Hawaiian Rainfall Estimates — Stidd 
265 
Fig. 1. Correlation field pattern of mean monthly 
700-millibar height versus monthly rainfall averaged 
for four stations in the vicinity of Hilo. Winter months 
(November through April); total of 102 cases. 
well-defined maxima or minima. Little, if any, 
smoothing is necessary in drawing isopleths 
to the plotted data. Although space does not 
allow the data to be shown on these figures, 
the previous paper (Stidd, 1954, fig. 6) con- 
tains the data and demonstrates how little 
smoothing is heeded. An example is given 
in Figure 1 . Here the rainfall parameter is the 
series of monthly rainfall amounts averaged 
for four stations in the immediate vicinity of 
Hilo (see map. Fig. 2). Figure 1 shows that 
increased pressure north of the islands favors 
rain at Hilo, and probably indicates that 
heavy rains are associated with stronger trade- 
wind gradients and that Hilo rainfall is very 
sensitive to changes in the trade-wind flow. 
The actual pattern of Figure 1 is suggestive 
of the anomalous flow pattern which is asso- 
ciated with heavy rainfall at Hilo. The extent 
to which this analogy is sound has been de- 
scribed in detail in the previous study (Stidd, 
1954), which showed that the regression co- 
efficients of rainfall on pressure fulfill the 
geostrophic equation in the same manner as 
the pressures themselves. Furthermore, if 
there were no spatial variation in the standard 
deviations of pressure, the correlation co- 
efficients would, themselves, fulfill this equa- 
Fig. 2. Map showing location of five groups of rainfall stations in Hawaii. Terrain contours are shown at 
2,000-foot intervals. 
