The weather map fails to indicate what shifts of direction and changes in velocity are likely to occur. The forecaster tries to anticipate these, but he bases his conclusions chiefly upon an expected movement of the low area; using the accumulated records of the paths of past storms. But each storm is in reality a law unto itself; and while we know something of the relations between pressure and flow of the air; as yet we know very little about the relations of wind and weather. The problem is complicated by the behavior of the load of water vapor.

Fig. 5. Euros—The Southeast Wind

The Chief Forecaster of one of the great national weather services recently wrote:

"Despite the fact that maps have now been drawn day by day for over half a century, we may safely say that no two maps have been identical."

It is perhaps unfortunate that so much attention has been given to the cyclone or depression or LOW, and comparatively little to the HIGH or anticyclone. For we are now beginning to understand that while there may seem at first to be nothing specially noteworthy about a mass of air where the pressure varies from 1020 to 1040 kilobars, that is, 2 to 4 per cent above a standard atmosphere, with isobars irregularly curved and feeble surface winds, yet the anticyclone is more important than the cyclone in determining weather sequence; for the progressive motion of the cyclone depends largely upon the strength of the anticyclone.