegetation
33. Which of the following is most likely to produce a higher than expected overnight low temperature?
a. Higher dewpoint overnight than expected
b. Less clouds overnight than expected
c. Lower wind speeds overnight than expected
d. Stronger CAA overnight than expected
34. Visible satellite imagery uses _____________ to determine the presence of clouds.
a. Temperature
b. Reflected solar radiation
c. Water vapor density
d. Longwave radiation
35. All the following ingredients are favorable for hurricane strengthening EXCEPT:
a. Strong upper tropospheric wind
b. Movement over warmer ocean water
c. Deepening layer of warm and moist air in the lower troposphere
d. Increasing forward motion of the hurricane
36. When frost dissipates during the day, one can expect the frost to first dissipate that is on a __________ facing hill slope in Kentucky in fall.
a. Southeast
b. Southwest
c. Northwest
d. Northeast
37. Statement 1: The greatest uplift from DPVA occurs directly under the vort max. Statement 2: Low level Cold Air Advection promotes rising air since it acts like a cold front.
a. Statement 1 and 2 are both true
b. Statement 1 and 2 are both false
c. Statement 1 is true and Statement 2 is false
d. Statement 1 is false and Statement 2 is true
38. For each answer below, the skies are clear overnight and the day of the year is the same. For which answer would you expect the greatest quantity of morning dew? The temperatures and dewpoints below are all for 8 pm the previous evening.
a. Temperature = 80, Dewpoint = 75
b. Temperature = 60, Dewpoint = 55
c. Temperature = 40, Dewpoint = 35
d. Temperature = 20, Dewpoint = 15
39. Assuming the strength of thermal advection type is the same for each answer and assuming the rate of the absolute value of vertical motion magnitude due to a jet streak alone is the same in each quadrant, which location with which thermal advection type should have the strongest upward dynamic vertical motion?
a. Left front quadrant, low level cold air advection
b. Right front quadrant, low level cold air advection
c. Left rear quadrant, low level warm air advection
d. Right rear quadrant, low level warm air advection
40. At which temperature is it too cold to snow?
a. 0 F
b. -10 F
c. -20 F
d. -30 F
e. None of the above
Answer Explanations:
21. The wind flow is cyclonic around hurricanes (counter-clockwise). If the wind is strong from the west that would mean the tropical storm is Northish of Miami. The answer is a.
22. Since we do not know how the temperature and dewpoint is changing then we can not be for certain that the amount of moisture in the air is increasing when the relative humidity increases. Daytime heating would generally decrease the relative humidity since the dewpoint depression would increase. There is no certain relationship between thermal advection and relative humidity. Each situation is unique. The only answer that is known for certain is c. 70% is closer to a saturation of 100% than 50% is.
23. A zonal jet stream would mean the flow is west to east. In a zonal flow the surface temperature will tend to decrease toward the pole but not much in the west to east direction. This would not allow from the large temperature swing in St. Louis. A meridional jet stream has alternating troughs and ridges. These troughs and ridges tend to progress toward the east over time. Likely in this situation, St. Louis is being influenced by a longwave ridge and then by a longwave trough. The ridge and trough would be fairly significant to cause the near record temperatures. A weak or retrograding jet stream would not be discriminating factors in this situation. The best answer is c.
24. The key is to pick the city that is typically driest. A dry PBL and soil with a relative lack of vegetation will typically warm more under the same sun and same initial weather conditions as compared to a place that has more moisture and more vegetation. This is because the latent heat absorption from evaporation and absorption of solar radiation by plants reduces the temperature. With a dry soil the solar radiation is converted into all sensible energy which in turn produces a warmer measured temperature. The best answer is Phoenix.
25. The parameters indicate extreme instability, strong shearing, a high threat for severe thunderstorms and tornadoes, a high value a low level moisture and a weak cap. All this together suggests severe storms are imminent. Best answer is d. See webpage below for parameter interpretations:
http://theweatherprediction.com/severe/indices/
26. See the webpage below. A low upstream relative humidity is the one answer that will reduce the lake-effect event. When air is dry, much of the evaporating moisture will be used to increase the relative humidity instead of going into precipitation production. The best answer is b.
http://theweatherprediction.com/winterwx/lesnow/
27. In this situation the melting snow will absorb latent heat. This will act to reduce the air temperature. Also, since the ice is colder than the air it is falling into initially, a cooling of the air would be expected through thermal equilibrium effects. The temperature should decrease down to the freezing point during the wet snow. Since this is a wet snow, a temperature of below freezing would not be expected since a rain/ice mixture will be 32 F and there are no factors to reduce the temperature below freezing. If the temperature tried to drop below freezing it would freeze some of the snow rather than decrease the temperature. Since the freezing process releases latent heat and thus warms the air, the temperature has a bear of a time dropping below freezing in this situation. The best answer is d.
28. A south wind in Atlanta will generally bring in higher dewpoints from the Gulf of Mexico and warmer air after frontal passage. The front passed through thus it is not stationary. Best answer is a.
29. The tendency is for barometric pressure to decrease as a warm or cold front approaches and rise after the front passes. This is because the greatest lifting and convergence often occurs along the frontal boundary. Rising air lowers barometric pressure. Thus, both c and d are correct. If a low pressure system is moving away from the area often a high pressure system will be building in. Answers a and b often work in conjunction with each other. Answer e is the best answer.
30. The definition of a severe thunderstorm according to the National Weather Service is winds of equal or greater than 50 knots (58 miles per hour), hail of the size 0.75 inches or greater in diameter or tornadic activity. Answer a does not meet the wind speed criteria; Answer b does not meet the hail size criteria; All thunderstorms have lightning thus answer c is not a discriminating factor between thunderstorms and severe thunderstorms and is not part of the definition. Often a special weather statement would be issued in cases for vivid lightning; Answer d is not part of the definition. A flash flood warning would often be issued. That leaves f (none of the above) as the best answer. It is important to remember the dangers that storms have even if they are not officially severe storms.
31. A strong temperature inversion traps pollution particulates near the earth's surface. This concentration of pollutants will enhance a smog problem. High pressure subsidence can promote a temperature inversion or stable lower troposphere. The urban environment will release more pollutants into the air (cars and factories) than will occur in a rural environment. When the relative humidity is high and the air is warm, moisture will condense upon pollution particles making them bigger. This reduces visibility and gives the air the whitish to brownish color. Strong wind will tend to mix the air more and blow the particulates downstream and fan them out over a larger area, thus diluting the smog. Answer b is the best answer.
32. Both a frozen top soil and urbanization will reduce the amount of rain that can soak into the earth's ground surface. This will increase run off. Snow melt adds run off to the rain's runoff. Dense vegetation however will trap some of the rain and soak up some of the rain. Dense vegetation also tends to have soils that allow rain to soak into fairly well. The best answer is d.
33. The process would need to be a warming process or a process that reduces the amount of cooling. Stronger Cold Air Advection is a cooling process thus that answer can be eliminated. Lower wind tends to have a cooling effect on temperatures since the earth's surface cools by longwave energy loss at night. If the wind is weak there will be less mixing of this chilling air at the earth's surface with air higher aloft. Now, answer c can be eliminated. Less cloud cover would increase the amount of longwave energy loss from the surface. This would cool the temperature more than expected thus answer b is not correct. If the dewpoint is higher than expected then there will be more moisture in the air to absorb longwave radiation. Also, a higher dew point can reduce cooling if the temperature drops to the dewpoint since dew formation releases latent heat. The best answer is a.
34. Infrared satellite imagery uses radiation emission to detect clouds. From this, the temperature of the cloud(s) can be determined. Water vapor imagery detects moisture in the middle troposphere by radiation given off from water vapor. Visible imagery detects reflected solar radiation from the clouds. The best answer is b.
35. An increasing forward motion will increase surface wind relative to the ground on one side of the hurricane and decrease them on the other. A deepening layer of warm and moist air will help further sustain the warm core structure of the storm. Deep moist air when lifted will release large amounts of latent heat. Movement over warmer ocean water will also add more latent heat release to the storm. Strong upper tropospheric wind will reduce the warm core structure of the storm by shearing it apart. Winds in the upper troposphere need to be light to enhance hurricane strengthening. The best answer is a.
36. Since Kentucky is in the mid-latitudes and it is the fall, the sun will be in the southern half of the sky during the day. The sun rises in the southeast. South and east facing hill slopes will be exposed to the sun's radiation in the morning. The best answer is a.
37. Both statements are false. See the following links:
http://theweatherprediction.com/habyhints/255/
http://theweatherprediction.com/habyhints/254/
38. The dewpoint depression is the same for each case. Since the skies will be clear overnight, dew would be expected for answer a and b. Frozen dew and some frost is likely in case c. For answer d all frost would be expected. Warmer air can have a greater quantity of water vapor in the air. Thus, with a higher dewpoint there will be more moisture available to condense out of the air once saturation and condensation occur. The best answer is a.
39. Low level cold air advection promotes sinking air while low level warm air advection promotes rising air. Thus the cold air advection answers can be eliminated. Upper level divergence and rising air is promoted in the right rear and left front quadrants of a jet streak. Thus, answer d is the best answer.
40. Visit the following link: http://www.theweatherprediction.com/habyhints/222/. The best answer is none of the above.