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

References Daniel 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 Definition Terminal 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

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

Flight Categories Flight Category Ceiling (ft) Visibility (SM) LIFR< 500and/or< 1 IFR$ 500 to < 1000 and/or$1 to < 3 MVFR  1000 to  3000 and/or$3 to  5 VFR> 3000and> 5

TAF Writing Avoid writing the:  Un-amendable TAF  Ambiguous 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 Lines!!

“Nearly Perfect” TAF 21 Lines !!

“Less Than Perfect” TAF 15 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 Z VFR FM0800 MVFR FM1100IFR FM1800VIFR FM0300VFR

2. Add Detail – First 6 Hrs KBGR Z KT P6SM SCT015 OVC060 FM KT P6SM –RA SCT018 OVC035 FM G30KT 3SM –SHRA BKN009 OVC015 FM KT 1/4SM FG OVC001 FM KT P6SM OVC040 KBGR Z KT P6SM SCT015 OVC060 FM KT P6SM –RA SCT018 OVC035 FM G30KT 3SM –SHRA BKN009 OVC015 FM KT 1/4SM FG OVC001 FM KT P6SM OVC040

3. Limit The TEMPO/PROB/BECMG 4. Double Check Your Work KBGR Z KT P6SM SCT015 OVC060 FM KT P6SM –RA SCT018 OVC035 TEMPO SM –RA BR BKN018 FM G30KT 3SM –SHRA BKN009 OVC015 FM KT 1/4SM FG OVC001 FM KT P6SM OVC040 You have a 6 line 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 End Result: Effective, User-Friendly, Practical TAFs Karen Oudeman NWS – Jackson, KY October 16, 2003