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 Masters Thesis Seminar 8 July 2010 NOAA/CSTAR Grant NA07NWS

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 L L 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 (%)

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 (mm) t = 00 h

Southeast Composite: Cyclone Track PG (N = 45) HY (N = 71) t = 00 h Loci of initial report 24 h +24 h

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

(%)

MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs); initial report (star) t = 00 h (mm)

t = 00 h (%) θ e (K, black); relative humidity(%, shaded); vertical motion (μb s 1, solid; red- upward, blue-downward); total wind (kt, barbs); initial report (star)

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

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 h 18 Z storm reports Composite

17 Feb 2006: Surface (mm) MSLP (hPa, solid); precipitable water (mm, shaded); 1000–500 hPa thickness (dam, dashed); 1000 hPa total wind (kt, barbs) t = 00 h 06 Z storm reports Composite

17 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 h 18 Z storm reports Composite

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 Gradient Thunderstorm Lightning

17 Feb 2006: Radar/Surface Obs 17 FEB 06: 15 Z t = +09 h Multiple Bowing Segments Post-Frontal Gusting Pre-Frontal Gusting

17 Feb 2006: Radar/Surface Obs 17 FEB 06: 15 Z t = +09 h Gradient Thunderstorm Lightning

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 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 h 12 Z storm reports t = +12 h 18 Z storm reports (J kg 1 )

17 Feb 2006: Dry Intrusion (%) ERI 42 N, 90 W42 N, 60 W BGMBOS 12 Z ERI BGM BOS θ (K, red); relative humidity(%, shaded); potential vorticity (10 6 K m 2 s 1 kg 1, black)

17 Feb 2006: θ e Advection ERI 42 N, 90 W42 N, 60 W BGMBOS 12 Z ERI BGM BOS θ (K, solid), θ e advection (10 4 K s1, shaded), potential instability (K km 1, dashed) (10 4 K s1 )

17 Feb 2006: Frontogenesis ERI 42 N, 90 W42 N, 60 W BGMBOS 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) ERI 42 N, 90 W42 N, 60 W BGMBOS 12 Z ERI BGM BOS

17 Feb 2006: Dry Intrusion (%) ERI 42 N, 90 W42 N, 60 W BGMBOS 18 Z ERI BGM BOS θ (K, red); relative humidity(%, shaded); potential vorticity (10 6 K m 2 s 1 kg 1, black)

17 Feb 2006: θ e Advection ERI 42 N, 90 W42 N, 60 W BGMBOS 18 Z ERI BGM BOS (10 4 K s1 ) θ (K, solid), θ e advection (10 4 K s1, shaded), potential instability (K km 1, dashed)

ERI 42 N, 90 W42 N, 60 W BGMBOS 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

ERI 42 N, 90 W42 N, 60 W BGMBOS 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 t = +06 h 12 Z t = +12 h 18 Z 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 θ e 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 t = 00 h 12 h centered composite pressure change (hPa per 12 h, dashed); MSLP (hPa, solid); ageostrophic wind (kt, barbs)