Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: James M. Gross x
  • All content x
Clear All Modify Search
M. A. Estoquf and James M. Gross

Abstract

Diurnal variations of wind and temperature were obtained from six rawinsonde stations surrounding Lake Ontario during a period favorable for lake breeze occurrence. The wind variations were unexpectedly found to be approximately the same in phase and amplitude at all stations, irrespective of location relative to the lake. The temperature variations were different, depending on whether the stations were located north or south of the lake. The northern stations exhibited diurnal warming above the surface which occurred at a much later time compared to those over the southern stations. Hypotheses are presented to explain the diurnal variations.

Full access
Mariano A. Estoque and James M. Gross

Abstract

The three-dimensional structure and behavior of the lake-land breeze circulation which is induced by Lake Ontario is studied by means of a numerical model. The model is a primitive equation model which incorporates the effects of orography and the temperature prediction of the earth surface. A series of integrations is made in order to examine the effects of the large-scale prevailing flow and orography. These effects, which are found to be important in determining the structure of the lake-induced mesoscale flow pattern, are described in detail. One of the integrations corresponds to a simulation of an actually observed lake-land breeze circulation. Comparison between the simulated and the observed structures shows good agreement.

Full access
Miles B. Lawrence and James M. Gross

Abstract

The 1988 hurricane season is summarized, including accounts of individual storms. Twelve tropical storms were tracked, of which five became hurricanes Gilbert and Joan were devastating hurricanes in the Caribbean Sea and Gulf of Mexico, and Glibert's sea level pressure fell to a new record minimum for Atlantic hurricanes.

Full access
James S. Goerss, Charles R. Sampson, and James M. Gross

Abstract

The tropical cyclone (TC) track forecasting skill of operational numerical weather prediction (NWP) models and their consensus is examined for the western North Pacific from 1992 to 2002. The TC track forecasting skill of the operational NWP models is steadily improving. For the western North Pacific, the typical 72-h model forecast error has decreased from roughly 600 km to roughly 400 km over the past ten years and is now comparable to the typical 48-h model forecast error of 10 years ago. In this study the performance of consensus aids that are formed whenever the TC track forecasts from at least two models from a specified pool of operational NWP models are available is examined. The 72-h consensus forecast error has decreased from about 550 km to roughly 310 km over the past ten years and is now better than the 48-h consensus forecast error of 10 years ago. For 2002, the 72-h forecast errors for a consensus computed from a specified pool of two, five, seven, and eight models were 357, 342, 329, and 309 km, respectively. The consensus forecast availability is defined as the percent of the time that consensus forecasts were available to the forecaster when he/she was required to make a TC forecast. While the addition of models to the consensus has a modest impact on forecast skill, it has a more marked impact on consensus forecast availability. The forecast availabilities for 72-h consensus forecasts computed from a pool of two, five, seven, and eight models were 84%, 89%, 92%, and 97%, respectively.

Full access
John A. Knaff, Mark DeMaria, Charles R. Sampson, and James M. Gross

Abstract

Tropical cyclone track forecasting has improved recently to the point at which extending the official forecasts of both track and intensity to 5 days is being considered at the National Hurricane Center and the Joint Typhoon Warning Center. Current verification procedures at both of these operational centers utilize a suite of control models, derived from the “climatology” and “persistence” techniques, that make forecasts out to 3 days. To evaluate and verify 5-day forecasts, the current suite of control forecasts needs to be redeveloped to extend the forecasts from 72 to 120 h. This paper describes the development of 5-day tropical cyclone intensity forecast models derived from climatology and persistence for the Atlantic, the eastern North Pacific, and the western North Pacific Oceans. Results using independent input data show that these new models possess similar error and bias characteristics when compared with their predecessors in the North Atlantic and eastern North Pacific but that the west Pacific model shows a statistically significant improvement when compared with its forerunner. Errors associated with these tropical cyclone intensity forecast models are also shown to level off beyond 3 days in all of the basins studied.

Full access
John A. Knaff, Charles R. Sampson, Mark DeMaria, Timothy P. Marchok, James M. Gross, and Colin J. McAdie

Abstract

An operational model used to predict tropical cyclone wind structure in terms of significant wind radii (i.e., 34-, 50-, and 64-kt wind radii, where 1 kt = 0.52 m s−1) at the National Oceanic and Atmospheric Administration/National Hurricane Center (NHC) and the Department of Defense/Joint Typhoon Warning Center (JTWC) is described. The statistical-parametric model employs aspects of climatology and persistence to forecast tropical cyclone wind radii through 5 days. Separate versions of the model are created for the Atlantic, east Pacific, and western North Pacific by statistically fitting a modified Rankine vortex, which is generalized to allow wavenumber-1 asymmetries, to observed values of tropical cyclone wind radii as reported by NHC and JTWC. Descriptions of the developmental data and methods used to formulate the model are given. A 2-yr verification and comparison with operational forecasts and an independently developed wind radii forecast method that also employs climatology and persistence suggests that the statistical-parametric model does a good job of forecasting wind radii. The statistical-parametric model also provides reliable operational forecasts that serve as a baseline for evaluating the skill of operational forecasts and other wind radii forecast methods in these tropical cyclone basins.

Full access
Christopher W. Landsea, James L. Franklin, Colin J. McAdie, John L. Beven II, James M. Gross, Brian R. Jarvinen, Richard J. Pasch, Edward N. Rappaport, Jason P. Dunion, and Peter P. Dodge

Hurricane Andrew of 1992 caused unprecedented economic devastation along its path through the Bahamas, southeastern Florida, and Louisiana. Damage in the United States was estimated to be $26 billion (in 1992 dollars), making Andrew one of the most expensive natural disasters in U.S. history. This hurricane struck southeastern Florida with maximum 1-min surface winds estimated in a 1992 poststorm analysis at 125 kt (64 m s−1). This original assessment was primarily based on an adjustment of aircraft reconnaissance flight-level winds to the surface.

Based on recent advancements in the understanding of the eyewall wind structure of major hurricanes, the official intensity of Andrew was adjusted upward for five days during its track across the Atlantic Ocean and Gulf of Mexico by the National Hurricane Center Best Track Change Committee. In particular, Andrew is now assessed by the National Hurricane Center to be a Saffir–Simpson Hurricane Scale category-5 hurricane (the highest intensity category possible) at its landfall in southeastern Florida, with maximum 1-min winds of 145 kt (75 m s−1). This makes Andrew only the third category-5 hurricane to strike the United States since at least 1900. Implications for how this change impacts society's planning for such extreme events are discussed.

Full access
Andreas Schäfler, George Craig, Heini Wernli, Philippe Arbogast, James D. Doyle, Ron McTaggart-Cowan, John Methven, Gwendal Rivière, Felix Ament, Maxi Boettcher, Martina Bramberger, Quitterie Cazenave, Richard Cotton, Susanne Crewell, Julien Delanoë, Andreas Dörnbrack, André Ehrlich, Florian Ewald, Andreas Fix, Christian M. Grams, Suzanne L. Gray, Hans Grob, Silke Groß, Martin Hagen, Ben Harvey, Lutz Hirsch, Marek Jacob, Tobias Kölling, Heike Konow, Christian Lemmerz, Oliver Lux, Linus Magnusson, Bernhard Mayer, Mario Mech, Richard Moore, Jacques Pelon, Julian Quinting, Stephan Rahm, Markus Rapp, Marc Rautenhaus, Oliver Reitebuch, Carolyn A. Reynolds, Harald Sodemann, Thomas Spengler, Geraint Vaughan, Manfred Wendisch, Martin Wirth, Benjamin Witschas, Kevin Wolf, and Tobias Zinner

Abstract

The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.

Open access