tharp_ridge.jpgOooh, exciting weather this morning. As already mentioned a tornado warning was in effect for about 15 minutes. No tornado was detected. The warning accompanied intense rain in upper Manhattan and the Bronx, leading to a flash flood warning. 1010 WINS is reporting scattered power outages and flooding across the area.

The reason for the storm activity is why Wednesday's forecasts for yesterday were all screwed up. Astute readers of Gothamist's Wednesday weather post will recall that we mentioned how the Weather Service, Weather Channel and AccuWeather all had three different forecasts for yesterday's weather. All three were wrong! At the time those forecasts were made all three forecasters had concluded that a relatively dry and weak cold front would sweep through town and pass out to sea. Instead, the front stalled out around Cape May. Humid air swept up over the frontal boundary and dumped on us yesterday afternoon and again this morning.

The stationary looks like it will remain stationary for a few days. We can expect occasional showers and thunderstorms for the entire weekend. The greatest chance for rain will be this evening and Sunday.

You may not know who Marie Tharp is but odds are you've seen her work in a classroom or textbook. Marie Tharp died earlier this week at the age of 86. She started working at Columbia University in the late-1940s, at a time when there were few women geologists. Based on new ocean soundings Tharp, and her colleague Bruce Heezen, began making maps of the sea floor and noticed something surprising. Not only were there enormous mountain ranges at the bottom of the sea, but rift valleys were located in the center of those ridges. Tharp realized that the presence of rift valleys meant the Atlantic Ocean basin was spreading –a radical idea at the time. A spreading ocean basin meant that Alfred Wegener's previously ridiculed idea of continental drift wasn't crazy but, in fact, true. With the acceptance of continental drift, and the development of the unifying theory of plate tectonics the study of the earth was revolutionized. Marie Tharp's maps played a key role in that revolution.

Map of the Mid-Atlantic ridge by Marie Tharp via Columbia University.