Weather Information: E - Aviation Weather Charts Flashcards
Give some examples of the various NWS weather charts you will use during preflight planning.
a. Surface analysis chart.
b. Ceiling and Visibility Analysis (CIG/VIS) .
c. Short-range surface prognostic chart.
d. Significant weather prognostic chart.
e. Convective outlook chart.
f. Constant pressure analysis chart—being phased out in favor of upper air constant pressure level forecasts.
g. Freezing level graphics.
(AC 00-45)
What is a surface analysis chart?
Surface analysis charts are analyzed charts of surface weather observations. The chart depicts the distribution of several items including sea level pressure, the positions of highs, lows, ridges, troughs, the location and character of fronts, and the various boundaries such as drylines, outflow boundaries, sea-breeze fronts, and convergence lines. The chart is produced eight times daily.
(AC 00-45)
Describe a Ceiling and Visibility Analysis (CVA).
A CVA is a real-time analysis (updated every 5 minutes) of current ceiling and visibility conditions across the continental United States. It is intended to aid situational awareness with a quick-glance visualization of current ceiling and visibility conditions across an area or along a route of flight. The CVA provides a viewer-selectable representation of ceiling height (AGL), surface visibility in statute miles (SM), and flight category designation. The overview provided by a CVA should be followed by further examination of METARs, TAFs, AIRMETs, GFAs, FAs, and other weather information.
(AC 00-45)
Define the terms: LIFR, IFR, MVFR, and VFR.
LIFR
Low IFR—ceiling less than 500 feet and/or visibility less than one mile
IFR
Ceiling 500 to less than 1,000 feet and/or visibility 1 to less than 3 miles.
MVFR
Marginal VFR—ceiling 1,000 to 3,000 feet and/or visibility 3 to 5 miles inclusive.
VFR
Ceiling greater than 3,000 feet and visibility greater than 5 miles; includes sky clear.
(AIM 7-1-7)
What are short-range surface prognostic charts?
Short-range surface prognostic (prog) charts provide a forecast of surface pressure systems, fronts and precipitation for a 2-1/2 day period. They cover a forecast area of the 48 contiguous states and coastal waters, and are prepared by the NWS Weather Prediction Center (and available on the AWC website). Predicted conditions are divided into five forecast periods: 12, 18, 24, 48 and 60 hours. Each chart depicts a snapshot of weather elements expected at the specified valid time. Charts are issued four times a day and can be used to obtain an overview of the progression of surface weather features during the included periods.
(AC 00-45)
Describe a U.S. low-level significant weather prog chart.
The low-level significant weather (SIGWX) charts provide a forecast of aviation weather hazards primarily intended to be used as guidance products for pre-flight briefings. The forecast domain covers the continental U.S. and the coastal waters for altitudes Flight Level 240 and below. Each depicts a “snapshot” of weather expected at the specified valid time. The charts depict weather flying categories, turbulence, and freezing levels, and are issued four times per day in two types: a 12-hour and a 24-hour prog.
(AC 00-45)
Describe a mid-level significant weather (SIGWX) chart.
The mid-level significant weather chart provides a forecast and an overview of significant en route weather phenomena over a range of flight levels from 10,000 feet MSL to FL450, and associated surface weather features. The chart is a “snapshot” of weather expected at the specified valid time and depicts numerous weather elements that can be hazardous to aviation. The AWC issues the 24-hour mid-level significant weather chart four times daily.
(AC 00-45)
What is a convective outlook chart?
The convective outlook chart depicts areas forecast to have the potential for severe (tornado, wind gusts 50 knots or greater, or hail ¾ inch diameter size or greater) and non-severe (general) convection and specific severe weather threats during the following three days. The chart defines areas of slight risk (SLGT), moderate risk (MDT) or high risk (HIGH) of severe thunderstorms for a 24-hour period beginning at 1200 UTC. The Day 1 and Day 2 Convective Outlooks also depict areas of general thunderstorms (GEN TSTMS), while the Day 1, Day 2, and Day 3 Convective Outlooks may use SEE TEXT for areas where convection may approach or slightly exceed severe criteria.
(AC 00-45)
What are constant pressure analysis charts?
Any surface of equal pressure in the atmosphere is a constant pressure surface. A constant pressure analysis chart is an upper air weather map where all information depicted is at the specified pressure of the chart. From these charts, a pilot can approximate the observed air temperature, wind, and temperature-dewpoint spread along a proposed route. They also depict highs, lows, troughs, and ridges aloft by the height contour patterns resembling isobars on a surface map. Twice daily, five constant pressure charts are issued from observed data obtained at 00Z and 12Z: 850 mb 5,000 ft 700 mb 10,000 ft 500 mb 18,000 ft 300 mb 30,000 ft 200 mb 39,000 ft (AC 00-45)
What information does a freezing level graphics chart provide?
Freezing level graphics are used to assess the lowest freezing level heights and their values relative to flight paths. The chart uses colors to represent the height in hundreds of feet above mean sea level (MSL) of the lowest freezing level(s). The initial analysis and 3-hour forecast graphics are updated hourly. The 6-, 9-, and 12-hour forecast graphics are updated every three hours.
