29 June 2005

TD2 upgraded to Bret, hits Mexico...

Just two hours after being classified as TD2, it was upgraded to 
TS Bret.  Despite being very close to land, the observed sustained 
winds as well as the convective banding pattern certainly warranted 
this upgrade.  The last time we witnessed two named storms in June was 
1986 (Andrew and Bonnie)!  However, unlike 1986, BOTH of this year's 
storms made landfall.

Bret made landfall at ~12Z today as a 35kt tropical storm.  Radar 
images from Tampico showed a weak eye/eyewall structure at landfall... 
remarkable organization for a minimal tropical storm.  The center of 
Bret passed over Tuxpan, about 100 miles south of Tampico.  It is now 
moving inland and weakening rapidly.
Please visit my tropical Atlantic headquarters.

28 June 2005

TD2 forms very near Mexican coast...

At 22Z today, an area of disturbed weather was upgraded to Tropical 
Depression 2 just 50 miles off the coast.  This will be very 
short-lived, as it's currently heading toward land (about 50 miles 
away).  Intensity measured by aircraft was 30kts and 1004mb.

It's located at 19.9N 95.7W and tracking WNW at 6kts.  Landfall is 
expected later this evening on the Mexican coast as a strong TD.  
There's a slight chance of it reaching minimal TS status before 
landfall, and if it does, it would be named Bret.  A Tropical Storm 
Warning has been issued for the coast between Tampico and Veracruz.
Please visit my tropical Atlantic headquarters.

23 June 2005

Western Caribbean becoming interesting...

Just during the day on Thursday, a concentrated area of convection 
formed over the extreme western Caribbean Sea, just off the tip of 
Honduras/Nicaragua (around 15N 82W).  There is visible evidence of
a defined mid-level circulation, and the trend with time is increasing 
cold cloud tops and more obvious circulation.

The SSTs in that region are 28-29C, and the vertical shear is 15kts 
and should decrease with time... making conditions favorable for 
development.  If a low-level circulation forms, this will become TD2, 
and would track WNW-NW, toward the Yucatan peninsula.  There is a 
chance the steering winds could be more easterly and this may drift 
over Central America which would remove any chance of development in 
the Atlantic basin.
Please visit my tropical Atlantic headquarters.

11 June 2005

Arlene about to make landfall near FL/AL border...

Although Arlene is still TS as of this writing, it is very close to being a hurricane.  A Tropical Storm Warning is in effect from eastern LA over to the entire FL panhandle.  A Hurricane Watch for MS, AL, and the western FL panhandle.  AND, a Hurricane Warning for MS and AL and extreme western FL panhandle.  The official forecast does bring Arlene up to a minimal hurricane by landfall, which is expected early this afternoon very close to where Ivan made its first US landfall last year.

Convection is still quite asymmetric and is much weaker now than it had been previously, but the wind field has tightened up drastically and short-term intensity changes are just not well understood.

Intensity as of 09Z this morning is 60kts and 990mb.  This is likely to be the intensity at landfall ± 5kts.  But locations to the east of landfall will experience higher winds and a higher likelihood of tornadoes generated by the hurricane.

Please visit my tropical Atlantic headquarters.

10 June 2005

Arlene strengthens as it heads toward the US...

TS Arlene passed over the extreme western tip of Cuba early this morning and has now entered the Gulf of Mexico, still bearing down on the US coast.  A Tropical Storm Warning has been issued for eastern LA over to St. Marks FL, and a Hurricane Watch has been issued for MS, AL, and the western FL panhandle.

The anticipated ridge to the north of the storm is indeed forming, and will steer Arlene slightly west of due north, and decrease the vertical wind shear as it does so.  This is the reason for the Hurricane Watch... it is possible that Arlene could intensify more rapidly as the shear lets up.  Currently, convection is still displaced to the east and north of the low-level center.

At 15Z today, it was located at 24.0N 84.9W and tracking N at 11kts.  Intensity is 50kts and 1000mb.  The forecast is for gradual strengthening, acceleration, and nudging to the NNW.  Landfall is expected Saturday afternoon as a strong tropical storm or even minimal hurricane, and the most likely area to experience the worst conditions still appears to be the MS/AL coasts.

Please visit my tropical Atlantic headquarters.

09 June 2005

TD1 becomes TS Arlene...

This morning, a ship near TD1 reported winds high enough to require upgrading TD1 to a Tropical Storm, the first of the season.  Arlene is still over very warm SSTs, but the shear has not relaxed as much as expected and the low-level center is exposed to the southwest.  This is still forecast to lessen in time as a ridge builds to the north of the storm.  The ridge would put Arlene in a more friendly shear environment, and will also be responsible for steering it toward the AL/MS coast.

At 21Z today, TS Arlene was located at 20.2N 84.2W and tracking N at 7kts.  Intensity estimated by satellite (a plane is en route) is 35kts and 1001mb.  It should accelerate and gradually intensify, making landfall on Saturday evening as a strong TS.

Please visit my tropical Atlantic headquarters.

08 June 2005

First Tropical Depression forms in western Caribbean...

An Air Force aircraft flew a recon mission into the system this afternoon, reaching it at about 4pm EDT and found a closed circulation, making it TD1.  The low-level center is located at 17.2N 84.0W.  Convection is not very centralized, but outflow aloft is improving in all quadrants.  Initial intensity measured by the aircraft is 25kts and 1004mb.

The vertical wind shear has relaxed to 15kts and is still decreasing as the subtropical jet lifts out of the area.  The SSTs are about 29C there, and the 26C water is roughly 100m deep (26C is the rule-of-thumb threshold for tropical cyclogenesis), so there is ample energy available to it even if it stalls for a bit.  The warm water is much shallower in the Gulf, so once there it must move more quickly to avoid cool upwelling.

The forecast is still for gradual strengthening and drifting north toward the US coastline.  Timing and location are the key questions, but the canned answer I'll give is "it's too early to know for sure".  Most likely is on Saturday between New Orleans and Appalachicola as tropical storm.

Please visit my tropical Atlantic headquarters.

07 June 2005

Something brewing in the western Caribbean...

For several days now, there has been a broad area of disturbed weather over Nicaragua, Honduras, and the extreme western Caribbean Sea.  It has gradually acquired a broad mid-level circulation and conditions are becoming more favorable for further development.

The SSTs in that area are 29C, which is actually about 2C above the average for this time of year!  Vertical wind shear (defined as the wind speed/direction difference between 850mb and 200mb) is currently 20-25kts, but is forecast to weaken in the coming 1-2 days.  Aircraft recon is tentatively scheduled to investigate the system tomorrow if it still shows signs of organization.

Most computer models intensify it and track it north toward the US coast... somewhere in the Louisiana to Florida panhandle vicinity.

Please visit my tropical Atlantic headquarters.