jared klein, lance f. bosart, and daniel keyser university at albany, suny, albany, ny
DESCRIPTION
Mesoscale Precipitation Structures Accompanying Landfalling and Transitioning Tropical Cyclones in the Northeast United States. Jared Klein, Lance F. Bosart, and Daniel Keyser University at Albany, SUNY, Albany, NY CSTAR II Grant NA04NWS4680005 David Vallee - PowerPoint PPT PresentationTRANSCRIPT
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Mesoscale Precipitation Structures Accompanying Landfalling and
Transitioning Tropical Cyclones in the Northeast United States
Jared Klein, Lance F. Bosart, and Daniel KeyserUniversity at Albany, SUNY, Albany, NY
CSTAR II Grant NA04NWS4680005
David ValleeNWS Weather Forecast Office, Taunton, MA
M.S. Thesis Seminar5 July 2007
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Objectives
• Examine the distribution of rainfall in relation to tropical cyclone (TC) track and identify smaller-scale areas of enhanced rainfall accompanying landfalling and transitioning TCs in the Northeast U.S.
• Identify key synoptic- and mesoscale processes that impact the precipitation distribution for these TCs.– Upstream thermal trough and downstream thermal
ridge–jet interactions– Upper-level jet (ULJ) and lower-level jet (LLJ)
interactions– TC-induced coastal frontogenesis– Orographic precipitation enhancement
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Motivation
• Timing and location of mesoscale features is difficult to predict.
• Inland flooding is responsible for nearly 60% of fatalities from landfalling TCs (Rappaport 2000).
• There has been a recent increase in frequency of TC-related flooding events over the Northeast.– 1950–2003: Average of 1 event every year– 2004–2005: 10 events in 2 years
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NPVU QPE
Total precip (in.) vs. TC track: 2004-2005 Total Precip (in.)–10 Storms
Max Rainfall: Max Rainfall:
35 in.35 in.
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Data and Methodology
• Identify TCs that produced ≥ 100 mm (4 in.) of rainfall in the Northeast U.S. for 1950–2006.
1950 Able1950 Dog1952 Able1953 Barbara1953 Carol1954 Carol1954 Edna1954 Hazel1955 Connie1955 Diane1955 Ione1958 Helene1959 Cindy
1959 Gracie1960 Brenda1960 Donna1961 Esther1962 Alma1962 Daisy1963 Ginny1969 Gerda1971 Doria1971 Heidi1972 Agnes1972 Carrie 1976 Belle
1979 David1985 Gloria1988 Chris1991 Bob1996 Bertha1996 Edouard1996 Fran1997 Danny1998 Bonnie1999 Floyd2001 Allison2002 Isidore2002 Kyle
2003 Bill2003 Isabel2004 Alex2004 Bonnie2004 Charley2004 Frances2004 Gaston2004 Ivan2004 Jeanne2005 Cindy2005 Katrina2005 Ophelia2006 Ernesto
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• Construct a climatology of precipitation distribution vs. TC track.– 2.5° NCEP–NCAR reanalysis for synoptic diagnostics– 0.25° NCEP 24 h daily (1200–1200 UTC) UPD– Higher resolution precipitation analysis produced by Ron
Horwood (NERFC)– 10 km RFC NPVU archived QPE– NHC best-track data
• Diagnose synoptic- and mesoscale processes associated with heavy precipitation for Ivan (2004) and Ernesto (2006).– Upper-air analyses and Q vector (geostrophic wind) diagnostics
using 1.0° GFS dataset– Surface analyses and F vector (full wind) diagnostics using ~0.6°
dataset created from GEMPAK
Data and Methodology
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Climatology Results
LOT = left of trackROT = right of track
0
5
10
15
20
25
30
35
Number of TCs
LOT ROT Distinct ROT toLOT Shift
Distinct LOT toROT Shift
No PreferredDistribution
Jun–Oct Climatology of Precipitation Distribution vs. TC Track: 1950–2006
Jun Jul Aug Sep Oct
34
3
5
1
9
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• Upper-level downstream ridge and jet development.– Occurred in nearly every case– Placed Northeast U.S. in equatorward jet-entrance region– Amplified LLJ and positive θe advection
• Enhanced precipitation as TC interacts with a pre-existing mesoscale boundary or coastal front.– Occurred in almost every case– Heavy precipitation region along and in cold sector of
coastal front (CF)– Stronger θ gradient when interacting with a upstream
midlatitude trough during extratropical transition (ET)
Climatology Results
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• Possible orographic enhancement of precipitation.– Occurred in almost half the cases– Track far enough inland so that low-level easterly flow
ahead of storm was upslope on the eastern sides of the Appalachian Mountains
Climatology Results
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Preferred Areas of Possible Orographic Precipitation Enhancement in the Northeast U.S.
http://fermi.jhuaple.edu/states.htmlBlue RidgeBlue Ridge
CatskillsCatskills
BerkshiresBerkshires
WhiteWhite
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Q vector: Time rate of change ofQ div–con: QG forcing for descent– ascent
Qs: Time rate of change of direction ofQs div–con: QG forcing for descent–ascent within thermal trough–ridge
Qn: Time rate of change of magnitude of Qn div–con: QG forcing for descent–ascent on cold–warm side of frontal zone
θΔθΔAdapted from Martin (1999)
Q Vector Partitioning in Natural Coordinates
θΔ
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Case Study 1:
Ivan
September 2004
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LOT PrecipDistribution
NPVU QPE
09/1709/17
09/1909/1909/1809/18
Dates denoteDates denote0000 UTC positions0000 UTC positions
Total precip (in.) vs. TC track: 1200 UTC 16 Sep–1200 UTC 19 Sep 2004
Ivan
Case Study 1: Ivan
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300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)
300 hPa Analyses: 1200 UTC 16 September 2004
300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
1.0° GFS
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Confluent flow in equatorward jet-entrance region
300 hPa Analyses: 1200 UTC 17 September 2004
300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)
300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
1.0° GFS
Frontogenesis in jet-entrance region
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300 hPa Analyses: 1200 UTC 18 September 2004
Strengthening downstream ULJ and ridge
300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)
300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
1.0° GFS
Strong frontogenesis in jet-entrance region
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925 hPa Analyses: 1200 UTC 16 September 2004
925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
WSI radar, 925 hPa θe (K) and wind barbs (kt)
Pre-existing baroclinic zoneSymmetric reflectivity structure
1.0° GFS
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925 hPa Analyses: 1200 UTC 17 September 2004
925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
WSI radar, 925 hPa θe (K) and wind barbs (kt)
Northeastward extension of precip field along baroclinic zone
1.0° GFS
Band of frontogenesis along baroclinic zone
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925 hPa Analyses: 1200 UTC 18 September 2004
925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
WSI radar, 925 hPa θe (K) and wind barbs (kt)
Highest reflectivity near nose of LLJ/θe ridge axis
1.0° GFS
Strong frontogenesis along warm frontal zone
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925 hPa Q Vector Diagnosis: 0000 UTC 18 September 2004
Radar at 1200 UTC 17 September 2004
Q Qn
QsRadar at 0000 UTC 18 September 2004
Highest reflectivity near strongest QG forcing for ascent
Radar at 0000 UTC 18 September 2004
WSI radar
Qs div–con couplet within thermal trough–ridge
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
Qn div–con bands within frontal zone
1.0° GFS
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Radar at 1200 UTC 17 September 2004
Q Qn
QsRadar at 0000 UTC 18 September 2004
Highest reflectivity near strongest QG forcing for ascent
Radar at 0600 UTC 18 September 2004
WSI radar
925 hPa Q Vector Diagnosis: 0600 UTC 18 September 2004
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
1.0° GFS
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Radar at 1200 UTC 17 September 2004Radar at 0000 UTC 18 September 2004Radar at 1200 UTC 18 September 2004
Q Qn
Qs
WSI radar
925 hPa Q Vector Diagnosis: 1200 UTC 18 September 2004
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
1.0° GFS
Highest reflectivity near strongest QG forcing for ascent
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Cross Section of Fn Magnitude: 0000 UTC 18 September 2004
Deep frontogenesis tilting toward cold air w/height
925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors
Fn magnitude [K (100 km)−1 (3 h)−1] shaded, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red1.0°
GFS
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Cross Section of Fn Magnitude: 1200 UTC 18 September 2004
Deep frontogenesis tilting toward cold air w/height
925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors
Fn magnitude [K (100 km)−1 (3 h)−1] shaded, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red1.0°
GFS
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Heaviest 6-h precip along and on cold side of surface boundary
6-h precipitation (in) ending at 0600 UTC 18 September 2004
0000 UTC 18 September 2004
NPVU QPE
Flow of tropical air into surface boundary
Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors
~0.6° surface data
0600 UTC 18 September 2004
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Heaviest 6-h precip along and on cold side of surface boundary
6-h precipitation (in) ending at 1200 UTC 18 September 2004
0600 UTC 18 September 2004
NPVU QPE
Flow of tropical air into surface boundary
Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors
~0.6° surface data
1200 UTC 18 September 2004
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Case Study 2:
Ernesto
August–September 2006
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ROT PrecipDistribution
NPVU QPE
Dates denoteDates denote0000 UTC positions0000 UTC positions
09/0109/01
09/0209/02
09/0309/03
Total precip (in.) vs. TC track: 1200 UTC 31 Aug–1200 UTC 1 Sep 2006
Case Study 2: Ernesto
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300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)
300 hPa Analyses: 1200 UTC 31 August 2006
300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
Jet much farther downstream than with Ivan
1.0° GFS
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300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)
300 hPa Analyses: 1200 UTC 1 September 2006
300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
1.0° GFS
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925 hPa Analyses: 1200 UTC 31 August 2006
925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
WSI radar, 925 hPa θe (K) and wind barbs (kt)
1.0° GFS
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925 hPa Analyses: 1200 UTC 1 September 2006
925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)
WSI radar, 925 hPa θe (K) and wind barbs (kt)
Highest reflectivity near nose of LLJ/θe ridge axis
Strong frontogenesis along warm frontal zone
1.0° GFS
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Radar at 0000 UTC 1 September 2006
Qn div–con bands within coastal boundary as Ernesto nears landfall
Strong forcing for descent–ascent associated with Qn and Qs div–con
925 hPa Q Vector Diagnosis: 0000 UTC 1 September 2006
Q Qn
Qs
WSI radar
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
1.0° GFS
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Radar at 0600 UTC 1 September 2006
925 hPa Q Vector Diagnosis: 0600 UTC 1 September 2006
Q Qn
Qs
WSI radar
Highest reflectivity near strongest QG forcing for ascent
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
1.0° GFS
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Radar at 1200 UTC 1 September 2006
925 hPa Q Vector Diagnosis: 1200 UTC 1 September 2006
Q Qn
Qs
WSI radar
Highest reflectivity near strongest QG forcing for ascent
Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors
1.0° GFS
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Cross Section of Fn Magnitude: 0000 UTC 1 September 2006
925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors
Fn magnitude [K (100 km)−1 (3 h)−1] shaded, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red
Strongest frontogenesis focused near surface
1.0° GFS
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Cross Section of Fn Magnitude: 1200 UTC 1 September 2006
925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors
Fn magnitude [K (100 km)−1 (3 h)−1] shaded, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red
Strongest frontogenesis focused near surface
1.0° GFS
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Heaviest 6-h precip along and on cold side of surface boundary
6-h precipitation (in) ending at 1200 UTC 1 September 2006
0600 UTC 1 September 2006
NPVU QPE
Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors
1200 UTC 1 September 2006
~0.6° surface data
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Heaviest 6-h precip along and on cold side of surface boundary
6-h precipitation (in) ending at 1800 UTC 1 September 2006
1200 UTC 1 September 2006
NPVU QPE
Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors
1800 UTC 1 September 2006
~0.6° surface data
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Upper-level
Upper-level
jet streak
jet streak
low-level Qn
LLJLLJ
QQss div div
QQ nn div div
QQss con con
QQ nn con con
low-level θ
Summary of Case Studies: Conceptual Model 1
Heavy
Heavy
ra
infa
ll
rain
fall
sfc boundary
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LOTLOTPrecipitation DistributionPrecipitation Distribution
ROTROTPrecipitation DistributionPrecipitation Distribution
ColdCold WarmWarm
ZZ
θθColdCold WarmWarm
ZZ
θθ
Strongest frontogenesis focused near surface
Deep frontogenesis tilting toward cold air w/height
Summary of Case Studies: Conceptual Model 2
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Acknowledgements
• Special thanks to:– Lance Bosart and Dan Keyser– David Vallee– John Cannon and Dan St. Jean - WFO
GYX– Kevin Tyle and Alan Srock– The rest of the grad students for
keeping me sane for the past two years!
– My family– Adrienne
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Summary of Case Studies
• Heaviest precipitation occurs in the presence of strong surface F vector convergence and upper-air Q vector convergence.– Qn forcing for descent–ascent bands located within low-
level frontal zone beneath equatorward jet-entrance region
– Qs forcing for descent–ascent couplet located within upstream–downstream thermal trough–ridge over eastern U.S.
• Heaviest 6-h precipitation occurs along and on cold side of mesoscale surface boundary.
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• Both environmental circulation of TC and downstream LLJ induce the poleward transport of high θe air into a pre-existing low-level baroclinic zone.
• LOT and ROT precipitation distribution is related to vertical structure of frontogenesis.– Ivan: LOT precipitation distribution with deep
frontogenesis tilting toward cold air with height– Ernesto: ROT precipitation distribution with strongest
frontogenesis focused near the surface
Summary of Case Studies
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• Introduction– Objectives– Motivation
• Data and Methodology
• Results– Climatology– Case Studies
• Conceptual Models
Outline