1w071n-02 CDC Volume 3

When trying to determine hail size, the concept that should be considered is the strength of the updraft. An updraft refers to the upward movement of air within a storm. The stronger the updraft, the more likely it is to support the growth of larger hailstones. This is because a strong updraft can keep the hailstones suspended in the storm for a longer period of time, allowing them to accumulate more layers of ice and grow in size. Therefore, the strength of the updraft is a crucial factor in determining the size of hail that can be produced by a storm.

Tornadic vortex signature detection beyond 55 nautical miles is difficult due to beam broadening. As the radar beam travels further, it spreads out, resulting in a larger coverage area. This makes it challenging to accurately detect and distinguish the specific characteristics of a tornadic vortex at such long distances. The broadened beam may also pick up clutter and interference from other objects, further complicating the detection process.

Decompression is not a type of lifting mechanism for convection. Convection refers to the transfer of heat through the movement of fluids, such as air or water. Frontal lifting occurs when warm and cold air masses collide, causing the warm air to rise. Orographic lifting happens when air is forced to rise over a mountain or elevated terrain. However, decompression does not involve the vertical movement of air but rather the reduction of atmospheric pressure, which can lead to the expansion of gases.

The line echo wave pattern (LEWP) signature indicates a favorable environment for severe weather development. This means that conditions are conducive for the formation and intensification of severe weather events such as thunderstorms, tornadoes, or heavy rainfall. The LEWP signature is a valuable tool for forecasters as it helps them identify the potential for severe weather and issue appropriate warnings to the public.

Classic supercell thunderstorms typically produce hail the size of a golf ball. Hail is formed when there are strong updrafts in the storm that carry raindrops upward into extremely cold areas of the storm, causing them to freeze. As the frozen raindrops are carried by the updrafts, they collide with supercooled water droplets, causing them to freeze onto the hailstone and grow in size. The size of the hailstone is determined by the strength of the updrafts and the amount of supercooled water available. In classic supercell thunderstorms, which are known for their intense updrafts, golf ball-sized hail is commonly observed.

When a modifying airmass is cooler than the ground below, the letter "k" is appended to its label. This convention is used in meteorology to indicate that the airmass is colder than the surface it is moving over. The "k" stands for "kool," which is a phonetic representation of the word "cool." Therefore, the correct answer is lower case k.

The Great Plains is a vast and flat geographic area located between the Mississippi River and the Rocky Mountains. This region covers parts of the United States and Canada, including states such as North Dakota, South Dakota, Nebraska, Kansas, and Oklahoma. It is characterized by its grasslands, agricultural productivity, and its importance as a transportation corridor.

The Storm Prediction Center advisory charts outline areas where severe weather is expected. These charts provide information on the likelihood of severe weather events such as tornadoes, thunderstorms, and hail. By identifying these areas, the charts help to alert and inform the public, emergency responders, and other relevant parties about the potential risks and allow them to take necessary precautions.

The goal of severe weather analysis is to identify the preconditions that allow storms to become severe. This involves analyzing various factors such as atmospheric conditions, temperature, humidity, and wind patterns to determine the likelihood of a storm becoming severe. By identifying these preconditions, meteorologists can issue timely warnings and take appropriate measures to mitigate the potential impact of severe weather events.

Low-precipitation supercell thunderstorms are most commonly found along the dry line of west Texas. These storms typically have a smaller amount of precipitation compared to other types of supercells, which means they produce less rainfall. The dry line acts as a boundary between dry desert air and moist air from the Gulf of Mexico, creating ideal conditions for the formation of low-precipitation supercells. These storms often have a more organized structure and are known for producing severe weather, including tornadoes and large hail, but with less rainfall.

The VAD algorithm is used to analyze the wind field based on the Doppler radar data. In this case, if the algorithm detects no difference between the zero velocity line (representing no wind) and the zeroth harmonic (representing uniform wind in all directions), it means that there is no offset or variation in the wind field. Therefore, the wind field is considered uniform, with the same wind speed and direction throughout the area being analyzed.

The correct answer is Type II Gulf Coast. The Gulf Coast region is known for its warm and moist climate due to its proximity to the Gulf of Mexico. This region experiences a tropical air mass, which is characterized by its origin in the tropics and its warm and moist nature. Therefore, Type II Gulf Coast is the correct answer as it aligns with the description of a tropical air mass that is warm and moist.

A dry slot is commonly found south of the center of a low pressure system and is indicated by a relatively cloud-free region. This occurs when dry air is pulled into the system, creating a clear area amidst the surrounding clouds. It is a result of the interaction between warm and cold air masses, causing the dry air to wrap around the low pressure system and create a region of clearing.

The correct answer is that the WSR-88D radar can detect embedded thunderstorms well because its 10cm wavelength can see through the stratiform precipitation. This means that the radar can penetrate through the lighter, more uniform precipitation that often accompanies thunderstorms, allowing it to identify the embedded thunderstorms within. The radar's ability to see through the stratiform precipitation helps in accurately detecting and tracking these storms.

Models used in weather forecasting are based on current weather observations. These observations include data such as temperature, humidity, wind speed, and atmospheric pressure. By analyzing these current conditions, meteorologists can input the data into weather models to generate forecasts. These models use complex mathematical equations to simulate the behavior of the atmosphere and predict future weather patterns. Therefore, current weather observations serve as the initial conditions for these models, allowing them to make accurate predictions about future weather conditions.

The color-coded root mean square of the displayed velocity azimuth display winds provides information about the reliability of the winds. This means that it indicates how accurate and trustworthy the displayed wind data is. The color coding helps to visually represent the level of reliability, with different colors indicating different levels of confidence in the wind measurements.

To generate a base reflectivity product, the Weather Service Radar (WSR) 88D antenna must complete one elevation slice. This means that the radar antenna needs to scan a single vertical layer of the atmosphere at various angles to gather data on the reflectivity of precipitation particles within that layer. This information is then used to create a base reflectivity product, which shows the intensity of precipitation in a specific area. The other options, such as completing a 360° circle or multiple volume coverage patterns, are not necessary for generating a base reflectivity product.

The characteristic that is not one of the single-cell thunderstorm is frequent tornadoes. Single-cell thunderstorms are typically short-lived and do not have the necessary conditions to produce frequent tornadoes. While they may have high winds and hail, and weak vertical and horizontal wind shear, tornadoes are not commonly associated with single-cell thunderstorms.

The National Weather Service is the agency that produces discussions on model output, in addition to the Air Force Operational Weather Squadrons. The Joint Army Air Force Weather Information Network, Air Force Weather Agency, and Air Weather Service are not responsible for producing these discussions.

The storm total precipitation product provides continuously updated information on precipitation accumulations within 124 nautical miles of the radar. This means that the product gives data on the amount of precipitation that has accumulated within a radius of 124 nautical miles from the radar location.

The freezing level refers to the altitude at which the temperature drops to 0 degrees Celsius (32 degrees Fahrenheit), causing precipitation to freeze and fall as snow. Therefore, for most precipitation to reach the surface as snow, the freezing level must be at or below the surface. Among the given options, 1,200 feet is the closest to the surface, making it the correct answer.

The correct answer is 3/4 inch. This means that the algorithm will specifically search for hail that is larger than 3/4 inch in diameter. This size threshold is chosen because hail of this size or larger is generally considered to be severe and can cause significant damage.

Multi-cell storms typically regenerate along the gust front. The gust front is the leading edge of cold air that rushes out from the downdraft of a thunderstorm. As this cold air collides with warm, moist air ahead of the storm, it lifts the warm air, creating new updrafts and initiating the formation of new storm cells. This process of regeneration along the gust front allows multi-cell storms to continue and persist over an extended period of time.

The storm cell centroid algorithm is designed to accurately locate and track individual storm cells. It performs best when isolated, well-defined thunderstorms are present because in such conditions, the algorithm can easily identify and track the distinct storm cells without interference from other storm systems. In contrast, solid lines of thunderstorms, a mesoscale convective complex, or embedded multicell thunderstorms may make it more challenging for the algorithm to accurately identify and track individual storm cells due to the complexity and overlapping nature of these storm systems.

Tornadoes most frequently occur in families with long and wide paths in the Great Plains type of tornado-producing airmass. This is because the Great Plains region, located in the central part of the United States, is known for its favorable atmospheric conditions for tornado formation. The flat terrain, warm moist air from the Gulf of Mexico, and cool dry air from the Rocky Mountains create an ideal environment for the development of severe thunderstorms and tornadoes.

A dew-point temperature difference greater than 10oF degrees should exist across a dry line. This means that the air on one side of the dry line is significantly drier than the air on the other side. The larger the temperature difference, the stronger the dry line is.

Base radial velocity is the correct answer because it is a product used in the detection and location of rotating thunderstorms and in determining wind field characteristics. Radial velocity measures the speed and direction of motion of objects towards or away from a radar, and by analyzing the radial velocities of precipitation particles, meteorologists can identify rotation within thunderstorms and assess the wind patterns associated with them. Base reflectivity, severe weather analysis, and severe weather probability are not specifically focused on detecting rotating thunderstorms or determining wind field characteristics.

The spectrum width product is most effective when used with other products. This is because the spectrum width provides information about the variability of the Doppler velocities within a radar beam, but it does not provide a complete picture of the weather conditions. By combining the spectrum width with other products such as reflectivity or velocity, meteorologists can gain a more comprehensive understanding of the atmospheric conditions and make more accurate weather predictions.

The storm total precipitation product is limited in its ability to accurately capture small-scale features. This means that it may struggle to accurately represent the precipitation patterns and amounts in localized areas within a storm. However, it is still able to provide a comprehensive analysis of total precipitation accumulations over the entire storm.

Positive vorticity advection indicates divergence or upward vertical motion. Vorticity refers to the rotation of fluid particles in a fluid flow. Positive vorticity advection occurs when an area of higher vorticity is transported into a region, causing the fluid to spread out or diverge. This divergence leads to upward vertical motion as the fluid particles move away from each other. Therefore, positive vorticity advection is associated with divergence or upward vertical motion.

The storm track information product algorithm provides data on past, present, and future positions of thunderstorms. This means that it can give information about where thunderstorms have been in the past, where they are currently located, and where they are expected to move in the future. This algorithm is useful for tracking and predicting the movement of thunderstorms, which can help with forecasting severe weather events and providing early warnings to potentially affected areas.

The approximate precipitable/non-precipitable threshold is considered to be +18 dBZ. Decibel (dBZ) values are used in weather radar to measure the intensity of precipitation. A value of +18 dBZ indicates light precipitation, which is generally considered to be the threshold for determining whether precipitation is occurring or not.

Type III Pacific Coast is the correct answer because this type of airmass is characterized by cold air at all levels. The Pacific Coast region experiences the influence of cold ocean currents, which results in the development of cold and stable air masses. These air masses bring cold temperatures and often lead to foggy and damp conditions along the coast.

When the Doppler zero line has a noticeable S-shaped pattern, it indicates that the winds are veering with height. Veering refers to a change in wind direction in a clockwise manner with increasing height. This S-shaped pattern is often observed in the lower atmosphere and is caused by the interaction of wind with various features such as topography or frontal boundaries. It signifies a change in wind direction with height, which is characteristic of veering winds.

The composite reflectivity product is a radar product that combines the reflectivity values from multiple radar angles to create a single image. It is commonly used to identify significant weather features and provide an instant snapshot of the most important reflectivity features. However, it does not provide information about the 3-D structure of the reflectivity pattern. To visualize the 3-D structure, other radar products such as the vertical reflectivity profile or the radar echo top product would be more appropriate.

A velocity azimuth display (VAD) winds profile is a graphical representation of wind speed and direction at different altitudes. It typically displays the wind profiles at various azimuth angles. The maximum number of vertical wind profiles that can be displayed on a single VAD winds profile is 11. This means that the VAD can provide information about the wind at 11 different altitudes and azimuth angles, allowing for a comprehensive understanding of the wind patterns in a specific area.

In straight line flow, the main diffluent areas of a jet are the left front and right rear quadrants. This means that the jet is spreading out more in these areas compared to the other quadrants. The left front quadrant refers to the area on the left side of the jet at the front, while the right rear quadrant refers to the area on the right side of the jet at the rear. These areas experience the maximum spread or diffusion of the jet flow.

During a major cyclone, the maximum severe activity occurs from the time of maximum heating to a few hours after sunset. This is because the intense heating of the sun during the day leads to the development of strong updrafts and instability in the atmosphere, which fuels the cyclone's intensity. As the sun sets, the heating decreases, causing the activity to gradually diminish. Therefore, the period from maximum heating to a few hours after sunset is when the cyclone reaches its peak severity.

A lifted index (LI) greater than zero indicates stability. Stability refers to atmospheric conditions that resist vertical air movement, which inhibits the development of severe weather. When the LI is greater than zero, it suggests that the air is stable and less likely to produce thunderstorms or other severe weather events.

The melting level is displayed on the composite reflectivity product as a circular pattern of higher reflectivities. This means that the reflectivities are higher in a circular shape, indicating the presence of melting at a certain level in the atmosphere. This circular pattern helps meteorologists identify and track areas where melting is occurring, which can be important for understanding precipitation processes and forecasting weather conditions.

The echo tops product is based on data from the Base reflectivity product. This means that the echo tops information is derived from the radar's measurement of the reflectivity of precipitation or other targets in the atmosphere. Base reflectivity provides valuable data on the intensity and location of precipitation, which is then used to determine the height of the highest echoes or cloud tops in a storm.

The correct answer is 24 because the question asks for the maximum number of hours that the user selectable precipitation product can be generated for. Among the given options, 24 is the highest number of hours.

Beam broadening refers to the spreading of a radar beam as it travels through the atmosphere. This phenomenon causes the beam to become wider, resulting in a decrease in resolution and the inability to detect small features at long distances. Therefore, beam broadening is the correct answer as it explains the limitation of velocity cross-section in detecting small features at long distances.

A strongly tilted storm may cause lower vertically integrated liquid values to be displayed. This is because a tilted storm typically indicates that the storm's updraft and downdraft are not vertically aligned. As a result, the storm's ability to transport moisture vertically is reduced, leading to lower values of vertically integrated liquid.

Single-cell storms typically last between 30 to 60 minutes.

Multi-cell thunderstorms are characterized by a straight-line or unidirectional profile, large hail near downdraft centers, and short-duration tornadoes. However, weak directional shear in the lower levels is not a characteristic of multi-cell thunderstorms. Directional shear refers to the change in wind direction with height, and in multi-cell thunderstorms, there is typically a stronger directional shear present. Weak directional shear can be associated with single-cell thunderstorms or other types of weather systems.

The wind speeds focused on at the 200 and 30 millibar level for severe weather analysis are 86 knots. This indicates that strong winds at these levels can be indicative of severe weather conditions.

The length of a forecast made by the storm position forecast algorithm is determined by the accuracy of the previous volume scan's forecast. This means that the algorithm relies on the accuracy of the previous forecast to determine how long the current forecast will be valid. If the previous forecast was accurate, the algorithm may project a longer forecast period. However, if the previous forecast was not accurate, the algorithm may project a shorter forecast period or require more frequent updates.

Moderate precipitation is not a type of supercell thunderstorm because supercell thunderstorms are characterized by strong rotating updrafts, which create severe weather conditions such as large hail, strong winds, and tornadoes. Moderate precipitation refers to a level of rainfall that is neither very high nor very low, and it does not specifically indicate the presence of a supercell thunderstorm. Therefore, it is not considered a type of supercell thunderstorm.

The question is asking which option is not a type of surface convergent zone. A surface convergent zone is a region where air masses of different characteristics come together and converge. The options "Dry line," "Frontal boundary," and "Outflow boundary" are all examples of surface convergent zones. However, a "Land breeze front" is not a type of surface convergent zone. A land breeze front occurs when cooler air from the land moves towards a body of water, creating a boundary between the two air masses.