Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Recent Northeastern U.S. Collaborative Science, Technology, and Research (CSTAR) Project - PowerPoint PPT Presentation

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Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Recent Northeastern U.S. Collaborative Science, Technology, and Research (CSTAR) Project

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Title: Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Recent Northeastern U.S. Collaborative Science, Technology, and Research (CSTAR) Project


1
Predecessor Rainfall Events (PRE) in Tropical
Cyclones - Results from a Recent Northeastern
U.S. Collaborative Science, Technology, and
Research (CSTAR) Project
  • Matthew Cote, Lance Bosart, and Daniel Keyser
  • State University of New York, Albany, NY
  • Michael L. Jurewicz, Sr.
  • National Weather Service, Binghamton, NY
  • July 10, 2008 HPC, Camp Springs, MD

2
Outline
  • Data Sources
  • Definition of PRE
  • Motivating factors / goals for this session
  • Methodologies for the project
  • Categorize PRE / Establish climatologies for the
    Eastern U.S. / Atlantic Basin TC
  • Provide operational forecasting resources
  • Composites / Conceptual models
  • Case Study Examples
  • Summary

3
Data Sources
  • WSI NOWRAD Radar Imagery
  • HPC Surface / Radar Analyses
  • SPC Upper-Air / Mesoanalyses
  • Archived TC Tracks / Positions from TPC
  • NARR 32-km Datasets
  • NWS WES Imagery
  • NPVU QPE Data from NWS RFCs

4
PRE What are They ?
  • Coherent areas of heavy rainfall observed
    poleward of Tropical Cyclones (TC)
  • Distinct from the main precipitation shields of
    TC, or their extra-tropical remnants
  • Yet, still indirectly tied to TC

5
PRE Example Frances (2004)
Main Precipitation Shield of the TC
PRE
6
Results of the Frances PRE
7
Motivation for Research
  • PRE can be particularly challenging phenomena for
    operational meteorologists
  • NWP models often underestimate / misplace heavy
    rainfall associated with PRE
  • Poor handling of diabatic heating transfer /
    upper-jet intensification
  • Attention is frequently diverted to different
    areas / times
  • Closer to where TC make landfall
  • Future time periods when the more direct impacts
    of TC or their remnants may be expected

8
Goals
  • To provide NWS forecasters / operational
    meteorologists with
  • Background Knowledge / Awareness of PRE
  • Forecast Tools
  • PRE Climatologies
  • Conceptual Models / Composite Charts
  • Case Study Examples

9
Methodology
  • We restricted classifications of PRE to systems
    that met the following criteria
  • 100 mm (4) of rainfall needed to be observed
    within a 24-hour period
  • Such rainfall had to be connected with a well
    defined region of precipitation
  • Not scattered / isolated convection

10
Frequency of Occurrence
  • Our period of study ran from 1998 to 2006
  • 47 PRE were identified, which were tied to a
    total of 21 TC
  • An average of about 2 PRE per PRE-producing TC
    (PPTC)
  • About 1/3 of all Atlantic Basin TC that made U.S.
    Landfall for this period were PPTC
  • A few outlier PPTC did not actually make landfall

11
PRE Statistics
Agnes PRE
Separation Distance 1086 482 km
Median 935 km
Bosart and Carr (1978) conceptual model of
antecedent rainfall indirectly associated with TC
Agnes (from 1972)
12
PRE Statistics (Continued)
Agnes PRE
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 indirectly associated with TC
Agnes (from 1972)
13
PRE Statistics (Continued)
AT
ROT
Separation Distance 1086 482 km
Median 935 km Event Duration 14 7 h
Median 12 h Time
Lag 45 29 h Median 36 h
LOT
Bosart and Carr (1978) conceptual model of
antecedent rainfall indirectly associated with TC
Agnes (from 1972)
14
PRE Track-Relative Positions
26
12
9
15
PRE Track-Relative Positions
Potential for excessive flooding beginning before
arrival of TC rainfall
26
12
9
16
PRE Track-Relative Positions
Potential for flooding in areas not directly
impacted by TC rainfall
26
12
9
17
Further Sub-Classifications
  • Separation by Similarity of TC Track
  • Southeast Recurvatures (SR)
  • Highest percentage of PPTC
  • Atlantic Recurvatures (AR)
  • Most common TC Track
  • Central Gulf Landfalls (CG)
  • Lower percentage of PPTC, but high frequency PRE
    production within those PPTC
  • Other Hybrid TC that were harder to categorize

18
SR TC Tracks and PRE Locations
All SR PPTC Tracks with PRE centroids (colored
dots)
All SR TC Tracks
19
AR TC Tracks and PRE Locations
All AR PPTC Tracks with PRE centroids (colored
dots)
All AR TC Tracks
20
CG TC Tracks and PRE Locations
All CG PPTC Tracks with PRE centroids (colored
dots)
All CG Tracks
21
Favorable Locations for PRE
  • Within the Right-rear quadrant (RRQ) of an
    Upper-level Jet
  • Ahead of the Mean Long-Wave Trough Axis at
    Mid-levels (trough axis is west of the parent
    TCs longitude)
  • Near or just upstream from Short-wave Ridging
  • Near a Low-level Front / Baroclinic Zone
  • On the periphery of a Tropical Moisture Plume
  • Near or just west of a Low-level Theta-E Ridge
    Axis

22
SR PPTC Composites (PRE - 12)
Trough axis
Ridge axis
?e-Ridge axis
700 mb heights (dam) and upward
vertical motion (shaded, µb s-1)
925 mb heights (dam), ?e (K), and
200 mb winds (shaded, m s-1)
Center of composite TC
23
SR PPTC Composites (At Time of PRE)
Trough axis
Ridge axis
?e-Ridge axis
700 mb heights (dam) and upward vertical motion
(shaded, µb s-1)
925 mb heights (dam), ?e (K), and
200 mb winds (shaded, m s-1)
Center of composite TC
Centroid of 1st composite PRE
24
SR PPTC Composites (PRE 12)
Ridge axis
Trough axis
?e-Ridge axis
700 mb heights (dam) and upward
vertical motion (shaded, µb s-1)
925 mb heights (dam), ?e (K), and
200 mb winds (shaded, m s-1)
Center of composite TC
Centroid of 1st composite PRE
Centroid of 2nd composite PRE
25
Common Detracting Elements for PRE Formation
  • A Zonal Flow Pattern is in place Poleward of the
    TC
  • Lack of merdional flow discourages northward
    return of deep tropical moisture away from the TC
    itself
  • The Long-wave Mid-level Trough Axis is already
    east of the TCs Longitude
  • A Low-level Blocking Ridge is located north /
    northeast of the TC
  • Tends to prevent significant moisture inflow into
    any frontal boundaries or jet circulations that
    may be poleward of the TC

26
SR Null-Case Composites
700 mb heights (dam) and upward vertical motion
(shaded, µb s-1)
925 mb heights (dam), ?e (K), and
200 mb winds (shaded, m s-1)
Center of composite TC
27
Case Study (TC Erin, 2007)
  • CG Landfall PPTC
  • Several PRE were associated with Erin (typical of
    CG PPTC)
  • Erins PRE exhibited many of the classic
    synoptic-scale ingredients
  • Within RRQ of an upper-level jet
  • Deep moisture was fed northward into the PRE /
    pronounced theta-e ridging developed
  • A low-level boundary was in the vicinity

28
Track of Erin (Aug. 15-20, 2007)
20/00z
19/12z
19/06z
19/00z
18/12z
29
Multiple PRE Producer (First 2 PRE)
PRE 2 4-8 (100-200 mm) of rain early on
8/18/07
PRE 1 3-6 (75-150 mm) of rain late on 8/17/07
(Along-track PRE)
30
Erins 3rd PRE
Locally 10
Locally 12 (300 mm) of rain on the evening of
8/18/07
31
Ramifications of PRE 3
  • 12 - 15 of rain fell in 6 hours or less over
    parts of Southeastern MN and Southwestern WI
  • Record flooding
  • Several fatalities

32
Water Vapor 02z, 8/19/07
Significant PRE
Erins Moisture Plume
L
TD Erin
MSLP Isobars and Mean 925-850 mb Winds
33
300 mb Analysis 00z, 8/19/07
PRE
Jet Entrance Region
34
850 mb Moisture Transport - 00z, 8/19/07
PRE
L
TD Erin
35
Surface Analysis Radar - 00z, 8/19/07
PRE
36
Flooding Pictures
37
Null-Case Study (TC Gabrielle, 2007)
  • Became a Tropical Storm over the western
    Atlantic, before brushing the Outer Banks of NC
  • Then recurved towards the east-northeast over the
    open Atlantic (Would be categorized as an AR TC)
  • No PRE were associated with this TC
  • Expansive ridge axis blocked advection of deeper
    moisture into the U.S.

38
Track of Gabrielle (Sept. 8-12, 2007)
39
24 Hour QPE Ending 12z, Sept. 10, 2007
Localized 1-2 (25-50 mm) rainfall amounts in a
24 hour period Available moisture was not
associated with Gabrielle
40
Water Vapor 09z, 9/09/07
Frontal Plume of MoistureDisconnected from
Gabrielle
Dry Wedge
Gabrielle
MSLP Isobars and Mean 925-850 mb Winds
41
300 mb Analysis 12z, 9/09/07
Trough Axis
Ridge Axis
L
Gabrielle
42
850 mb Moisture Transport 12z, 9/09/07
Axis of minimum Theta-e
L
Gabrielle
43
Surface Analysis Radar - 12z, 9/09/07
Ridge axis blocks inflow of moisture towards
poleward front
44
Conceptual Model LOT PRE (SR/AR TC)
UL Jet
LL ?e-Ridge Axis
PREs
See inset
ML Streamlines
TC Rainfall
Revised and updated from Fig. 13 of Bosart and
Carr (1978)
Representative TC Tracks
45
Conceptual Model (More Detailed Inset)
UL Jet
LL ?e-Ridge Axis
Mountain Axes
LL Temp/ Moisture Boundary
UL Jet
LL ?e-Ridge Axis
PREs
PREs
Idealized LL Winds
ML Streamlines
TC Rainfall
TC Tracks
46
Summary Forecast Challenges
  • NWP models are often poor with the placement /
    intensity of PRE
  • Attention is frequently diverted away from
    potential PRE development
  • PRE can impact almost any area of the CONUS

47
Summary PRE Statistics
  • About 1/3 of U.S. Landfalling TC in our period of
    study (1998-2006) were PPTC
  • LOT PRE were the most common
  • Typically the best synoptic enhancement
  • AT PRE can be the most dangerous
  • Double-shot of heavy rainfall
  • ROT PRE tended to display the highest rainfall
    rates
  • Typically slower moving PRE, with less synoptic
    forcing
  • Orography perhaps more important

48
Summary Similarity of TC Tracks
  • SR TC had the highest percentage of PPTC
  • AR TC were the most common in our period of study
  • However, had a lower percentage of PPTC
  • CG TC had the lowest percentage of PPTC
  • However, CG PPTC were the most prolific PRE
    producers (an average of 3-4 PRE per TC)

49
Summary Favored PRE Locations
  • Within the RRQ of a strengthening poleward
    upper-level jet streak
  • Downstream of a mid-level trough, which is well
    west of the parent TCs longitude
  • Near a low-level boundary
  • On the northern or western fringes of a deep
    tropical moisture plume (evident on water vapor
    imagery)
  • Near or just west of a low-level theta-e ridge
    axis

50
Summary Unfavorable Setup for PRE
  • A de-amplified, zonally oriented flow pattern is
    in place north of the TC
  • The main poleward mid-level trough axis is
    already at, or east of the TCs longitude
  • A low-level blocking ridge is north / northeast
    of the TC

51
Future Work
  • Expand PRE database to include the western U.S.
    (Pacific Basin TC)
  • Add composites / conceptual models for AT and ROT
    PRE, and possibly other TC tracks (i.e. CG)
  • Develop a technique to identify / quantify PRE
    rainfall in TC precipitation analyses
  • Perform modeling studies to interrogate the role
    that TC have in modulating the strength of
    poleward jets

52
References
  • Atallah, E. H., and L. F. Bosart, 2003 The
    extratropical transition and precipitation
    distribution of Hurricane Floyd (1999). Mon. Wea.
    Rev., 131, 10631081.
  • Atallah, E., L. F. Bosart, and A. R. Aiyyer,
    2007 Precipitation distribution associated with
    landfalling tropical cyclones over the eastern
    United States. Mon. Wea. Rev., 135, 21852206.
  • Bosart and F. H. Carr, 1978 A case study of
    excessive rainfall centered around Wellsville,
    New York, 20-21 June 1972. Mon. Wea. Rev., 106,
    348362.
  • Bosart and D. B. Dean, 1991 The Agnes rainstorm
    of June 1972 Surface feature evolution
    culminating in inland storm redevelopment. Wea.
    and Forecasting, 6, 515537.
  • Brooks, H. E., and D. J. Stensrud, 2000
    Climatology of heavy rain events in the United
    States from hourly precipitation observations.
    Mon. Wea. Rev., 128, 11941201.
  • DeLuca, D. P., 2004 The distribution of
    precipitation over the Northeast accompanying
    landfalling and transitioning tropical cyclones.
    M.S. thesis, Department of Earth and Atmospheric
    Sciences, University at Albany, State University
    of New York, 177 pp.
  • DiMego, G. J., and L. F. Bosart, 1982a The
    transformation of tropical storm Agnes into an
    extratropical cyclone. Part I The observed
    fields and vertical motion computations. Mon.
    Wea. Rev., 110, 385411.
  • LaPenta, K. D., and Coauthors, 1995 The
    challenge of forecasting heavy rain and flooding
    throughout the eastern region of the National
    Weather Service. Part I Characteristics and
    events. Wea. Forecasting, 10, 7890.
  • Schumacher, R. S., and R. H. Johnson, 2005
    Organization and environmental properties of
    extreme-rain-producing mesoscale convective
    systems. Mon. Wea. Rev., 133, 961976.
  • Uccellini, L. W., and D. R. Johnson, 1979 The
    coupling of upper and lower tropospheric jet
    streaks and implications for the development of
    severe convective storms. Mon. Wea. Rev., 107,
    682703.
  • Ulbrich, C. W., and L. G. Lee, 2002 Rainfall
    characteristics associated with the remnants of
    tropical storm Helene in upstate South Carolina.
    Wea. Forecasting, 17, 12571267.

53
Any Questions ??
  • Thank You !!

54
WFO BGM Usage of HPC Products
  • Days 4-7 Gridded Output (Medium Range)
  • Common starting point
  • HPC has access to more model data / better
    ensembling capabilities (Master Blender)
  • Preferable to always populating with one model
    (GMOS grids)
  • Lets us focus on short-term issues

55
Usage of HPC Stuff (Shorter Range)
  • Model diagnostics
  • Will view discussions / graphics in more
    complicated scenarios
  • Especially when theres significant model
    discrepancies
  • QPF / Excessive Rainfall
  • Will often use HPC QPF, or a blend of HPC and
    other model QPFs in the first 24 48 hours
  • Depending on timing, may use data from a previous
    model cycle
  • Will utilize Excessive Rainfall discussions /
    graphics as guidance in heavy precipitation
    situations
  • Winter Weather Desk
  • Will typically view WWD graphics as a reality
    check against our thinking
  • Particularly with mixed phase events / model
    disagreements
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