02 October 2012

As Nadine fizzles, Oscar may be forming

Stubborn Nadine is still a strong tropical storm with 55kt sustained winds, and is expected to remain a tropical system for another couple of days before finally getting obliterated by a mid-latitude trough.  It has been on the books for 20 days... in yesterday's post I highlighted the longevity record holders for reference. 

One thing a storm does when it sits over the same area for a long time is upwell colder water from the depths of the ocean.  In some places, the surface water might be warm, but that warm water doesn't extend very deep, making it easy for a storm to mix it out.  Nadine has been in the vicinity of the Azores for a couple weeks now, and has generated quite a patch of anomalously cold water as shown here.  A 2-degree Celsius anomaly is pretty significant, and greatly reduces the potential intensity of a storm.

As you can see in the satellite image below, it is a respectable tropical cyclone with an eye, indicating that it remains well-organized... the Azores islands are the yellow outlines on the right side of the image.

Now, there's another disturbance getting organized.  It's an easterly wave that left the African coast back on September 28, and is now centered near 12N 39W (about 850 miles west of the Cape Verde islands) with a 1009mb central pressure.  It appears to be on its way to becoming Tropical Depression 15 and then Tropical Storm Oscar this week.

The majority of models do intensify this to a hurricane, but also agree on a sharp turn to the north very soon, keeping it far away from land.  Oh, and if you're in the Azores, you might get another tropical visitor this weekend... as if the current guest hasn't already overstayed its welcome.

Assuming it gets named this week, it will be the 15th named storm of the season.  That is impressive, but far from a record.  In 2005 and 2011, we saw the 15th named storm form on September 7, and then in 1936, the same thing on September 19.  However, only about 8% of years ever reach the 15th named storm, so it's still an outlier in that regard.

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