16 TOR BERGERON 
of Georgia, it was still quite vigorous. At its cen- 
ter the sea-temperature was about +26°C, and 
the temperature of the air that was rising from 
the sea-surface was probably very near this 
yalue, corresponding to a great amount of la- 
bility energy. Twenty-four hours later the hur- 
ricane center had entered land and began to 
fill rapidly. This effect is generally ascribed to 
friction. According to my view, however, the 
main reason for the filling is the precipitative 
cooling of the air over land within the friction 
layer, that is, of the only air that can flow into 
the hurricane and form an updraft. That air 
was in this case cooled by the rain itself down to 
+19°C near the center, which implies that the 
lability energy had become negative. That is 
like putting a very powerful brake on the whole 
mechanism, similar to braking a motor car by 
the engine. 
if | =. , 
19. 1X. 1947 ie | 
ooMesT | 
This is a precipitation conference, and the 
hurricanes were mentioned mainly because they 
also represent a very important precipitation 
problem. In fact, a lot of the hurricane damage 
is done by precipitation. Figure 9 displays the 
distribution of the precipitation intensity within 
the major hurricane of September 1947 when 
passing Florida. It is, of course, analyzed keep- 
ing the idea in mind that it should have an ‘eye’ 
without precipitation, and that the region of 
intense precipitation should form a ring; evi- 
dently it does. The several small maps show how 
the precipitation area moves across Florida, and 
also how it widens during this passage. Gradually 
it gets two eyes, or even multiple eyes, and parts 
where the precipitation in the ring is much more 
intense. Instead of a complete rmg of maximum 
rainfall all sorts or irregularities occur, presuma- 
bly because the precipitation area lies over land 
DEGENID = =s \aj}-— | 0 Isohyetol SOuoY, 
*Noran 2 os ‘ - 
= Rain, but amount unknown 4 mall 10 = | ee 
A = 23N h | P T o 5 23N— 
HOeGE Sin 8S" es O3s"EST | astw TB. 1950 aecil swe | 
Mii, 
Y 
GH, 
Fic. 10—Maps of hourly rainfall from the same hurricane as in Fig. 9, developing spiral arms of pre- 
cipitation 
