2. Ch 17 – Weather Evaluation for Flight

3. Ch 17 – Weather Evaluation for Flight
Introduction
A fact of aviation today is that you must have a better understanding of weather than your predecessors
There are at least two primary reasons for this.
First, approximately 25% of aircraft accidents are weather-related
A weather-wise pilot is much less likely to become a statistic

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Second, the rapid growth in the aviation industry and the increasing automation of weather information places a greater burden on you to obtain and interpret weather information pertinent to your flight

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The concept of a “self-briefing” to augment official briefings requires that you develop a procedure to obtain and integrate weather observations and forecasts into your preflight preparations
This chapter provides guidelines to help you develop a self-briefing procedure
That procedure is then demonstrated by applying it to an actual weather situation

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Finally, an outlook for improvements in aviation weather observations, forecasts, products, and information delivery is also provided.
When you complete Chapter 17 you will understand the process of combining a variety of weather information via an effective self-briefing procedure

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You will also be aware of important future developments that will lead to significant improvements in your operational application of aviation weather knowledge and in-flight safety

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Section A – Self – Briefing Procedure
Self Evaluation
Aircraft Capability
Flight Description

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Section B – Weather – Evaluation Process
Overview
Preflight Evaluation
In-Flight Evaluation

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Section C – Developments in Aviation Weather Resources
Observation Systems
Weather Forecasting
Weather Information Systems

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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

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A flow diagram outlining this process is shown in figure 17-1
Weather Awareness
Knowledge of available and relevant weather products
Self evaluation
Aircraft Capability

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Flight description
Weather Overview
Preflight Weather Evaluation (cancel, go, delay)
In-flight Weather Evaluation
No change – proceed to destination
Divert – Alternate

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Is your meteorological training adequate?
Are you familiar with relevant weather products and their sources?

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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?

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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

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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

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***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

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departure airport
route of flight
Destination
flight altitude(s)
estimated time of departure and estimated time en-route or estimated time of arrival

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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

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Misinterpretations of weather observations and forecasts are usually due to not knowing one or more of the following:
What is available
What the information means
Where you can get it
When it is available

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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

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About 24 hours in advance of your departure, ask yourself these questions:
Where are the areas of potentially adverse weather currently located?
How have those areas been moving/developing in the last 24 hours or so?
Where will those areas be at the time of your flight?

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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

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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

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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

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This includes satellite images and maps of various weather phenomena
Plotted in-flight weather advisories and maps showing recent PIREPs are particularly useful

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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)

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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

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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

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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

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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)

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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

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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

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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

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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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Summary
The future holds exciting advancements in aviation weather technology including improved observations and forecasts, and better access to weather products that are more comprehensive, yet easier to interpret

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In order to make the best use of these developments for safe and enjoyable flying, you must continually make an effort to stay abreast of new systems and weather products as they become operational.

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Your meteorology education has only started here
It is a continuing process
As with flying, it is up to you to stay current with aviation weather