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 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 Warm season continental closed anticyclones (CAs) link weather and climate on intraseasonal time scales Can persist for most of 90-day warm season Can persist for most of 90-day warm season Surface temperature/rainfall anomalies with CAs can determine overall seasonal anomalies for a given region 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 High-impact severe weather on CA periphery associated with mesoscale disturbances

Goals Examine the CA of July 1995 over the US Examine the CA of July 1995 over the US Impact on rainfall distribution Impact on rainfall distribution Behavior of mesoscale disturbances on periphery of CA and their role in MCS development Behavior of mesoscale disturbances on periphery of CA and their role in MCS development

Data and Methods 2.5  NCEP–NCAR Reanalysis 2.5  NCEP–NCAR Reanalysis  ECMWF Reanalysis (ERA-40)  ECMWF Reanalysis (ERA-40) 0.25  NCEP Unified Precipitation Dataset (UPD) 0.25  NCEP Unified Precipitation Dataset (UPD) University of Wyoming sounding archive University of Wyoming sounding archive National Lightning Detection Network (NLDN) National Lightning Detection Network (NLDN) Dynamic tropopause defined at 1.5 PVU surface Dynamic tropopause defined at 1.5 PVU surface

July 1995 CA over US

11-15 Jul hPa HGHT 500 hPa Height (dam) Mean and Anomaly and Wind (m/s) 5–10 July –15 July 1995 Height Anomaly Wind Fig. A1 from Galarneau et al ridge building eastward progression 2.5  NCEP–NCAR Reanalysis

hPa 21  C Isotherm Continuity Map 0000 UTC 5–15 July 1995 Fig. A5 from Galarneau et al  NCEP–NCAR Reanalysis

00Z/13 DT  (K) and wind (knots) NLDN CG lightning X X X MCS #1 PV tail mesoscale disturbance  ECMWF Reanalysis +/-+/-

12Z/13 DT  (K) and wind (knots) X MCS #1 PV tail mesoscale disturbance X X X X X X X X  ECMWF Reanalysis +/-+/- NLDN CG lightning

00Z/14 DT  (K) and wind (knots) X MCS #1 PV tail mesoscale disturbance X X X X X X X X  ECMWF Reanalysis +/-+/- NLDN CG lightning MCS #2

12Z/14 DT  (K) and wind (knots) X MCS #2 PV tail mesoscale disturbance X X X X X X X X X X  ECMWF Reanalysis +/-+/- NLDN CG lightning

00Z/15 DT  (K) and wind (knots) X MCS #3 PV tail mesoscale disturbance X X X X X X X X  ECMWF Reanalysis +/-+/- NLDN CG lightning

12Z/15 DT  (K) and wind (knots) X MCS #3 PV tail mesoscale disturbance X X X X X X  ECMWF Reanalysis +/-+/- NLDN CG lightning

H L PV Tail Strong Jet mesoscale disturbance source region Schematic for 13–15 July 1995 DT flow X X X

CG Lightning 12–15 July –1313–1414–15+/- NLDN

Storm Reports 12–15 July 1995 MCS #1 MCS #2 MCS #3 Reports associated with PV tail tornado wind hail + Generated using SeverePlot v2.5 Source: Storm Prediction Center tornado/wind reports near persistent trough

850  e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km -1 ) 00Z/13–15 July  ECMWF Reanalysis

850  e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km -1 ) 00Z/13–15 July J kg -1 00Z/  ECMWF Reanalysis Univ. Wyoming

850  e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km -1 ) 00Z/13–15 July J kg -1 00Z/  ECMWF Reanalysis Univ. Wyoming

850  e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km -1 ) 00Z/13–15 July J kg -1 00Z/  ECMWF Reanalysis Univ. Wyoming

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

% Contribution of 12–15 Jul to JJA Climo % UPD ~25% ~20–30%

Case Study Summary Downstream development led to ridge building over the Intermountain West 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 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 Serial severe MCSs formed on poleward side High CAPE, high shear environment High CAPE, high shear environment Scattered convection formed on equatorward side Scattered convection formed on equatorward side Moderate CAPE, low-moderate shear environment Moderate CAPE, low-moderate shear environment

Climate Implications Rainfall Rainfall MCSs on periphery contributed ~25% of climatological JJA precipitation MCSs on periphery contributed ~25% of climatological JJA precipitation Mesoscale disturbances can produce intense rain events and/or severe weather events Mesoscale disturbances can produce intense rain events and/or severe weather events Temperature Temperature Subset of CAs that build over Intermountain West, then move eastward can produce heat waves 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 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 ) 00Z/20 PV tail thinning and breaking Source: NCDC GIBBS GOES-12

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 ) 00Z/21 Source: NCDC GIBBS GOES-12

DT  (K), wind (knots), and 925–850 hPa  (10 -5 s -1 ) 06Z/21 Jerry?

1345Z/21 VIS

1445Z/21 VIS

1545Z/21 VIS

1645Z/21 VIS

Source: Source: 17Z/21

~40 knots at landfall TPC Forecast from 12Z/21 Source:

Source:

Extra slides

July 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/16 DT  (K) and wind (knots) 380 J kg J kg -1 Univ. of Wyoming X X

1.0  NCEP–GFS Analyses 12Z/16 DT  (K) and wind (knots) 1500 J kg -1 Univ. of Wyoming X X X X

Date/Time (UTC) Height MSL (m) NOAA Profiler Obs 12Z/14 DT  (K) and wind (knots) X

Lapse Rate Climatology 1973–2007 Summer (JJA) 1200 UTC soundings Conditions: > 8.5 K km -1 > 2500 m deep 850–400 hPa layer

February 2004 over Australia

200 hPa Height and Anomaly (dam), and Wind (m/s) for 1–22 Feb  NCEP–NCAR Reanalysis

12Z/14 DT  (K) and wind (knots) IR X PV tail mesoscale disturbance 1.0  NCEP–GFS Analyses T1 T2

12Z/17 DT  (K) and wind (knots) IR X PV tail mesoscale disturbance X X 1.0  NCEP–GFS Analyses X X T1 T2

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