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

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Presentation on theme: "What have we learned from NAME? Erik Pytlak NOAA/NWS Tucson, AZ."— Presentation transcript:

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

2 NORTH AMERICAN MONSOON EXPERIMENT (NAME) YEAR (2000+) Planning | Preparations | Data Collection | Principal Research | Data Management | 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

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

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

6 6 Four Different Monsoons Mean subtropical (cT) high position generally reveals what the monsoon looked like in any given summerMean subtropical (cT) high position generally reveals what the monsoon looked like in any given summer

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

8 8 Monsoon Moisture Sources

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

10 10 Gulf of California LLJ Up-Gulf flow common during the monsoon, especially in JulyUp-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 gradientsTC passage SW of the Gulf will enhance the thermal and pressure gradients Direct TC move into the southern Gulf will disrupt the surface highDirect TC move into the southern Gulf will disrupt the surface high H L

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

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

13 13 TC-initiated surges during NAME

14 14 The Dewpoint Rule No Longer Used Ancient monsoon monitoring toolAncient monsoon monitoring tool –Started in Phoenix in the 1950s –Done when weather radar (in AZ, anyway) and weather satellites didnt 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 daysTucson dewpoint had to average 54 degrees each day for three consecutive days Easy to trackEasy to track VERY misleadingVERY misleading NWS now uses a fixed monsoon season : June 15-September 30NWS now uses a fixed monsoon season : June 15-September 30

15 15 Upper Tropospheric Lows of them a year affect North American Monsoon12-20 of them a year affect North American Monsoon –More (less) of them during La Niña (El Niño) summers Subtropical systemsSubtropical systems Mid June - early SeptemberMid June - early September Move east-to-westMove east-to-west Relatively cold/sinking centersRelatively cold/sinking centers Can cause widespread severe weather and flash floodingCan cause widespread severe weather and flash flooding Difficult to track at timesDifficult to track at times

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

17 17 NAME Cross Section 7/13/04 1°x1° res. Courtesy Paul Cieleski, Colorado State University C

18 Conceptual Model: Upper Tropospheric Lows

19 19 …especially when theres several of them

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

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

22 22 Direct Hit and Indirect Impact Track Density

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

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

25 25 Lester: Aug 23-24, 1992 Captured by strong, positively-tilted trough (BC-S CA)Captured by strong, positively-tilted trough (BC-S CA) ET transitionET transition Valley sustained winds mphValley sustained winds mph Mountaintop wind gusts mphMountaintop wind gusts 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)Lowest pressure measured in AZ: 996.9mb at Ft. Huachuca/Sierra Vista, AZ) Widespread 2-5 rains SE AZWidespread 2-5 rains SE AZ

26 Lester ET Transition Case of Chen and Yau (2003) eyewall destruction, followed by inner rain band redevelopmentCase 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 bandCloud 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!Simulated restrengthening ~12hrs after landfall! –Pressure drop to 985mb –Max wind ~80kts at sigma.865 (~1500m AGL) Translates to 45kt sustained/G60ktsTranslates to 45kt sustained/G60kts –Chen and Yau 2003

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

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

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

31 31 Parting thoughts:


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