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How To Read The ‘Surface’ Weather Maps?

katrina-surface-weather-map

We have considerably more weather data at our disposal than we can ever use. Our phones beep data points at us on demand. On social media, meteorologists from all around the world are sharing their forecasts. When severe weather is on the way, the weather channel on television transforms into a college-level meteorology class. Even with all of the data we collect, the easiest way to keep track of weather conditions in every area is to use an old-fashioned surface map—the Basics Of Surface Map Reading.

A surface map depicts what is currently occurring and what will occur in the future. It also tells you how long things like rain or snow are expected to last. When viewing these maps, the essential thing to remember is that they only reflect current situations. They can’t foresee what will happen in the future. There will be no precipitation depicted on the map if there is no precipitation expected for your region.

When looking at a surface map, pay attention to:

1. What time does the map cover?

This tells you if the map covers today, tomorrow, this week, etc.

2. Where do the lines go?

These indicate wind direction and speed.

3. How much precipitation has fallen so far?

You’ll see different colors representing various amounts of rainfall.

4. Is there a storm system currently affecting your region?

A red circle indicates one.

5. Are there areas of high pressure or low pressure over your region?

High pressures tend to bring dry air into the atmosphere, while lows usually mean wetter air moves in.

6. Do you need to prepare for bad weather?

Look out for yellow warnings, which may include tornado watches, flash flood alerts, winter storms, blizzard watches, ice storm warnings, hurricane/typhoon watches, and other extreme weather advisories

The Station Plots

Scientists needed to find a way to provide as much data as possible while maintaining the map’s legibility. The station plot is a creative way to present a lot of data in a bit of space. It takes some getting used to, but if you get the hang of it, you can get a broad sense of the weather in a given location in only a few mins.

In the basic image, temperature, dew point, wind direction, wind speed, cloud cover, precipitation, and air pressure are tracked at the weather stations worldwide. That’s a lot of data packed into one little image, and other maps provide even more data, such as visibility and cloud heights.

Station-plot

The current temperature is always in the top left corner of a station plot, the dew point is always in the bottom left corner, and the air pressure is always in the top right corner. The map’s source determines temperature and dew point units; most surface maps produced in the United States use Fahrenheit, while most other countries use Celsius.

Barometric Pressure:

Air pressure measurements are significant because they indicate how the atmosphere is flowing around you. Low pressure implies stormy weather and precipitation, while high pressure means clear skies that are excellent for hiking. Rapid pressure changes over small distances cause strong winds.

katrina-surface-weather-map

Decoding air pressure on weather maps necessitates memorization and context cues. The air pressure is typically shown as a three-digit number, such as 994 or 112. The air-pressure value of a station’s last three digits are shown to the nearest tenth of a millibar (mb); the previous number comes after the decimal point. For example, 994 denotes a pressure reading of 999.4 millibars, whereas 112 denotes a reading of 1011.2 millibars. (Meteorologists place a nine in front of more significant numbers and a ten in front of lesser digits.) It’s crucial to note that air pressures exceeding 1,040 millibars are unusual outside of a severe cold period.

Wind Direction And Speed

The wind barbs are the most visible feature of a station layout. The wind speed and direction are given to you at the station. The barb always points in the wind’s direction: if it points southeast, the wind is blowing southeast.

On a wind barb, half-lines, full lines, and flags are used to show wind speeds. Temperatures and dew points are always expressed in knots, regardless of the units used (kts). (A knot is roughly the same as 1.151 miles per hour.) A half-line represents five knots, a whole line represents ten knots, and flags indicate fifty knots.

Winds of 35 knots from the northwest (figure A) and 75 knots from the southeast (plot B) is seen in the wind barbs above (plot B). A tight circle will develop around the station plot (plot C).

Cloud Cover and Precipitation :

In a station-plot icon, cloud cover is indicated by the amount of shadow inside the plot’s center dot. A complete circle denotes overcast weather, making a hike difficult, but a hollow circle denotes a sunny sky. Scattered clouds (25 percent filled), partly cloudy (50 percent), and primarily cloudy situations are represented by each quarter shade of the dot (75 percent).

To the left of a station plot, symbols representing the kind and intensity of precipitation will appear. Rain is denoted by solid dots, whereas snow is marked by asterisks, with intensity indicated by two symbols (light precipitation), three symbols (moderate rainfall), or four symbols (heavy rainfall) (heavy rainfall). A long arrow indicates a thunderstorm in the shape of the letter R. There are several other symbols representing precipitation types, such as freezing drizzle and snow flurry, in addition to.

Pressure Systems and Isobars

Computer programs or human forecasters examine some surface maps to offer extra information to understand current circumstances and forecast what is to come. The most common value-added analyses on surface maps are isobars, pressure systems, and boundaries.

The Isobars

A blue H indicates a high-pressure system, whereas a red L indicates a low-pressure system. Usually, the wind blows from high-pressure to low-pressure zones. Even if the letters aren’t displayed on the map, these features may usually be detected using isobars—lines drawn on maps that connect areas with comparable high or low air pressure measurements.

These solid concentric lines are beneficial for outdoor enthusiasts planning their next trip since they help pinpoint pressure centers and provide a general idea of where it’s windy. Closely packed isobars show greater pressure changes over short distances, implying rapidly changing weather and strong winds.

Cold Fronts

The boundary between two air masses is known as a front, commonly observed in weather forecasts. For example, a severe cold front may drop temperatures by hundreds of degrees in minutes, and the difference between the two areas can be minor or spectacular.

Cold fronts mix cooler, drier air with warmer, more humid air, resulting in powder days. Usually, they’re blue farmers with triangle flags pointing forward in the direction of progress. When warmer, moist air collides with colder, drier air at the front edge of a storm, warm fronts emerge. A red line usually identifies them with semicircles pointing in the direction of the fronds, and they’re sometimes accompanied by severe weather.

The border between colder and warmer air masses that aren’t traveling in the same direction is marked by a stationary front. These are represented by alternating flags and semicircles (in the same colors as the above) pointing toward their respective air masses.

Occluded fronts are shown in purple on weather maps. An occlusion happens when cold air replaces warm air in the center of a low-pressure storm, pinching a region of warm air above the earth’s surface.

The confluence of a cold front, a warm front, and an occluded front, known as a “triple point,” can occasionally be the focal point for severe thunderstorms, which can ruin an afternoon run.

Only the southern plains have dry lines, which appear on surface maps as beige lines with hollow semicircles pointing in the direction of movement. They serve as a barrier between the humid air from the Gulf of Mexico and the extremely dry air from the desert west. A dryline moves eastward in huge jumps during the afternoon as a result of midday temperature. Across the spring, these fronts have the potential to cause catastrophic tornado outbreaks in Texas and Oklahoma.

Conclusion: 

Weather forecasting has come a long way since the days of the old Farmer’s Almanac. Today we use satellites, radar, Doppler radars, radiosondes, computer models, and other tools to predict what will happen tomorrow. But there are still some things you should know about how weather works before heading out on your next adventure.

The best time to plan your next hike? It depends on whether you want to see rain clouds roll in or clear skies. If you prefer sunny days, then wait until after the summer solstice, June 21st. This marks the beginning of fall, so expect fewer hours of daylight than usual. However, this also means less heat and humidity, making hiking easier.

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