Search Results

You are looking at 51 - 60 of 834 items for :

  • Weather and Forecasting x
  • All content x
Clear All
S. F. Corfidi, J. H. Meritt, and J. M. Fritsch

the convective systems is well correlated to the mean flow in the cloud layer. Similarly, the propagation component is shown to be directly proportional ( but opposite in sign) and well correlated to the speed and direction of the low-level jet. Correlation coefficients between forecast and observed values for the speed and direction of the mesobeta-scale convective elements are 0.80 and 0.78, re- spectively. Mean absolute errors of the speed and direction are 2.0 m s0 1 and 177. These errors

Full access
Philip N. Schumacher and Joshua M. Boustead

are displayed on time–height cross sections with boldface numbers. In a few instances, the rotational velocity could not be determined from the available data, so BD (for bad data) was placed on the time–height cross section. 3. Environmental discussion The 250-hPa 0000 UTC 25 June analysis indicated a 45 m s −1 jet from the central Rocky Mountains to the northern plains ( Fig. 2a ). The region from eastern South Dakota into central and southern Minnesota was located in the exit region of the jet

Full access
Paul J. Neiman and M. A. Shapiro

(Manuscript received 13 September 1988, in final form 19 January 1989)ABSTRACT Vertical wind shears measured by the Plattcville, Colorado wind profiler were used in conjunction with thegeostrophic thermal wind equation to retrieve the horizontal thermal gradients and associated advections for acase involving an upper-tropospheric jet stream/frontal zone on 23-24 November 1986. The profiler-retrievedthermal gradients and adveclions and the/r evolutions compared favorably w/th those observed by the

Full access
Rebecca E. Morss and F. Martin Ralph

and associated hazards may help alleviate these negative effects. However, accurately forecasting these events remains challenging, due in part to the complex coastal topography and the limited observations available over the Pacific Ocean (e.g., Ralph et al. 1999 , 2003 ; McMurdie and Mass 2004 ). To address these issues, the California Land-falling Jets (CALJET) and Pacific Land-falling Jets (PACJET-2001 1 ) experiments were conducted during the winters of 1997/98 and 2000/01, respectively

Full access
Steven E. Koch, Randolph Ware, Hongli Jiang, and Yuanfu Xie

only EF3-rated tornado ever recorded near the Front Range with such a track. S10 discussed how this event included a southerly upper-level jet streak exceeding 40 m s −1 , a pronounced low pressure center located just east of Denver, a strengthening warm front to the east-northeast of the surface cyclone that had advanced northward the previous night in response to the approach of the upper-level trough, and a dryline that developed in late morning to its south. Dry, gusty, southerly winds

Full access
Kristian Horvath, Stjepan Ivatek-Šahdan, Branka Ivančan-Picek, and Vanda Grubišić

-level data The observed flow structure derived from the flight-level data from a coast-parallel track of the National Center for Atmospheric Research (NCAR) Electra at 1500–1600 UTC 7 November 1999 is compared here with the results from the ALADIN/HR simulation. Figures 4a and 4b show the magnitude of the 10-min wind speed component normal to the flight track AX (cf. Fig. 1 ) at 330 and 660 m MSL as a function of latitude. 2 The main feature in these diagrams is a strong and relatively wide NE jet

Full access
Robert A. Weisman, Keith G. McGregor, David R. Novak, Jason L. Selzler, Michael L. Spinar, Blaine C. Thomas, and Philip N. Schumacher

individual storm or precipitation maximum get lost when they are averaged with many other cases. Even if some mesoscale features such as jet streaks, deformation zones, and fronts do recur among several cases, their strength can be reduced or even lost because of the compositing process. This loss is especially likely if mesoscale features appear in different locations relative to the cyclone or inverted trough during individual cases. Such a smearing effect has been documented by several researchers (e

Full access
Xiaohui Shi, Xiangde Xu, and Chungu Lu

Oscillation (NPO; Wu and Wang 2002 ; Gong and Wang 2003 ; Gong et al. 2004 ; Chen and Kang 2006 ), El Niño and the Southern Oscillation (ENSO; Tao and Zhang 1998 ; Gong and Wang 1999 ; He et al. 2007 ), the Siberian high ( Qian et al. 2001 ; Gong et al. 2002 ), the western Pacific teleconnection ( Y. Li et al. 2007 ), and the East Asian jet stream ( Yang et al. 2002 ; Mao et al. 2007 ); all of which may have influenced China’s winter precipitation and temperature to some extent. On the other hand

Full access
Christopher S. Velden and Graham A. Mills

track of the low and compares this with a climatological study of significant latespring cyclone tracks over this region for the,, past 20years. The period of study is from 0000 UTC 29 November to 0000 UTC 2 December 1987, which coversthe cyclone's passage across the continent, its rapidintensification stage, and the subsequent adverseweather effects over southeastern Australia. A series ofassimilated analyses are utilized to diagnose the respective roles of jet streak circulations and

Full access
Helen J. Reid

as a ridge of high pressure follows the cold frontal system but precipitation is not usual. A southerly buster is generated when a cold front is blocked and experiences anticyclonic deformation near the southern parts of the Great Dividing Range in Victoria ( McInnes 1993 ). The surge of air propagates northward as a coastally trapped orographic jet up the east coast of Australia, the duration usually being about 24 h ( Baines 1980 ), from the time the cold front reaches the Great Dividing Range

Full access