chap1_035 - 16 CHAPTER 1 9 8 W eather Analysis TheTools of...

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Unformatted text preview: 16 CHAPTER 1 9 8 W eather Analysis: TheTools of theTrade 7 6 O I4 I LL 5 3 2 1 III 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 i n i ii 53 55 57 59 61 ii 63 65 67 69 Maximum Temperature (°F) FIGURE 1 .9 This histogram, or frequency distribution, shows the number of times that a particular daily maximum (high) temperature has been observed on January 8 in Philadelphia, PA, during the period 1874 to 2008. The "normal," or average high, on this date, is 39°F. give pause before you forecast a high (or low) tempera­ ture that's, say, 25°F above (or below) the average high for the date. Not that such large departures from climatology are impossible. They're just not a common occurrence. Starting the forecasting process for temperature with climatology tends to work better in summer than in win­ ter. That's because during summer, the relatively high angle of the sun and the infrequency of dramatic changes in air masses allow warm-season temperatures to be less variable, on balance, than their winter counterparts. Only on summer days when clouds and rain have the upper hand do high temperatures stray far below climatology. August 19, 2007 was such a day over a large swath from the Northern Plains across the Great Lakes into Pennsyl­ vania and New Jersey. A thick canopy of clouds (shown in Figure 1.10) and occasional rain set the stage for the FIGURE 1.10 A satellite image on the afternoon of August 19, 2007, with some high temperatures from that day superimposed. Beneath the shield of clouds stretching from the Northern Plains to the East Coast, high tempera­ tures remained well below average, setting more than 100 records for lowest daily maximum temperature. ...
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This note was uploaded on 08/11/2010 for the course METEO 003 taught by Professor Victoryanuzzi during the Spring '08 term at Penn State.

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