cool-season high wind events in the northeast u.s. jonas v. asuma, lance f. bosart, daniel keyser...

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

• Motivation– 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

Overview

From Ashley and Black (2008)

Fatalities due to various wind-related hazards, 1980–2005.

Nonconvective wind fatalities

Tree-related nonconvective wind fatalities

• Background

• Data/Methodology

• Climatology

• Composite Analysis

• Case Study

• Synthesis/Conclusions

Outline

• 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)

• Johns (1993): – Described favorable cool-season

pattern for development of squall lines with extensive bow echo-induced wind damage

Background: Thunderstorm winds

From Johns (1993)

From Kelley et. al (1985)

• 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)

Background: Gradient winds

t = −12 h t = 00 h t = +12 h

LL

L

• 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

Background: Case Studies

• 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

Data

• 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 (1 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

Methodology (2 of 2)

Shaded represents the percentage of the total days (N = 3260) studied that high winds occurred.

Climatology: High-wind days

Gradient Thunderstorm

(%)

Histogram depicting the frequency of occurrence based upon the type of event

Climatology: Event type

Histogram depicting the frequency of occurrence based upon the month in which the initial NE report occurred

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 time of the initial NE report

Climatology: Hourly

Histogram depicting the frequency of occurrence based upon the number of reports accumulated

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 either the location of the initial report or upper-level flow pattern

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

MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs); initial report (star)

Southeast Composite: Surface

HY (N = 71)

PG (N = 45)

(mm)

t = 00 h

Six Hourly Southeast Composite Cyclone Track: Pure Gradient vs. Hybrid; MSLP (hPa) is boxed; initial NE report (star)

Southeast Composite: Cyclone Track

PG (N = 45)

HY (N = 71)

t = 00 h

Loci of initial report

−24 h

+24 h

HY Southeast Composite: Cross Section

HY (N = 71)

(%)

θe (K, black); relative humidity(%, shaded); vertical motion (μb s−1, solid; red-upward, blue-downward); total wind (kt, barbs); initial report (star)


PG Southeast Composite: Cross Section

PG (N = 45)

(%)

MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs); initial report (star)

PG Southwest Composite: Surface

PG (N = 55)

t = 00 h

(mm)

t = 00 h

(%)

PG (N = 55)

PG Southwest Composite: Cross Section


Composite sounding taken at the location of composite initial NE report at t = −06 h, t = 00 h, and t = +06 h

PG (N = 55)

PG Southwest Composite: Sounding

• 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)– 242 gradient reports– 25 thunderstorm reports

• Fits the HY southeast and PG southwest paradigms

Gradient

Thunderstorm

All High Wind Reports

85 kt gust at 15 Z

17 Feb 2006: Overview

Six Hourly Cyclone Track: MSLP (hPa) is boxed; initial NE report (star)

17 Feb 2006: Cyclone Track

−24 h

+24 h

17 Feb case

HY composite (N = 71)

t = 00 h

Loci of initial NE report

16 Feb 2006: Surface

(mm)

MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs)

t = −12 h18 Z

storm reportsComposite


(mm)


t = 00 h06 Z



(mm)


t = +12 h18 Z


17 Feb 2006: Radar/Surface Obs17 FEB 06: 12 Z

t = +06 h


t = +06 h

Gradient

Thunderstorm

Lightning


t = +09 h

Multiple Bowing Segments

Post-Frontal Gusting

Pre-Frontal Gusting


t = +09 h

Gradient

Thunderstorm

Lightning


t = +12 h


t = +12 h

Gradient

Thunderstorm

Lightning

500 hPa Z (hPa, solid); CAPE (J kg−1, shaded);1000–500 hPa shear (kt, barbs)

17 Feb 2006: CAPE/Shear

t = +06 h12 Z

storm reports

t = +12 h18 Z

storm reports

(J kg−1)

17 Feb 2006: Dry Intrusion

(%)

ERI42 N, −90 W 42 N, −60 WBGM BOS

12 Z

ERI BGM BOS

θ (K, red); relative humidity(%, shaded); potential vorticity (10−6 K m2 s−1 kg−1, black)

17 Feb 2006: θe Advection

ERI42 N, −90 W 42 N, −60 WBGM BOS

12 Z

ERI BGM BOS

θ (K, solid), θe advection (10−4 K s−1, shaded), potential instability (K km−1, dashed)

(10−4 K s−1)

17 Feb 2006: Frontogenesis

ERI42 N, −90 W 42 N, −60 WBGM BOS

12 Z

ERI BGM BOS

[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

θ (K, solid), vertical motion (μb s−1, dashed; red-upward, blue-downward),

total wind (kt, barbs)

ERI42 N, −90 W 42 N, −60 WBGM BOS

12 Z

ERI BGM BOS

17 Feb 2006: Dry Intrusion

(%)

ERI42 N, −90 W 42 N, −60 WBGM BOS

18 Z

ERI BGM BOS

θ (K, red); relative humidity(%, shaded); potential vorticity (10−6 K m2 s−1 kg−1, black)

17 Feb 2006: θe Advection

ERI42 N, −90 W 42 N, −60 WBGM BOS

18 Z

ERI BGM BOS

(10−4 K s−1)

θ (K, solid), θe advection (10−4 K s−1, shaded), potential instability (K km−1, dashed)

ERI42 N, −90 W 42 N, −60 WBGM BOS

18 Z

ERI BGM BOS

[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: Frontogenesis

ERI42 N, −90 W 42 N, −60 WBGM BOS

18 Z

ERI BGM BOS

θ (K, solid), vertical motion (μb s−1, dashed; red-upward, blue-downward),

total wind (kt, barbs)

17 Feb 2006: Wind Profile

MSLP (hPa, solid), 12-hr centered pressure change (hPa (12 h)−1, dashed);

1000 hPa isallobaric wind (kt, barbs)

17 Feb 2006: Isallobaric Wind

+24

−28

t = +06 h12 Z

t = +12 h18 Z

+28

−32

storm reports storm reports

• 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

Case Study 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

Conceptual Model of the typical HY event

Synthesis/Conclusions

• HY event conceptual model

• High wind threat area in red shading

Tstorm

Gradient

• 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

Thank You!

Conceptual Model of the typical HY event

Conceptual Models

• One PG event model

• Average number of reports:– total

• High wind threat area in red shading

Gradient

Southeast Composite: Surface

HY (N = 71)

PG (N = 45)

t = 00 h

12 h centered composite pressure change (hPa per 12 h, dashed); MSLP (hPa, solid); ageostrophic wind (kt, barbs)

cool-season high wind events in the northeast u.s. jonas v. asuma, lance f. bosart, daniel keyser...

Documents

occurrence of high wind

high wind definition

frequency of high wind

high wind reports ncepncar

event type slide

hourly slide

strong winds

yearly slide