1. Summer Dust Storms In Phoenix Updated Station Climatology and Pattern Classifications Craig Shoemaker NWS WFO Tucson Jeffrey T. Davis NWS WFO Tucson

2. Objectives of Study  Update and Validate Dust Storm Events at Sky Harbor International Airport. Premise of Studies: Sky Harbor International Airport is centrally located enough with respect to the metropolitan area so that storms identified in the study can be assumed to be of major areal importance.

3. Objectives of Study  Classify Large-Scale Patterns Associated with Dust Storms Events. McCollum (1993) – “Large-scale Patterns Associated with Severe Summertime Thunderstorms over Central Arizona.” Identified 3 distinct patterns based on 31 cases from 1978-1990. Brazel and Nickling (1986) – “The Relationship of Weather Types to Dust Storm Generation in Arizona (1965-1980).” Used large-scale patterns to identify 4 dust storm generation weather types: Type 1 - Frontal Type 2 - Thunderstorm Type 3 - Tropical Disturbances Type 4 - Upper-level/cut off lows

4. Objectives of Study  Classify Mesoscale Patterns Associated with Dust Storms Events. MacKeen (2001) – “Summertime Storm Initiation and Evolution in central Arizona.” Identified 3 storm repeat regimes.

5. Objectives of Study  Study the Annual Variability in Dust Storms for Possible Seasonal Predictors.

6. Overview What do Summer Dust Storms look like? A Wall of Dust!

7. Overview Source Areas for Dust

8. Study Methodology  Surface Data - Hourly Surface Observations for Phoenix Sky Harbor International Airport (PHX) for June through September 1948 to 2002. Climate Data from NCDC.  Upper-air Data – NCEP/NCAR reanalysis 12Z charts for identified Dust Storm days. Upper-air data from CDC.  Storm Data – Local Storm Data from 1959 to 2002. Storm Data from NCDC. Data Criteria  Visibility and Present Weather - Visibility reduced to ½ a mile or less with blowing dust reported (BLDU).  Wind – Directional shift and/or increase in speed accompanying or following the reduced visibility in blowing dust.

9. Objective 1: Updated Dust Storm Events Average Statistics 1948-2002 Average Number of Dust Storms– 2.8 per year. Last 30 years- 1.6 per year. Average Arrival Time – 6:33 PM MST Average Wind Direction – Southeast (121 Degrees) Average Max Wind Speed – 43 MPH Average Visibility – ¼ of a mile Total Number of Cases: 161

10. Summer Dust Storms Frequency by Month Peak in Late July and Early August

11. Summer Dust Storms Frequency by Time Peak between 5 and 8 PM MST

12. Summer Dust Storms Frequency by Wind Direction Dominated by East to Southeast Approaches

13. Summer Dust Storms Frequency by Visibility 33% that hit the airport do not meet NWS warning criteria

14. Summer Dust Storms Frequency by Wind Speed Very few are accompanied by severe winds

15. Objective 2: Classified Large-Scale Patterns Severe Thunderstorm and Dust Storm Patterns This study used 161 cases to identify 5 distinct Large-Scale Patterns Associated with Dust Storms. 8 cases could not be classified. McCollum (1993) used 31 cases to identify 3 distinct Large-Scale Patterns Associated with Severe Thunderstorms. 4 cases could not be classified.

16. McCollum (1993) Severe Thunderstorm Pattern I Sources: http://www.wrh.noaa.gov/tucson/monsoon/severel.html http://www.cdc.noaa.gov/Composites/Day 9 cases out of 31 fit this pattern. Broad High over Southern ½ US. Deep Easterly Flow over TX, NM, AZ.

17. Phoenix Dust Storm Pattern I Source: http://www.cdc.noaa.gov/Composites/Day/ 40 cases out of 161 fit this pattern. Broad High over US. Deep Easterly Flow over TX, NM, AZ.

18. Dust Storm Pattern I

19. McCollum (1993) Severe Thunderstorm Pattern II Sources: http://www.wrh.noaa.gov/tucson/monsoon/severel.html http://www.cdc.noaa.gov/Composites/Day / 9 cases out of 31 fit this pattern. High Amplitude Ridge over Wrn US. Northeast to East Flow over AZ. Occasional weak cold front will move into AZ from the east with moisture from the high plains.

20. Phoenix Dust Storm Pattern II a Source: http://www.cdc.noaa.gov/Composites/Day/ 25 cases out of 161 fit this pattern. High Amplitude Ridge over Wrn US. High cell centered near Srn NV or Srn UT. North to East flow over AZ.

21. Dust Storm Pattern II a

22. Phoenix Dust Storm Pattern II b Source: http://www.cdc.noaa.gov/Composites/Day/ 38 cases out of 161 fit this pattern. High Amplitude Ridge with High cell centered near 4 corners area. Deep Easterly Flow over NM & AZ.

23. Dust Storm Pattern II b

24. McCollum (1993) Severe Thunderstorm Pattern III Sources: http://www.wrh.noaa.gov/tucson/monsoon/severel.html http://www.cdc.noaa.gov/Composites/Day/ 9 cases out of 31 fit this pattern. Broad High over Srn 1/3 of US. High cell positioned West of AZ and near FL. Easterly flow over Nwrn Mexico.

25. Phoenix Dust Storm Pattern III Source: http://www.cdc.noaa.gov/Composites/Day/ 21 cases out of 161 fit this pattern. Broad High over Southern US. Secondary High cell usually centered West of AZ. Deep Easterly Flow over Nrn Mexico.

26. Dust Storm Pattern III

27. Phoenix Dust Storm Pattern IV Source: http://www.cdc.noaa.gov/Composites/Day/ 29 cases out of 161 fit this pattern. Sharp Trough along the West coast. Southwest to Southeast Flow over AZ.

28. Dust Storm Pattern IV

29. Objective 4: Study Annual Variability Future Work Maricopa County population growth does not totally explain why some years experience no dust storms at PHX.  JFM and AMJ La Nina (cold) and El Nina (warm) episodes from NCEP/CPC.  Winter and Spring precipitation for AZ Climate Division 6.  Average Palmer Drought Severity Index for AZ Climate Division 6.  Satellite-derived vegetation Index. Investigate the relationship between various parameters to dust storm frequency.

30. SUMMARY  Updated Dust Storm Events (1948-2009) for PHX Sky Harbor International Airport.  Classified 5 distinct Large-Scale Pattern Associated with Dust Storm Events.  Study 16 Dust Storm Events for possible classification of repeated storm regimes.  Study various parameters for possible seasonal predictors of Summer Dust Storm frequency.

31. Any Questions and/or Comments?