Peter J. Bowyer

Bio: Peter J. Bowyer is an academic researcher from Dartmouth College. The author has contributed to research in topics: Tropical cyclone forecast model & Precipitation. The author has an hindex of 1, co-authored 1 publications receiving 440 citations.

The extratropical transition of tropical cyclones : forecast challenges, current understanding, and future directions

Abstract: A significant number of tropical cyclones move into the midlatitudes and transform into extratropical cyclones. This process is generally referred to as extratropical transition (ET). During ET a cyclone frequently produces intense rainfall and strong winds and has increased forward motion, so that such systems pose a serious threat to land and maritime activities. Changes in the structure of a system as it evolves from a tropical to an extratropical cyclone during ET necessitate changes in forecast strategies. In this paper a brief climatology of ET is given and the challenges associated with forecasting extratropical transition are described in terms of the forecast variables (track, intensity, surface winds, precipitation) and their impacts (flooding, bush fires, ocean response). The problems associated with the numerical prediction of ET are discussed. A comprehensive review of the current understanding of the processes involved in ET is presented. Classifications of extratropical transition ...

Coastal flooding by tropical cyclones and sea-level rise

Abstract: The future impacts of climate change on landfalling tropical cyclones are unclear. Regardless of this uncertainty, flooding by tropical cyclones will increase as a result of accelerated sea-level rise. Under similar rates of rapid sea-level rise during the early Holocene epoch most low-lying sedimentary coastlines were generally much less resilient to storm impacts. Society must learn to live with a rapidly evolving shoreline that is increasingly prone to flooding from tropical cyclones. These impacts can be mitigated partly with adaptive strategies, which include careful stewardship of sediments and reductions in human-induced land subsidence.

Clouds in Tropical Cyclones

Abstract: Clouds within the inner regions of tropical cyclones are unlike those anywhere else in the atmosphere. Convective clouds contributing to cyclogenesis have rotational and deep intense updrafts but tend to have relatively weak downdrafts. Within the eyes of mature tropical cyclones, stratus clouds top a boundary layer capped by subsidence. An outward-sloping eyewall cloud is controlled by adjustment of the vortex toward gradient-wind balance, which is maintained by a slantwise current transporting boundary layer air upward in a nearly conditionally symmetric neutral state. This balance is intermittently upset by buoyancy arising from high-moist-static-energy air entering the base of the eyewall because of the radial influx of low-level air from the far environment, supergradient wind in the eyewall zone, and/or small-scale intense subvortices. The latter contain strong, erect updrafts. Graupel particles and large raindrops produced in the eyewall fall out relatively quickly while ice splinters left...

Influence of Environmental Humidity on Tropical Cyclone Size

Abstract: Observations demonstrate that the radius of maximum winds in tropical cyclones (TCs) can vary by an order of magnitude; similar size differences are evident in other spatial measures of the wind field as well as in cloud and precipitation fields. Many TC impacts are related to storm size, yet the physical mechanisms that determine TC size are not well understood and have received limited research attention. Presented here is a hypothesis suggesting that one factor controlling TC size is the environmental relative humidity, to which the intensity and coverage of precipitation occurring outside the TC core is strongly sensitive. From a potential vorticity (PV) perspective, the lateral extent of the TC wind field is linked to the size and strength of the associated cyclonic PV anomalies. Latent heat release in outer rainbands can result in the diabatic lateral expansion of the cyclonic PV distribution and balanced wind field. Results of idealized numerical experiments are consistent with the hypothe...

Globally Gridded Satellite Observations for Climate Studies

Abstract: Geostationary satellites have provided routine, high temporal resolution Earth observations since the 1970s. Despite the long period of record, use of these data in climate studies has been limited for numerous reasons, among them that no central archive of geostationary data for all international satellites exists, full temporal and spatial resolution data are voluminous, and diverse calibration and navigation formats encumber the uniform processing needed for multisatellite climate studies. The International Satellite Cloud Climatology Project (ISCCP) set the stage for overcoming these issues by archiving a subset of the full-resolution geostationary data at ~10-km resolution at 3-hourly intervals since 1983. Recent efforts at NOAA's National Climatic Data Center to provide convenient access to these data include remapping the data to a standard map projection, recalibrating the data to optimize temporal homogeneity, extending the record of observations back to 1980, and reformatting the data for broad ...

The key role of diabatic processes in modifying the upper-tropospheric wave guide: a North Atlantic case-study

Abstract: This study highlights the importance of diabatic processes for the complex interaction of weather systems in the North Atlantic–European sector during the week of 7–14 September 2008. A chain of events occurred including the extratropical transition (ET) of hurricane Hanna, a subsequently developing extratropical cyclone, the formation of an upper-level potential vorticity (PV) streamer that protruded towards Europe and triggered intense rainfall, and the genesis of a Mediterranean cyclone. A PV perspective is adopted along with trajectory calculations to elucidate the diabatic modification of the midlatitude flow. Important diabatic PV modifications occurred at upper levels, associated with the cross-isentropic transport of low-PV air within warm conveyor belts (WCBs). These were diagnosed during the ET of Hanna and the development of the extratropical cyclone near Newfoundland. The WCBs contributed to the amplification of ridges downstream of each cyclone and to the subsequent elongation of Hanna's upstream trough into a PV streamer. This streamer eventually triggered the Mediterranean cyclogenesis. The second major effect of the diabatic processes occurred on smaller scales, in the low and middle troposphere. The remnants of Hanna's tropical PV core advected moist air towards the baroclinic zone leading to condensational PV production in the lower troposphere. In contrast, in the case of the extratropical cyclone, diabatic PV production occurred within its WCB at mid levels. These diagnostic analyses corroborate the potential of diabatic processes associated with extratropical flow systems for the modification of both the low-level vortices and the upper-level Rossby wave guide. Copyright © 2011 Royal Meteorological Society