PRACTICAL TAF WRITING
PRACTICAL TAF WRITING
Karen Oudeman
NWS – Jackson, KY
October 16, 2003
ReferencesDaniel Cobb Jr.
“Practically Perfect TAF” Presentation
DLAC Web Module “Writing Effective TAFs”
Today’s Objectives and Format
• Present a methodology for forecasters
• Skills in writing effective, practical, user-friendly TAFs
• Run through an example
• Summery of TAF creation thought process
Practical TAF Writing
Formal TAF DefinitionTerminal Aerodrome Forecast (TAF)
• A NWS TAF will consist of the expected meteorological conditions significant to aviation at an airport (terminal) for a specified time period.
• The U.S. definition of a terminal is the area within five (5) statute miles (SM) of the center of an airport's runway complex.
• Forecasters will prepare and monitor TAFs using the best professional judgment to optimize timeliness and
representativeness, with an awareness of the potential operational impact of each forecast element.
• Forecasters will also keep in mind the Critical TAF Period Philosophy; defined as hours 2-6 from the current valid time
within the TAF.
NWSI 10-813
Keep in Mind…
“Worst case scenario” drives operational decisions
Flight categories
Impact thresholds
Critical TAF period (2-6 hrs)
Know your airfields: restrictions and minimums
Commercial vs. GA
Amendment Thresholds
If the ceiling/visibility falls below, or if below, increases to equal or exceed:
Cig: 3000 ft, 2000 ft, 1000 ft, 600 ft (800 ft), 200 ft
Vis: 5 SM, 3SM, 2SM, 1SM,
½ SM - NWSI 10-813
Flight Categories
Flight Category
Ceiling (ft)
Visibility (SM)
LIFR < 500 and/or < 1
IFR 500 to
< 1000
and/or 1 to
< 3
MVFR 1000 to 3000
and/or 3 to
5VFR > 3000 and > 5
TAF Writing• Avoid writing the:
Un-amendable TAFAmbiguous TAF
Instead, try to strive for an effective, practical, user-friendly TAF
Don’t look at it completely through a meteorologist’s eyes – think about it through the user’s eyes
Let’s Work Through an Example
The “Perfect” TAF
32 32 Lines!!Lines!!
“Nearly Perfect” TAF
21 21 Lines !Lines !
!!
“Less Than Perfect” TAF
15 15 Lines !!Lines !!
How Do We Make a Practical TAF?
1. Write to flight categories first; establish trends.
2. Add specific cig/vis detail to the first 6 hours.
3. Limit the use of TEMPO groups to the first 6 hours. Avoid BECMG and PROB.
4. Review for consistency and check that you addressed the flight category changes.
1. Write to flight categories; trends
Where are the Break Points?
• KBGR 030530Z 030606 VFR
FM0800 MVFR
FM1100 IFR
FM1800 VIFR
FM0300 VFR
2. Add Detail – First 6 Hrs
KBGR 030530Z 030606 16005KT P6SM SCT015 OVC060 FM0800 14010KT P6SM –RA SCT018 OVC035 FM1100 17015G30KT 3SM –SHRA BKN009 OVC015 FM1800 18010KT 1/4SM FG OVC001 FM0300 32010KT P6SM OVC040
KBGR 030530Z 030606 16005KT P6SM SCT015 OVC060 FM0800 14010KT P6SM –RA SCT018 OVC035 FM1100 17015G30KT 3SM –SHRA BKN009 OVC015 FM1800 18010KT 1/4SM FG OVC001 FM0300 32010KT P6SM OVC040
3. Limit The TEMPO/PROB/BECMG4. Double Check Your Work
KBGR 030530Z 030606 16005KT P6SM SCT015 OVC060
FM0800 14010KT P6SM –RA SCT018 OVC035
TEMPO 0811 4SM –RA BR BKN018
FM1100 17015G30KT 3SM –SHRA BKN009 OVC015
FM1800 18010KT 1/4SM FG OVC001
FM0300 32010KT P6SM OVC040
You have a 6 line You have a 6 line Practical TAF!!!Practical TAF!!!
What About Verification Scores?
Don’t Worry!• LIFR: • FCST = 108 POD=1.00• HITS = 89 FAR=0.16• OBS = 89 CSI =0.75
• IFR: • FCST = 86 POD=0.94• HITS = 80 FAR=0.07• OBS = 85 CSI =0.88
• MVFR: • FCST = 15 POD=0.75• HITS = 15 FAR=0.00• OBS = 20 CSI =0.75
Practical TAF Writing – Summary
1. Write to flight categories first; establish trends.
2. Add specific cig/vis detail to the first 6 hours.
3. Limit the use of TEMPO groups to the first 6 hours. Avoid BECMG and PROB.
4. Review for consistency and check that you addressed the flight category changes.
Practical TAF Writing - Summary• No more than 5 lines per TAF • Avoid multiple unnecessary
modifiers (PROB or BECMG) • Link similar visibility and
ceilings into similar categories (scenario forecasting)
• Consider the local critical thresholds for the airport
• Focus on the aviation critical weather—spend most of your energy on the forecast period that is expected to be below VFR
Practical TAF Writing - Summary
• If you can’t get exact numbers, at least show the trend
• Limit your use of conditional groups—don’t hedge, make a decision!
• When you do use a TEMPO group, try not to jump more than one category (e.g., from VFR to IFR)
• Coordinate with others (e.g., CWSU, AWC, neighboring WFO)
• Limit forecast length of convection
PRACTICAL TAF WRITING
PRACTICAL TAF WRITING
End Result: Effective, User-Friendly, Practical
TAFs
Karen OudemanNWS – Jackson, KY
October 16, 2003