PRACTICAL TAF WRITING Karen Oudeman NWS – Jackson, KY October 16, 2003.

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