A Severe Weather Outbreak Associated with a Great Lakes Cutoff Cyclone

1
A Severe Weather Outbreak Associated with a Great
Lakes Cutoff Cyclone
Nicholas D. Metz and Lance F. Bosart Department
of Earth and Atmospheric Sciences University at
Albany/SUNY, Albany, NY 12222 E-mail
nmetz_at_atmos.albany.edu Support provided by the
NSF ATM-0646907 33rd Northeastern Storm
Conference
15
March 2008
2
Motivation
Associated with Cutoff
Previous Convection

• Investigate how a Great Lakes cutoff cyclone can
  produce a widespread severe weather event

3
Purpose

• Describe the large-scale flow evolution and
  subsequent formation of the Great Lakes cutoff
  cyclone
• Detail the mesoscale environment within which
  500 reports of severe weather occurred

4
Datasets

• 2.5? ? 2.5? NCEP/NCAR Reanalysis
• 1? ? 1? GFSFNL
• 20-km RUC analysis (RUC20) grids
• NOWRAD radar mosaics
• GOES-12 water vapor satellite imagery from UCAR
• Archived soundings from the University at Wyoming
• Archived surface data from the University at
  Albany

5
Large-Scale Flow Evolution and Formation of
Cutoff Cyclone
6

• Typhoon Chanchu reached 930 hPa and began
  recurving on 15 May 2006
• Ridging and subsequent downstream development
  occurred
• Cutoff formed out of quasi-stationary trough near
  140?W

500-hPa heights averaged 25?45?N
7
0000 UTC 17 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
TY CHANCHU
QUASI-STATIONARYTROUGH
K
8
1200 UTC 17 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
9
0000 UTC 18 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
10
1200 UTC 18 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
11
0000 UTC 19 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
12
1200 UTC 19 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
13
0000 UTC 20 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
14
1200 UTC 20 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
15
0000 UTC 21 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
16
1200 UTC 21 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
17
0000 UTC 21 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
18
1200 UTC 21 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
19
0000 UTC 22 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
20
1200 UTC 22 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
21
0000 UTC 23 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
K
22
1200 UTC 23 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
23
0000 UTC 24 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
24
1200 UTC 24 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
25
0000 UTC 25 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
26
1200 UTC 25 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
27
0000 UTC 26 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
28
1200 UTC 26 May 06
? on the DT (K), 925850-hPa Relative Vorticity
(gt 4 ? 10-5 s-1), Winds on the DT (kt)
L
K
1000500-hPa Thickness (dam), SLP (hPa), 850-hPa
?e (K), Sfc. Winds (kt)
K
29
SLP and Thickness with Cutoff
Lee Trough Phase
Cutoff Phase
30
Back Trajectories from 1200 UTC 25 May 2006
K
144 h at 300 hPa
31
Back Trajectories from 1200 UTC 25 May 2006
K
144 h at 850 hPa
32
Convective Development and Evolution
33
0545 UTC 25 May 06
Water Vapor
34
0845 UTC 25 May 06
Water Vapor
35
1445 UTC 25 May 06
Water Vapor
36
1545 UTC 25 May 06
Water Vapor
37
1645 UTC 25 May 06
Water Vapor
38
1745 UTC 25 May 06
Water Vapor
39
1845 UTC 25 May 06
Water Vapor
40
1945 UTC 25 May 06
Water Vapor
41
2045 UTC 25 May 06
Water Vapor
42
Necessary Condition for Barotropic Instability
Holton (2004)

• Occurs where the basic-state meridional absolute
  vorticity gradient is lt 0
• Fulfilled in vicinity of dry slot associated with
  cutoff

43
1445 UTC 25 May 06
? 10-11 m-1 s?1
Time-mean 500-hPa heights and negative meridional
absolute vorticity gradient (12001800 UTC 25 May)
44
0600 UTC 25 May 06
500 hPa Heights (dam), Absolute Vorticity (gt 16 ?
10-5 s-1), and Winds (kt)
? 10-5s?1
45
0900 UTC 25 May 06
500 hPa Heights (dam), Absolute Vorticity (gt 16 ?
10-5 s-1), and Winds (kt)
? 10-5s?1
46
1200 UTC 25 May 06
500 hPa Heights (dam), Absolute Vorticity (gt 16 ?
10-5 s-1), and Winds (kt)
? 10-5s?1
47
1200 UTC 25 May 06
Absolute Vorticity (gt 16 ? 10-5 s-1), ? (K),
Winds (kt)
A
A
48
1200 UTC 25 May 06
CAPE (J kg-1) and 06 km Shear (kt)
J kg-1
49
1500 UTC 25 May 06
J kg-1
50
1500 UTC 25 May 06
18
00
22
04
14
26
08
12
SLP (hPa), Surface Temperature (?C), and Surface
Mixing Ratio (gt 14 g kg-1)
51
1800 UTC 25 May 06
J kg-1
52
p
T (?C)
J kg-1
53
p
T (?C)
J kg-1
54
1800 UTC 25 May 06
18
00
22
26
04
30
14
08
SLP (hPa), Surface Temperature (?C), and Surface
Mixing Ratio (gt 14 g kg-1)
55
1900 UTC 25 May 06
J kg-1
56
2000 UTC 25 May 06
J kg-1
57
2100 UTC 25 May 06
J kg-1
58
2200 UTC 25 May 06
J kg-1
59
2300 UTC 25 May 06
J kg-1
60
0000 UTC 26 May 06
J kg-1
61

p
T (?C)
J kg-1
62

p
T (?C)
J kg-1
63
0300 UTC 26 May 06
J kg-1
64
0600 UTC 26 May 06
J kg-1
65
Conclusions

• Cutoff formed from PV tail and injected into
  midlatitudes in association with downstream
  development
• Barotropic instability may have played role in
  convective development
• Region of severe development had moderate CAPE
  (1250 J kg-1) and shear (30 kt)
• Enhanced baroclinicity near lakes and convergence
  boundary from old convection acted to focus
  convection initially