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What have we learned from NAME?

What have we learned from NAME?. Erik Pytlak NOAA/NWS Tucson, AZ. NORTH AMERICAN MONSOON EXPERIMENT (NAME). HYPOTHESIS: The NAMS provides a physical basis for determining the degree of predictability of warm season precipitation over the region. OBJECTIVES: Better understanding and

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What have we learned from NAME?

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  1. What have we learned from NAME? Erik Pytlak NOAA/NWS Tucson, AZ

  2. NORTH AMERICAN MONSOON EXPERIMENT (NAME) HYPOTHESIS: The NAMS provides a physical basis for determining the degree of predictability of warm season precipitation over the region. • OBJECTIVES: • Better understanding and • simulation of: • warm season convective • processes in complex terrain • (TIER I); • intraseasonal variability of • the monsoon (TIER II); • response to oceanic and • continental boundary • conditions (TIER III); • monsoon evolution and • variability (TIER I, II, III). Low-level (925 mb) winds and observed precipitation YEAR (2000+) 00 01 02 03 04 05 06 07 08 Planning --------------| Preparations ---------------| Data Collection - - - - - - --------| Principal Research ---------------------------------| Data Management -----------------------------------------|

  3. WHAT WAS THE NAME 2004 FIELD CAMPAIGN? • The NAME 2004 Field Campaign was an unprecedented opportunity to gather extensive atmospheric, oceanic, and land-surface observations in the core region of the North American Monsoon over NW Mexico, SW United States, and adjacent oceanic areas.

  4. What really is The Monsoon? • A seasonal change in upper level winds from the polar westerlies to tropical easterlies • Change from very dry west winds aloft to moist winds aloft from the east or southeast • North American Monsoon is just one of several • Indian Monsoon • Asian Monsoon • Australian Monsoon • African Monsoon • South American Monsoon • An individual thunderstorm is NOT a “monsoon” • The monsoon IS a large scale flow pattern

  5. 500 mb mean flow The North American Monsoon Notice the positioning of the subtropical (cT) upper level high.

  6. Mean subtropical (cT) high position generally reveals what the monsoon looked like in any given summer Four Different Monsoons 2004 2006 2008 2009

  7. Positioning of the high determines general severe weather pattern The hotly? debated pattern

  8. Monsoon Moisture Sources

  9. Sierra Madres… Subtropical Seasonal Rain Forest = Lots of Moisture!!!

  10. Gulf of California LLJ • Up-Gulf flow common during the monsoon, especially in July • Averages 5-10 m/s daily • Cool water pool reinforced by California Current • Up-Gulf oriented thermal and pressure gradient • Channeled flow • TC passage SW of the Gulf will enhance the thermal and pressure gradients • Direct TC move into the southern Gulf will disrupt the surface high L H

  11. Gulf Surge during NAME 2004 Dewpoint = 55F Dewpoint = 75-82F!!!

  12. Shallow/Strong Gulf Surge Impact at KTUS Residual PBL Modified Gulf of CA PBL

  13. TC-initiated surges during NAME

  14. “The Dewpoint Rule”No Longer Used • Ancient monsoon monitoring tool • Started in Phoenix in the 1950s • Done when weather radar (in AZ, anyway) and weather satellites didn’t exist • PHX dewpoint was used for the entire state • Adopted for Tucson (due to our higher elevation in 1997) • Tucson dewpoint had to average 54 degrees each day for three consecutive days • Easy to track • VERY misleading • NWS now uses a fixed monsoon season : June 15-September 30 http://www.wrh.noaa.gov/twc/monsoon/dewpoint_tracker.php

  15. Upper Tropospheric Lows • 12-20 of them a year affect North American Monsoon • More (less) of them during La Niña (El Niño) summers • Subtropical systems • Mid June - early September • Move east-to-west • Relatively cold/sinking centers • Can cause widespread severe weather and flash flooding • Difficult to track at times

  16. Original Conceptual Models Whitfield and Lyons 1992 Kelley and Mock 1982 Moore, Gall and Adang 1989

  17. NAME Cross Section7/13/04 C 1°x1° res. Courtesy Paul Cieleski, Colorado State University

  18. Conceptual Model: Upper Tropospheric Lows

  19. …especially when there’s several of them

  20. Ongoing Research: PV Anomalies SUNY Albany: Bosart, Matusiak, Sikup, Melino PV Trough PV Fracture PV Tail =350 K =350 K =350 K Lower  Lower  Lower  2 x Width > Length 2 x Width < Length Circular or Linear

  21. Tropical Cyclones and the Monsoon • Modulate monsoon-related convection • Gulf Surges • Moisture injection into the SMO • Do not have to recurve • Those that do follow a general recurvature pattern • Interaction with the East Pacific trough is critical • ENSO conditions: • Warmer SSTs = more TCs • Cooler SSTs = stronger E Pac trough/higher recurvature chance

  22. Direct Hit and Indirect Impact Track Density

  23. Octave: Sep 28-Oct 2, 1983 • Classic indirect impact scenario • Pieces broke off parent circulation • Three separate waves of convection • Sep 30, Oct 1, Oct 2 • $500M damage ($1B in 2008 dollars)

  24. AZ Tropical CyclonesDirect Hits • Eight since 1965 (once every 5-8 years) • Incoming Pacific trough captures TC and interacts • Decaying TD or TS races N-NE • Unusually large TC, or enlarging TC • Begin ET transition • Major wind damage threat • Mountains extend above 2000m • Weak building codes • Somewhat reduced flash flood threat

  25. Lester: Aug 23-24, 1992 • Captured by strong, positively-tilted trough (BC-S CA) • ET transition • Valley sustained winds 35-50 mph • Mountaintop wind gusts 60-85 mph • 85mph at Ft. Huachuca (Cochise County) Mountain mesonet Site • 74mph at Carderoga RAWS (Graham County) • KTUS: Fastest 2-min wind: 27kts, peak gust 41kts • Lowest pressure measured in AZ: 996.9mb at Ft. Huachuca/Sierra Vista, AZ) • Widespread 2-5” rains SE AZ

  26. Lester ET Transition • Case of Chen and Yau (2003) eyewall destruction, followed by inner rain band redevelopment • Cloud top temps cool to -72°C as PV transfers from eye to inner rain band Courtesy Scott Bachmeier, CIMSS

  27. Lester: MM5 Simulation • Simulated restrengthening ~12hrs after landfall! • Pressure drop to 985mb • Max wind ~80kts at sigma .865 (~1500m AGL) • Translates to 45kt sustained/G60kts • Chen and Yau 2003

  28. Nora, Sep 25-26, 1997 • Captured by moderate, but weaker-than-forecast E Pacific trough • Aborted ET transition • Widespread 3-7” rain in SE CA • 12.04” at Harquahala Mtn, AZ. • Highest wind in US: SW UT (estimates 80-100mph)) • Wind/ convective bursts on right-front quad • NWP models and NHC called for recurvature into SE AZ at H+48-72hrs

  29. Nora, Sep 25-26, 1997 92kts at 5000 ft (reduces to ~50G65kt)

  30. Dew point graphs Winds for 700, 500 and 300 mb Heights for 500 mb Satellite-derived vegetation index Satellite water vapor imagery Radar precipitation estimates for 1, 3, 6, 12 and 24 hours Upper air plots Links to Maricopa and Pima county rainfall data Extensive safety information Extensive reference list Yes, you can still track dewpoint Companion Tropical Cyclone page Educating the Public:Monsoon Tracking Page

  31. Parting thoughts: http://www.eol.ucar.edu/projects/name http://www.wrh.noaa.gov/twc/monsoon/monsoon_tracker.php

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