A Better Use of TAFs Southwest Aviation Weather Safety Workshop II A Better Use of TAFs Southwest Aviation Weather Safety Workshop II Leslie Wanek Aviation Program Leader WFO Phoenix October 23-24, 2008

Objectives for today… TAF Review and TerminologyTAF Review and Terminology NWS TAF Writing PhilosophiesNWS TAF Writing Philosophies Forecaster Best PracticesForecaster Best Practices Use of Cumulonimbus (CB) & Vicinity (VC)Use of Cumulonimbus (CB) & Vicinity (VC) TAF ExampleTAF Example Aviation Forecaster Written DiscussionAviation Forecaster Written Discussion 30-Hour TAF Format Change30-Hour TAF Format Change

TAF Review & Terminology Terminal Aerodrome Forecast Terminal Aerodrome Forecasts, also known as Aerodrome Forecasts, are prepared by National Weather Service (NWS) Weather Forecast Offices (WFOs). The U.S. definition of terminal is an area within five (5) statute miles (SM) of the center of an airport’s runway complex. A NWS TAF will consist of expected meteorological conditions significant to aviation at an airport (terminal) for a specified time period. TAFs are a critical element of NWS aviation weather services because they are a key product in decisions on aircraft movement within the National Airspace System (NAS). NWSI November 2007

TEMPO Defined as…Temporary fluctuations in forecast meteorological conditions which are expected to last less than one (1) hour in each instance and, in the aggregate, to cover less than half of the indicated period. TEMPO Defined as…Temporary fluctuations in forecast meteorological conditions which are expected to last less than one (1) hour in each instance and, in the aggregate, to cover less than half of the indicated period. Used for high probability (greater than 50%) expectationsUsed for high probability (greater than 50%) expectations Will not be substituted to indicate a low probability event (less than 50%)Will not be substituted to indicate a low probability event (less than 50%) Will not exceed four (4) hoursWill not exceed four (4) hours NWSI November 2007 KABC Z KT P6SM SCT010 BKN020 OVC090 TEMPO SM RA SCT010 BKN015 OVC040… Example…

PROB30 Defined as…Probability of occurrence of a thunderstorm or other precipitation event, with associated weather elements as necessary (wind, visibility, and/or sky condition) whose occurrences are directly related to, and contemporaneous with, the thunderstorm or precipitation event. PROB30 Defined as…Probability of occurrence of a thunderstorm or other precipitation event, with associated weather elements as necessary (wind, visibility, and/or sky condition) whose occurrences are directly related to, and contemporaneous with, the thunderstorm or precipitation event. PROB30 groups only, indicating a 30% probability of the specified element occurringPROB30 groups only, indicating a 30% probability of the specified element occurring PROB30 groups will not include forecasts of significant weather in the vicinity (VC) or non-convective Low Level Wind Shear (LLWS)PROB30 groups will not include forecasts of significant weather in the vicinity (VC) or non-convective Low Level Wind Shear (LLWS) Will not be used in the first nine (9) hours of every TAF valid period, including amendmentsWill not be used in the first nine (9) hours of every TAF valid period, including amendments NWSI November 2007

Low Level Wind Shear (LLWS) Defined as… Wind Shear (WS), a change in horizontal wind speed and/or directions, and/or vertical speed with distance, measured in a horizontal and/or vertical direction. WS is a vector difference, composed of wind direction and wind speed, between two wind velocities. Low Level Wind Shear (LLWS) Defined as… Wind Shear (WS), a change in horizontal wind speed and/or directions, and/or vertical speed with distance, measured in a horizontal and/or vertical direction. WS is a vector difference, composed of wind direction and wind speed, between two wind velocities. LLWS in a NWS TAF will refer only to non-convective LLWS from the surface up to and including 2K ft AGLLLWS in a NWS TAF will refer only to non-convective LLWS from the surface up to and including 2K ft AGL Used only in FM groups (no TEMPO/PROB30), remains prevailing until next FM change groupUsed only in FM groups (no TEMPO/PROB30), remains prevailing until next FM change group NWSI November 2007 KABC Z KT 3SM BR SCT030 WS015/29065KT FM KT 1SM TSRA BR OVC010CB FM KT 1SM TSRA BR OVC010CB FM FM Example…

NWS TAF Writing Philosophies Keep in mind the varying degree of NWS TAF users, including… domestic and international commercial airlines, General Aviation (GA), Civilian and Military Operations, etc.Keep in mind the varying degree of NWS TAF users, including… domestic and international commercial airlines, General Aviation (GA), Civilian and Military Operations, etc. AFCCeiling (ft)Visibility (SM) LIFR< 500and/or< 1 IFR500 to < 1000and/or1 to < 3 MVFR1000 to 3000and/or3 to 5 VFR> 3000and> 5 Optimize timeliness and representativeness using the best Optimize timeliness and representativeness using the best professional judgment professional judgment Be aware of the potential operational impact of each forecast Be aware of the potential operational impact of each forecast element and it’s associated change in Aviation Flight Category element and it’s associated change in Aviation Flight Category (AFC) (AFC) Know your airfield’s Know your airfield’s restrictions and restrictions and minimums minimums

The Un-Amendable TAF… Many pilots find TAFs are often written with such complexity that they lose utilityMany pilots find TAFs are often written with such complexity that they lose utility NWS Verification statistics indicate that PROB and TEMPO groups are overused and can hurt the value of the forecastNWS Verification statistics indicate that PROB and TEMPO groups are overused and can hurt the value of the forecast The cost to an airline for adding fuel for an alternate can also be high, especially for some carriersThe cost to an airline for adding fuel for an alternate can also be high, especially for some carriers GA Pilot…it’s a go / no goGA Pilot…it’s a go / no go Un-Amendable TAF

NWS TAF Writing Philosophies Common Needs… ClearClear ConciseConcise ConsistentConsistent RelevantRelevant TimelyTimely AccurateAccurate Through the TAF, NWS Forecasters have a great opportunity to enhance flight safety and save customers both time and money.

Forecaster Best Practices Goal: Avoid writing the un-amendable, ambiguous TAF and strive for an effective, practical, user-friendly TAF by… 1.Establishing trends and writing to Aviation Flight Categories first 2.Add detail to the first 6 hours of the TAF, known as the critical TAF period 3.Limit the use of TEMPO groups to the first 6 hours 4. Avoid PROB30, which users have indicated can be confusing confusing

Use of Vicinity (VC) & Cumulonimbus (CB) Used only in the initial time period or in from (FM) groups, all of which forecast prevailing conditionsUsed only in the initial time period or in from (FM) groups, all of which forecast prevailing conditions Used in combination with fog (FG), showers (SH), and thunderstorms (TS)Used in combination with fog (FG), showers (SH), and thunderstorms (TS) Less stringent operational impacts on users than PROB30 groupsLess stringent operational impacts on users than PROB30 groups CB = used to indicate instability in the atmosphereCB = used to indicate instability in the atmosphere Vicinity = A donut-shaped area between circles with radii of 5 and 10 SM from the center of the runway complex of an airport.

Forecast Example KTAF Z KT P6SM SCT080 CB BKN200 FM G22KT P6SM VCTS SCT050 CB BKN070 FM G22KT P6SM VCTS SCT050 CB BKN070 TEMPO 2224 VRB20G30KT TSRA BKN030CB Forecast Scenario: A 70% chance for showers and thunderstorms is forecast for a zone in the afternoon, 18 – 00 UTC (local time 11am is forecast for a zone in the afternoon, 18 – 00 UTC (local time 11am – 5pm). At a TAF site in that zone, a 30% chance for showers and – 5pm). At a TAF site in that zone, a 30% chance for showers and thunderstorms is forecast for early afternoon and a 70% chance for thunderstorms is forecast for early afternoon and a 70% chance for late afternoon. late afternoon. Public Zone (area) forecast reads… PARTLY CLOUDY. SOUTH WIND 10 TO 15 MPH. SHOWERS AND THUNDERSTORMS LIKELY IN THE AFTERNOON. CHANCE OF RAIN 70 PERCENT. TAF reads…

AFD Aviation Discussion… Area Forecast Discussion Change in Flight CategoriesChange in Flight Categories –VFR/MVFR/IFR/LIFR Frontal PassageFrontal Passage –timing / cause Precipitation TypePrecipitation Type –start/stop Visibility ObstructionsVisibility Obstructions –smoke / haze ThunderstormsThunderstorms –coverage / intensity WindsWinds –cross winds / LLWS AFD is one of the most used products the NWS issuesAFD is one of the most used products the NWS issues Routinely issued 2-4 times/dayRoutinely issued 2-4 times/day Insight into Forecasters’ thought processInsight into Forecasters’ thought process Basic weather discussion (in non-technical wording), identifying weather-related items which may affect the operations of an airport terminalBasic weather discussion (in non-technical wording), identifying weather-related items which may affect the operations of an airport terminal Provide users a better understanding of expected weather during Critical TAF PeriodProvide users a better understanding of expected weather during Critical TAF Period

AFD Aviation Discussion…

30-Hour TAF Format Change What is it? In response to request by long haul operations for better service, the International Civilian Aviation Organization (ICAO) made provisions for a 30-hour TAF in Annex 3 for the Meteorological Service for International Air Navigation, Amendment 74.In response to request by long haul operations for better service, the International Civilian Aviation Organization (ICAO) made provisions for a 30-hour TAF in Annex 3 for the Meteorological Service for International Air Navigation, Amendment 74. Will likely impact TAF software de-coders worldwide since each change group will now have a date (applies to ALL locations, even those not providing 30-hour TAFs).Will likely impact TAF software de-coders worldwide since each change group will now have a date (applies to ALL locations, even those not providing 30-hour TAFs). When is it? New format is expected to start for the US and most other countries 00Z on the Nov 5th 2008 (5pm local MST on Nov 4th).New format is expected to start for the US and most other countries 00Z on the Nov 5th 2008 (5pm local MST on Nov 4th). However some countries may delay etc…so vendors will need to be able to decode both formats for some period of time.However some countries may delay etc…so vendors will need to be able to decode both formats for some period of time.

30-Hour TAF Format Change Old Format… Old Format… KABC Z KT P6SM BKN020 TEMPO G45KT 1SM TSRA SCT010CB BKN020 TEMPO G45KT 1SM TSRA SCT010CB BKN020 FM KT P6SM BKN020 FM KT P6SM BKN020 New Format… New Format… KABC Z 1600/ KT P6SM BKN020 KABC Z 1600/ KT P6SM BKN020 TEMPO 1608/ G45KT 1SM TSRA SCT010CB TEMPO 1608/ G45KT 1SM TSRA SCT010CB FM KT P6SM BKN020 FM KT P6SM BKN020 New Format for 24-Hour TAF Locations… New Format for 24-Hour TAF Locations… KABC Z 1600/ KT P6SM BKN020

30-Hour TAF Format Change 32 U.S. locations will go to 30 Hour Where is it produced?

30-Hour TAF Format Change The NOAA Aviation Services Branch (ASB) has a 30 hour testbed…where vendors and users can go to download further material and practice TAFs… Where to find more information…

Closing Remarks –TAF terminology –NWS TAF Writing Philosophies and Forecaster Best Practices –Example TAFs –AFD Aviation Discussion –Upcoming 30-Hour TAF Format Change Questions or comments after today…you can reach me at Thank you!

Additional Resources & References… “TAF Writing Tips from Medford, OR”. James Reynolds, WFO Hastings“TAF Writing Tips from Medford, OR”. James Reynolds, WFO Hastings COMET Distance Learning Aviation Course DLAC2 Modules 1-2COMET Distance Learning Aviation Course DLAC2 Modules 1-2 “TAF Writing Philosophy”. Bill South, WFO Key West“TAF Writing Philosophy”. Bill South, WFO Key West “TAF Best Practices from Phoenix, AZ”. Leslie Wanek, NWS Phoenix“TAF Best Practices from Phoenix, AZ”. Leslie Wanek, NWS Phoenix “Practical TAF Writing”. Karen Oudeman, NWS Jackson“Practical TAF Writing”. Karen Oudeman, NWS Jackson “Writing Better Aviation AFDs (or) Do you know who your customer“Writing Better Aviation AFDs (or) Do you know who your customer really is?” Dustin Harbage & Brian Schoettmer, WFO Jackson “Aviation AFD Guidance, An Airline Perspective”. Ken Widelski, WFO Lubbock“Aviation AFD Guidance, An Airline Perspective”. Ken Widelski, WFO Lubbock “The 30-Hour TAF, What When and Where?”, Mike Graf; NOAA Aviation Services Branch“The 30-Hour TAF, What When and Where?”, Mike Graf; NOAA Aviation Services Branch NATIONAL WEATHER SERVICE INSTRUCTION , TERMINAL AERODROME FORECASTS. November 2007NATIONAL WEATHER SERVICE INSTRUCTION , TERMINAL AERODROME FORECASTS. November 2007 Cartoon: Adapted from Artist: Hagen, RalphCartoon: Adapted from Artist: Hagen, Ralph

Low Level Wind Shear (non-convective) The format of the non-convective low-level wind shear group is WShwshwshws/dddffKT, where: WS= Indicator for non-convective LLWSWS= Indicator for non-convective LLWS hwshwshws = Height of the top of the WS layer in hundreds of feet AGLhwshwshws = Height of the top of the WS layer in hundreds of feet AGL ddd= True direction in ten degree increments at the indicated heightddd= True direction in ten degree increments at the indicated height ff= Speed in knots of the forecast wind at the indicated heightff= Speed in knots of the forecast wind at the indicated height KT= Unit indicator for windKT= Unit indicator for wind