Jeremy Mazon and Curtis N. James, Ph.D. Embry-Riddle Aeronautical University

ACKNOWLEDGMENTS Phoenix TRACON provided the air traffic data for this study (July - September 2010) NCDC provided the Level III radar imagery Rick Curtis, Southwest Airlines Mr. Brent Spencer, Chair of our Air Traffic Management program

EMBRY-RIDDLE AERONAUTICAL UNIVERSITY (PRESCOTT, AZ CAMPUS) Degrees offered: B.S. Aeronautics B.S. Aeronautical Science B.S. Aerospace Studies B.S. Air Traffic Management B.S. Applied Meteorology B.S. Aviation Business Administration B.S. Aviation Environmental Science B.S. Engineering (AE, EE, ME, CS, CE) B.S. Global Security and Intelligence Studies B.S. Space Physics M.S. Safety Science

OVERVIEW Impacts of convective weather on commercial aviation Air traffic considerations Methodology A climatology of the convective events affecting PHX Sky Harbor operations during the 2010 Monsoon

COST OF WEATHER TO AVIATION 440 fatalities annually (weather related)! More than hurricane, tornado, flash flood deaths combined (mostly from low ceiling and visibility) Total economic impact: $6.5 Billion/yr (ATA) Cost per delay hard to quantify One Flight Cancellation Costs ~ $40,000 One Flight Diversion Costs ~ $150,000 One diversion can cause 50 more delays

CAUSES OF AIRPORT DELAYS (2004) By the year 2017, the costs from these delays and increased traffic congestion could offset airline profits completely (source: FAA).

Source: Bruce Carmichael--NCAR CLIMATOLOGY OF AIRPORT DELAYS

CONVECTIVE WEATHER DELAYS AT PHX TRACON restricts the arrival and departure rates around adverse weather Go/No go decision is made by the pilot in command Delays caused by wind, blowing dust, precipitation, lightning in vicinity of airport or along flight corridors Being able to anticipate delays can help airlines strategically avoid economic losses.

PHOENIX FLIGHT CORRIDORS

PHOENIX CLIMATOLOGY Summer thunderstorms are generally weakly influenced by synoptic-scale forcing Inverted easterly waves occasionally embedded in monsoonal flow Orographic triggering is consistent, however, for a given wind flow and stability profile Low-level shear governs multicellular organization and propagation into PHX airport and across flight corridors Surface wind is generally westerly (5-15 kt) late morning to evening

NORTH AMERICAN MONSOON (NAM) Mean 700-mb Height October - JuneMean 700-mb Height July - September The Gulf of California is a significant source of low-level moisture when SST > 29.5 C (Mitchell et al. 2002)

PHOENIX WIND ROSE ( ) Surface thermal circulation over the sloping terrain of southern Arizona enhances afternoon and evening low-level shear when 700-mb wind has an easterly component.

METHODOLOGY We identified all convective events (13) during 2010 monsoon in which weather delays occurred at PHX (all associated with convection). Superposed epoch analyses (e.g. Reed and Recker 1971) helped identify the synoptic patterns favoring convective delays (NOAA ESRL). Convective echo tracks were drawn and analyzed in relation to PHX flight corridors (echoes exceeding 40 dBZ). Events were stratified by storm organization and propagation (N/NE, SE, SW),and merged soundings created.

29 JULY 2010 – CASE STUDY Convective activity began in the late morning and lasted 9.5 h Affected all four flight corridors, 72 delays at Sky Harbor Airport Cells initiated over terrain, then propagated into the Phoenix area along gust fronts from the southeast (merged with another northerly line)

29 JULY 2010 – CASE STUDY

NORTH/NORTHEASTERLY EVENTS Storm Types: Two broken multicellular squalls and two airmass thunderstorm events 600-hPa wind: ENE (10 kt) Low-level Shear: 20 kt per 10 kft Deep convective boundary layer with lower CIN values compared to the other events About 4 cm precipitable water 00Z12Z

00Z12Z SOUTHEASTERLY EVENTS Storm Types: Mainly broken squall lines (multicell or airmass) 600-hPa Wind: ESE (10 kt) Low-level Shear: 20 kt per 10 kft Slightly higher CIN (builds CAPE) About 4.6 cm precipitable water Numerous flight delays

SOUTHWESTERLY EVENTS Storm Types: Mainly airmass thunderstorms (one anomalous morning event – broken squall) 600-hPa wind: SSW (15 kt) Storm propagation faster than other events Low-level Shear: limited during the afternoon Fewer flight delays at PHX About 3.2 cm precipitable water (less moisture) 00Z12Z

SUMMARY / CONCLUSIONS We have stratified convective events from the 2010 NAM Monsoon based on their cell organization and propagation characteristics. Synoptic forcing was generally weak, but evidence that easterly waves helped enhance CAPE, shear, moisture, and lifting (not shown). Orographic triggering and the mid-level wind direction influenced the propagation of storms across flight corridors and into PHX. Broken squall-lines were most common amid southeasterly mid-level flow, apparently due to greater low-level moisture and shear. Southwesterly cells propagated the fastest and had the weakest convective organization, thus having less impact on aviation operations.