PICTURE OF THE MONTHGravity Waves Following Severe ThunderstormsCARL 0. ERICKSON and LINWOOD F. WHITNEY. JR.-Meteorological Satellite Laboratofy,National Environmental Satellite Service, NOAA, Hillcrest Heights, Md.Visible and infrared pictures (figs. 1, 2) from the Very over the Southern Great Plains. Picture times are identicalHigh Resolution Radiometer (VHRR) aboard the and are approximately 1010 CDT (1510 GMT) on May 22,NOAA 2 satellite both show the eastern half of the United 1973. A partial grid has been superimposed on the infraredStates after a night of severe thunderstorm activity view.FIQURE ].-View of the Eastern United Stat,es as seen through the visible channel of the Very High Resolution Radiometer aboard the NOAA #2 satellite (0.6-0.7pm). Picture time is approximately 1510 QMT, May 22, 1973.708 / Vol. 101, No. 9 / Monthly Weather ReviewOf particular interest is the wave-cloud formation at A,which extends from east-central Arkansas to northeasternTexas. Figure 3 is an enlargement of the visible view ofthe area. This cloud formation at A is believed to repre-sent southeastward-moving gravity waves initiated bythe earlier violent convection to the north and northwest.During the night of May 21 and the early morning ofMay 22, numerous severe thunderstorms were reportedfrom the five-state area of Texas, Arkansas, Oklahoma,Kansas, and Missouri, a few storms persisting until aft-ersunrise. Tornadoes also occurred over Kansas, Missouri,Iowa, and Arkansas. Cloud debris associated with theearlier convection is indicated by B.During and following that thunderstorm activity, anumber of surface observing stations in the area reportedeither the paqsage of a pressure jump or the occurrenceof markedly unsteady surface pressure. Over northeasternTexas and Arkansas, there were also a few reports in-dicating the existence of a traveling roll cloud and windshiftline during the 2-4 hr preceding picture t,ime. Figure 4gives the surface analysis for 1500 GMT-~O minutes priorto picture time. The analysis shows that a travelingsurface disturbance continued to exist in the form of apressure surge and meso-High. The trough line precedingthe meso-High is nearly coincident with the satellite-viewed wave clouds.Most of the wave-cloud formation appears to be atmiddle tropospheric levels. Both the relative brightnessof the formation in the infrared picture of figure 2 andthe conventional meteorological data in the area indicateFIGURE 2.-Same as figure 1, an infrared view through the water vapor window channel (10.5-12.5 pm).September 1973 / Erickson and Whitney / 709FIGURE 3.-Enlarged view of figure 1 showing wave-cloud area.710 / Vol. 101, No. 9 / Monthly Weather ReviewSeptember 1973 f Erickson and Whitney f 711
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