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Breaking down a surface weather map

todayJanuary 7, 2024

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ROCHESTER, N.Y. (WROC) — Surface weather maps can come in a variety of different styles, all giving different levels of information. But even on the most complex of maps, there are some common features that are found on all surface maps. Let’s break down the common features found on these surface weather maps.

HIGH/LOW PRESSURE

Do you ever see those uppercase L’s and H’s across a weather surface map? Well, they are actually representing areas of high and low pressure. An area of high pressure is indicated by an uppercase, blue H and usually represents areas of settled weather. Meteorologists use areas of high pressure to describe the stable weather that could be moving into their area. Areas of high pressure tend to give areas a “break” from the weather. On the other hand, an area of low pressure is indicated by an uppercase, red L and usually represents areas of inclement weather. In most cases, when you spot an area of low pressure on a surface map, it usually is surrounded by different fronts. But what exactly do fronts indicate?

FRONTS

Fronts are a very common feature found on surface maps. A front can be described as a boundary separating two different air masses. Fronts could also indicate a change in weather. It could vary from a slight change in temperature to a major change in weather conditions. There are four different types of fronts. They include a warm front, cold front, stationary front, and occluded front. These four types of fronts are vastly different from one another and bring different types of weather along with them. Let’s break them down even more.

Cold Front

A cold front can be described as the leading edge of a colder air mass that will be replacing or pushing out a warmer air mass. It is depicted by a blue line with triangles pointing in the direction of motion. As a cold front moves into the area, this allows for the more dense (colder) air to push underneath the less dense (warmer) air, allowing for the warmer air to rise. This allows for cumulus or cumulonimbus clouds to form, which are often associated with rain and/or thunderstorms. Cold fronts can bring severe weather, such as tornadoes, thunderstorms, snow squalls, and hailstorms. Another thing that happens when a cold front moves through the area is it brings gusty winds and temperatures begin to drop. This type of front generally moves from northwest to southeast. With that in mind, the temperatures on the left (west) side of the front are going to appear colder than those on the right (east) side.

Warm Front

A warm front can be described as the leading edge of a warmer air mass that will be replacing or pushing out a colder air mass. It is depicted by a red line with half-circles pointing in the direction of motion. Unlike cold fronts, warm fronts move more slowly because it is harder for warmer (less dense) air to take over colder (more dense) air. However, like cold fronts, warm fronts can bring stormy weather. Ahead of warm fronts, there are high clouds, like cirrus clouds, or middle clouds, like altostratus clouds. As the warm front passes through the area, those clouds begin to lower and could bring rain. If the warmer air is unstable enough, it could also produce thunderstorms. This type of front generally moves from southwest to northeast. With that in mind, the temperatures you see on the left (west) side of the front are going to appear warmer than those on the right (east) side.

Stationary Front

A stationary front forms when either a warm or cold front stops moving. This happens when two air masses are pushing against each other but neither is strong enough to overtake the other. It is depicted by an alternating red and blue line with triangles on the blue portion pointing away from the cold air mass and half-circles on the red portion of the line pointing away from the warm air mass. The wind direction is also very different when it comes to stationary fronts. The wind direction with a cold or warm front flows parallel while the wind direction with a stationary front flows perpendicular. The perpendicular wind flow helps the stationary front stay mostly still (hence the name “stationary front’). Because stationary fronts are usually the boundary between two different air masses, there tend to be different wind directions as well as different temperatures on the different sides. While warm and cold fronts usually tend to bring stormy weather, the skies tend to stay cloudy along a stationary front with a slight chance of some rain or snow falling.

Occluded Front

An occluded front occurs when a cold front “catches up” to a warm front and overtakes it. The front is depicted by a purple line with alternating triangles and half-circles on the side of its motion. Warm fronts move slower than cold fronts, so this allows for the cold front to overtake the warm front. The warm air mass gets “cut off” and pushed upward. The newly formed occluded front now is a boundary that separates the new cold air mass (to the west) from the old cold air mass that was previously there before the warm front. Since the warm air mass gets pushed upward, this creates the potential for strong winds and heavy precipitation to form along an occluded front.

OTHER FEATURES

Fronts and areas of high/low pressure are the most common features found on a surface map. But that doesn’t necessarily mean they are the ONLY feature found on these maps. A dryline is indicated by a brown line with close half-circles and represents a boundary that separates humid (moist) air from dry air. Dry lines are an important factor when it comes to severe weather and are usually found in the Great Plains. A squall line is indicated by a red line with dashes and two dots and represents a line of thunderstorms. Squall lines often move very quickly and are not capable of producing tornadoes but are capable of producing strong winds and heavy rain. A trough is indicated by a dark brown line with dashes and represents an elongated area of relatively low pressure. Since troughs are associated with low pressure, troughs can bring in cloudy skies as well as precipitation.

​ ROCHESTER, N.Y. (WROC) — Surface weather maps can come in a variety of different styles, all giving different levels of information. But even on the most complex of maps, there are some common features that are found on all surface maps. Let’s break down the common features found on these surface weather maps.

HIGH/LOW PRESSURE

Do you ever see those uppercase L’s and H’s across a weather surface map? Well, they are actually representing areas of high and low pressure. An area of high pressure is indicated by an uppercase, blue H and usually represents areas of settled weather. Meteorologists use areas of high pressure to describe the stable weather that could be moving into their area. Areas of high pressure tend to give areas a “break” from the weather. On the other hand, an area of low pressure is indicated by an uppercase, red L and usually represents areas of inclement weather. In most cases, when you spot an area of low pressure on a surface map, it usually is surrounded by different fronts. But what exactly do fronts indicate?

FRONTS

Fronts are a very common feature found on surface maps. A front can be described as a boundary separating two different air masses. Fronts could also indicate a change in weather. It could vary from a slight change in temperature to a major change in weather conditions. There are four different types of fronts. They include a warm front, cold front, stationary front, and occluded front. These four types of fronts are vastly different from one another and bring different types of weather along with them. Let’s break them down even more.

Cold Front

A cold front can be described as the leading edge of a colder air mass that will be replacing or pushing out a warmer air mass. It is depicted by a blue line with triangles pointing in the direction of motion. As a cold front moves into the area, this allows for the more dense (colder) air to push underneath the less dense (warmer) air, allowing for the warmer air to rise. This allows for cumulus or cumulonimbus clouds to form, which are often associated with rain and/or thunderstorms. Cold fronts can bring severe weather, such as tornadoes, thunderstorms, snow squalls, and hailstorms. Another thing that happens when a cold front moves through the area is it brings gusty winds and temperatures begin to drop. This type of front generally moves from northwest to southeast. With that in mind, the temperatures on the left (west) side of the front are going to appear colder than those on the right (east) side.

Warm Front

A warm front can be described as the leading edge of a warmer air mass that will be replacing or pushing out a colder air mass. It is depicted by a red line with half-circles pointing in the direction of motion. Unlike cold fronts, warm fronts move more slowly because it is harder for warmer (less dense) air to take over colder (more dense) air. However, like cold fronts, warm fronts can bring stormy weather. Ahead of warm fronts, there are high clouds, like cirrus clouds, or middle clouds, like altostratus clouds. As the warm front passes through the area, those clouds begin to lower and could bring rain. If the warmer air is unstable enough, it could also produce thunderstorms. This type of front generally moves from southwest to northeast. With that in mind, the temperatures you see on the left (west) side of the front are going to appear warmer than those on the right (east) side.

Stationary Front

A stationary front forms when either a warm or cold front stops moving. This happens when two air masses are pushing against each other but neither is strong enough to overtake the other. It is depicted by an alternating red and blue line with triangles on the blue portion pointing away from the cold air mass and half-circles on the red portion of the line pointing away from the warm air mass. The wind direction is also very different when it comes to stationary fronts. The wind direction with a cold or warm front flows parallel while the wind direction with a stationary front flows perpendicular. The perpendicular wind flow helps the stationary front stay mostly still (hence the name “stationary front’). Because stationary fronts are usually the boundary between two different air masses, there tend to be different wind directions as well as different temperatures on the different sides. While warm and cold fronts usually tend to bring stormy weather, the skies tend to stay cloudy along a stationary front with a slight chance of some rain or snow falling.

Occluded Front

An occluded front occurs when a cold front “catches up” to a warm front and overtakes it. The front is depicted by a purple line with alternating triangles and half-circles on the side of its motion. Warm fronts move slower than cold fronts, so this allows for the cold front to overtake the warm front. The warm air mass gets “cut off” and pushed upward. The newly formed occluded front now is a boundary that separates the new cold air mass (to the west) from the old cold air mass that was previously there before the warm front. Since the warm air mass gets pushed upward, this creates the potential for strong winds and heavy precipitation to form along an occluded front.

OTHER FEATURES

Fronts and areas of high/low pressure are the most common features found on a surface map. But that doesn’t necessarily mean they are the ONLY feature found on these maps. A dryline is indicated by a brown line with close half-circles and represents a boundary that separates humid (moist) air from dry air. Dry lines are an important factor when it comes to severe weather and are usually found in the Great Plains. A squall line is indicated by a red line with dashes and two dots and represents a line of thunderstorms. Squall lines often move very quickly and are not capable of producing tornadoes but are capable of producing strong winds and heavy rain. A trough is indicated by a dark brown line with dashes and represents an elongated area of relatively low pressure. Since troughs are associated with low pressure, troughs can bring in cloudy skies as well as precipitation. Read More Local NewsRochesterFirst  

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