Private pilot check ride (WEATHER)

Low pressure

inward, upward, counterclockwise

High pressure

outward, downward, clockwise

Trough

o Elongated area of relatively low pressure

o At surface must go upward (rising air)

o Conductive to cloudiness and precipitation

o Low pressure = bad weather

Ridge

o Elongated area of relatively high pressure

o Descending air

o Favors dissipation of cloudiness

o High pressure = good weather

Standard Temperature and Pressure Values for Sea Level

15'C and 29.92" Hg

Coriolis Effect

o Causes winds to flow parallel to the isobars

o Rotation of earth deflects large bodies of air

Surface Winds (how do they flow)

Generally flow across isobars at an angle due to surface friction

Dew Point

• Temperature which air must be cooled to attain a state of saturation

• When temperature = Dew point = You get FOG

• Temp and Dew point are close- clouds, dew, fog = carburetor icing

Stability

1.quality to resist vertical motion

2. Determined by type and vertical extent of the clouds

Characteristics of stable air

o Clouds: Stratiform

o Turbulence: Smooth

o Precipitation: Steady

o Visibility: Fair to Poor

Characteristics of unstable air

o Clouds: Cumuliform

o Turbulence: Rough

o Precipitation: Showery

o Visibility: Good

Calculating Altitude of Clouds

• Temp- Dew Point / 4 x 1,000 = Base of Clouds

Freezing level

• Lowest altitude at which air temperature reaches 0' C.

Where to find freezing level?

• Area Forecasts, PIREPS, AIRMETS, SIGMETS, and convective SIGMETS, low level significant weather charts, surface analysis, FIP (Forecast Icing Prediction) and winds and temperatures aloft contain icing information.

• Aviationweather.gov/adds/icing/

Icing conditions?

• Conditions in which icing occurs req. visible moisture and freezing temps

Effects of icing

• Aircraft may encounter: Structural, Induction System, and Instrument Icing

What to do when you encounter icing?

• If encountered- change course/altitude

what is needed for formation of thunderstorms?

o Source of lift

o Unstable Air

o High Moisture content

3 stages of thunderstorm?

o Cumulus (updraft of moisture)

o Mature (rain, lightening, rolling clouds)

o Dissipating (downdrafts, dissipation)

Temperature inversions

• Increase in temperature with height (not the norm)

• Permits warm rain to fall through cool air (icing)

• Favors poor visibility trapping restrictions in low level atmosphere

• Air is stable

What is needed for Fog?

o Cooling air to dew point

o Adding moisture to the air

Steam fog?

(Cold dry air over warm water)

Upslope fog

(Moist stable air forced upslope land)

Precipitation fog

(Warm rain falls through cool air)

Radiation fog

(Clear cool still night)

advection fog

(Warm moist air over water moves to cool land *by wind.. Along coastal areas in the winter)

wind shear

• Sudden drastic change in wind speed and direction

• Hazardous at low altitudes on approach and departing airports

when do wind shears occur?

o Low level temperature inversion

o Frontal zone of thunderstorm

o Clear air turbulence at high levels (jet stream)

How to obtain weather briefings?

• Primary: 1-800-WX-BRIEF

• TIBS (telephone briefs)

• DUATS (terminal computers)

• TWEBS (transcribed broadcasts)

Standard briefing

o Planning flight and preliminary information

Abbreviated briefing

o Updating previous briefing

Outlook briefing

o Request once proposed time is set (within 6 hr.)

Inflight briefing

o Update preflight briefing

What is in a briefing?

• Adverse Conditions

• VFR Flight not recommended

• Synopsis

• Current conditions

• Enroute Forecast

• Destination Forecast

• Winds Aloft

• NOTAMs

• ATC Delay

EFAS?

• En Route Flight Advisory Service

• "Flight Watch" freq. 122.0MHz. (Service between 5k ^ 17,500ft.)

HIWAS?

• Hazardous In-flight Weather Advisory Service

• Depicted on sectional charts with an "H"

• Continuous broadcast of in light weather advisories including

o Summarized aviation weather warnings

o SIGMETs

o Weather Advisories

o AIRMETs

o Urgent PIREPs

METAR?

• Hourly surface observation of conditions observed at airport

• 2 types:

o METAR report every hour

o Special weather report (SPECI)- given for rapidly changing conditions

Manual operatios weather briefing?

o Airport locations staffed by FAA or NWS personal

AWOS?

o Automated weather observation system

• ASOS/AWSS

o Automated surface observation system

o Primary US surface weather observations system

o Generate the METARS

o Found on NAVAID freq. max 25 NM from station

PIREPS

• Information concerning weather observed by pilots en route

o Location, time, flight level, type of aircraft, weather element encountered

Radar weather reports

• Contain information about precipitation observed by weather radar

• LONG. Should only be used if nothing else available.

o Location, time, configuration, coverage, precipitation, intensity, maximum tops, cell moment, remarks

TAF

o Type of reports

o ICAO station identifier

o Date and time of origin

o Valid period date and time

o Forecasts

2. Aviation Area Forecast (FA

• Forecast of specified weather phenomena covering a flight information region

• Used in conjunction with AIRMETs and SIGMETs to determine forecast weather enroute

• Issued 3 times daily in 6 areas in the contiguous 48 states (AK, HI also)

INFO in area Forecast?

o Synopsis

o Clouds and Weather

o Cloud Amount

o Cloud Base and Top

o Precipitation

o Visibilities

o Surface Winds

o 12-18 hr. categorical outlook (IFR, MVFR, VFR)

3. Inflight Aviation Weather Advisories

• Forecasts to advise enroute development of potentially hazardous weather

Types of inflight weather advisories

o SIGMET

o AIRMET

o Convective SIGMET

• Heights referenced in MSL except in case of ceilings AGL

Convective SIGMET

• Issued Hourly

• Severe Thunderstorms, Severe Icing, Low Level Wind Shear

• Examples:

o Surface winds >50KT

o Hail at surface >= ¾ inch diameter

o Tornados

o Embedded T-storms

SIGMET

• Advises non-convective weather that is potentially hazardous

• 4 hour Maximum forecast period

o Severe Icing (Not T-storm related)

o Clear Air Turbulence (CAT)

o Dust storms and Sand storms lowering visibility below 3 miles

o Volcanic Ash

AIRMET

• Significant weather phenomena conditions that are lower than those issued for SIGMETS

• Used in preflight and enroute phase of flight for safety

• Every 6 hours issued

• Contains:

o IFR

o Extensive mountain obscuration

o Turbulence

o Strong surface winds

o Icing

o Freezing levels

TYPES OF AIRMET

• Sierra

o IFR conditions and/or extensive mountain obscurations

• Tango

o Moderate Turbulence

o Sustained surface winds 30KT or greater

o Non-convective low level wind shear

• Zulu

o Moderate icing

o Provides freezing level heights

8. Winds and Temperatures Aloft Forecasts (AF)

• Forecasts of wind direction, speed, and temperature at specified times, altitude and locations

• Produced 4 times daily

• Includes:

o Date and Time of observations collected & Validity Date and Time

o Altitudes up to 15,000ft MSL

o Temperature indicated in Celsius(C)

o Wind direction and Wind speed

9. Center Weather Advisories (CWA)

• Aviation warning to anticipate and avoid adverse weather conditions in the enroute and terminal environments

• Reflects current conditions expected at the time of issuance

• Valid 2 Hours (NOT flight planning product)

• If expected to continue beyond 2 hours a statement will be included

Surface analysis

o Locates pressure systems and fronts

o Overview of winds, temp, dew point

o Transmitted every 3 hrs.

Weather depiction

o Analysis from METAR reports

o Broad overview "Birds Eye" View (Good place to start Flight Plan)

o Transmitted every 3 hrs.

LIFR

• (LOW) Ceiling <500ft/Visibility < 1mile

IFR

• Ceiling 500 to less than 1,000ft and/or Visibility < 3 miles

MVFR

• (MARGINAL) Ceiling 1-3,000ft and/or Visibility 3-5 miles

VFR

• Ceiling > 3,000ft and Visibility > 5 miles

Radar summary

o Displays areas of precipitation

o Type, Intensity, Configuration, Coverage, Cell Movement

o Valid 35 minutes past the hour

Short range surface prognostic

o "Progs"- forecasts selected weather conditions at specific valid times.

o Progression of surface weather features over the next 2 days.

o Validity Times: 12hr, 24hr, 36hr, and 48hr

Low level sig weather prig

o "Day One" Forecast of significant weather

o Pertains to the layer from surface ^ FL420

o Two forecast periods, 12 hrs. and 24hrs

o Composed of 4 panels

• 2 lower- 12 and 24 hr. surface progs

• 2 upper- 12 and 24 hr. significant weather

o Issued 4 times a day (00Z, 06Z, 12Z, 18Z)

Mide level sig weather prig

o Significant En-route weather for flight levels 10,000MSL → FL450

Convective outlook

o Area forecasts having potential for severe and non severe convection and specific severe weather threats during the following 3 days

• (SLGT) Slight Risk

• (MDT) Moderate Risk

• (HIGH) High Risk

Constant pressure analysis

o Surface of Equal Pressure

o Can approximate observed air temp, wind, dew point, spread along planned route

o Depict High/Lows, Troughs/Ridges

o Updated Twice Daily

o Pilots can approximate observed air temperatures, wind, and temp/dew point spread along a route.

• 850mb.................5,000ft

• 700mb.................10,000ft

• 500mb.................18,000ft

• 300mb.................30,000ft

• 200mb..................39,000ft

Sub freezing temperatures and a temperature/dew point spread of 5 degrees C or less suggest possible icing.

CIP

• Hourly 3 dimensional diagnosis of the icing environment

• Issued hourly 15 minutes after the hour

FIP

• 3 dimensional forecast of icing potential using numerical weather prediction model output

• Issued hourly and generates an hourly forecast for 3 hours into the future.