Fly - Fight - Win 25 th Operational Weather Squadron USAF Operational Turbulence Forecasting Capt Bill Ryerson Mission Execution Flight Commander 23 Oct 08

Fly - Fight - Win Overview 25 th Operational Weather Squadron Mission Turbulence in All Its Forms Recent Turbulence Forecasting Technology

Fly - Fight - Win Overview 25 th Operational Weather Squadron Mission Turbulence in All Its Forms Recent Turbulence Forecasting Technology

Fly - Fight - Win 25 OWS Mission Provide forecasts and severe weather support for 82 DoD locations (~1,500 aircraft) in 11 W CONUS states Over 12,000 forecast products per month, including 2,200 Flight Weather Briefings Forecasts for 5 bombing ranges / military operating areas Total Assigned: 21 Officer, 134 Enlisted

Fly - Fight - Win 25 OWS Mission

Fly - Fight - Win 25 OWS Mission Provide thunderstorm and low-level (below FL180) icing and turbulence forecasts for W NORTHCOM Provide upper-level (above FL180) icing and turbulence forecasts for all of NORTHCOM Once-day production cycle with forecasts out to 48hr Continuously amended

Fly - Fight - Win Overview 25 th Operational Weather Squadron Mission Turbulence in All Its Forms Recent Turbulence Forecasting Technology

Fly - Fight - Win Turbulence in All Its Forms Turbulence is all the same – rapid variation in wind velocities but… The mechanisms and conceptual models differ

Fly - Fight - Win Turbulence in All Its Forms Low-level turbulence (affected by the ground) Thermal Vertical wind shear Mechanical Untrapped lee waves Trapped lee waves Upper-level turbulence (above effects of ground) Vertical wind shear Pattern recognition Atmospheric Deformation Frontogenesis

Fly - Fight - Win Thermal Turbulence Associated with rising “thermals” above a heated ground If temperature decreases by >3°C between ground and 1000ft, very good chance for thermal turbulence Normally LGT Extends to height where lapse rate no longer >3°C / 1000ft

Fly - Fight - Win Vertical Wind Shear Variation of wind velocity vector (direction and speed) with height Very reliable, “straightforward” turbulence producer (at all levels) Thresholds for turbulence highly dependent on mean wind speed of the layer Different from horizontal shear, which also produces turbulence

Fly - Fight - Win Mechanical Turbulence Caused by various frictional effects of wind flow over the Earth Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa)

Fly - Fight - Win Mechanical Turbulence In an unstable environment, wave is quickly dissipated by mixing downstream of barrier Turbulence can still be SVR, but covers smaller volume A stable environment favors less mixing, more downstream propagation Mountain wave turbulence caused by a specific type of propagating wave

Fly - Fight - Win Pattern Recognition Identifies most likely areas for upper-level turbulence in relation to meteorological features Ahead of shortwave troughs (leading edge of cool air in upper levels) Jet Stream Shortwave Trough Area of Turbulence Strong cold air advection of 0.5°C/hr or more Turbulence centered north of jet Turbulence rarely found behind trough

Fly - Fight - Win Pattern Recognition Cyclogenesis (development of low pressure) at the surface MDT if low is deepening at 1mb/hr MDT-SVR if deepening >1mb/hr and jet stream is >140kts

Fly - Fight - Win Pattern Recognition “Digging” jet stream / jet maximum Jet max (localized maximum in jet wind speeds) pushing southward Shortwave trough ahead of jet max MDT turbulence in region where jet speeds rapidly decrease Jet Max

Fly - Fight - Win Pattern Recognition Two jets in close proximity There exists several branches of the jet stream Different jets usually at different heights Turbulence expected if within 5° latitude

Fly - Fight - Win Pattern Recognition Sharp ridge / anticyclonic curvature Wind speeds typically decelerate at top of ridge MDT if jet is >100kts and decelerates >25kts/°lat SVR if jet is >140kts and decelerates >50kts/°lat Typical height of turbulence is 6000ft below tropopause to 1000ft above it Ridge

Fly - Fight - Win Atmospheric Deformation A measure of 3-D “non uniformity” of the wind Combines: Vertical and horizontal wind shear Horizontal “stretching” Horizontal convergence Calculated using model-predicted wind flow and computer-based algorithm (Ellrod-Knapp index) Turbulence thresholds found empirically, vary based on model resolution Ellrod-Knapp = VWS (total deformation + convergence)

Fly - Fight - Win Frontogenesis The increase in the horizontal temperature gradient Demonstrated to be one of best upper- level turbulence predictors in recent research by National Center for Atmospheric Research (NCAR) Frontogenesis inherently leads to vertical wind shear Frontogenesis = (horizontal temperature gradient) (component of convergence perpendicular to temperature gradient) Positive Frontogenesis Negative Frontogenesis

Fly - Fight - Win Overview 25 th Operational Weather Squadron Mission Turbulence in All Its Forms Recent Turbulence Forecasting Technology

Fly - Fight - Win Forecast Production Turbulence Forecaster Dashboard provides access to all tools leveraging various techniques Utilizes overlay technology User selects combination of products he/she wants to see Enables end user to see products used to make forecast

Fly - Fight - Win Forecast Production

Fly - Fight - Win Vertical Wind Shear Vertical Wind Shear w/ barbs Vertical Wind Shear w/ threshold barbs MDT Turbulence (with kt winds)

Fly - Fight - Win Mechanical Turbulence Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa) Maximum Wind Speed Near Ridge Height

Fly - Fight - Win Mechanical Turbulence Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa) Most Favorable Wind Direction and Height for Selected Ridges

Fly - Fight - Win Mechanical Turbulence Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa) Ridge-Top Wind Direction and Perpendicular Speed Component

Fly - Fight - Win Mechanical Turbulence Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa) Terrain Roughness

Fly - Fight - Win Mechanical Turbulence Terrain Roughness Max WindSpeed Terrain Roughness

Fly - Fight - Win Mechanical Turbulence Magnitude and downstream behavior of wave depends on: Wind Speed Perpendicularity of wind to the barrier Roughness / abruptness of terrain Stability of atmosphere (warm air over cold air, or vice-versa) Low-Level Lapse Rates (Stability)

Fly - Fight - Win Mechanical Turbulence Panofsky Index Combines wind speed, vertical wind shear, stability into one product Used from Surface to 5000ft Panofsky Index LGT MDT SVR Panofsky Index = (Wind speed) 2 (1-((Richardson Number) / (Critical Richardson Number)) * Critical Richardson Number = 0.25

Fly - Fight - Win Atmospheric Deformation Ellrod-Knapp Index Single-Layer Image Multi-Level Contoured

Fly - Fight - Win Atmospheric Deformation Ellrod-Knapp Index Deep and Organized Deep but DisorganizedDisorganized and Dispersed

Fly - Fight - Win Frontogenesis Automated Frontogenesis Product

Fly - Fight - Win Graphical Turbulence Guidance (GTG) Upper-level turbulence verification and short-range (12hr) diagnostic Combines 11 upper- level indices into single product, meshes it with live reports Produced by NCAR and ingested into Dashboard at verification and forecasting tool

Fly - Fight - Win Overview 25 th Operational Weather Squadron Mission Turbulence in All Its Forms Recent Turbulence Forecasting Technology

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Fly - Fight - Win Additional Upper-Level Turbulence Patterns Backup Slides