Upper-level Mesoscale Disturbances on
the Periphery of Closed Anticyclones
Thomas J. Galarneau, Jr. and Lance F. Bosart
University at Albany, State University of New York
Albany, NY 12222 USA
Fourth Symposium on Southwest Hydrometeorology
21 September 2007 – Tucson, AZ
Motivation


Warm season continental closed anticyclones
(CAs) link weather and climate on
intraseasonal time scales
Can persist for most of 90-day warm season


Surface temperature/rainfall anomalies with CAs
can determine overall seasonal anomalies for a
given region
High-impact severe weather on CA periphery
associated with mesoscale disturbances
Goals

Examine the CA of July 1995 over the US
Impact on rainfall distribution
 Behavior of mesoscale disturbances on periphery
of CA and their role in MCS development

Data and Methods






2.5 NCEP–NCAR Reanalysis
1.125 ECMWF Reanalysis (ERA-40)
0.25 NCEP Unified Precipitation Dataset (UPD)
University of Wyoming sounding archive
National Lightning Detection Network (NLDN)
Dynamic tropopause defined at 1.5 PVU surface
July 1995 CA over US
500 hPa Height (dam) Mean
and Anomaly and Wind (m/s)
Fig. A1 from Galarneau et al. 2007
2.5 NCEP–NCAR Reanalysis
ridge building
Height Anomaly
5–10 July 1995
Wind
11–15 July 1995
Wind
eastward progression
Height Anomaly
11-15 Jul 1995 500 hPa HGHT
850 hPa 21C Isotherm Continuity Map
0000 UTC 5–15 July 1995
11
910
7
6
12
8
13
14
15
5
2.5 NCEP–NCAR Reanalysis
Fig. A5 from Galarneau et al. 2007
00Z/13
+/-
DT  (K) and wind (knots)
X
NLDN CG lightning
MCS #1
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
12Z/13
+/X
X
DT  (K) and wind (knots)
X
X
NLDN CG lightning
MCS #1
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
X
X
X
+/-
00Z/14
X
X
X
DT  (K) and wind (knots)
X
X
NLDN CG lightning
MCS #2
MCS #1
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
X
X
12Z/14
+/X
X
X
DT  (K) and wind (knots)
X X
NLDN CG lightning
X
X
MCS #2
X
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
X
+/-
00Z/15
X
DT  (K) and wind (knots)
X
X
X
X
NLDN CG lightning
MCS #3
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
X
X
12Z/15
+/-
X
DT  (K) and wind (knots)
X
X
NLDN CG lightning
MCS #3
PV tail
X mesoscale
disturbance
1.125 ECMWF Reanalysis
X
X
X
Schematic for 13–15 July 1995
L
Strong Jet
X
X
DT flow
X
H
mesoscale disturbance
source region
PV Tail
CG Lightning 12–15 July 1995
+/- 12–13
NLDN
+/- 13–14
+/- 14–15
Storm Reports 12–15 July 1995
MCS #1
MCS #3
MCS #2
tornado/wind reports
near persistent trough
tornado
Reports associated
+ wind
with PV tail
hail
Generated using SeverePlot v2.5
Source: Storm Prediction Center
850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1)
00Z/13–15 July 1995
1.125 ECMWF Reanalysis
850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1)
00Z/13–15 July 1995
1.125 ECMWF Reanalysis
2300 J kg-1
00Z/13
Univ. Wyoming
850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1)
00Z/13–15 July 1995
1.125 ECMWF Reanalysis
7000 J kg-1 Univ. Wyoming
00Z/13
850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1)
1800 J kg-1 Univ. Wyoming
00Z/13–15 July 1995
1.125 ECMWF Reanalysis
00Z/14
% Contribution of JJA to Yearly
Precipitation 1948–2003
UPD
%
% Contribution of 12–15 Jul to JJA Climo
~25%
~20–30%
UPD
%
Case Study Summary


Downstream development led to ridge
building over the Intermountain West
As CA moved eastward, convection formed
on the periphery in association with
mesoscale disturbances and a PV tail

Serial severe MCSs formed on poleward side


High CAPE, high shear environment
Scattered convection formed on equatorward side

Moderate CAPE, low-moderate shear environment
Climate Implications

Rainfall
MCSs on periphery contributed ~25% of
climatological JJA precipitation
 Mesoscale disturbances can produce intense
rain events and/or severe weather events


Temperature
Subset of CAs that build over Intermountain
West, then move eastward can produce heat
waves
 Climatologically hot air over Intermountain West
must be displaced to “anomalous” regions

Postscript:
Upper-level disturbances,
PV tails, and tropical systems
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
06Z/16
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
12Z/16
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
18Z/16
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
00Z/17
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
06Z/17
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
12Z/17
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
18Z/17
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
00Z/18
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
06Z/18
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
12Z/18
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
18Z/18
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
00Z/19
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
06Z/19
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
12Z/19
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
18Z/19
Low-level
Vorticity center
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
Source: NCDC GIBBS
GOES-12
PV tail thinning
and breaking
00Z/20
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
06Z/20
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
12Z/20
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
18Z/20
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
Source: NCDC GIBBS
GOES-12
00Z/21
DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1)
Jerry?
06Z/21
1345Z/21
VIS
1445Z/21
VIS
1545Z/21
VIS
1645Z/21
VIS
Source: http://www.rap.ucar.edu/weather/surface
Source: http://www.coolwx.com/buoydata
17Z/21
TPC Forecast from 12Z/21
~40 knots at landfall
Source: http://cimss.ssec.wisc.edu/tropic2/
Source: http://euler.atmos.colostate.edu/%7Evigh/guidance/index.htm
Extra slides
July 2006 CA over US
500 hPa mean  (dam; solid contours),
15–22 July 2006
anomaly  (dam; shaded), and wind (knots; standard barbs)
00Z/16
DT  (K) and wind (knots)
380 J kg-1
X
1680 J kg-1
Univ. of Wyoming
X
1.0 NCEP–GFS Analyses
12Z/16
DT  (K) and wind (knots)
1500 J kg-1
X
X
X
X
1.0 NCEP–GFS Analyses
Univ. of Wyoming
DT  (K) and wind (knots)
12Z/14
X
NOAA Profiler Obs
16000
15000
14000
13000
12000
11000
Height MSL (m)
10000
Date/Time (UTC)
100200
200
Lapse Rate Climatology
• 1973–2007
• Summer (JJA)
• 1200 UTC soundings
100
300
500
700
Conditions:
• > 8.5 K km-1
• > 2500 m deep
• 850–400 hPa layer
100
200
100
February 2004 over Australia
2.5 NCEP–NCAR Reanalysis
200 hPa Height and Anomaly (dam),
and Wind (m/s) for 1–22 Feb 2004
12Z/14
T1
T2
IR
PV tail
X mesoscale
disturbance
1.0 NCEP–GFS Analyses
DT  (K) and wind (knots)
12Z/17
X
T1
X
T2
DT  (K) and wind (knots)
IR
X
X
PV tail
X mesoscale
disturbance
1.0 NCEP–GFS Analyses
Mean Resultant Gradient-level Wind for January
Monsoon flow
Trade winds
Monsoon trough
Australia
Is there a significant contribution from DT disturbances on the
equatorward side of continental anticyclones to climatological
monsoon precipitation over northern Australia?
Figure from Atkinson (1971)