﻿12 EQUIPMENT AND WORK OF AN AERO-PHYSICAL OBSERVATORY. 



If p = pressure reduced and corrected for diurnal variation, 



C= twelve-hour change, 



V = velocity of wind in miles per hour, 



r = distance from the centre of cyclone, 

 dp 

 'dt 



rate of fall of pressure per hour, 



d/T) 



— ^= gradient or fall per mile toward the centre, 



d^ 



dt rate of fall dr 



dp gradient 



dt 



rate of approach, 



as a first approximation for the time of arrival, divide the distance by 

 the rate of approach. These values are given in column "A," in the 

 table below. 



A = dr or 

 'df 



rdt 

 dr 



f=l-^(dr~dt). 



It must be pointed out that in a calculation of this kind we are re- 

 stricted to the use of such data as are available for the forecaster at a 

 particular time. We think that the following, which could have been 

 obtained at the times indicated, would have been serviceable in forecast- 

 ing this storm, and particularly the values which are underscored as 

 indicating the probable path and duration of the storm : 



Approach of Storm of August 25, 26, 27, 28, 1893. 



Date. 



Station. 



t 

 p 



C 



V 



r 



dp 

 dt 



dv 

 dr 



'a 



f 



Aug. 26, 1893, 

 8 a. m. 



Aug. 27, 1893, 

 8 a. m. 



Aug. 28, 1893, 

 8 a. m. 



JTitusville. .. 



( Jupiter 



f Savannah 



J Charleston .. . . 

 1 Jacksonville . . 



iTitusville 



r Lynch burg... . 



J Raleigh 



1 Charlotte 



I Augusta 



29.90 

 29.80 

 29.78 

 29.84 

 29.62 

 29.34 

 29.84 

 29.64 

 29.30 

 28.96 



—.06 

 -.10 

 —.16 

 -.12 

 —.24 

 —.38 

 -.12 

 —.26 

 —.54 



22 

 24 

 20 

 24 

 20 

 40 

 8 

 22 

 24 

 26 



250 

 160 

 200 

 230 

 120 



-80 

 230 

 220 

 100 



-20 



.004 



.008 



.012 



.01 



.02 



.036 



.01 



.03 



.014 



.06 



.001 

 .014 

 .002 

 .002 

 .003 

 .003 

 .002 

 .002 

 .003 

 .01 



30 

 24 

 30 

 50 

 20 



—8 



70 



25 



6 



-1 



.20 

 .15 

 .15 

 .20 

 .17 

 .30 

 .25 

 .12 

 .8 



