Search Results

You are looking at 1 - 2 of 2 items for :

  • Author or Editor: R. D. Hart x
  • Monthly Weather Review x
  • Refine by Access: All Content x
Clear All Modify Search
H. L. Johnson Jr.
,
R. D. Hart
,
M. A. Lind
,
R. E. Powell
, and
J. L. Stanford

Abstract

Thunderstorm radio noise measurements at several frequencies in the range 0.01–74 MHz have been made with specially designed remote recording stations in Iowa. The data were recorded during the spring and summer of 1974 when a series of severe storm systems produced a great number of large hail and tornado reports in Iowa. Computer analyses were made of nearly a billion bits of data, corresponding to 170 h of real-time recordings. Careful compilations of surface severe weather reports, hail damage information from insurance companies, and studies on the Des Moines WSR-57 radar echoes were compared with the analyzed radio noise data. The results include the following:

1) In agreement with earlier work, large‐amplitude radio noise impulse rates were found to he generally good indicators of thunderstorm severity. Although the majority of the radio energy radiated from major lightning strokes occurs in the 0.01 MHz range, this frequency was found to be a poor indicator of storm severity; the higher frequencies (megahertz range) were considerably better. The character of the noise appears similar at 2.5 and 74 MHz.

2) In at least five cases, tornadic events correlated in time with radio noise count rate peaks. One funnel cloud was reported equidistant at 60 km from two recording stations and coincident with count rate peaks at both stations, lending credence to the idea that the peak was associated with the storm occurrence, rather than with corona or other local effects.

3) No unusual radio noise was recorded during the lifetime of a small, verified tornado at 19 km range. In addition, the count rates for its parent thunderstorm would not have indicated severity.

In spite of inherent atmospheric variableness, the radio noise technique is a useful complementary indicator of storm severity.

Full access
Clark Evans
,
Kimberly M. Wood
,
Sim D. Aberson
,
Heather M. Archambault
,
Shawn M. Milrad
,
Lance F. Bosart
,
Kristen L. Corbosiero
,
Christopher A. Davis
,
João R. Dias Pinto
,
James Doyle
,
Chris Fogarty
,
Thomas J. Galarneau Jr.
,
Christian M. Grams
,
Kyle S. Griffin
,
John Gyakum
,
Robert E. Hart
,
Naoko Kitabatake
,
Hilke S. Lentink
,
Ron McTaggart-Cowan
,
William Perrie
,
Julian F. D. Quinting
,
Carolyn A. Reynolds
,
Michael Riemer
,
Elizabeth A. Ritchie
,
Yujuan Sun
, and
Fuqing Zhang

Abstract

Extratropical transition (ET) is the process by which a tropical cyclone, upon encountering a baroclinic environment and reduced sea surface temperature at higher latitudes, transforms into an extratropical cyclone. This process is influenced by, and influences, phenomena from the tropics to the midlatitudes and from the meso- to the planetary scales to extents that vary between individual events. Motivated in part by recent high-impact and/or extensively observed events such as North Atlantic Hurricane Sandy in 2012 and western North Pacific Typhoon Sinlaku in 2008, this review details advances in understanding and predicting ET since the publication of an earlier review in 2003. Methods for diagnosing ET in reanalysis, observational, and model-forecast datasets are discussed. New climatologies for the eastern North Pacific and southwest Indian Oceans are presented alongside updates to western North Pacific and North Atlantic Ocean climatologies. Advances in understanding and, in some cases, modeling the direct impacts of ET-related wind, waves, and precipitation are noted. Improved understanding of structural evolution throughout the transformation stage of ET fostered in large part by novel aircraft observations collected in several recent ET events is highlighted. Predictive skill for operational and numerical model ET-related forecasts is discussed along with environmental factors influencing posttransition cyclone structure and evolution. Operational ET forecast and analysis practices and challenges are detailed. In particular, some challenges of effective hazard communication for the evolving threats posed by a tropical cyclone during and after transition are introduced. This review concludes with recommendations for future work to further improve understanding, forecasts, and hazard communication.

Open access