There are officially only 16 more days left to the 2008 hurricane season, but it appears unlikely that we’ll see another named storm this year.  Certainly, the Gulf of Mexico has shut down as far as any tropical threat.  Strong wind shear has prevailed across the Gulf for several weeks, and that shear will be increasing as the weather pattern across the U.S. changes to one resembling winter rather than fall.

Long-range models continue to forecast a southward dip in the jet stream over the coming week, bringing a series of very cold Canadian fronts southward to the Gulf of Mexico.  The first of these fronts arrives tonight.  These early-season cold fronts can produce quite strong winds offshore.   When cold air blows across the still very warm Gulf of Mexico, the wind can accelerate to speeds greater than tropical storm force with gusts approaching hurricane force.  Tonight’s front won’t produce hurricane force wind gusts, most likely, but it should produce wind speeds offshore above tropical storm force on Saturday.

Many years ago, I learned of a general rule of thumb to predict how strong the winds will get across the northwest Gulf following a frontal passage.   The key is to look at the high pressure center behind the front.    Air pressure can be measured in inches of mercury or millibars.  I know that the more meteorologically-correct term now is “hectopascals”, but I’ll never be converted.  To estimate how strong the sustained winds will be offshore, look at the strength of the high pressure behind the front.  If it’s, say, 1045 millibars, then just remove the 10 from the front and the wind offshore will approach 45 kts.  This method actually works quite well, particularly with these early-season fronts.

With tonight’s front, the high pressure behind it will be 1029-1033 millibars,so we should expect winds offshore in the 30 knot range on Saturday, with gusts as high as 40-45 knots.  Along the east coast of Mexico down to the Bay of Campeche, the winds will be even stronger than that, as the wind tends to accelerate southward along the coast of Mexico.  The blast of cool air and rough seas won’t last long  By Sunday morning, the high center will push out into the Gulf and wind and seas will quiet down quite quickly.

In the long range, both the American GFS model and the European (ECMWF) model have been forecasting a major pattern change across the U.S. which could bring some very cold air southward to the Gulf of Mexico as early as next weekend, around the 21-23 of November.  However, I’m seeing way too much variability from one model run to another to have much confidence in the timing of any big cold air push across the Gulf a week or more from now.   But there is some very, very cold air building in northwest Canada and Alaska now.  At some point over the next 2-3 weeks I do expect some of this cold air to break loose and race southward toward the Gulf.  Such a cold front could produce winds offshore to 40-50 knots, along with very rough seas.

So it’s time to stop looking to the south for the rough weather across the Gulf.  The rough weather will be coming from the north from here on out.

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