Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones

transcript

Upper-level Mesoscale Upper-level Mesoscale Disturbances on the Periphery of Disturbances on the Periphery of

Closed AnticyclonesClosed Anticyclones

Thomas J. Galarneau, Jr. and Lance F. BosartThomas J. Galarneau, Jr. and Lance F. BosartUniversity at Albany, State University of New YorkUniversity at Albany, State University of New York

Albany, NY 12222 USAAlbany, NY 12222 USA

Fourth Symposium on Southwest Hydrometeorology21 September 2007 – Tucson, AZ

MotivationMotivation Warm season continental closed Warm season continental closed

anticyclones (CAs) link weather and climate anticyclones (CAs) link weather and climate on intraseasonal time scaleson intraseasonal time scales

Can persist for most of 90-day warm seasonCan persist for most of 90-day warm season Surface temperature/rainfall anomalies with Surface temperature/rainfall anomalies with

CAs can determine overall seasonal anomalies CAs can determine overall seasonal anomalies for a given regionfor a given region

High-impact severe weather on CA High-impact severe weather on CA periphery associated with mesoscale periphery associated with mesoscale disturbances disturbances

GoalsGoals

Examine the CA of July 1995 over the Examine the CA of July 1995 over the USUS Impact on rainfall distributionImpact on rainfall distribution Behavior of mesoscale disturbances on Behavior of mesoscale disturbances on

periphery of CA and their role in MCS periphery of CA and their role in MCS developmentdevelopment

Data and MethodsData and Methods

2.52.5 NCEP–NCAR Reanalysis NCEP–NCAR Reanalysis 1.1251.125 ECMWF Reanalysis (ERA-40) ECMWF Reanalysis (ERA-40) 0.250.25 NCEP Unified Precipitation Dataset (UPD) NCEP Unified Precipitation Dataset (UPD) University of Wyoming sounding archiveUniversity of Wyoming sounding archive National Lightning Detection Network (NLDN)National Lightning Detection Network (NLDN) Dynamic tropopause defined at 1.5 PVU surfaceDynamic tropopause defined at 1.5 PVU surface

July 1995 CA over USJuly 1995 CA over US

11-15 Jul 1995 500 hPa HGHT

500 hPa Height (dam) Meanand Anomaly and Wind (m/s)

5–10 July 1995

11–15 July 1995

Height Anomaly

Fig. A1 from Galarneau et al. 2007

ridge building

eastward progression

2.5 NCEP–NCAR Reanalysis

13 14 15

850 hPa 21C Isotherm Continuity Map0000 UTC 5–15 July 1995

Fig. A5 from Galarneau et al. 20072.5 NCEP–NCAR Reanalysis

00Z/13

DT (K) and wind (knots)

NLDN CG lightning

MCS #1

PV tail

mesoscaledisturbance

1.125 ECMWF Reanalysis

12Z/13

MCS #1

PV tail

NLDN CG lightning

00Z/14

MCS #1

PV tail

NLDN CG lightning

MCS #2

12Z/14

MCS #2

PV tail

NLDN CG lightning

00Z/15

MCS #3

PV tail

NLDN CG lightning

12Z/15

MCS #3

PV tail

NLDN CG lightning

PV Tail

Strong Jet

mesoscale disturbancesource region

Schematic for 13–15 July 1995

DT flow X

CG Lightning 12–15 July CG Lightning 12–15 July 19951995

12–13 13–14 14–15+/- +/- +/-

Storm Reports 12–15 July Storm Reports 12–15 July 19951995

MCS #1

MCS #2

MCS #3

Reports associatedwith PV tail

tornadowindhail

+Generated using SeverePlot v2.5Source: Storm Prediction Center

tornado/wind reportsnear persistent trough

850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1)

00Z/13–15 July 19951.125 ECMWF Reanalysis

00Z/13–15 July 1995

2300 J kg-1

00Z/13

Univ. Wyoming

00Z/13–15 July 1995

7000 J kg-1

00Z/13

Univ. Wyoming

00Z/13–15 July 19951800 J kg-1

00Z/14

Univ. Wyoming

% Contribution of JJA to Yearly % Contribution of JJA to Yearly Precipitation 1948–2003Precipitation 1948–2003

% Contribution of 12–15 Jul to JJA % Contribution of 12–15 Jul to JJA ClimoClimo

~20–30%

Case Study SummaryCase Study Summary

Downstream development led to ridge Downstream development led to ridge building over the Intermountain Westbuilding over the Intermountain West

As CA moved eastward, convection As CA moved eastward, convection formed on the periphery in association formed on the periphery in association with mesoscale disturbances and a PV tailwith mesoscale disturbances and a PV tail Serial severe MCSs formed on poleward sideSerial severe MCSs formed on poleward side

High CAPE, high shear environmentHigh CAPE, high shear environment Scattered convection formed on equatorward Scattered convection formed on equatorward

sideside Moderate CAPE, low-moderate shear environmentModerate CAPE, low-moderate shear environment

Climate ImplicationsClimate Implications RainfallRainfall

MCSs on periphery contributed ~25% of MCSs on periphery contributed ~25% of climatological JJA precipitationclimatological JJA precipitation

Mesoscale disturbances can produce intense Mesoscale disturbances can produce intense rain events and/or severe weather eventsrain events and/or severe weather events

TemperatureTemperature Subset of CAs that build over Intermountain Subset of CAs that build over Intermountain

West, then move eastward can produce heat West, then move eastward can produce heat waveswaves

Climatologically hot air over Intermountain Climatologically hot air over Intermountain West must be displaced to “anomalous” West must be displaced to “anomalous” regionsregions

Postscript:Postscript:Upper-level Upper-level

disturbances, disturbances, PV tails, and tropical PV tails, and tropical

systemssystems

DT (K), wind (knots), and 925–850 hPa (10-5 s-1)

06Z/16

12Z/16

18Z/16

00Z/17

06Z/17

12Z/17

18Z/17

00Z/18

06Z/18

12Z/18

18Z/18

00Z/19

06Z/19

12Z/19

18Z/19

Low-levelVorticity center

00Z/20

PV tail thinningand breaking

Source: NCDC GIBBSGOES-12

06Z/20

12Z/20

18Z/20

00Z/21

Source: NCDC GIBBSGOES-12

06Z/21

Jerry?

1345Z/21VIS

1445Z/21VIS

1545Z/21VIS

1645Z/21VIS

Source: http://www.coolwx.com/buoydata

Source: http://www.rap.ucar.edu/weather/surface

17Z/21

~40 knots at landfall

TPC Forecast from 12Z/21

Source: http://cimss.ssec.wisc.edu/tropic2/

Source: http://euler.atmos.colostate.edu/%7Evigh/guidance/index.htm

Extra slidesExtra slides

July 2006 CA over USJuly 2006 CA over US

500 hPa mean (dam; solid contours),anomaly (dam; shaded), and wind (knots; standard barbs)

15–22 July 2006

1.0 NCEP–GFS Analyses

00Z/16DT (K) and wind (knots)

380 J kg-1

1680 J kg-1

Univ. of Wyoming

12Z/16DT (K) and wind (knots)

1500 J kg-1

Univ. of Wyoming

Date/Time (UTC)

NOAA Profiler Obs

12Z/14

Lapse Rate Climatology• 1973–2007• Summer (JJA)• 1200 UTC soundings

Conditions:• > 8.5 K km-1

• > 2500 m deep• 850–400 hPa layer

100200200

200100

February 2004 over February 2004 over AustraliaAustralia

200 hPa Height and Anomaly (dam),and Wind (m/s) for 1–22 Feb 2004

2.5 NCEP–NCAR Reanalysis

12Z/14

PV tail

12Z/17

PV tail

Mean Resultant Gradient-level Wind for January

Figure from Atkinson (1971)

Monsoon trough

Trade winds

Monsoon flow

Is there a significant contribution from DT disturbances on the equatorward side of continental anticyclones to climatological monsoon precipitation over northern Australia?

Australia

Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones

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