Weather Flashcards
What does SIGMET stand for and what are the categories?
SIGnificant METeorological Information, is a weather advisory that contains meteorological information concerning the safety of all aircraft. There are two types of SIGMETs - convective and non-convective.
Non-convective SIMGETs:
- Severe Icing
- Severe or Extreme Turbulence
- Dust storms and/or sand storms lowering visibilities to less than three (3) miles
- Volcanic Ash
Convective SIMGETs:
- Severe surface weather (surface winds greater 50+ knots, hail 3/4”+ in diameter, tornadoes)
- Embedded thunderstorms
- Line of thunderstorms
- Thunderstorms affecting 40% or more of an area at least 3000 square miles
What does AIRMET stand for and what are the categories?
AIRmen’s METeorological Information, is a concise description of weather phenomena that are occurring or may occur along an air route that may affect (smaller) aircraft safety.
- Mountain Obscuration
- Turbulence
- Icing
What is a METAR?
METeorological Aerodrome Report is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
What are the categories of cloud cover?
- SKC (SKy Clear)
- CLR (CLeaR): No clouds below 12,000 ft (U.S.)
- FEW (FEW): 1/8–2/8 cloud coverage
- SCT (SCaTtered): 3/8 – 4/8 cloud coverage
- BKN (BroKeN): 5/8 – 7/8 cloud coverage
- OVC (OVerCast): 8/8 cloud coverage
- VV (Vertical Visibility): Clouds cannot be seen because of fog or heavy precipitation, so vertical visibility is given instead
What is a TAF?
Terminal Aerodrome Forecast, issued every 6 hours and generally apply to a 24 or 30-hour period within an area approximately five statute miles from the center of an airport runway complex.
TAF
KXYZ 051730Z 0518/0624 31008KT 3SM -SHRA BKN020
FM052300 30006KT 5SM -SHRA OVC030
PROB30 0604/0606 VRB20G35KT 1SM TSRA BKN015CB
FM060600 25010KT 4SM -SHRA OVC050
TEMPO 0608/0611 2SM -SHRA OVC030
RMK NXT FCST BY 00Z=
What are some of the weather forcasts available to pilots?
- TAF (Terminal Aerodrome Forecast)
- Prognostic chart (or “prog chart”)
- Winds aloft
What are some of the weather reports available to pilots?
- ATIS (Automatic Terminal Information Service)
- METAR (METorlogical Aerodrom Report)
- PIREP (PIlot REPort)
- EFAS (Enroute Flight Advisory Service or “Flight watch”)
- Preflight briefing (like 1-800-WX-BRIEF)
- Standard
- Abreviated
- Outlook
- CWA (Center Weather Advisory, through ATC or “Flight watch”)
Name the 3 types of icing
- Clear ice
- Rime ice
- Mixed ice
Define clear icing:
Clear icing forms when liquid water flows over the surface of a cold aircraft surface gradualy freezing into a smooth sheet of solid ice.
Because clear icing heavy and smooth the danger comes from its weight more than reducing lift or increasing drag.
(AC 00-6 Chapter 10)
Define rime icing:
Rime icing forms when liquid drops are small, after impact with the aircraft the remaining portion of water freezes rapidly before spreading over the surface. The small frozen droplets trap air betwen them giving the ice a white appearance.
Rime ice is light however the rough surface reduces lift and increases drag. Rime icing is brittle and generally easier to remove than clear icing.
(AC 00-6 Chapter 10)
Define mixed icing:
Mixed ice forms when liquid drops vary in size or intermingle with snow or ice particles. Ice particles become imbedded in clear ice, building a very rough accumulation. Because mixed icing is both heavy and rough it can reduce lift by 30% and increase drag by 40%.
Where will icing build up first?
Icing accumulates on the smallest surfaces of an aircraft first, such as the antennas, wing struts and horizontal stabilizor.
What are the main dangers of icing?
Icing can reduce lift, increase drag, increase weight, reduce prop effectivness, induce tailplane icing stalls, block the air induction system, block the pitot tube or block the static air port.
Define radiation fog:
Also known as “ground fog” - radiation fog forms when skys are clear, low to no wind with high humidity (small temp/dewpoint spread). Cool ground cools the air in contact with it, when the air reaches its dewpoint radiation fog forms.
(AC 00-6 Chapter 12)
Define advection fog:
Also known as a “marine layer”, advection fog forms when moist air moves over cold ground or water which cools it to dewpoint. Advection fog is very similar to radiation fog but advection fog is much more wide ranging and more persistant.
(AC 00-6 Chapter 12)
