Much of the decline was due to a sharp drop in imports, almost a million barrels a day, because fog closed the Houston Ship Channel last week, said Jim Ritterbusch, president of Ritterbusch and Associates in Galena, Ill.

"That's basically what drew crude supplies lower," Ritterbusch said.

People need to also bear in mind that 'Days supply' is not the most useful concept, a la the idea that 'The world has 40 years supply of Oil at current rates of usage'. Currently the USA is at about 20 "days" supply of crude, excluding the Strategic stockpile. However, massive problems would be encountered long before this number reaches zero days.

And all the analysts who predicted only a 1.5 mb drop didn't know this? Or maybe the problem is they didn't know how much oil a ship holds or how many ships were held up.

In reality, I think it is hard to make the case that the fog is responsible for much more than a 1.5mb drop.

The fog had nothing to do with it. In fact more crude entered the Houston Ship Channel during the week of 8-15 December, which the 19 December TWIP is based than the previous week of 1-7 Dec. 12 December TWIP.

For example, I ran a spreadsheet on all the shuttle tankers and Aframax tankers that entered the ports of Texas City and Houston to come up with the astonishing numbers.