a multiscale analysis of major transition season northeast snowstorms rebecca steeves, andrea l....

A Multiscale Analysis of Major Transition Season Northeast Snowstorms

Rebecca Steeves, Andrea L. Lang, and Daniel KeyserDepartment of Atmospheric and Environmental Sciences

University at Albany

Northeast Regional Operational Workshop XVI4 November 2015

Supported by the NOAA Collaboration Science, Technology, and Applied Research Program (NA13NWS4680004)

• Investigate major transition season snowstorms in the northeast U.S. that result in widespread socioeconomic disruption and that are difficult to forecast

Overview

Motivation

• Major transition season snowstorms have the potential to produce widespread socioeconomic disruption• Infrastructure damage• Transportation delays • Power outages

• Heavy wet snow occurring in major transition season events can be especially damaging when trees arein full leaf

Damage in Belmont, MA, from the 28–30 October 2011 snowstorm. Source: Washington Post

Objectives

• Project research focuses on documenting:

• Synoptic-to-mesoscale atmospheric conditions occurring prior to and during major transition season Northeast snowstorms, with emphasis on the formation and maintenance of regions of lower-tropospheric cold air that coincide with areas of heavy snowfall

Objectives

• Project research focuses on documenting:

• Synoptic-scale atmospheric conditions occurring prior to and during major transition season Northeast snowstorms, with emphasis on the role of tropical moisture transport occurring within atmospheric rivers (ARs) in the formation and evolution of this class of snowstorms

Motivation

• Understand the ingredients of major transition season Northeast snowstorms from a Lagrangian perspective

• What is the source region of the cold air at the surface?• What is the source region of moist parcels in

areas of heavy snowfall?

Datasets

• General:• Quantum Geographic Information System

(QGIS)• NWS GIS - AWIPS Shapefile Database

• Event compilation:• NY State Department of Environmental

Conservation• NOAA/NCDC Storm Data (SD) Monthly

Publications• PA Tourism Office

Datasets

• Snowfall accumulation maps:• Global Multi-resolution Terrain Elevation Data

2010• NCDC GHCN Daily Summaries

• Case studies:• NEXRAD• Iowa Environmental Mesonet ASOS • NCEP CFSR global reanalysis (Saha et al.

2010)• 6-h time interval• 0.5° grid spacing• 1979–present

Methodology

• Defined and compiled list of major transition season Northeast snowstorms

• Categorized distinctive types of lower-tropospheric cold air that coincide with areas of heavy snowfall

• Selected a fall event and a spring event that illustrate the following types:• A cold pool type for the 28–30 October 2011

event• A baroclinic zone type for the 8–9 March 2005

event

Methodology

• Calculated 72-h kinematic backward trajectories using CFSR• Diagnosed evolution of selected

thermodynamic quantities• Identified source regions of moist parcels

• Applied the objective AR identification algorithm of Lavers and Villarini (2015)

Objective Definition

• To be objectively defined as a major transition season Northeast snowstorm, an event in SD must have at least three separate county warning areas (CWA) report: • “Heavy Snow” (HS)• “Winter Storm”(WS) • “Blizzard” (B) • A combination of

any of the three • WS and B must meet

12-h snow warningcriterion for the reporting CWA

Northeast domain outlined in dark black with thin black CWA borders

28–30 October 2011 Event

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa)

• Approximately 3 million power outages

• Significant travel disruptions

• Emergencies declared in multiple states

• Indirect fatalities

0000 UTC 30 October 2011

Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries


250-hPa wind speed (shaded, m s−1) and 500-hPa geopotential height (contoured, dam) at 0000 UTC 28 October 2011

Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 28 October 2011




L

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011

Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries

• 1000–850-hPa thickness values support snowfall


• Cold pool coincident with snowfall accumulation ≥ 20 in.

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011


A A’ A A’

Snowfall accumulation (shaded, in.) map displayed over terrain for the 28–30 October 2011 event produced from NCDC GHCN Daily Summaries• Cold pool coincident with

snowfall accumulation ≥ 20 in.

• 1000–850-hPa thickness values support snowfall


A A’

A A’1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above)

Cross section along 43°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 30 October 2011 (right)

e

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 30 October 2011 (above)


e


A A’



e


Level selection based on Fuhrmann and Konrad (2013)

A A’

975-hPa

850-hPa



e



A A’

975-hPa

500-hPa–600-hPa DGZ

850-hPa



e



A A’

975-hPa

72-h Backward Trajectories (975 hPa)

72-h backward trajectories for 975 hPa (blue) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories


72-h backward trajectories for 975 hPa (blue) and 850 hPa (green) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

72-h Backward Trajectories (DGZ)

72-h backward trajectories for 975 hPa (blue), 850 hPa (green), and DGZ (red) ending at 0000 UTC 30 October 2011 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

• AR objectively identified at 1200 UTC 30 October 2011

• Precipitation is only occurring over coastal Maine at this time

Vertically integrated water vapor transport (IVT; shaded, kg m−1 s−1), IVT vectors, MSLP (contoured, hPa), and AR axis (blue line) at 1200 UTC 30 October 2011

Atmospheric River: 1200 UTC 30 Oct 2011

• DGZ trajectories and AR trajectories originate in different locations

• DGZ trajectories originate over the southeastern U.S. and western North Atlantic, and AR trajectories originate in the subtropicsIVT magnitude (shaded, kg m−1 s−1), MSLP

(contoured, hPa), AR axis (black line), and 72-h backward trajectories (red) at 1200 UTC 30 October 2011

Atmospheric River: 1200 UTC 30 Oct 2011

• The configuration of the trajectories ending over Concord, NH, and the occurrence of heavy snowfall suggest cold pool formation and maintenance through diabatic cooling

• The objective AR identification algorithm and trajectory analysis reveal that an AR did not contribute to the heavy snowfall in Concord, NH• An AR was objectively identified at 1200 UTC

30 October 2011• DGZ trajectories and AR trajectories originate

in different locations

28–30 October 2011 Event Summary

8–9 March 2005 Event

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005

0000 UTC 9 March 2005

Snowfall accumulation (shaded, in.) map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries• Flash freeze due to ~11°C

temperature change in 3 hoccurred in CT

• Nearly 70,000 power outages• Many forms of travel

disruption

250-hPa wind speed (shaded, m s−1) and 500-hPa geopotential height (contoured, dam) at 0000 UTC 7 March 2005

Precipitable water (shaded, mm) and MSLP (contoured, hPa) at 0000 UTC 7 March 2005

0000 UTC 7 March 2005

L

L

1200 UTC 7 March 2005



L

0000 UTC 8 March 2005



L

1200 UTC 8 March 2005



L

0000 UTC 9 March 2005



L

1200 UTC 9 March 2005



0000 UTC 9 March 2005

• Heavy snowfall resulted from a combination of an Arctic frontal passage and secondary coastal cyclogenesis

Snowfall (shaded, in.) accumulation map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries


B B’

0000 UTC 9 March 2005

B B’

Snowfall (shaded, in.) accumulation map displayed over terrain for the 8–9 March 2005 event produced from NCDC GHCN Daily Summaries

• Heavy snowfall resulted from a combination of an Arctic frontal passage and secondary coastal cyclogenesis


1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005 (above)

Cross section along 42.5°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 9 March 2005 (right)

e

B B’

0000 UTC 9 March 2005

B B’

950-hPa

850-hPa

1000–850-hPa thickness (shaded, dam) and MSLP (contoured, hPa) at 0000 UTC 9 March 2005 (above)

Cross section along 42.5°N of θ (shaded, K) and temperature (contoured, °C) at 0000 UTC 9 March 2005 (right)

e Level selection based on Fuhrmann and Konrad (2013)

500-hPa–600-hPa DGZ

B B’

0000 UTC 9 March 2005


72-h backward trajectories for 950 hPa (blue) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories


72-h backward trajectories for 950 hPa (blue) and 850 hPa (green) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

72-h Backward Trajectories (DGZ)

72-h backward trajectories for 950 hPa (blue), 850 hPa (green), and DGZ (red) ending at 0000 UTC 9 March 2005 with representative trajectories bolded (above) and corresponding time series (right) for the representative trajectories

IVT magnitude (shaded, kg m−1 s−1), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) at 0600 UTC 8 March 2005

Atmospheric River: 0600 UTC 8 March 2005

• AR objectively identified for entire duration of the event

• DGZ trajectories travel in close proximity to AR axis beginning at 0600 UTC 8 March 2005


IVT magnitude (shaded, kg m−1 s−1), MSLP (contoured, hPa), AR axis (black line), and 72-h backward trajectories for the DGZ (red) and AR axis (pink) at 0000 UTC 9 March 2005

• DGZ trajectories and AR trajectories originate in the subtropics

• Source of cold air was an Arctic frontal passage

• The objective AR identification algorithm and the trajectory analysis suggest that an AR was an important ingredient for the event• An AR was objectively identified for the

duration of the event• DGZ trajectory parcels travel in close

proximity to the AR axis• AR trajectories and DGZ trajectories originate

in the subtropics

8–9 March 2005 Event Summary

Conclusions

• Source of cold air differed for each event• 28–30 October 2011: cold pool is suggested

to have formed in-situ from diabatic cooling• 8–9 March 2005: advection of cold air

following an Arctic frontal passage

• ARs have differing roles in each event• Not an ingredient for the 28–30 October 2011

event• Important ingredient for the 8–9 March 2005

event

Special thanks to Alicia Bentley and Benjamin Moore

Atmospheric River Objective Identification

• Methodology adopted fromLavers and Villarini (2015)

• Finds maximum IVT at each latitude that exceeds a climatological threshold

• Determines if 13 continuous latitudinal points crossing 40°N exceed the IVT threshold

• Longitudinal differences between points can be no greater than 4°

12 h Snow Warning Criteria

Source: NWS Forecast Office Philadelphia/Mt Holly

a multiscale analysis of major transition season northeast snowstorms rebecca steeves, andrea l....

Documents

major transition season

class of snowstorms

spring event

fall event

lowertropospheric cold

atmospheric rivers ars

objectivesproject research

cold pool type