predecessor rain events in tropical cyclones
DESCRIPTION
Predecessor Rain Events in Tropical Cyclones. Matthew R. Cote 1 , Lance F. Bosart 1 , Daniel Keyser 1 , and Michael L. Jurewicz, Sr 2 1 Department of Earth and Atmospheric Sciences University at Albany, SUNY, Albany, NY. - PowerPoint PPT PresentationTRANSCRIPT
Predecessor Rain Events in Tropical Cyclones
Matthew R. Cote1, Lance F. Bosart1, Daniel Keyser1, and Michael L. Jurewicz, Sr2
1Department of Earth and Atmospheric Sciences University at Albany, SUNY, Albany, NY
2National Weather Service Forecast Office Binghamton, NY
CSTAR II Grant NA04NWS4680005Ninth Northeast Regional Operational Workshop
Albany, New York,Thursday 8 November 2007
1200 UTC 8 Sep'04
Surface______ SLP (hPa)______ (K) 1200 UTC 8 Sept ‘04
OUTLINEOUTLINE
• Explain the PRE identification process
• Present climatology and statistics of PREs for 1998–2006
• Show a synoptic-scale flow composite at time of PRE initiation
• Examine the synoptic-scale and mesoscale factors important in producing two PREs ahead of Gaston (2004)
DATA SOURCESDATA SOURCES
• NCDC and WSI NOWRAD radar imagery
• NHC best-track data
• NPVU QPE and NWS rainfall products
• NCEP/NARR gridded datasets
IDENTIFYING PREs: 1998IDENTIFYING PREs: 1998––20062006• Coherent area of rain displaced poleward of TC
• Maximum rainfall rates exceeded 100 mm in 24 h
• Moisture transport from TC toward PRE
1800 UTC 040830 WSI NOWRAD Radar Mosaic
PRE
Gaston
IDENTIFYING PREs: 1998IDENTIFYING PREs: 1998––20062006• Coherent area of rain displaced poleward of TC
• Maximum rainfall rates exceeded 100 mm in 24 h
• Moisture transport from TC toward PRE
47 PREs associated with 21 TCs were identified 47 PREs associated with 21 TCs were identified (~2 PREs per TC)(~2 PREs per TC)
~1/3 of all U.S. landfalling TCs produced at least one ~1/3 of all U.S. landfalling TCs produced at least one PREPRE
Five cases where TC did not make U.S. landfallFive cases where TC did not make U.S. landfall
SEPARATION BY TC TRACK SEPARATION BY TC TRACK SIMILARITYSIMILARITY
SOUTHEAST RECURVATURESSOUTHEAST RECURVATURES
• 7/11 (64%) produced at least one PRE
• 16 PREs from 7 TCs
• Influential geographical features:
- Gulf of Mexico - Atlantic Ocean - Appalachians
• Approximate point of PRE formation
ATLANTIC RECURVATURESATLANTIC RECURVATURES
• Approximate point of PRE formation
• 6/15 (40%) produced at least one PRE
• 12 PREs from 6 TCs
• Influential geographical features:
- Atlantic Ocean - Appalachians
Bosart and Carr (1978) conceptual model of antecedent rainfall
PAST RESEARCH ON PRE WITH AGNES (1972)PAST RESEARCH ON PRE WITH AGNES (1972)
Separation Distance
1086 ± 482 km Median: 935 km
Bosart and Carr (1978) conceptual model of antecedent rainfall
PRE STATISTICSPRE STATISTICS
Separation Distance
1086 ± 482 km Median: 935 km
Event Duration
14 ± 7 h Median: 12 h
Bosart and Carr (1978) conceptual model of antecedent rainfall
PRE STATISTICSPRE STATISTICS
Bosart and Carr (1978) conceptual model of antecedent rainfall
PRE STATISTICSPRE STATISTICS
Separation Distance
1086 ± 482 km Median: 935 km
Event Duration
14 ± 7 h Median: 12 h
Time Lag
45 ± 29 h Median: 36 h
PRE Locations Relative to TC Track (1998-2006)
0
5
10
15
20
25
30
PRE Left of TC Track PRE Along TC Track PRE Right of TC Track
Relative Locations
Number of PREs
PRE TRACK-RELATIVE POSITIONSPRE TRACK-RELATIVE POSITIONS
26
129
PRE Locations Relative to TC Track 1998–2006
PRE Locations Relative to TC Track (1998-2006)
0
5
10
15
20
25
30
PRE Left of TC Track PRE Along TC Track PRE Right of TC Track
Relative Locations
Number of PREs
PRE TRACK-RELATIVE POSITIONSPRE TRACK-RELATIVE POSITIONS
26
129
PRE Locations Relative to TC Track 1998–2006
Potential for flooding in areas not directly impacted by TC rainfall
PRE Locations Relative to TC Track (1998-2006)
0
5
10
15
20
25
30
PRE Left of TC Track PRE Along TC Track PRE Right of TC Track
Relative Locations
Number of PREs
PRE TRACK-RELATIVE POSITIONSPRE TRACK-RELATIVE POSITIONS
26
129
PRE Locations Relative to TC Track 1998–2006
Potential for excessive flooding beginning before arrival of TC rainfall
SE RECURVATURE PRE COMPOSITE SE RECURVATURE PRE COMPOSITE TIME OF PRE INITIATIONTIME OF PRE INITIATION
700 hPa Ht (dam) and UVM (μb s-1) 925 hPa Ht (dam), θe (K), and 200 hPa wind speeds (m s-1)
• Significant midlevel trough with weak UVM well poleward of TC
• Deep meridional flow transports tropical moisture up East Coast
• PRE forms: - in right-entrance region of
intensifying upper-level jet
- on western edge of θe ridge
GASTONGASTON (2004)(2004)
Radar Overview
0000 UTC 040831 WSI NOWRAD Radar Mosaic
Gaston
PRE 2PRE 3
0000 UTC 040830 WSI NOWRAD Radar Mosaic
Gaston
PRE 1
925 hPa h (dam), θe (K), and 200 hPa wind speed (m s-1) 700 hPa h (dam) and WSI NOWRAD reflectivity (dBZ)
2100 UTC30 Aug'04
2100 UTC 30 Aug'04
Maddox et al. (1979) Frontal Flash Flood Pattern
Ridge axis
Developing PRE
Trough axis
Gaston
925 hPa h (dam), θe (K), and 200 hPa wind speed (m s-1) 700 hPa h (dam) and WSI NOWRAD reflectivity (dBZ)
2100 UTC30 Aug'04
2100 UTC 30 Aug'04
Maddox et al. (1979) Mesohigh Flash Flood Pattern
Ridge axis
Developing PRE
Trough axis
Gaston
a b
c
1200 UTC 30 Aug 2004
SLP (hPa) and radar reflectivity (dBZ) Streamlines, q (g kg-1) and MFC (shaded 10-7 s-1)
(K) and gradient (shaded every 2.5 10-5 K m-1)
PRE 2
Weak Low
1200 UTC 30 Aug 2004
Cross section: 43.5°N, 79°W to 41°N, 72.5°W. e (dashed red),UVM (blue every 3 micro μs-1 below 3 μ s-1), relative humidity (shaded every 10% above 70%), frontogenesis(shaded K (100 km)-1 (3 h)-1), and winds (kt).
Buffalo (72518; BUF), NY, skew T-log p diagram:1200 UTC 30 Aug 2004
SLP (hPa) and radar reflectivity (dBZ) Streamlines, q (g kg-1) and MFC (shaded 10-7 s-1)
(K) and gradient (shaded every 2.5 10-5 K m-1)
a
2100 UTC 30 Aug 2004
b
c
PRE 2
PRE 3
SLP (hPa) and radar reflectivity (dBZ) Streamlines, q (g kg-1) and MFC (shaded 10-7 s-1)
(K) and gradient (shaded every 2.5 10-5 K m-1)
a
0000 UTC 30 Aug 2004
b
c
PRE 2
PRE 3
2100 UTC 30 Aug 2004
Cross section: 43.5°N, 79°W to 41°N, 72.5°W. e (dashed red),UVM (blue every 3 μs-1 below 3 micro μ s-1), relative humidity (shaded every 10% above 70%), frontogenesis(shaded K (100 km)-1 (3 h)-1), and winds (kt).
Gray (74389; GYX), ME, skew T-log p diagram: 0000 UTC 10 Aug 2004
ML Streamlines
Representative TC Tracks
TC Rainfall
PREs
LL θe-Ridge Axis
See inset
UL Jet
CONCEPTUAL MODEL: LOT PREs AHEAD OF SR OR AR TCsCONCEPTUAL MODEL: LOT PREs AHEAD OF SR OR AR TCs
Revised and updated from Fig. 13 of Bosart and Carr (1978)
ML Streamlines
Representative TC Tracks
TC Rainfall
PREs
ML θe-Ridge Axis
UL Jet
UL Jet
LL θe-Ridge Axis
PREs
Mountain Axes
Idealized LL Winds
LL Temp/Moisture Boundary
CONCEPTUAL MODEL: LOT PREs AHEAD OF SR OR AR TCsCONCEPTUAL MODEL: LOT PREs AHEAD OF SR OR AR TCs
• ~1/3 of U.S. landfalling TCs produce at least one PRE, but landfall is not necessary
• TCs recurving over the Southeast and along the East Coast have the greatest likelihood of producing PREs
• PREs form ~1000 km away from their parent TCs and ~1–2 days in advance
• LOT PREs are most common, but AT PREs produce the risk of most extreme flooding
CONCLUSIONSCONCLUSIONS
• Ahead of a midlevel short-wave trough and near a midlevel ridge axis
• In the right-entrance region of an upper-level jet
• Within a low-level θe gradient along and just on the “cool” side of a surface boundary
• Near a low-level θe-ridge axis on the “warm” side of the surface boundary
• In areas of orographic uplift
CONCLUSIONSCONCLUSIONS
Gaston (2004) case study illustrates that favored Gaston (2004) case study illustrates that favored locations for PRE development are:locations for PRE development are: