Saturday, June 23, 2012

Tropical Storm Debby Forms in the Gulf... Now What?

Above is a recent visible satellite image showing the center of Tropical Storm Debby (circled in yellow). At 4pm CDT, the center of the storm was located about 220 miles South of the mouth of the Mississippi River, and was drifting slowly Northward.

An Air Force Hurricane Hunter aircraft found a maximum surface wind of 50 mph in the Northeast quadrant of the storm this afternoon, prompting the National Hurricane Center (NHC) to declare the system Tropical Storm Debby. On a trivial aside, this is the first time in the history of the Atlantic basin that a 4th named storm has developed during the month of June.

As I mentioned in a facebook post earlier this afternoon, the declaration that this system is Tropical Storm Debby is the easy part.  The hard part is figuring out where she'll go next...

To give you an idea as to just how much of a challenge forecasters face with this one, take a look at the composite map below, which shows the various solutions of the "top" computer forecast models over the next 5 days:

We have an Easterly track, a Westerly track, a continued Northerly track, and almost everything in between.  That's enough to make even the most experienced forecaster pull his or her hair out.  So, I would advise you at this point to take any forecast track of Debby with a grain of salt.  For reasons I will attempt to explain below, it will be at least this time tomorrow before any reasonable level of certainty can be expressed in this situation, and that might even be a stretch as well...

The bottom line - at this point - is that if you live along the U.S. Gulf Coast, you will want to keep a close eye on the latest information concerning Debby over the upcoming days.

Getting back to the more recent developments and trends... Overnight last night and into the pre-dawn hours this morning, the center of Debby that we were observing yesterday dissipated and was replaced by the new center that we now see on the satellite image at the top of the post.  The "replacement" of the center of a storm is not uncommon, particularly during the infancy and mature stages of the system.  In this case, however, the replacement may prove to be very significant.

Why, you ask?  The new center is quite a bit further West than the one we were observing yesterday.  It could turn out to be just far enough to the West to prevent the system from being drawn up into the trough of low pressure that is forming in the Eastern third of the U.S. (the same trough that it  appeared would eventually cause the system to turn more toward Florida at about this time yesterday).

If the system fails to be drawn into the trough, it would not likely turn toward the East or Northeast.  That would leave two options:  a continued Northward movement toward the central Gulf Coast, or a Westward turn, toward the western Gulf Coast.

By this time tomorrow, we should have seen a turn toward the East or Northeast if this is going to take place.  If it does not, all bets are off, and folks from the central through western Gulf Coast will be under the gun.

The National Hurricane Center is currently siding with the European forecast models, and calling for a Westward turn and eventual track toward the Texas coast by mid-week next week:

While such a move is possible, I'm not completely sold on it at this point.

Check back tomorrow for more...and remember to watch for that Easterly or Northeasterly wobble between now and then.  If such a move happens, I think the Easterly track solution will win this one (as a disclaimer, I've been favoring that particular track all along).

For additional details including the latest satellite and radar imagery and loops of this system, please visit this dedicated page on our sister site,

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