The Contribution of Eastern North Pacific Tropical Cyclones to the Warm Season Rainfall Climatology of the Southwest US

Kristen L. Corbosiero (UCLA) Michael Dickinson (AEF) and Lance Bosart (SUNY Albany) Nora 1997 Lester 1992 Motivation: • Easterly waves and tropical cyclones (TCs) of the eastern North Pacific initiate Gulf of moisture surges that account for a significant portion of summer rainfall in the southwest US

• The eastern North Pacific is the most active basin for development per unit area, per unit time (length of the TC season) Henriette 2007 Marie 1984

Motivation: • Do tropical cyclones ever reach the southwest US?

• Englehart and Douglas (2001) examined TC rainfall in western Mexico and found 3-4 storms per year affect the region bringing as much as 60% of the summer rainfall

• Extend the study of Englehart and Douglas (2001) north into the southwest US Data and Methdology:

• National Hurricane Center (NHC) Best Track data set to find all storms that crossed 25˚N between June 16th and October 15th 1958 to 2003

• Climate Prediction Center’s daily (12 UTC-12 UTC), gridded (.25˚ x .25˚) Unified Precipitation Dataset (UPD) (http://www.cdc.noaa.gov/cdc/data.unified.html)

• European Centre for Medium-range Weather Forecasting re-analysis (ERA40; 1.125˚ resolution)

• Examined maps of rainfall and 700 hPa heights and relative vorticity to determine on which days, if any, rainfall associated with a tropical cyclone fell over the southwest US National Hurricane Center Best Track 35 TCs that affected the SW US 1958-2003

TS10 H11 H10 Diana Claudia Jen-Kath Emily Kirsten Katrina Hyacinth Pauline Norma Olivia Hyacinth Joanne Kathleen Liza Doreen Glenda Heather Olivia Manuel Marie Norbert Newton Raymond Lester Hilary Ismael Fausto Nora Isis Hilary Ignacio Marty 475 450 Number of days with 425 ys 400 at least one active 375 Eastern Pacific TC 350 c TC Da

fi 1958-2003 i 325 300 275 East Pac 250 225 200 50 6/16 7/1 7/16 8/1 8/16 9/1 9/16 10/1 6/30 7/15 7/31 8/15 8/31 9/15 9/30 10/15 45 Date 40 Number of days rainfall 35

associated with an Rainfall 30 C Eastern Pacific TC fell in 25 th T i 20

the southwest US w s 15

1958-2003 Day 10 5 0 6/16 7/1 7/16 8/1 8/16 9/1 9/16 10/1 6/30 7/15 7/31 8/15 8/31 9/15 9/30 10/15 Date Average Daily Precipitation Southwest US (31°-40°N, 104°-118°W) 1958-2003 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5

Precipitation (mm / day) Precipitation (mm 0.4 0.3 0.2 Jan Jan Feb Mar Apr May May Jun Jul Aug Sep Oct Oct Nov Dec 1 25 19 15 9 4 29 23 18 12 6 1 26 20 15 Date NHC Best Track All Eastern Pacific TCs 1958-2003

Return rate of a TC of any intensity to the southwest US 1958-2003 Average September Eastern Pacific SSTs, 850-200 hPa vertical wind shear, & 500-700 hPa layer averaged winds 1968-1996 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T-5 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T-4 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T-3 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T-2 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T-1 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T+1 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T+2 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T+3 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T+4 NCEP/NCAR Reanalysis Mean and standardized anomaly, 500 hPa heights Day T+5 1976

Storm total Storm contribution to precipitation (mm) warm season rainfall (%) DT pressure (hPa), DT winds, & 700 hPa vorticity 00 UTC 11 September 1976

Kathleen Hurricane Lester 1992

Storm total Storm contribution to precipitation (mm) warm season rainfall (%) DT pressure (hPa), DT winds, & 700 hPa vorticity 00 UTC 24 August 1992

Lester Tropical Storm Claudia 1962

Storm total Storm contribution to precipitation (mm) warm season rainfall (%) DT pressure (hPa), DT winds, & 700 hPa vorticity 06 UTC 25 September 1962

Claudia Average percentage of the warm season precipitation associated with Eastern Pacific TCs Southwest US Warm Season Standardized Rainfall Anomalies 3.0

2.5

2.0 omaly 1.5 n

1.0

0.5

0.0

-0.5

-1.0

-1.5 Standardized Rainfall A Standardized -2.0

-2.5 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 Year Southwest US Warm Season Standardized Rainfall and NINO3 Anomalies 3.0 Monsoon 2.5 MAM NINO3

2.0

1.5 omaly n 1.0

0.5

0.0

-0.5

Standardized A Standardized -1.0

-1.5

-2.0 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 Year Southwest US Warm Season Standardized Rainfall and NINO3 Anomalies 3.0 Monsoon 2.5 JAS NINO3

2.0

1.5 omaly n 1.0

0.5

0.0

-0.5

Standardized A Standardized -1.0

-1.5

-2.0 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 Year Isis 1998 Lester 1992 Summary: • 35 Eastern Pacific TCs brought significant rainfall to the southwest US between 1958 and 2003

• On average, 10-15% of the summer rainfall is contributed by TCs, increasing from east to west across

• Two main tracks for TCs into the monsoon region: 1) south to north path into CA and NV, and 2) southwest-northeast “recurvature” track through AZ, NM and CO NHC Best Tracks (black) ERA40 700 hPa vorticity tracks (colors) 14 long lived east Pacific TCs