Cool-Season High Wind Events
in the Northeast U.S.
Jonas V. Asuma, Lance F. Bosart, Daniel Keyser
Department of Atmospheric and Environmental Sciences
University at Albany/SUNY
John S. Quinlan, Thomas A. Wasula,
Hugh W. Johnson, Kevin S. Lipton
NOAA/NWS, Albany, NY
Master’s Thesis Seminar
8 July 2010
NOAA/CSTAR Grant NA07NWS4680001
Overview
• Motivation
Nonconvective wind fatalities
– Cool-season high wind events
can be damaging and in some
cases challenging to forecast
• Objectives
– Assess frequency of high wind
events
– Identify mechanisms that lead to
severe surface winds
– Present case study of one
extraordinary event
Tree-related nonconvective wind fatalities
Fatalities due to various wind-related
hazards, 1980–2005.
From Ashley and Black (2008)
Outline
• Background
• Data/Methodology
• Climatology
• Composite Analysis
• Case Study
• Synthesis/Conclusions
Background: Thunderstorm winds
• Thunderstorm wind climatology
– Kelley et al. (1985): Nontornadic
severe thunderstorm wind
• Thunderstorm winds driven by
evaporatively-cooled downdrafts
– Downbursts (Fujita and Byers 1977),
bow echos (e.g., Fujita 1978),
derechos (Johns and Hirt 1987)
– Mesovortices can modulate location
of strongest winds (e.g., Trapp and
Weisman 2003)
From Kelley et. al (1985)
• Johns (1993):
– Described favorable cool-season
pattern for development of squall
lines with extensive bow echoinduced wind damage
From Johns (1993)
Background: Gradient winds
• Kapela et al. (1995) constructed a checklist of features
associated with the occurrence of strong post cold-frontal
winds:
– Strong unidirectional flow throughout the troposphere,
tropospheric-deep cold advection, steep low-level lapse rates,
subsidence, presence of a dry intrusion, strong isallobaric
gradient
• Niziol and Paone (2000): Identified typical cyclone track
associated with high winds impacting Buffalo, NY
– Also noted many features determined by Kapela et al. (1995)
L
L
L
t = −12 h
t = 00 h
t = +12 h
Background: Case Studies
• McCann (1978) determined necessary conditions for
convective storms to produce high winds without
lightning:
– Small amount of potential instability, synoptic scale lifting, strong
winds at 3 to 5 km above surface
• Conditions met during winter
• Koch and Kocin (1991) and Browning and Reynolds
(1994) studied high-wind producing rain bands
– Noted importance of dry intrusion on rain band and high wind
development
– High winds occurred during and shortly after cold front passed
• Van den Broeke et. al (2005) studied the lightning
production of two low CAPE, high shear convective lines
– Conclusions suggest the occurrence of high wind during the cool
season not as dependent on CAPE as in the warm season
Data
• Climatology
– NCDC thunderstorm and high wind reports
– National Lightning Detection Network (NLDN) data
• Composites
– NCDC thunderstorm and high wind reports
– NCEP/NCAR 2.5° Reanalysis data
• Case Studies
–
–
–
–
–
NCDC thunderstorm and high wind reports
1° Global Forecasting System (GFS) analyses
WSI 2-km NOWRAD Radar composites
National Lightning Detection Network (NLDN) data
Hourly surface observation data
Methodology (1 of 2)
• Event determination
– Domains: High wind reports from the Northeast (NE) for
15 Oct 1993 through 31 Dec 2008
– High wind definition: Wind measured ≥ 25 m s−1 or
damaging winds of any magnitude
– Event definition: Any series of storm reports that are
separated from each other by ≤ 12 h
• Events defined by type:
– Pure Gradient (PG): Only gradient wind reports
– Hybrid (HY): Both thunderstorm and gradient wind reports
– Pure Convective (PC): Only thunderstorm wind reports
• PG events: If lightning struck within 1° radius and 1 h from any
gradient wind report, PG event becomes HY event
Methodology (2 of 2)
• Composite
– HY and PG event types subdivided based upon location
of initial NE report relative to surface cyclone
• Northeast, Southeast, Southwest, Northwest quadrants
• PC events subdivided into trough and ridge categories
– Composite time (t = 00 h): Determined to be hour (00, 06,
12, or 18 Z) closest to initial NE report
• For reports at 03, 09, 15, or 21 Z  earlier hour chosen
• Events composited by event type and subcategory
– Created report-relative composites
• Grids shifted to location of initial NE report
• Composites centered on centroid of initial NE reports for each
event type and subcategory
Climatology: High-wind days
Gradient
Thunderstorm
(%)
Shaded represents the percentage of the total days (N = 3260)
studied that high winds occurred.
Climatology: High-wind days
Gradient
Thunderstorm
(%)
Shaded represents the percentage of the total days (N = 3260)
studied that high winds occurred.
Climatology: Event type
Histogram depicting the frequency of occurrence
based upon the type of event
Climatology: Yearly
Histogram depicting the frequency of occurrence
based upon the month in which the initial NE report occurred
Climatology: Monthly
Histogram depicting the frequency of occurrence
based upon the month in which the initial NE report occurred
Climatology: Hourly
Histogram depicting the frequency of occurrence
based time of the initial NE report
Climatology: Societal Impact
Events that accumulated > 100 reports:
HY: 27; PG: 2; PC: 0
Approximate average reports per event:
HY: 60; PG: 20; PC: 11
Histogram depicting the frequency of occurrence
based upon the number of reports accumulated
Climatology: Subcategories
Histogram depicting the frequency of occurrence
based either the location of the initial report or upper-level flow pattern
Climatology: Subcategories
Focus on these for composite analysis
Histogram depicting the frequency of occurrence
based either the location of the initial report or upper-level flow pattern
Southeast Composite: Surface
t = 00 h
(mm)
MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness
(dam, dashed); 1000 hPa total wind (kt, barbs); initial report (star)
Southeast Composite: Cyclone Track
+24 h
PG (N = 45)
−24 h
HY (N = 71)
t = 00 h
Loci of initial
report
Six Hourly Southeast Composite Cyclone Track:
vs.
; MSLP (hPa) is boxed; initial NE report (star)
Southeast Composite: Cross Section
(%)
θe (K, black); relative humidity(%, shaded); vertical motion (μb s−1, solid; redupward, blue-downward); total wind (kt, barbs); initial report (star)
Southeast Composite: Cross Section
(%)
θe (K, black); relative humidity(%, shaded); vertical motion (μb s−1, solid; redupward, blue-downward); total wind (kt, barbs); initial report (star)
Southwest Composite: Surface
t = 00 h
(mm)
MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness
(dam, dashed); 1000 hPa total wind (kt, barbs); initial report (star)
Southwest Composite: Cross Section
t = 00 h
(%)
θe (K, black); relative humidity(%, shaded); vertical motion (μb s−1, solid; redupward, blue-downward); total wind (kt, barbs); initial report (star)
Southwest Composite: Sounding
Composite sounding taken at the location of composite
initial NE report at t = −06 h, t = 00 h, and t = +06 h
17 Feb 2006: Overview
• Resulted in two fatalities
• Caused $3.5 million in
damage in New York
State
• Produced 85 kt wind gust
recorded at Saratoga
County Airport
• Accumulated most high
wind reports in the NE
(267 total reports)
85 kt gust
at 15 Z
All High Wind Reports
– 242 gradient reports
– 25 thunderstorm reports
• Fits the HY southeast
and PG southwest
paradigms
Gradient
Thunderstorm
17 Feb 2006: Cyclone Track
+24 h
−24 h
17 Feb case
HY composite (N = 71)
t = 00 h
Loci of initial
NE report
Six Hourly Cyclone Track:
MSLP (hPa) is boxed; initial NE report (star)
16 Feb 2006: Surface
t = −12 h
18 Z
Composite
storm reports
(mm)
MSLP (hPa, solid); precipitable water (mm, shaded);
1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs)
17 Feb 2006: Surface
t = 00 h
06 Z
Composite
storm reports
(mm)
MSLP (hPa, solid); precipitable water (mm, shaded);
1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs)
17 Feb 2006: Surface
t = +12 h
18 Z
Composite
storm reports
(mm)
MSLP (hPa, solid); precipitable water (mm, shaded);
1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs)
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 12 Z
t = +06 h
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 12 Z
t = +06 h
Lightning
Gradient
Thunderstorm
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 15 Z
t = +09 h
Post-Frontal Gusting
Pre-Frontal Gusting
Multiple
Bowing
Segments
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 15 Z
t = +09 h
Lightning
Gradient
Thunderstorm
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 18 Z
t = +12 h
17 Feb 2006: Radar/Surface Obs
17 FEB 06: 18 Z
t = +12 h
Lightning
Gradient
Thunderstorm
17 Feb 2006: CAPE/Shear
t = +12 h
18 Z
t = +06 h
12 Z
storm reports
storm reports
(J kg−1)
500 hPa Z (hPa, solid); CAPE (J kg−1, shaded);
1000–500 hPa shear (kt, barbs)
17 Feb 2006: Dry Intrusion
12 Z
ERI
42 N, −90 W
ERI
BGM
BGM
BOS
BOS
42 N, −60 W
(%)
θ (K, red); relative humidity(%, shaded);
potential vorticity (10−6 K m2 s−1 kg−1, black)
17 Feb 2006: θe Advection
12 Z
ERI
42 N, −90 W
ERI
BGM
BGM
BOS
BOS
42 N, −60 W
(10−4 K s−1)
θ (K, solid), θe advection (10−4 K s−1, shaded),
potential instability (K km−1, dashed)
17 Feb 2006: Frontogenesis
12 Z
ERI
42 N, −90 W
ERI
BGM
BOS
BGM
BOS
42 N, −60 W
[K (100 km)−1 (3 h)−1]
θ (K, solid), Petterssen front. [K (100 km)−1 (3 h)−1, shaded],
vertical motion (μb s−1, dashed; red-upward, blue-downward)
17 Feb 2006: Wind Profile
12 Z
ERI
42 N, −90 W
ERI
BGM
BOS
BGM
BOS
42 N, −60 W
θ (K, solid),
vertical motion (μb s−1, dashed; red-upward, blue-downward),
total wind (kt, barbs)
17 Feb 2006: Dry Intrusion
18 Z
ERI
42 N, −90 W
ERI
BGM
BGM
BOS
BOS
42 N, −60 W
(%)
θ (K, red); relative humidity(%, shaded);
potential vorticity (10−6 K m2 s−1 kg−1, black)
17 Feb 2006: θe Advection
18 Z
ERI
42 N, −90 W
ERI
BGM
BGM
BOS
BOS
42 N, −60 W
(10−4 K s−1)
θ (K, solid), θe advection (10−4 K s−1, shaded),
potential instability (K km−1, dashed)
17 Feb 2006: Frontogenesis
18 Z
ERI
42 N, −90 W
ERI
BGM
BOS
BGM
BOS
42 N, −60 W
[K (100 km)−1 (3 h)−1]
θ (K, solid), Petterssen front. [K (100 km)−1 (3 h)−1, shaded],
vertical motion (μb s−1, dashed; red-upward, blue-downward)
17 Feb 2006: Wind Profile
18 Z
ERI
42 N, −90 W
ERI
BGM
BOS
BGM
BOS
42 N, −60 W
θ (K, solid),
vertical motion (μb s−1, dashed; red-upward, blue-downward),
total wind (kt, barbs)
17 Feb 2006: Isallobaric Wind
t = +12 h
18 Z
t = +06 h
12 Z
storm reports
storm reports
MSLP (hPa, solid),
12-hr centered pressure change (hPa (12 h)−1, dashed);
1000 hPa isallobaric wind (kt, barbs)
Case Study Conclusions
• Strong forcing associated with the passage of a
front in the presence of a potentially unstable air
mass leads to development of a convective line
– Vertical differential θe advection and an upper-tropospheric dry
intrusion lead to mid-level drying
• Deep cold-air advection in the presence of steep
low-level lapse rates and strong low-level flow
leads to high winds behind the cold front
– Boundary layer stability and kinematic profile favorable for
turbulent momentum transport
– Isallobaric wind likely enhanced low-level flow
Synthesis/Conclusions
• This work represents the first time thunderstorm
AND gradient wind events have been looked at
from a climatology and composite perspective
• 17 Feb 2006 case is consistent with previous
studies of cool-season high wind events
• HY events tend to be the highest impact events
• HY synoptic set up is essentially a combination of
the composites constructed by Niziol and Paone
(2000) and the conceptual model of Johns (1993)
Synthesis/Conclusions
• HY event
conceptual
model
Gradient
Tstorm
• High wind threat
area in red
shading
Conceptual Model of the typical HY event
Thank You!
•
•
•
•
Lance and Dan
John, Tom, Hugh, and Kevin
Stuart Hinson at NCDC
Fellow graduate students
– Most notably: Ben, Natalie, Melissa, Tom, Jay, Nick,
Heather, Alan, Matt
• Professors and Faculty
– Ross, Kevin, Vince, Paul, Mathias, Chris, Ryan, etc.
• And of course, my family
Conceptual Models
• One PG event
model
Gradient
• Average number
of reports:
– total
• High wind threat
area in red
shading
Conceptual Model of the typical HY event
Southeast Composite: Surface
t = 00 h
12 h centered composite pressure change (hPa per 12 h, dashed);
MSLP (hPa, solid); ageostrophic wind (kt, barbs)