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Jared Klein, Lance F. Bosart, and Daniel Keyser University at Albany, SUNY, Albany, NY

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

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Jared Klein, Lance F. Bosart, and Daniel Keyser University at Albany, SUNY, Albany, NY

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  1. 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 NWS Weather Forecast Office, Taunton, MA M.S. Thesis Seminar 5 July 2007

  2. 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

  3. 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

  4. NPVU QPE Max Rainfall: 35 in. Total precip (in.) vs. TC track: 2004-2005 Total Precip (in.)–10 Storms

  5. 1979 David 1985 Gloria 1988 Chris 1991 Bob 1996 Bertha 1996 Edouard 1996 Fran 1997 Danny 1998 Bonnie 1999 Floyd 2001 Allison 2002 Isidore 2002 Kyle 2003 Bill 2003 Isabel 2004 Alex 2004 Bonnie 2004 Charley 2004 Frances 2004 Gaston 2004 Ivan 2004 Jeanne 2005 Cindy 2005 Katrina 2005 Ophelia 2006 Ernesto 1950 Able 1950 Dog 1952 Able 1953 Barbara 1953 Carol 1954 Carol 1954 Edna 1954 Hazel 1955 Connie 1955 Diane 1955 Ione 1958 Helene 1959 Cindy 1959 Gracie 1960 Brenda 1960 Donna 1961 Esther 1962 Alma 1962 Daisy 1963 Ginny 1969 Gerda 1971 Doria 1971 Heidi 1972 Agnes 1972 Carrie 1976 Belle Data and Methodology • Identify TCs that produced ≥ 100 mm (4 in.) of rainfall in the Northeast U.S. for 1950–2006.

  6. Data and Methodology • 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

  7. Climatology Results LOT = left of track ROT = right of track

  8. Climatology Results • 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)

  9. Climatology Results • 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

  10. Preferred Areas of Possible Orographic Precipitation Enhancement in the Northeast U.S. Catskills White Berkshires Blue Ridge http://fermi.jhuaple.edu/states.html

  11. Q Vector Partitioning in Natural Coordinates Adapted from Martin (1999) Qn: Time rate of change of magnitude of Qn div–con: QG forcing for descent–ascent on cold–warm side of frontal zone Q vector: Time rate of change of Q div–con: QG forcing for descent– ascent Qs: Time rate of change of direction of Qs div–con: QG forcing for descent–ascent within thermal trough–ridge θΔ θΔ θΔ

  12. Case Study 1: Ivan September 2004

  13. NPVU QPE Case Study 1: Ivan LOT Precip Distribution 09/19 09/18 Ivan 09/17 Dates denote 0000 UTC positions Total precip (in.) vs. TC track: 1200 UTC 16 Sep–1200 UTC 19 Sep 2004

  14. 300 hPa Analyses: 1200 UTC 16 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

  15. 300 hPa Analyses: 1200 UTC 17 September 2004 Confluent flow in equatorward jet-entrance region Frontogenesis in jet-entrance region 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

  16. 300 hPa Analyses: 1200 UTC 18 September 2004 Strengthening downstream ULJ and ridge Strong frontogenesis in jet-entrance region 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

  17. 925 hPa Analyses: 1200 UTC 16 September 2004 Pre-existing baroclinic zone Symmetric reflectivity structure WSI radar, 925 hPa θe (K) and wind barbs (kt) 925 hPa frontogenesis [K (100 km)−1 (3 h)−1],θ(K), and wind barbs (kt) 1.0° GFS

  18. 925 hPa Analyses: 1200 UTC 17 September 2004 Northeastward extension of precip field along baroclinic zone Band of frontogenesis along baroclinic zone WSI radar, 925 hPa θe (K) and wind barbs (kt) 925 hPa frontogenesis [K (100 km)−1 (3 h)−1],θ(K), and wind barbs (kt) 1.0° GFS

  19. 925 hPa Analyses: 1200 UTC 18 September 2004 Highest reflectivity near nose of LLJ/θe ridge axis Strong frontogenesis along warm frontal zone WSI radar, 925 hPa θe (K) and wind barbs (kt) 925 hPa frontogenesis [K (100 km)−1 (3 h)−1],θ(K), and wind barbs (kt) 1.0° GFS

  20. 925 hPa Q Vector Diagnosis: 0000 UTC 18 September 2004 Q Qn Qn div–con bands within frontal zone Qs Radar at 1200 UTC 17 September 2004 Radar at 0000 UTC 18 September 2004 Radar at 0000 UTC 18 September 2004 Highest reflectivity near strongest QG forcing for ascent WSI radar Qs div–con couplet within thermal trough–ridge 1.0° GFS 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

  21. 925 hPa Q Vector Diagnosis: 0600 UTC 18 September 2004 Q Qn Qs Radar at 1200 UTC 17 September 2004 Radar at 0000 UTC 18 September 2004 Radar at 0600 UTC 18 September 2004 Highest reflectivity near strongest QG forcing for ascent WSI radar 1.0° GFS 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

  22. 925 hPa Q Vector Diagnosis: 1200 UTC 18 September 2004 Q Qn Qs Radar at 1200 UTC 17 September 2004 Radar at 0000 UTC 18 September 2004 Radar at 1200 UTC 18 September 2004 Highest reflectivity near strongest QG forcing for ascent WSI radar 1.0° GFS 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

  23. 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 (ms−1), and ω<0 (µb s−1) contoured in red 1.0° GFS

  24. 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 (ms−1), and ω<0 (µb s−1) contoured in red 1.0° GFS

  25. NPVU QPE 0000 UTC 18 September 2004 Heaviest 6-h precip along and on cold side of surface boundary 6-h precipitation (in) ending at 0600 UTC 18 September 2004 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 0600 UTC 18 September 2004 ~0.6° surface data

  26. NPVU QPE 0600 UTC 18 September 2004 Heaviest 6-h precip along and on cold side of surface boundary 6-h precipitation (in) ending at 1200 UTC 18 September 2004 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 1200 UTC 18 September 2004 ~0.6° surface data

  27. Case Study 2: Ernesto August–September 2006

  28. NPVU QPE Case Study 2: Ernesto 09/03 09/02 ROT Precip Distribution 09/01 Dates denote 0000 UTC positions Total precip (in.) vs. TC track: 1200 UTC 31 Aug–1200 UTC 1 Sep 2006

  29. 300 hPa Analyses: 1200 UTC 31 August 2006 Jet much farther downstream than with Ivan 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

  30. 300 hPa Analyses: 1200 UTC 1 September 2006 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

  31. 925 hPa Analyses: 1200 UTC 31 August 2006 WSI radar, 925 hPa θe (K) and wind barbs (kt) 925 hPa frontogenesis [K (100 km)−1 (3 h)−1],θ(K), and wind barbs (kt) 1.0° GFS

  32. 925 hPa Analyses: 1200 UTC 1 September 2006 Highest reflectivity near nose of LLJ/θe ridge axis Strong frontogenesis along warm frontal zone WSI radar, 925 hPa θe (K) and wind barbs (kt) 925 hPa frontogenesis [K (100 km)−1 (3 h)−1],θ(K), and wind barbs (kt) 1.0° GFS

  33. 925 hPa Q Vector Diagnosis: 0000 UTC 1 September 2006 Q Qn Qn div–con bands within coastal boundary as Ernesto nears landfall Strong forcing for descent–ascent associated with Qn and Qs div–con Qs Radar at 0000 UTC 1 September 2006 WSI radar 1.0° GFS 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

  34. 925 hPa Q Vector Diagnosis: 0600 UTC 1 September 2006 Q Qn Qs Radar at 0600 UTC 1 September 2006 Highest reflectivity near strongest QG forcing for ascent WSI radar 1.0° GFS 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

  35. 925 hPa Q Vector Diagnosis: 1200 UTC 1 September 2006 Q Qn Qs Radar at 1200 UTC 1 September 2006 Highest reflectivity near strongest QG forcing for ascent WSI radar 1.0° GFS 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

  36. Cross Section of Fn Magnitude: 0000 UTC 1 September 2006 Strongest frontogenesis focused near surface 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 (ms−1), and ω<0 (µb s−1) contoured in red 1.0° GFS

  37. Cross Section of Fn Magnitude: 1200 UTC 1 September 2006 Strongest frontogenesis focused near surface 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 (ms−1), and ω<0 (µb s−1) contoured in red 1.0° GFS

  38. NPVU QPE 0600 UTC 1 September 2006 Heaviest 6-h precip along and on cold side of surface boundary 6-h precipitation (in) ending at 1200 UTC 1 September 2006 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

  39. NPVU QPE 1200 UTC 1 September 2006 Heaviest 6-h precip along and on cold side of surface boundary 6-h precipitation (in) ending at 1800 UTC 1 September 2006 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

  40. Summary of Case Studies: Conceptual Model 1 Upper-level jet streak Qn div Qn con Heavy rainfall LLJ Qs con Qs div low-level Qn low-level θ sfc boundary

  41. Summary of Case Studies: Conceptual Model 2 Z Z θ θ Cold Warm Cold Warm LOT Precipitation Distribution ROT Precipitation Distribution Deep frontogenesis tilting toward cold air w/height Strongest frontogenesis focused near surface

  42. 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

  43. 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.

  44. Summary of Case Studies • 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

  45. Outline • Introduction • Objectives • Motivation • Data and Methodology • Results • Climatology • Case Studies • Conceptual Models

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