Referring again to the map of January 9, 1886, and following the course of the isotherms, or temperature lines, we see that abnormally cold weather prevailed over the Middle Western and Southern States. The isotherm of zero dips far south across northern Texas, Arkansas, Mississippi, Alabama, and Tennessee; while in the upper Mississippi and Missouri Valleys the temperatures were from 20 to 40 degrees below zero. These regions were, in fact, in the grip of a severe "cold wave," which had entered the country a day or two before, preceding the anticyclone here seen central north of Dakota. Cold northwesterly winds were sweeping over the Great Plains, and as far south as the Gulf.
HOARFROST
Minute crystals of ice deposited from the air. Under a magnifying-glass they show a variety of beautiful forms
The same map shows typical weather accompanying the cyclone central on the Atlantic coast. From the seaboard west to the Mississippi Valley rain or snow had fallen within the previous twenty-four hours (indicated by shading), and snow (indicated by S) was falling at the moment of observation at a majority of stations within this area. Elsewhere in the same region the weather was cloudy.
The foregoing remarks indicate in a general way the significance of the weather map and the principles upon which scientific weather predictions are based. The endless procession of highs and lows brings to any place on the map constant alternations of heat and cold, storm and sunshine. The forecaster watches the procession, and draws his inferences as to what will happen in this or that part of the country within the next day or two (forty-eight hours is about the limit of his outlook). "Long-range" forecasting is still a thing of the remote future. Forecasts for a week in advance, are, indeed made by the Weather Bureau with the aid of reports from a chain of stations extending round the globe, but these are in very general terms.
In January, 1914, the Bureau began publishing a "daily weather map of the Northern Hemisphere." This publication is, at present, suspended on account of the war.
SOME WEATHER MISCELLANIES
