Title: Intense Surface Cyclone Activity in the Arctic during the 200506 and 200607 Cool Seasons
1Intense Surface Cyclone Activity in the Arctic
during the 200506 and 200607 Cool Seasons
- Brian Silviotti, Lance F. Bosart, and Daniel
Keyser - Department of Earth and Atmospheric Sciences
- University at Albany, Albany, New York
- NSF Grant ATM-0434189
- 10th Northeast Regional Operational Workshop
- 5 November 2008
2Motivation
Major Arctic Shipping Routes
- Arctic cyclones not extensively studied
- Intense arctic cyclones
- pose economic hazards,
- especially to shipping
Source www.hofstra.edu
3Purpose
- Establish a limited track climatology of intense
arctic surface cyclones - Relate track climatology to large-scale arctic
flow - Examine cyclone mergers
- Perform a brief case study of a cyclone merger
event
4Datasets
- GFS 0.5 analysis
- Storm-track climatology and case study
- NCEPNCAR Reanalysis
- Large-scale mean/anomaly computations
- CPC daily teleconnection indices
- 1 Jan 1950 30 Jun 2008
- Sources
- UAlbany DEAS data archive
- ESRL
- CPC
5Methodology
- Definitions
- Cool season 1 Oct 31 Mar
- Arctic poleward of 50N
- Intense cyclone central MSLP 980 hPa
- Manually analyzed surface maps
- Genesis/lysis time
- Position and track
- Central pressure
- Merger/nonmerger
6Large-scale Arctic Flow Representation
- Use teleconnection indices
- Arctic Oscillation (AO) and North Atlantic
Oscillation (NAO) - Normalize CPC datasets
- Obtain a mean (µ) of 0 and a standard deviation
(s) of 1 for each index dataset
7Large-scale Arctic Flow Representation
- Define regimes
- AO/NAO must remain in the positive or negative
phase for at least five consecutive days for a
time period to qualify as a positive or negative
regime - All other time periods qualify as neutral regimes
8200506 Cool-season AO/NAO Time Series
AO
NAO
Red shading positive regime Blue shading
negative regime
9200607 Cool-season AO/NAO Time Series
AO
NAO
Red shading positive regime Blue shading
negative regime
10200506 Cool-season 300 hPa Height Anomaly and
Wind Speed
Wind Speed
Height Anomaly
CI 2.5 m s-1
CI 10 m
µAO
-0.35
Source www.esrl.noaa.gov
µNAO
-0.22
11200607 Cool-season 300 hPa Height Anomaly and
Wind Speed
Wind Speed
Height Anomaly
CI 2.5 m s-1
CI 10 m
µAO
0.52
Source www.esrl.noaa.gov
µNAO
0.13
12Large-scale Arctic Flow Summary
- 200506 Cool Season
- Mainly negative AO/NAO pattern
- Weakened polar jet
- 200607 Cool Season
- Mainly positive AO/NAO pattern
- Strengthened polar jet
13200506 Cool-season Storm Tracks
OctNov DecJan FebMar
- 50 Storms
- OctNov 20
- DecJan 21
- FebMar 9
14200607 Cool-season Storm Tracks
OctNov DecJan FebMar Case Study
- 95 Storms
- OctNov 25
- DecJan 46
- FebMar 24
15Cyclogenesis Events vs. AO/NAO Regime (200507)
- Arctic more active during neutral to positive
AO/NAO regimes (strengthened polar jet)
16Merger Locations by Month (200507)
OctNov DecJan FebMar Case Study
- 39 Mergers
- OctNov 11
- DecJan 17
- FebMar 11
ArcticArctic Mergers 21 ArcticMidlatitu
de Mergers 18
17Merger Locations by Strength (200507)
970980 hPa 960969 hPa 950959 hPa lt 950 hPa
Case Study
- 39 Mergers
- 970980 hPa 15
- 960969 hPa 13
- 950959 hPa 9
- lt 950 hPa 2
ArcticArctic Mergers ArcticMidlatitude
Mergers
18Case Study
- Example of an arcticmidlatitude cyclone merger
event - Occurred over the North Atlantic southeast of
Greenland during 711 Dec 2006 - Two surface cyclones and three positive potential
vorticity (PV) anomalies merged
19Surface Low Tracks and 500 hPa Mean Height
500 hPa mean height (dam) for 612 Dec 2006
20MSLP Time Series
- Well-developed, rapidly strengthening
midlatitude cyclone absorbs arctic cyclone - System deepens 53 hPa in 24 h (1800 UTC 8 Dec
1800 UTC 9 Dec) - Merged cyclone reaches lowest MSLP value of 928
hPa on 1200 UTC 10 Dec
21PV Anomaly Tracks
- PV anomaly A breaks off high PV reservoir over
Siberia (21 Nov) - PV anomalies C and D break off high PV
reservoir over North Pole (34 Dec) - PV anomaly B breaks off PV
anomaly A over Labrador Sea (6 Dec) - PV anomalies B, C, and D merge over North
Atlantic (10 Dec)
22Surface Lows and PV Anomalies
- PV anomaly B induces arctic cyclone on 0000
UTC 7 Dec - PV anomaly D induces midlatitude cyclone on
0000 UTC 8 Dec - PV anomaly C merges with B and D, helping
merged cyclone intensify
231200 UTC 8 Dec 2006 Sounding for Upton, NY
Dynamic Tropopause Height 2630 m QG Rossby
Penetration Depth for PV anomaly D 10320 m
PV anomaly D
240000 UTC 7 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
251200 UTC 7 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
260000 UTC 8 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
271200 UTC 8 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
280000 UTC 9 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
291200 UTC 9 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
300000 UTC 10 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
311200 UTC 10 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
320000 UTC 11 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
331200 UTC 11 Dec 2006 300 hPa Wind Speed (kt),
1000500 hPa Thickness (dam), MSLP (hPa)
34Conclusions
- 145 intense arctic surface cyclones occurring
over both cool seasons yielding a frequency of
1015 per month - High intraseasonal and interannual variability
- Arctic most active in neutral to positive AO/NAO
regimes - Strengthened polar jet associated with higher
frequency of intense arctic storms
35Conclusions
- Storms most frequent over Gulf of
Alaska/Aleutians and North Atlantic/East Arctic
Oceans - Clustering near end of well-known storm tracks
- Atlantic more active than the Pacific
- More storms tend to form farther north in the
Atlantic
36Conclusions
- All mergers occur poleward of 50N
- Storms stay or move into the arctic
- Arcticmidlatitude mergers typically occur when
southern storm is well developed - Arctic storm provides extra vorticity expedites
vorticity growth
37Further Research
- Use automated tracking program to include several
more cool seasons - Other aspects of cyclones vs. regimes
- Intensity
- Mean location
- Merger/nonmerger
- Merger Behavior
- Strongest mergers southeast of Greenland
- Arcticarctic vs. arcticmidlatitude mergers
38Questions/Comments?