Katia, Maria, and Nate keeping the basin active

Hurricane Katia has not changed too much since my update this morning, but I wanted to highlight once again the buoy that it is going  to pass over.  It's a special occasion when a hurricane eye manages to pass directly over a tiny stationary buoy in the middle of the ocean.  And today, Buoy 41048 is that lucky one.  As of this writing, the buoy is 110 nautical miles NW of Katia's eye, and Katia is moving NW at 9kts (and a knot is a nautical mile per hour)... so that's about 12 hours until closest approach.  Already though, huge waves over 30' tall are rocking the buoy ("significant wave height" is defined as the average of the highest 1/3 of the waves), and wind gusts up to 54kts have been measured.  You can view current data and additional plots at http://www.ndbc.noaa.gov/station_page.php?station=41048

Maria is still a tropical storm, but I hunted through some historical tracks that matched Maria in terms of location, month, and intensity.  One very noteworthy result stuck out: Hurricane Hugo.  The track plot below shows Hugo's track, and the gray circle is a 100-mile circle around Maria's current location.  Hugo was located where Maria is now on September 13, 1989.  This of course doesn't mean that Maria will be a Hugo, but it's certainly worth paying close  attention to history.

Last but not least, the disturbance in the Bay of Campeche was upgraded to Tropical Storm Nate, the 14th named storm of the season, based on aircraft reconnaissance.  The intensity is 40kts and 1004mb, and it's basically stationary.  In such weak steering flow, a track forecast is extremely difficult to make, for both models and humans.  Models are all over the place with it, and justifiably so... but the official NHC forecast keeps it stationary for another 2 days, then ever so slowly tracks it northwest toward Mexico.  All of this time over the warm Gulf of Mexico should allow for some intensification, probably becoming the season's 3rd hurricane by the weekend.


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Katia weakens, Maria forms

Katia continues to lose its organization in the face of increasing vertical shear.  At 15Z today, the intensity is down to 75kts, and the forecast is for a very gradual weakening and loss of tropical characteristics. It is going to pass over a buoy located near 32N 70W later today... you can view observations (wave height, wind, pressure, etc) at http://www.ndbc.noaa.gov/station_page.php?station=41048  The infrared image below shows Katia, then Bermuda is the yellow speck near 32N 65W, and the buoy I mentioned is shown by the red dot.

Shortly after I sent out yesterday's update, the easterly wave that was near 35W was upgraded to TD14.  Then 18 hours later (15Z today), it was upgraded to Tropical Storm Maria, the 13th named storm of the season.  Maria's estimated intensity is 45kts with a 1003mb central pressure.  It's located at 13N 42W (about 1300 miles east of the Lesser Antilles) and cruising westward at 20kts.  The environment that it's in is only marginal for intensification... the SST is a healthy 28C, but the vertical shear is 12kts and increasing.  So, it will probably just slowly strengthen over the next several days, while tracking WNW toward the northern Leeward Islands.  This is a storm to keep a very close eye on if you're on the US coast; though at this point it's too early to say if it's heading for the Gulf coast or the east coast.

The trailing end of a front extending from the northeast US through Florida and into the Gulf of Mexico has been showing signs of organization.  The front ends in the Bay of Campeche, and the pressures are dropping in the area... with this disturbance at approximately 1007mb.  The 06Z surface analysis shown below illustrates the position of the front, and the terminal Low in the Bay of Campeche.  Also note the Low in western VA/NC associated with the remnants of TS Lee.

The steering flow in this area is very weak, so it's not going anywhere in a hurry.  It's also surrounded by dry air, so even if it does make to a TD or TS, it shouldn't get much stronger.  If named, the next name on the list is Nate.

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Katia becomes season's 2nd major hurricane

The intensification trend I mentioned in Sunday's update did indeed continue, and on Monday at 21Z, Katia was upgraded to a Category 3 storm with 100kt sustained winds... then just six hours later, was upgraded again to a Category 4 storm with 115kt winds.   In the 18-hour period from 09Z on Monday through 03Z today, the pressure fell 26mb and the winds increased by 30kts.
As of 15Z today, the intensity is down a little to 105kts with a central pressure of 954mb.

The tiny yellow speck you see on that image near 32N 65W is Bermuda... and they now have a tropical storm watch in effect.  Models are now in excellent agreement on the track, and they indicate a recurvature by about 72W, safely off the US east coast, and safely west of Bermuda (though Bermuda could certainly feel some outer effects like tropical storm force winds and very large ocean swells).
The shear is also expected to increase again, and the mid-level relative humidity is quite low, so it appears that Katia will be on a steady weakening trend now until it ends up in the TC graveyard of the north central Atlantic.

The easterly wave that exited the African coast on Sep 2 (AL95) is now near 35W, or almost 1800 miles east of the Lesser Antilles.  It continues to show signs of organization, and will likely be upgraded to TD14 or even TS Maria within the next 24-48 hours.  The environment it's moving into isn't the best, so if it does develop, it should be slow to intensify for the next several days.  It is very far from land, but it will be something to keep a close eye on simply because of its location and potential track (the southeast US is about 11 days away).

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