A quick response to concerns over GOM SSTs

May 8, 2006

Brendan Loy had a post this evening on a graphic that has been making the rounds depicting seemingly boiling Sea Surface Temperatures in the Gulf of Mexico. I don't have time for a lengthy response, but given the treatment of it, I feel obliged to give some kind of response now.

A couple of brief points…
– SSTs can be volatile on a daily basis

The image on the left shows the 3 day average on April 28, 2006 (the same image as in Brendan's post). The image on the right is a 3 day average from May 2, 2006.

Because of this it is more useful to look at at a longer term average and compare it to a long term norm. On the left is the global departure from normal. On the right is the same data zoomed in to the Gulf of Mexico (created by following these instructions.

While there is a localized area of abover average temperatures, most of the Gulf was at an average. Also note that such anomalies aren't that anomalous. Below is the same data for April 2002.


– Across the basin, heat potential is lower than it was at this time last year

Image on the left is Tropical Cyclone Heat Potential as of May 4, 2005. Image on the right is TCHP for same day, 2006. While TCHP is subtley higher in the GOM, it is markedly lower elsewhere, especially in the Carribean.

LATER: Brendan correctly jigged me in his comment. The scales of the two SST images are different. Clicking between the two now it's bloody obvious as the area of warmest water on the southern Cuba coast is identical in both images. But what is obvious at 1:40 AM isn't so obvious after 4 AM… sigh. Thanks to my Navy certified lack of normal color perception I won't attempt to make further comparisions, but any differences but they are probably less than a degree, not the oh three to four degrees that I was imagining (Celsius even! I really scare myself sometimes)…. anyhow, thanks Brendan for setting me straight on that.

LATER YET: An easier way to look at the difference between 2006 and 2005 April SSTs using this nifty tool (and note scales are different between the two images although they do convey the same data in the GOM)…



One Response to “A quick response to concerns over GOM SSTs”

  1. Brendan Loy Says:

    Charles, I don’t often have occasion to correct you, as you’re way more knowledgeable than me about this stuff… but for once, just this once, I’m right and you’re wrong! 🙂 Look at the SCALE on those two images, April and May, that you put side-by-side. The difference in colors has nothing to do with temperature and everything to do with the scale changing on May 1 in 2006 (but not in 2005 – presumably because the temps were lower so they didn’t need to change it).

    That said, I do appreciate your insight about variability of these things, and the other measures we should be looking at. I will probably post something about this later. But wanted to give you a heads up about the scale. I would have gotten confused about that, too, if the guy who tipped me off to the maps in the first place hadn’t pointed it out.

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