David Vollaro - Academia.edu (original) (raw)

Papers by David Vollaro

Research paper thumbnail of Monsoon Gyres of the Northwest Pacific: Influences of ENSO, the MJO, and the Pacific-Japan Pattern

Research paper thumbnail of Tropical Cyclone Outflow Layer Structure and Balanced Response to Eddy Forcings

Journal of the Atmospheric Sciences, 2016

Research paper thumbnail of Tropical Cyclone Formation in a Sheared Environment: A Case Study

Journal of the Atmospheric Sciences, Nov 1, 2004

The development of Hurricane Danny (1997) from depression to hurricane was examined using cloud-t... more The development of Hurricane Danny (1997) from depression to hurricane was examined using cloud-to-ground lightning data, reconnaissance aircraft data, and satellite imagery. Vertical wind shear between 850 and 200 hPa of 5 11 m s-1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development. Early in the period the storm intensified steadily in the presence of this downshear convection. During the last and most intense outbreak, a second vortex appeared to develop within the convection. Evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original. Based on these events, it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process.Equivalent potential temperature fields within 500 m of the surface were examined. Only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of equivalent potential temperature appear. This came about by the virtual elimination of both low θe values in the core and high θe values outside the core that had been present at previous hours.The growth of Hurricane Danny is viewed in terms of the wind-induced surface heat exchange (WISHE) theory. During the tropical depression and early tropical storm (“pre-WISHE”) periods, few if any of the assumptions of WISHE were met: vertical wind shear exceeded 5 m s-1, considerable azimuthal asymmetry was present, transient highly buoyant convection occurred, and low values of θe in the storm core suggested the presence of convective downdrafts. It is proposed that 1) vortex interactions and subsequent axisymmetrization produced a single dominant vortex at the surface, and 2) vertical mixing of moist entropy by strong convection moved the sounding toward moist neutrality. By this reasoning, the disturbance then met the key tenets of the known finite-amplitude WISHE instability, and the storm intensified to hurricane strength.

Research paper thumbnail of Origins and Mechanisms of Eastern Pacific Tropical Cyclogenesis: A Case Study

Monthly Weather Review, 2000

Abstract The genesis of Hurricane Hernan (1996) in the eastern Pacific was investigated using gri... more Abstract The genesis of Hurricane Hernan (1996) in the eastern Pacific was investigated using gridded analyses from the European Centre for Medium-Range Weather Forecasts and gridded outgoing longwave radiation. Hernan developed in association with a wave ...

Research paper thumbnail of Paradigms of Tropical Cyclogenesis in the Western Pacific

Research paper thumbnail of Interactions of Middle Latitude Troughs and Tropical Disturbances on 4-6 Week Time Scales

Research paper thumbnail of Distribution of Helicity, CAPE, and Shear in Tropical Cyclones

... J. Atmos. Sci., 67, 274–284. Distribution of Helicity, CAPE, and Shear in Tropical Cyclones. ... more ... J. Atmos. Sci., 67, 274–284. Distribution of Helicity, CAPE, and Shear in Tropical Cyclones. John Molinari and David Vollaro ... Rev., 136, 631–643. [Abstract]. Barnes, GM, JF Gamache, MA LeMone, and GJ Stossmeister, 1991: A convective cell in a hurricane rainband. Mon. Wea. ...

Research paper thumbnail of Low Richardson Number in the Tropical Cyclone Outflow Layer

Http Dx Doi Org 10 1175 Jas D 14 0005 1, Aug 28, 2014

ABSTRACT

Research paper thumbnail of Potential Vorticity, Easterly Waves, and Eastern Pacific Tropical Cyclogenesis

Monthly Weather Review, Oct 1, 1997

During the same season, a correlation existed between the strength of the negative potential vort... more During the same season, a correlation existed between the strength of the negative potential vorticity gradient in the Caribbean and subsequent cyclogenesis in the eastern Pacific. The meridional PV gradient, convective heating measured by outgoing longwave radiation data, and ...

Research paper thumbnail of Incorporation of equatorial wave modes into tropical synoptic meteorology: Is It worth the trouble?

Research paper thumbnail of Planetary- and synoptic-scale influences on eastern Pacific tropical cyclogenesis

Monthly Weather Review, May 1, 2000

... 1999), wind surges (Zehr 1992; McBride 1995), and the many complex mesoscale interactions tha... more ... 1999), wind surges (Zehr 1992; McBride 1995), and the many complex mesoscale interactions that are likely of critical importance in the actual depression development and growth (eg, Ritchie and Holland 1993; Harr et al. ... McBride, JL, 1995: Tropical cyclone formation. ...

Research paper thumbnail of Applications of long-range lightning data to hurricane formation and intensification

2. RESULTS Vertical wind shear represents a key variable in tropical cyclone intensity change. Sh... more 2. RESULTS Vertical wind shear represents a key variable in tropical cyclone intensity change. Shelton (2005) showed that vertical wind shear was strong from the southwest and west-southwest during most of the lifetime of TS/Hurricane Claudette. The distribution of ...

Research paper thumbnail of Potential Vorticity Analysis of Tropical Cyclone Intensification

Journal of the Atmospheric Sciences, Aug 1, 1998

The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive poten... more The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive potential vorticity anomaly was examined. The intensification mechanism proposed earlier for mature Hurricane Elena appears to be valid for Danny as well, despite significant differences in the synoptic-scale environment and in the stage of the tropical cyclone prior to the interaction. Both storms experienced rapid pressure falls as a relatively small-scale positive upper potential vorticity anomaly began to superpose with the low-level tropical cyclone center.The interaction is described in terms of a complex interplay between vertical wind shear, diabatic heating, and mutual advection among vortices at and below the level of the outflow anticyclone. Despite this complexity, the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions.

Research paper thumbnail of External influences on hurricane intensity. III: Potential vorticity structure

Journal of the Atmospheric Sciences, 1995

Research paper thumbnail of Symmetric Instability in the Outflow Layer of a Major Hurricane

Journal of the Atmospheric Sciences, 2014

Research paper thumbnail of Projected increase in lightning strikes in the United States due to global warming

Science, 2014

Lightning plays an important role in atmospheric chemistry and in the initiation of wildfires, bu... more Lightning plays an important role in atmospheric chemistry and in the initiation of wildfires, but the impact of global warming on lightning rates is poorly constrained. Here we propose that the lightning flash rate is proportional to the convective available potential energy (CAPE) times the precipitation rate. Using observations, the product of CAPE and precipitation explains 77% of the variance in the time series of total cloud-to-ground lightning flashes over the contiguous United States (CONUS). Storms convert CAPE times precipitated water mass to discharged lightning energy with an efficiency of 1%. When this proxy is applied to 11 climate models, CONUS lightning strikes are predicted to increase 12 ± 5% per degree Celsius of global warming and about 50% over this century.

Research paper thumbnail of Low Richardson Number in the Tropical Cyclone Outflow Layer

Journal of the Atmospheric Sciences, 2014

ABSTRACT

Research paper thumbnail of Incorporation of Equatorial Wave Modes Into Tropical Synoptic Meteorology: Is It Worth the Trouble?

Research paper thumbnail of Forecasting Challenges Associated with Tropical Cyclones within Subtropical Gyres

Weather and Forecasting, 2014

Research paper thumbnail of Extreme Helicity and Intense Convective Towers in Hurricane Bonnie

Monthly Weather Review, 2008

... Towers in Hurricane Bonnie Advanced Search. Volume 136 Issue 11 (November 2008). ... in Hurri... more ... Towers in Hurricane Bonnie Advanced Search. Volume 136 Issue 11 (November 2008). ... in Hurricane Bonnie. Mon. Wea. Rev., 136, 4355–4372. doi: 10.1175/2008MWR2423.1. Extreme Helicity and Intense Convective Towers in Hurricane Bonnie. John Molinari and David Vollaro ...

Research paper thumbnail of Monsoon Gyres of the Northwest Pacific: Influences of ENSO, the MJO, and the Pacific-Japan Pattern

Research paper thumbnail of Tropical Cyclone Outflow Layer Structure and Balanced Response to Eddy Forcings

Journal of the Atmospheric Sciences, 2016

Research paper thumbnail of Tropical Cyclone Formation in a Sheared Environment: A Case Study

Journal of the Atmospheric Sciences, Nov 1, 2004

The development of Hurricane Danny (1997) from depression to hurricane was examined using cloud-t... more The development of Hurricane Danny (1997) from depression to hurricane was examined using cloud-to-ground lightning data, reconnaissance aircraft data, and satellite imagery. Vertical wind shear between 850 and 200 hPa of 5 11 m s-1 produced persistent downshear convective outbreaks that became progressively more intense and closer to the center during the development. Early in the period the storm intensified steadily in the presence of this downshear convection. During the last and most intense outbreak, a second vortex appeared to develop within the convection. Evidence is presented that the new downshear vortex became the dominant vortex and absorbed the original. Based on these events, it is hypothesized that the presence of moderate vertical wind shear accelerated the early development process.Equivalent potential temperature fields within 500 m of the surface were examined. Only well after the period of vortex interaction did the characteristic mature tropical cyclone radial profile of equivalent potential temperature appear. This came about by the virtual elimination of both low θe values in the core and high θe values outside the core that had been present at previous hours.The growth of Hurricane Danny is viewed in terms of the wind-induced surface heat exchange (WISHE) theory. During the tropical depression and early tropical storm (“pre-WISHE”) periods, few if any of the assumptions of WISHE were met: vertical wind shear exceeded 5 m s-1, considerable azimuthal asymmetry was present, transient highly buoyant convection occurred, and low values of θe in the storm core suggested the presence of convective downdrafts. It is proposed that 1) vortex interactions and subsequent axisymmetrization produced a single dominant vortex at the surface, and 2) vertical mixing of moist entropy by strong convection moved the sounding toward moist neutrality. By this reasoning, the disturbance then met the key tenets of the known finite-amplitude WISHE instability, and the storm intensified to hurricane strength.

Research paper thumbnail of Origins and Mechanisms of Eastern Pacific Tropical Cyclogenesis: A Case Study

Monthly Weather Review, 2000

Abstract The genesis of Hurricane Hernan (1996) in the eastern Pacific was investigated using gri... more Abstract The genesis of Hurricane Hernan (1996) in the eastern Pacific was investigated using gridded analyses from the European Centre for Medium-Range Weather Forecasts and gridded outgoing longwave radiation. Hernan developed in association with a wave ...

Research paper thumbnail of Paradigms of Tropical Cyclogenesis in the Western Pacific

Research paper thumbnail of Interactions of Middle Latitude Troughs and Tropical Disturbances on 4-6 Week Time Scales

Research paper thumbnail of Distribution of Helicity, CAPE, and Shear in Tropical Cyclones

... J. Atmos. Sci., 67, 274–284. Distribution of Helicity, CAPE, and Shear in Tropical Cyclones. ... more ... J. Atmos. Sci., 67, 274–284. Distribution of Helicity, CAPE, and Shear in Tropical Cyclones. John Molinari and David Vollaro ... Rev., 136, 631–643. [Abstract]. Barnes, GM, JF Gamache, MA LeMone, and GJ Stossmeister, 1991: A convective cell in a hurricane rainband. Mon. Wea. ...

Research paper thumbnail of Low Richardson Number in the Tropical Cyclone Outflow Layer

Http Dx Doi Org 10 1175 Jas D 14 0005 1, Aug 28, 2014

ABSTRACT

Research paper thumbnail of Potential Vorticity, Easterly Waves, and Eastern Pacific Tropical Cyclogenesis

Monthly Weather Review, Oct 1, 1997

During the same season, a correlation existed between the strength of the negative potential vort... more During the same season, a correlation existed between the strength of the negative potential vorticity gradient in the Caribbean and subsequent cyclogenesis in the eastern Pacific. The meridional PV gradient, convective heating measured by outgoing longwave radiation data, and ...

Research paper thumbnail of Incorporation of equatorial wave modes into tropical synoptic meteorology: Is It worth the trouble?

Research paper thumbnail of Planetary- and synoptic-scale influences on eastern Pacific tropical cyclogenesis

Monthly Weather Review, May 1, 2000

... 1999), wind surges (Zehr 1992; McBride 1995), and the many complex mesoscale interactions tha... more ... 1999), wind surges (Zehr 1992; McBride 1995), and the many complex mesoscale interactions that are likely of critical importance in the actual depression development and growth (eg, Ritchie and Holland 1993; Harr et al. ... McBride, JL, 1995: Tropical cyclone formation. ...

Research paper thumbnail of Applications of long-range lightning data to hurricane formation and intensification

2. RESULTS Vertical wind shear represents a key variable in tropical cyclone intensity change. Sh... more 2. RESULTS Vertical wind shear represents a key variable in tropical cyclone intensity change. Shelton (2005) showed that vertical wind shear was strong from the southwest and west-southwest during most of the lifetime of TS/Hurricane Claudette. The distribution of ...

Research paper thumbnail of Potential Vorticity Analysis of Tropical Cyclone Intensification

Journal of the Atmospheric Sciences, Aug 1, 1998

The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive poten... more The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive potential vorticity anomaly was examined. The intensification mechanism proposed earlier for mature Hurricane Elena appears to be valid for Danny as well, despite significant differences in the synoptic-scale environment and in the stage of the tropical cyclone prior to the interaction. Both storms experienced rapid pressure falls as a relatively small-scale positive upper potential vorticity anomaly began to superpose with the low-level tropical cyclone center.The interaction is described in terms of a complex interplay between vertical wind shear, diabatic heating, and mutual advection among vortices at and below the level of the outflow anticyclone. Despite this complexity, the superposition principle appears to be conceptually useful to describe the intensification of tropical cyclones during such interactions.

Research paper thumbnail of External influences on hurricane intensity. III: Potential vorticity structure

Journal of the Atmospheric Sciences, 1995

Research paper thumbnail of Symmetric Instability in the Outflow Layer of a Major Hurricane

Journal of the Atmospheric Sciences, 2014

Research paper thumbnail of Projected increase in lightning strikes in the United States due to global warming

Science, 2014

Lightning plays an important role in atmospheric chemistry and in the initiation of wildfires, bu... more Lightning plays an important role in atmospheric chemistry and in the initiation of wildfires, but the impact of global warming on lightning rates is poorly constrained. Here we propose that the lightning flash rate is proportional to the convective available potential energy (CAPE) times the precipitation rate. Using observations, the product of CAPE and precipitation explains 77% of the variance in the time series of total cloud-to-ground lightning flashes over the contiguous United States (CONUS). Storms convert CAPE times precipitated water mass to discharged lightning energy with an efficiency of 1%. When this proxy is applied to 11 climate models, CONUS lightning strikes are predicted to increase 12 ± 5% per degree Celsius of global warming and about 50% over this century.

Research paper thumbnail of Low Richardson Number in the Tropical Cyclone Outflow Layer

Journal of the Atmospheric Sciences, 2014

ABSTRACT

Research paper thumbnail of Incorporation of Equatorial Wave Modes Into Tropical Synoptic Meteorology: Is It Worth the Trouble?

Research paper thumbnail of Forecasting Challenges Associated with Tropical Cyclones within Subtropical Gyres

Weather and Forecasting, 2014

Research paper thumbnail of Extreme Helicity and Intense Convective Towers in Hurricane Bonnie

Monthly Weather Review, 2008

... Towers in Hurricane Bonnie Advanced Search. Volume 136 Issue 11 (November 2008). ... in Hurri... more ... Towers in Hurricane Bonnie Advanced Search. Volume 136 Issue 11 (November 2008). ... in Hurricane Bonnie. Mon. Wea. Rev., 136, 4355–4372. doi: 10.1175/2008MWR2423.1. Extreme Helicity and Intense Convective Towers in Hurricane Bonnie. John Molinari and David Vollaro ...