APPENDIX 3
Weather Analysis
The weather analysis for August 31, 1940, prepared by meteorologists is as follows: A weak occluded low pressure area was located over the Lake Superior region, with its principal front occluded at the center of the system, becoming a cold front of weak intensity extending from the central portion of Lake Erie south-southwestward across Ohio, where it became too diffuse to remain of any importance. There were indications of a cold front of more active nature running from the center of the depression south and southwestward across Lake Michigan to the Missouri-Iowa state line, where it also became too diffuse to be carried any further. East of Illinois the pressure gradient was comparatively flat. An anti-cyclonic circulation prevailed along the Coast north of the Virginia Capes produced by a high pressure system situated some distance off shore in the Cape Cod area. The very sluggish circulation resulting from this pressure distribution and the saturated state of the lower layer was such that a widespread low cloud deck, with considerable fog, was reported in all sections of the area extending from the northern Smoky Mountains northeastward to the central St. Lawrence Valley.
The meteorologists stated that while the fronts did not exert a dominating influence over weather conditions in any section southeast of the Lakes, the approach of any front, no matter how weak, would contribute to the vertical lifting of an air mass which was already being acted upon by other forces such as convergence, aerographic lift, etc. There was no temperature differential in the horizontal between Pittsburgh and Washington.
