How to Read a Surface Analysis Chart (2024)

FAQs

What do the numbers on a surface analysis chart mean? ›

Forecast pressure values are written with 2 digits omitting the preceding 10 or 9. As an example a high pressure center with a central pressure of 1032 mb would be 32 and low pressure of 974 mb would be 74. For intense low pressure centers below 1000 mb, the analyst may use a dashed line to depict the 1000 mb isobar.

A surface analysis chart overlays weather conditions on a map. Pilots use it to get a visual understanding of phenomena like pressure, temperature, wind, and precipitation in the area at a given time. The National Weather Service (NWS) generates surface analysis charts.

A half line represents five knots, a full line denotes ten knots, and flags are reserved for increments of 50 knots. The wind barbs above show winds blowing from the northwest at 35 knots (plot A) and the southeast at 75 knots (plot B). If the winds are calm, a thin circle will appear around the station plot (plot C).

To read air pressure on a surface analysis weather map, check for isobars (iso = equal, bar = pressure) – plain, curved lines that indicate areas of equal air pressure. Isobars play a major role in determining the speed and direction of wind.

Numbers on a nautical chart are depth measurements.

Soundings, or water depth measurements, are represented by numbers on nautical charts. Water depths are measured by soundings usually acquired by hydrographic surveys. The depths may be in either feet or fathoms (the chart will indicate which).

Lower numbers indicate a smoother finish. Ra: Known as the arithmetic mean, this measurement represents the average of all peaks and valleys. Lower numbers indicate a smooth finish.

Orange lines show low-pressure troughs (these lines are dashed).

Surface chart

This chart is useful when you want to find optimum combinations between two sets of data. As in a topographic map, colors and patterns indicate areas that are in the same range of values. You can create a surface chart when both categories and data series are numeric values.

A report that depicts an analysis of the current surface weather. Shows the areas of high and low pressure, fronts, temperatures, dewpoints, wind directions and speeds, local weather, and visual obstructions.

Issuance & Validity:

Issued every 3 hours. Valid Time (VT) of the chart on the lower left corresponds to the time of the observations.

How to identify a dry line? ›

A typical dry line passage results in a sharp drop in humidity (hence the name), clearing skies, and a wind shift from south or southeasterly to west or southwesterly.

On weather maps, the surface location of a warm front is represented by a solid red line with red, filled-in semicircles along it, like in the map on the right (B). The semicircles indicate the direction that the front is moving. They are on the side of the line where the front is moving.

The surface analysis chart is a good tool for choosing a route of flight, understanding what weather to expect along a given route, and for estimating wind directions and velocities in the initial steps of route selection.

Forecast wind speeds of 100 through 199 knots are indicated by subtracting 100 from the speed and adding 50 to the coded direction. 1) EXAMPLE: A forecast of wind from 250 degrees at 145 knots is encoded as 7545. c. Forecast wind speeds of 200 knots or greater are indicated as a forecast speed of 199 knots.

Accordingly, the wind direction is indicated by an arrow, with the base indicating the direction and the end (triangle) indicating WHERE the wind is blowing to. Next to the arrow the direction is usually written in letters: SW, NE, S, N and so on. Wind speed.

Open, high, low and previous close. The open is the first price at which a stock trades during regular market hours, while high and low reflect the highest and lowest prices the stock reaches during those hours, respectively. Previous close is the closing price of the previous trading day.

Your profile will consist of two numbers (ex: 5/1, 1/3, etc.) The first number represents the part of you that you're more aware of, and the second number reflects how others see you (so you may be less aware of these qualities). Work on embracing the second number while honoring the first.

The Surface Analysis Chart depicts actual frontal positions, pressure patterns, temperature, dewpoint, wind, weather, and obstructions to vision at the valid time of the chart. Isobars are depicted by solid lines and indicate lines of equal pressure.

The air temperature is plotted on the chart to the upper left of the station model, while the dewpoint value is placed below the temperature, or to the lower left of the station circle. A negative sign is included when the air temperature or dewpoint is less than 0 degrees F.