Turbulence: Preflight Decision Aids Gregory S. Harris Aviation Weather Center SAWS V Virtual Conference

Goals Why Preflight? Better understand the AIRMET Tango Series – Turbulence – Sustained Surface winds ≥ 30KT – Low-level wind shear (LLWS) Review strengths of G-AIRMET Aviation Forecast Discussion Verification

Visible Signs of Turbulence At times mother nature provides clues as to where turbulence may be so we can avoid it, as seen in the images above. However, it is not always as obvious.

Why Preflight? Great place to start for all hazards! First step in hazard mitigation Best time to consider Go and No-Go as well as next day options / considerations Good preflight planning eliminates surprises Important step in determining altitudes, routes, alternates, etc.

Preflight Decision Aids The Aviation Weather Center (AWC) produces and provides Aviation Weather Hazard forecasts, advisories and warnings. AIRMETs – SIERRA – SIERRA: Instrument Flight Rules (IFR) and Mountain Obscuration – ZULU – ZULU: Icing and Freezing Level – TANGO – TANGO: Turbulence, Strong Sustained Surface Winds ≥ 30KT, and Low-level Wind Shear (LLWS)

Preflight Decision Aids The Weather Forecast Office (WFO) produces and provides Aviation Forecast Discussion (AFD). May be found on AWC website – – AFDs are taken from the.AVIATION... section of local WFO Area Forecast Discussions. – Provides forecaster's thoughts, reasoning, and uncertainty factors considered for aviation weather

AIRMET TANGO Relevant turbulence guidance may be found in the AIRMET TANGO Series. This series of AIRMETs provide:

Turbulence Moderate from Surface to 40Kft MSL – Divided into – High Turbulence generally 18Kft MSL and above – Low Turbulence generally 18Kft MSL and below Note: 18Kft is generally used, however Low Turb may be 20Kft to SFC depending on situation

Sustained Surface Winds Surface winds ≥ 30 KTs – Smooth surface can create light-mod turb – Rugged terrain can create mod or greater turb – Approach and Departure Turbulent eddies from hangers, buildings, tree lines, etc. Possible cross wind issues – Blowing sand and dust for arid / desert regions

Low Level Wind Shear (LLWS) Low Level Wind Shear – Non-convective low-level wind shear potential below 2,000 feet AGL (LLWS POTENTIAL) – Variations of +/- 20KT – Areas of rugged terrain especially coastal ranges Santa Ana Winds Problematic for runways lee side of ranges / terrain

The Graphical AIRMET is: A graphical forecast of en-route weather hazards A series of snapshots at 3 hour intervals valid for up to 12 hours  00 hour represents the initial conditions  the subsequent 3-hourly graphics depict the area affected by the particular hazard at that valid time Routinely issued every 6 hours Updated, Amended or Corrected as needed Definition: Graphical AIRMET

F00 Aerial Coverage Depth F03 F06 G-AIRMET SnapshotsArea of Text AIRMET F00F03F06=++6HR Smear Differences from Text AIRMET

Finding the Graphical AIRMET AWC Menu SelectionSIGMET/AIRMET Page

G-AIRMET Examples Low Level Turbulence High Level Turbulence

G-AIRMET Examples

Aviation Forecast Discussion AWC Menu SelectionAFD Page

AFD Examples AFD ExcerptsG-AIRMET (EXTRACTED FROM FXUS66 KLOX ) NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 925 AM PDT THU MAY /1155Z …GUSTY NW WINDS WILL CAUSE SOME LLWS AROUND KSBA LATE THIS AFTERNOON THROUGH THE EARLY EVENING. WINDS SHOULD NOT BE AS STRONG OR LAST AS LONG AS RECENT DAYS… (EXTRACTED FROM FXUS66 KHNX ) NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 422 AM PDT THU MAY …ACROSS THE KERN COUNTY MOUNTAINS AND DESERTS...SURFACE WIND GUSTS OF 35 KNOTS OR GREATER CAN BE EXPECTED THROUGH AT LEAST 12Z FRIDAY...WITH PATCHY BLOWING SAND AND DUST. OTHERWISE...VFR CONDITIONS WILL PREVAIL ACROSS THE CENTRAL CALIFORNIA INTERIOR DURING THE NEXT 24 HOURS. (EXTRACTED FROM FXUS65 KREV ) NATIONAL WEATHER SERVICE RENO NV 315 AM PDT THU MAY BUILDING RIDGE TO THE WEST WILL RESULT IN LIGHT WINDS THROUGH FRIDAY FOR MOST AREAS AND VFR CONDITIONS. THE ONLY EXCEPTION COULD BE INCREASED EASTERLY WINDS ALONG AND JUST WEST OF THE SIERRA RESULTING IN SOME TURBULENCE WEST OF THE CREST…. (EXTRACTED FROM FXUS65 KVEF ) NATIONAL WEATHER SERVICE LAS VEGAS NV 246 AM PDT THU MAY …FOR THE REST OF SOUTHERN NEVADA...NORTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA... SOUTHWESTERLY WINDS ARE EXPECTED TODAY BUT NOT AS STRONG AS WEDNESDAY...WITH THE STRONGEST WINDS EXPECTED ACROSS MOHAVE COUNTY WITH GUSTS AROUND 20KTS ON AVERAGE… (EXTRACTED FROM FXUS65 KGJT ) NATIONAL WEATHER SERVICE GRAND JUNCTION CO ISSUED AT 439 AM MDT THU MAY …EXPECT MECHANICAL TURBULENCE WITH SURFACE GUSTS OF KTS FAIRLY COMMON THIS AFTERNOON...ESPECIALLY AT KHDN...KGUC AND KDRO… (EXTRACTED FROM FXUS65 KBOU ) NATIONAL WEATHER SERVICE DENVER/BOULDER CO 315 AM MDT THU MAY …SURFACE WINDS WILL INCREASE AND SHIFT WEST AND NORTHWEST LATER THIS AM AND AFTERNOON WITH SPEEDS IN THE 20-35KT RANGE EXPECTED AS LOW LEVELS MIX OUT. BJC ALREADY SEEING SOME OF THESE DOWNSLOPE WINDS AND HAVE INCREASED THEM ALREADY. AIRMASS TOO DRY FOR STORMS TODAY WITH JUST SOME MID LEVEL WAVE CLOUDS ESPECIALLY THIS AM. (EXTRACTED FROM FXUS65 KPUB ) NATIONAL WEATHER SERVICE PUEBLO CO ISSUED AT 430 AM MDT THU MAY …THE OTHER FLIGHT CONCERN COULD BE THE SURFACE WINDS. THEY WILL GET QUITE BRISK AND GUSTY FROM THE WEST TO NORTHWEST TODAY...PICKING UP SHORTLY AFTER SUNRISE AS MIXING GETS UNDERWAY. SUSTAINED SPEEDS OVER 20 MPH AND GUSTS OVER 40 MPH WILL BE QUITE COMMON STARTING Z...INCLUDING KCOS...KPUB AND KALS TAF SITES. WINDS SHOULD CALM DOWN AROUND SUNSET…. (EXTRACTED FROM FXUS65 KABQ ) NATIONAL WEATHER SERVICE ALBUQUERQUE NM 536 AM MDT THU MAY …AXIS OF STRONG UPPER JET LOCATED JUST NORTH OF THE STATE BUT IN A FAVORABLE POSITION AND ORIENTATION TO GENERATE MOUNTAIN WAVES AND ASSOCIATED IMPACTS OVER THE NORTHERN MOUNTAINS AND ESPECIALLY THE SANGRE DE CRISTO AND IMMEDIATE EAST SLOPES. SFC WINDS GUSTS FREQUENTLY IN THE KT RANGE EXPECTED FOR ALL TERMINAL SITES EXCEPT KROW WHERE SOMEWHAT LIGHTER WIND CONDITIONS EXPECTED… (EXTRACTED FROM FXUS64 KEPZ ) NATIONAL WEATHER SERVICE EL PASO TX/SANTA TERESA NM 335 AM MDT THU MAY VALID 30/12Z-31/12Z. WESTERLY WINDS WILL TRANSPORT DRY AIR INTO THE REGION RESULTING IN VFR MOSTLY CLEAR CONDITIONS. WINDS WILL GUST TO NEAR 30 MPH OVER A FEW AREAS BETWEEN 20Z AND 02Z.

Verification Pilot Reports (PIREPs) All reports are important! – Negative PIREPs as valuable as Moderate – Critical feedback loop for forecaster and gridded forecasts – Aids in determining areal scope of forecast areas – Essential in issuing SIGMETs

Questions?