Exam 3 – Review - ASU



Exam 4 – Review

**Exam 4 will be a multiple choice exam consisting of 35 questions

**Focus on definitions - (blue highlighted concepts in text)

**Focus on blue boxes - (important information given in these boxes)

Chapter 16 – Aviation Weather Resources

Section A: The Weather Forecasting Process

- There are three important steps in the forecasting process: data collection, data processing and forecasting

Collecting Weather Data

- The World Meteorological Organization (WMO), a United Nations agency is responsible for the standardization of observations and the international exchange of weather data

Processing Weather Data

- The National Weather Service (NWS), a part of the National Oceanic and Atmospheric Administration (NOAA), is the U.S. government agency that is primarily responsible for gathering and processing meteorological data and for providing weather forecasts and warnings

- These continuing and complicated tasks are conducted by several NWS offices including the National Centers for Environmental Protection (NCEP) and local Weather Forecast Offices (WFO)

- One of the components of the NCEP is the Aviation Weather Center (AWC) which specializes in the preparation of aviation weather information

Forecasting Methods

- The most comprehensive forecast technique today is numerical weather prediction (NWP) which solves a set of mathematical equations (a numerical model) to predict the weather

Forecasting Accuracy

- In comparison to persistence forecasts, the accuracy of meteorological forecasts, which are based on scientific knowledge as used by NWP and weather forecasters, is much better and decreases much more slowly as the forecast period increases

- However, for the longest forecast periods, the accuracy of meteorological forecasts is no better than that of climatological forecasts, which are based purely on past averages and are typically not very accurate at all

- Forecasting the weather is somewhat chaotic, which is not too far from the mark. As applied to weather forecasting, chaos theory describes the potential difficulty in making forecasts for long periods of time

- The science of chaos began in the early 1960s with a mathematician and atmospheric scientist named Edward Lorenz and his exploration of computer forecasts

Section B: Aviation Weather Forecast Products

- Decoding keys for aviation weather forecast products are included in Appendix D

- In addition, FAA Advisory Circular 00-45 Aviation Weather Services contains further information

- Selectivity – requires that you know exactly what you need, what is available and where and when it is available

- Visualization – forming a mental image of current and forecast weather conditions

Forecast Products in Text Format

- Forecast products in text format include:

Terminal Aerodrome Forecasts (TAF) – describes weather conditions that are expected to occur within a 5 nm radius of an airport over a 24 hour period. In the US routine TAFs are issued 4 times daily at 0000Z, 0600Z, 1200Z, and 1800Z. The TAF is one of the most valuable sources for the predicted weather at a specific airport. Predicted sky condition, visibility, weather and obstructions to vision, wind direction and speed, and expected changes during the forecast period can be derived from TAFs.

Area Forecasts (FA) – expected VMC, clouds and general weather conditions over an area the size of several states are described in an Area Forecast (FA). An FA is used to determine enroute weather, including conditions at airports that do not have terminal forecasts. An FA should always be used in conjunction with the most recent inflight weather advisories. Area forecasts are normally issued three times daily and are valid for 18 hours. An FA has four sections:

1. Header – describes the source of the FA, the date and time of issue, the valid times and the areas the FA covers

2. Precautionary Statements – describe IFR and mountain obscurations, thunderstorm hazards, and states that all heights are MSL unless otherwise noted

3. Synopsis – a brief summary identifying the location and movement of pressure systems, fronts, and circulation patterns for the 18 hour forecast period.

4. VFR Clouds and Weather – this section lists expected sky condition, visibility and weather for the next 12 hours and an outlook for the following 6 hours

- Area forecasts are issued by the Aviation Weather Center (AWC) for the six regions in the contiguous US. The Alaskan Aviation Weather Unit issues an FA for the state of Alaska while the Honolulu WFO handles Hawaii. Special FAs are also issued for the Gulf of Mexico and international airspace

- Within its prescribed area, an FA describes weather features and conditions relative to common geographical regions and features

- The contiguous US is divided into 6 forecast areas (SFO – San Francisco, SLC – Salt Lake City, DFW – Dallas / Fort Worth, CHI – Chicago, BOS – Boston, MIA – Miami)

***The area forecast covers an area of several states and can be used to determine en-route weather and conditions at your destination if no TAF has been issued

In-flight Weather Advisories (WS, WST, WA)

- consist of either an observation and a forecast, or just a forecast for the development of potentially hazardous weather

- SIGMET (WS) – describes conditions which can pose hazards to all aircraft. SIGMETs are valid for up to four hours.

- If the following phenomena are observed or expected to occur, a SIGMET is issued

1. Severe icing not associated with thunderstorms

2. Severe or extreme turbulence or clear air turbulence not associated with thunderstorms

3. Dust storms or sandstorms lowering surface or inflight visibilities to below three miles

4. Volcanic ash

***SIGMETs are issued as warnings of hazardous weather, such as severe icing, which is of operational interest to all aircraft

- Convective SIGMETs (WST) – describes convective activity that is potentially hazardous to all categories of aircraft

- Bulletins are issued hourly with special advisories issued as required

- The forecast period for a WST is two hours or less

- Criteria for issuance are any of the following conditions

1. Severe thunderstorms (surface winds greater than or equal to 50 knots and/or hail at the surface greater than or equal to ¾ inches in diameter and/or tornadoes)

2. Embedded thunderstorms

3. A line of thunderstorms

4. Thunderstorms producing precipitation with an intensity greater than or equal to heavy and affecting 40% or more of an area at least 3,000 square miles

- Convective SIGMET bulletins are issued for the Eastern (E), Central (C), and Western (W) United States

- Convective SIGMET text is presented in figure 16-7

- AIRMET (WA) – issued for significant weather at intensities lower than those required for the issuance of a SIGMET

- Although AIRMETs are of operational interest to all aircraft, the weather conditions specified are particularly hazardous to light aircraft having limited capability or minimal equipment and instrumentation

- There are three different AIRMETs

- AIRMET Sierra – describes IFR conditions and/or extensive mountain obscurations

- AIRMET Tango – describes areas of moderate turbulence, sustained surface winds in excess of 30 knots and areas of non-convective low-level wind shear

- AIRMET Zulu – describes moderate icing and provides freezing level heights

- Pilots with limited experience or qualifications should pay special attention to these advisories

- AIRMETs are issued every six hours with unscheduled updates and corrections issued as necessary

- Each bulletin contains any current AIRMETs that are in effect, an outlook for weather that is expected after the AIRMET valid period and any significant conditions that do not meet AIRMET criteria

- Examples of AIRMETs Sierra, Tango and Zulu are given in figure 16-8

***Weather conditions that are particularly hazardous to small, single-engine aircraft are contained in an AIRMET

- AIRMETs and SIGMETs are issued for the 6 regions corresponding to the FA areas

- These widespread advisories must be either affecting or forecasted to affect at least 3,000 square miles at any one time

- International SIGMETs are issued worldwide by ICAO Meteorological Watch Offices (MWOs); see figure 16-9

- The criteria for International SIGMETs are broader than the criteria for either WS or WST for the US

1. Thunderstorms in lines, embedded in clouds, or in large areas producing tornadoes or large hail

2. Tropical cyclones

3. Severe icing

4. Severe or extreme turbulence

5. Dust storms or sand storms lowering visibility to less than 3 miles (5 km)

6. Volcanic Ash

Transcribed Weather Broadcasts (TWEB)

- A Transcribed Weather Broadcasts (TWEB) is a synopsis and forecast for a 50-mile-wide corridor along a specific flight route or within 50 nm of the FSS

- TWEBs are prepared for more than 200 flight routes and local vicinities around the US

- TWEB forecasts are valid for 12 hours

- They are updated 4 times daily

- TWEBs do not include areas of icing and turbulence

- TWEB example given in figure 16-10

Winds and Temperatures Aloft Forecasts (FD)

- FDs furnish a prediction of wind speed (knots), wind direction (degrees True), and temperature (degrees C) for selected altitudes at specific locations across the US, including Alaska, Hawaii and over some US coastal waters

- Figure 16-11 gives the distribution of forecast stations

- Winds and temperatures aloft contain wind direction in relation to true north, wind speed in knots and temperature in degrees Celsius for a range of altitudes

- FDs wind speeds between 100 and 199 knots are encoded so direction and speed can be represented by four digits

- These winds are decoded by subtracting 50 from the two digit wind direction and adding 100 to the wind speed

- The negative sign for temperatures above 24,000 feet MSL is not included

- A wind code of 9900 is interpreted as light and variable

- Forecast winds greater than or equal to 199 knots are reported as 199 knots

-

Other Advisories, Watches, and Warnings

- Center Weather Service Unit (CWSU) – operated by NWS meteorologists within the confines of each ARTCC

- Meteorological impact statements (MIS) / center weather advisories (CWA) – produced by the CWSU of each ARTCC

- Hurricane advisories (WH) – issued to alert the aviation community to the presence of a hurricane located at least 300 nm offshore and threatening the coastline

- Severe watch bulletin (WW) – an unscheduled message that defines areas of possible severe thunderstorms or tornado activity

- Severe watch alert (AWW) – a preliminary notice to alert forecasters, briefers and pilots that WW is being issued

- Severe thunderstorm warnings / tornado warnings – public notifications that those phenomena have been sighted visually or by radar

- Convective outlook (AC) – SPC also produces a convective outlook (AC) for the occurrence of thunderstorms (non-severe and severe) five times a day for the next 24 hours (day 1 convective outlook) and twice a day for the following 24 hours (day 2 convective outlook)

Forecast Products in Graphic Format

- Descriptions of examples of all common forecast and analysis graphics are given in Appendix D

Significant Weather Prognostic Chart

- The significant weather prognostic chart can be used to determine areas to avoid, such as forecast locations of low visibilities or turbulence

- See figure 16-13

- Lower left hand corner of each panel gives the valid times for the forecast

- The surface prog in the lower panel uses standard symbols to depict fronts, isobars, pressure centers and areas of forecast precipitation

- Regions of continuous precipitation and unstable showery precipitation are within a solid green line with hatching

- Intermittent precipitation is only enclosed with a solid green line

- The upper panel portrays forecast areas of IFR (solid red lines)

- MVFR (scalloped green lines)

- VFR conditions

- Areas and layers of expected moderate or greater turbulence are enclosed with dashed yellow lines

- The highest freezing level (dashed green lines) and the intersection of the freezing level with the surface are also shown

- High-level significant weather prog chart – covers the airspace from 25,000 feet to 60,000 feet pressure altitude

- Charts from some world area forecast centers (WAFC) cover the layer from FL240 to FL630

- A wide range of information can be interpreted from this chart including forecast of thunderstorm areas, tropical cyclones, surface positions of well-defined convergence zones, movement of frontal systems and the locations and speeds of jetstreams; see figure 16-14

- The positions of jet streams with speeds greater than 80 knots are indicated by long, heavy lines with arrowheads showing the direction of flow

- Each jet is labeled with altitude; speed and direction of the maximum wind in the jet core is shown with conventional wind barbs

- Heights of the tropopause are indicated in boxes; relatively high and low tropopause heights are indicated with H and L respectively

- Areas of significant CB (thunderstorm) activity are enclosed in scallooed lines with heights of tops and bases indicated

- If the base of the layer is below 25,000 feet it is indicated by xxx

- These areas include CB embedded in clouds, haze, or dust

- Areas of moderate and greater turbulence are enclosed in dashed lines

- Predicted intensities and heights of bases and tops of the turbulent layers are also given

- The high-level significant weather prog chart also includes positions of surface fronts, squall lines and the location of volcanic eruptions; see Appendix D for more details

Forecast Winds and Temperatures Aloft Chart

- The third forecast graphic that is useful for flight planning is the forecast winds and temperatures aloft chart

- This is simply a graphical presentation of the information given in FD forecast bulletins

- See figure 16-15 for a sample FD chart for international flights

- Wind and temperature predictions are produced at regularly spaced latitude and longitude positions on international charts

- Other useful forecast charts include the convective outlook chart and the volcanic ash forecast transport and dispersion (VAFTAD) chart

Section C: Aviation Weather Information Sources

FAA Flight Service Stations (FSS)

- The flight service station (FSS) is one of the most common sources of weather information for pilots

- Automated flight service stations (AFSS) – about one per state; these are the result of consolidating older, manual stations

- More aviation weather briefing services are provided by FAA flight service stations than any other government service

- The most common method of obtaining weather information from an FSS is a briefing over the telephone

- You can obtain one of three types of briefings: standard, abbreviated and outlook

- An FSS briefing can be obtained by dialing 1-800-WX-BRIEF

- A standard briefing – provides you with the most complete weather picture tailored to your specific flight; figure 16-16 lists the items included in a standard briefing

- For a telephone briefing it is helpful to have examined these data ahead of time

- An abbreviated briefing – enables you to supplement mass disseminated data, update a previous briefing, or request specific information

- If your proposed departure time is six or more hours in the future an outlook briefing provides a general overview of forecasted weather

***You should request a standard briefing if you have received no preliminary weather information and are departing within the hour. To supplement mass disseminated data, an abbreviated briefing should be requested. The FSS provides an outlook briefing 6 or more hours in advance of your proposed departure time

- Transcribed information briefing service (TIBS) – an AFSS service that provides continuous telephone recordings of meteorological and/or aeronautical information 24 hours a day

- TIBS provides route briefings and depending on user demand aviation weather observations, forecasts and wind and temperature aloft forecasts

- TIBS information is frequently updated to ensure current and accurate weather data

- Local numbers for TIBS are available in the AFD (Airport Facility Directory)

- En route flight advisory service (EFAS) – probably the most familiar inflight service to pilots

- To use this service contact the specific EFAS by using the words “Flight Watch”

- The frequency for flight watch below 18,000 feet MSL is 122.0 MHz

- Upon your request, the flight watch specialist can provide aviation weather information and time-critical enroute assistance

- If you are facing hazardous or unknown weather conditions, EFAS may recommend alternate or diversionary routes

- The receipt and rapid dissemination of pilot weather reports is a primary responsibility of EFAS

***At altitudes below 18,000 feet, you can contact Flight Watch on 122.0 MHz for information regarding current weather along your proposed route of flight

Continuous Broadcasts of Weather Information (TWEB, HIWAS)

- TWEB is aired continuously over selected low and medium frequency NDBs (nondirectional beacons), on 190 – 535 kHz and over VORs (very high frequency omni-directional ranges) on 108.0 – 117.95 MHz

***TWEBs contain in-flight cross-country weather information including winds and temperatures aloft forecasts

- Hazardous inflight weather advisory service (HIWAS) – another in-flight service that provides a continuous broadcast over selected VORs to inform you of hazardous flying conditions such as turbulence, icing, IFR conditions and high winds

Other Weather Information Sources

- Automatic terminal information service (ATIS) – available at most major airports that have operational control towers

- ATIS is a pre-recorded report, broadcast on a dedicated frequency which includes information regarding current weather and pertinent local airport conditions

- ATIS is normally recorded every hour but may be updated any time

- ATIS frequencies are listed in the AFD (Airport Facility Directory)

- Direct user access terminal service (DUATS) – The FAA supports the DUATS service

- This computer-based program provides NWS and FAA products that are normally used in pilot weather briefings

- By using a personal computer and modem you can access weather information prior to flight

- Flight plans can also be filed and amended through DUATS

- Other weather sources include weather forecasts by local news broadcasts, the Weather Channel, airing on cable television and Jeppesen DataPlan

Weather on the Internet

- The internet is probably one of the fastest growing sources of aviation weather

- Appendix F gives a large number of US and international agencies that provide both aviation weather information and general weather information

Chapter 17 – Weather Evaluation for Flight

Section A: Self – Briefing Procedure

- To improve your proficiency in weather evaluation, the development of a system for processing information during flight planning is valuable

- A flow diagram outlining this process is shown in figure 17-1

1. Weather Awareness

2. Knowledge of available and relevant weather products

3. Self evaluation

4. Aircraft Capability

5. Flight description

6. Weather Overview

7. Preflight Weather Evaluation (cancel, go, delay)

8. In-flight Weather Evaluation

9. No change – proceed to destination

10. Divert – Alternate

- Is your meteorological training adequate?

- Are you familiar with relevant weather products and their sources?

Self Evaluation

- Are you current to flying in the weather conditions of the proposed flight?

- Is your weather knowledge current

- Are you up-to-date on the latest weather resources?

Aircraft Capability

- A complete understanding of your aircraft’s performance capability and limitations is essential in evaluating the weather’s impact

- The equipment onboard your aircraft is another factor to consider when assessing aircraft capabilities

- Based on a complete assessment of yourself and your aircraft you can set specific weather restrictions for your flights

Flight Description

- The next step in the self-briefing process is to establish a complete flight description

- Figure 17-2; a flight plan form can be used as a reference for the flight description items supplied to a briefer

***When you request a briefing, identify yourself as a pilot and supply the briefer with the following information: type of flight planned (VFR or IFR), aircraft number or pilot’s name, aircraft type, departure airport, route of flight, destination, flight altitude(s), estimated time of departure and estimated time en-route or estimated time of arrival

Section B: Weather Evaluation Process

- Once the initial steps of the self-briefing procedure are complete, the analysis of weather for a specific flight can begin

- Your misinterpretation of a critical piece of weather information is a pilot error

- Misinterpretations of weather observations and forecasts are usually due to not knowing one or more of the following:

1. What is available

2. What the information means

3. Where you can get it

4. When it is available

Overview

- It is worthwhile to begin assessing the general weather situation a day or two before the flight

- Pay attention to weather reports and forecasts on radio and television

- As time goes on, details should be added to the general patterns

- The Internet or an FSS outlook briefing is helpful at this point

- About 24 hours in advance of your departure, ask yourself these questions:

1. Where are the areas of potentially adverse weather currently located?

2. How have those areas been moving/developing in the last 24 hours or so?

3. Where will those areas be at the time of your flight?

4. What are the specific flight hazards?

- Refer to the surface analysis charts

- In many weather situations, the intensity and organization of the weather system becomes clearer when you examine upper air conditions

- Refer to constant pressure analysis charts

- Refer to low-level significant weather prognostic charts

- Your efficient use of weather information requires that you determine all of the weather hazards significant to your flight

- An outlook briefing from flight service furnishes additional information at this stage

Preflight Evaluation

- The preflight weather evaluation is usually accomplished within a few hours of the proposed departure time due to the importance of procuring the latest information prior to the flight

- Graphic weather material makes it much easier and faster to visualize the weather situation

- This includes satellite images and maps of various weather phenomena

- Plotted in-flight weather advisories and maps showing recent PIREPs are particularly useful

- One of your important tasks at this stage is to make use of all advisories or warnings issued for the area at the time of your flight; look at area forecast, AIRMETS - Sierra, Tango, Zulu, SIGMETS, CONVECTIVE SIGMETS, surface analysis charts, weather depiction charts

- To conclude the weather evaluation, you must make a decision based on your analysis

- An important component of the self-briefing procedure is your own weather observation

In-Flight Evaluation

- Your evaluation of the weather does not end if a go decision is made

- The dynamic nature of weather makes in-flight weather evaluation essential to safety

- While en-route you should also use in-flight weather services such as recorded surface observations and forecasts (TWEB, HIWAS)

- Figure 17-16; Flight Watch is a valuable weather service provided by flight service stations

Section C: Developments in Aviation Weather Resources

- The worldwide aviation community is making major changes in the way weather data are gathered, processed and disseminated

- In the US, the FAA and the National Weather Service are implementing plans leading to an advanced and improved aviation weather system

- This system will integrate present and pending technologies to develop higher resolution and more accurate observations of atmospheric variables

- Increased computer power and modeling capabilities will significantly enhance weather analyses and forecasts

- Weather information will be transformed into aviation decision aids based on weather variables impacting flight

Observation Systems

- The focus of modernized weather observation is the production of high-quality data in nearly real time

- It is expected that there will be 1,500 automated surface-observation stations such as ASOS and AWOS

- The Doppler weather radar (WSR-88D) was deployed initially as NEXRAD and is now the primary tool of the US weather radar network

- Terminal Doppler weather radar (TDWR) has been installed at numerous large airports in the US where thunderstorms and microbursts are most common

- Low-level wind shear alert systems (LLWAS) have been installed at 110 airports in the US

- The radiosonde network has been the primary upper-air data source for weather forecasting for many years

- The wind profiler is a vertically pointing microwave radar that measures horizontal wind speed and direction at 72 levels between about 1,500 feet AGL and 53,000 feet MSL

- Another on-going development in upper-air observations has been the development of the international aircraft meteorological data reporting (AMDAR) system using commercial aircraft as observational platforms

- There are two primary data-gathering systems by AMDAR

- The first is the aircraft-to-satellite data relay (ASDAR) system which uses specially designed hardware that must be fitted to and certified for the aircraft on which it is installed

- The second method for the gathering of meteorological information from aircraft is the aircraft communications, addressing and reporting system (ACARS)

- The AMDAR (ASDAR/ACARS) system has been highly successful

- The modern weather satellite has developed far beyond the acquisition of images of cloud patterns

- Satellites such as the geostationary operational environmental satellite (GOES) provide simultaneous imaging as well as temperature and moisture profiles

Weather Forecasting

- In addition to more and better meteorological observations, a better understanding of atmospheric processes, faster computers, and better numerical techniques are leading to significant improvements in weather forecasting

- A strong US government initiative in support of aviation has resulted in the development of the aviation gridded forecast system (AGFS)

- The purpose of AGFS is to use the output from NCEP models, such as RUC and other specialized computer code to generate high resolution Aviation Impact Variables (AIV)

- The Aviation Division of the NOAA Forecast Systems Laboratory works cooperatively with the Aviation Weather Center (AWC) to integrate AIVs into the aviation forecast process

- Other on-going efforts to improve aviation weather forecasts are aimed at thunderstorms, ceiling and visibility predictions, ground deicing, and the prediction of wake vortex behavior at air terminals

Weather Information Systems

- Effective aviation weather information systems must meet two important requirements

- The world area forecast system (WAFS) is a satellite communications system to provide the worldwide aviation community with weather information for flight planning and to support the en-route phase of flight

- In the US, the FAA’s Aviation Weather Research (AWR) program supports a research project that is addressing the need for improved weather presentation

- Two other significant components of the AWR program are the aviation weather products generator (AWPG) and the integrated terminal weather system (ITWS)

- The purpose of the AWPG is to provide analysis and forecast products tailored for the en-route phase of flight

- ITWS is designed to enhance the FAA’s ability to monitor and predict weather that impacts aircraft in the vicinity of the terminal

- Input into ITWS includes LLWAS, weather radar, automated weather observations, aircraft observations and forecast model output

- By 1999, ITWS had been deployed to 34 locations serving 45 of the busiest airports in the US

- In the future, the weather requirements for free flight and other planned improvements to the national and global air navigation systems will make rapid delivery of better weather information to the cockpit a priority

- Beyond TWIP, the FAA is developing standards and procedures for the transmission of enhanced weather information directly to the cockpits of aircraft in all phases of flight

- As these cockpit request/display systems become a reality, concern for simplicity in operation and interpretation will be critical in order to reap the maximum safety benefits in an already busy cockpit

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