31 July 2003

Disturbance still trekking across eastern Atlantic...

The significant tropical wave and embedded Low that I mentioned
yesterday has changed little in the past 24 hours.  Late Wednesday
night, there was a cold CDO, but by Thurs morning, it was largely gone. 
Banding features are still evident though, and a return of deep
convection is expected later tonight.  While shear and SST are
favorable, it's in a general environment that is stable and dry, so that
has been hindering a more rapid development.

The low is presently at about 10N 37W and tracking W at 20kts.  Models
vary on whether or not the system will survive.  Just for future
reference, the next number/name on deck is 8/Erika.

Please visit my tropical Atlantic headquarters.

30 July 2003

Some old news, and some new excitement in the far eastern Atlantic...

Since my last update on 7/21, TD6 dissipated before becoming a named
storm, in the neighborhood of the Lesser Antilles.  However, the wave
remained intact and spawned TD7 four days later.  TD7 formed off the
northeast Florida coast and headed straight for the Georgia coast not
long after.  Landfall was around 06Z on 7/26 just south of Savannah.

Now onto the new excitement.  An impressive tropical wave that exited
the African coast on Monday is becoming better organized, and a 1012mb
Low has formed within the wave at about 9N 24W.  Motion is W at 15kts.
In addition to the traditional visible and infrared satellite imagery,
microwave imagery also reveals a nice spiral band on the western side of
the circulation.  It's in an environment of moderate shear (10-15kts
easterly), the SST is 27.5C, and there is a broad vorticity center.
Conditions should improve over the next few days, and so the likelihood
of this becoming TD8 is fairly high.

Please visit my tropical Atlantic headquarters.

21 July 2003

Danny dissipates, TD6 neary a Tropical Storm...

At 21Z Sunday, the last advisory was written on Danny, as his path over
cool waters killed off all convection.  The low-level circulation is
still evident and easily found at about 37N 36W.  He is indeed orbiting
around the subtropical High; an ellipse approximately 700 miles N-S by
1100 miles E-W should be completed by the weekend.  Regeneration is not
impossible by later in the week, but unlikely.

TD6 suffered a brief hiccup in intensification Sunday evening when the
deep convection nearly ceased.  Then it made a comeback and is once
again on the intensifying trend.  At 15Z today, TD6 was located at 14.2N
58.8W and tracking W at 20kts.  Intensity is estimated at 30kts and
1009mb.  Although the SSTs and heat content are quite favorable in the
Caribbean, the vertical wind shear will be westerly at 20-25kts, so any
development should be slow.  A Tropical Storm Watch is in effect for the
US Virgin Islands, St. Lucia (south of Martinique), and Puerto Rico, and
a Tropical Storm Warning is in effect for Dominica (north of
Martinique).  It will very soon pass over Martinique in the Windward
Islands, then is expected to graze southern Hispaniola and Cuba.  Their
mountainous terrain could limit development for the next couple days,
although a hurricane is not out of the question if it tracks just a bit
further south than forecast.  Beyond that, it's expected to enter the
eastern Gulf where it must be watched much more closely.

As an aside, I checked the track history and if I'm not mistaken, the
last time there were three Atlantic hurricanes during July was 1966
(Becky, Celia, and Dorothy).  So if TD6 makes it to Hurricane Erika by
the end of the month, we can update that record! (also, 7 of the 11
named storms in 1966 made it to hurricane, and if TD6 goes to hurricane,
this season will be at 3 out of 5 so far)

Please visit my tropical Atlantic headquarters.

20 July 2003

Danny became a hurricane, TD6 forms...

At 21Z Friday, Danny was upgraded to a hurricane with a MSLP of 1006mb.  After
some record searching by several people, this is apparently the highest pressure
at which an Atlantic cyclone transitioned to a hurricane.  Emily '93 was 1004mb
and Bob '85 was 1003mb.  Since then, he has entered cooler waters and is back to
a Tropical Storm again, forecast to continue weakening.  At 15Z today, TS Danny
was located at 41.6N 40.0W and tracking ESE at 14kts.  Intensity is 35kts and
1008mb.  Although not expected to remain a defined tropical system, the
circulation is forecast to continue circling around the Bermuda High, eventually
heading S then SW.

At 21Z Saturday, TD6 formed from the disturbance I had mentioned in the central
deep tropics, east of the Lesser Antilles.  It continues to organize and is
forecast to reach Tropical Storm status later tonight or Monday morning.  As of
15Z today, TD6 is at 13.0N 50.4W and heading W at 20kts.  Winds are 30kts and
the MSLP is 1008mb.  It has the potential to become the third hurricane by
mid-week.  Once named, this storm will be Erika.  The forecast track takes it
across the central Lesser Antilles, then skimming just south of Dominican
Republic, Haiti, and Cuba, entering the Gulf of Mexico by the end of the week. 
Conditions are favorable for this to develop.

So far, 2003 is on par to match the record seasons of 1933 and 1995, since we
are nearing the 5th named storm and it's not August yet.

Please visit my tropical Atlantic headquarters.

18 July 2003

Danny nearly a hurricane...

As forecast, the weak shear over Danny has allowed him to intensify, and
the satellite presentation is impressive, with symmetric outflow and
well-defined bands.  However, the convection is not very centralized. 
The cloud tops temps aren't very cold either, but keep in mind that the
storm is at nearly 40N, so the tropopause height isn't as high (cold) as
it is in the deep tropics.  And once again, I'll draw your attention to
another difference one must consider when watching a tropical cyclone so
far north... the central pressure is 1009mb, and he's nearly a
hurricane.  In the deep tropics, that same pressure would barely be a

At 15Z today, TS Danny was located at 38.7N 54.3W and tracking NE at
14kts.  Maximum sustained winds are 60kts with a MSLP of 1009mb.  The
forecast is for gradual weakening, but any slight spike in intensity
would bring him to hurricane intensity (65kts+).  Although the shear is
still favorable, the SSTs are dropping off now that he's crossed the
Gulf Stream axis... presently 25.5C and decreasing as he heads NE.  As
I've mentioned before, his track has been governed by the Bermuda High
sitting over the north central Atlantic (centered at about 35N 40W). 
Flow around the High is clockwise.  Most models keep a traceable system
(maybe not quite a tropical cyclone) for several days, eventually
wrapping (ex-)Danny back around into the warmer part of the basin, so
we'll have to keep an eye on this vortex for a while perhaps.

Ironically, the last time we had two hurricanes during July was 1997,
and they were Bill and Danny.  So maybe this cycle's Danny will also
become a second July hurricane??

Two tropical waves in the deep tropics seem to be ingesting very dry air
from the Saharan Air Layer (SAL).  This is a plume of silicate-laden air
from the African desert that blows westward across the tropical
Atlantic, sometimes reaching the central Caribbean.  It varies in
intensity, but apparently is unfavorable for convective development. 
shows a GOES-12 visible image from this morning at 1145Z.  Note the
milky color streaming across the deep tropics from Africa.  You're not
seeing DRY air, but actually the silicates and sand aerosols from the
Sahara (the air is dry, but you couldn't prove that with visible imagery

Please visit my tropical Atlantic headquarters.

17 July 2003

TD5 becomes TS Danny...

The Tropical Depression east of Bermuda has gotten much better organized
(quicker than forecast) and was made the fourth named storm of the
season at 03Z today.

At 15Z today, TS Danny was located at 34.9N 56.7W and tracking NNW at
11kts.  Maximum sustained winds are 55kts and the MSLP is 1010mb (again,
remember the ambient pressure is presently in the low 1020's at that
latitude).  The cyclone is over 26C water and minimal shear, which has
allowed him to intensify, and this trend is expected to continue,
possibly becoming a hurricane by Friday morning.  It looks like an eye
could form very soon, and the banding features are quite impressive.  He
will not threaten any land, as he continues the long curve around the
periphery of the Bermuda High.

Elsewhere, a significant tropical wave is making its way across the
eastern Atlantic, presently at about 9N 35W.  It has a 1014mb Low
embedded in it, and is in 15kts of easterly shear and over 27.5C water. 
It will be watched for development, although the vast majority of models
do not develop it.

Please visit my tropical Atlantic headquarters.

16 July 2003

Claudette inland and dissipated, TD5 forms over open ocean...

Claudette made landfall yesterday at about 16Z near Port O' Connor, TX
as a CAT1 hurricane.  Damage was not severe, but certainly there was
some caused by beach erosion, storm surge, wind gusts up to 100mph, and
torrential rain both along the coast and inland.  Advisories ceased at
03Z today, making her the 2nd longest lived named storm in July ever
with 7.5 Named Storm Days (the record is 8.0 NSD).

As if the Atlantic is running through a queue, TD5 just formed in the
north central part of the basin, well east of Bermuda.  At 15Z, TD5 was
located at 31.5N 54.5W and tracking NW at 11kts.  Intensity is 25kts and
1015mb, and this is not forecast to change much, probably leaving it
below TS status for the next few days.  Keep in mind that a MSLP of
1015mb at that latitude is roughly equivalent to a MSLP of 1004mb in the
deep tropics right now, in terms of pressure deficit relative to its
environment.  It's over 27C water now, but as it wraps around the
Bermuda High, it will be taken north then northeast over much cooler
water (23C).  Outflow is improving, but the convection is not very
centralized.  Should it get named, the next name is Danny.

Please visit my tropical Atlantic headquarters.

15 July 2003

Claudette making landfall as a hurricane...

Throughout Monday afternoon and evening, the vertical wind shear over
Claudette weakened as forecast and as a result, she was able to better
organize and intensify.  At 05Z today she was upgraded to a hurricane,
and the Houston NEXRAD clearly showed an eye and eyewall in the storm,
which aircraft recon confirmed.  This makes her the first July hurricane
since Bill '97.  Another interesting statistic that Phil Klotzbach (CSU)
pointed out to me is that Claudette is one of the longest-lived named
storms in July ever.  This afternoon at 21Z, she will be tied for 2nd
place with Dorothy '66, and if she lasts until Wednesday at 15Z she will
tie Bonnie '96 for 1st place.  The last US hurricane landfall was Lili

At 15Z today, Hurricane Claudette was located at 28.5N 96.1W and
tracking WNW at 9kts.  Instenisty is 70kts and 981mb, with a 30 nautical
mile wide eye.  This will put landfall near Port O'Connor, TX at about
noon local time.  A Hurricane Warning is in effect for much of the TX
coast, and some optional evacuations have already taken place.  The
storm surge is about 8' above normal tides, and places along her path
can expect about 8" of rain.  Coastal and inland flooding will be the
primary threat.  She will weaken rapidly once the eyewall makes
landfall, as that cuts off the fuel source for the hurricane's engine.

You can monitor the eyewall making landfall at

Please visit my tropical Atlantic headquarters.

14 July 2003

Claudette once again near hurricane status...

Although vertical shear is still the primary reason Claudette is not a
hurricane, it is decreasing and she has historically been very quick to
respond to subtle changes in the environment (because of her small size
and modest intensity).  For the first time in a couple days, there are
convective features on the west semicircle of her circulation.  The
steering flow in the central Gulf is nearly non-existent right recently,
so her track has looked more like a child's drawing of a camel than that
of a gently curving line.  However, a more westward heading should
commence shortly.

At 18Z today, TS Claudette was located at 27.3N 92.8W and drifting NNW
at 5kts.  This will take her further north than previous track forecasts
predicted.  Intensity is 55kts and 989mb (traditionally, this pressure
is borderline hurricane).  Since the shear is expected to lessen even
more, the forecast is for her to become a hurricane later today or early
tomorrow just prior to landfall.  A Tropical Storm Warning is in effect
for extreme western LA coast and extreme eastern TX coast; a Hurricane
Watch is in effect from Brownsville to Baffin bay; and a Hurricane
Warning is in effect from Baffin Bay to San Luis Pass.  Landfall is
predicted near Port O'Connor sometime Tuesday evening.

Should she become a hurricane, it would be the first July hurricane
since Bill '97.

Please visit my tropical Atlantic headquarters.

13 July 2003

Claudette heads for Gulf coast...

Since entering the Gulf of Mexico, TS Claudette has battled westerly wind shear,
and this has kept her from intensifying, much to the delight of coastal Texans
I'm sure.  Although deep convection has been persistent, it's unable to remain
centralized, and in fact, the low-level circulation was exposed for much of the

At 21Z today, Claudette was located at 25.3N 92.4W and stationary.  Maximum
sustained winds are still 50kts and the MSLP is 997mb.  She is forecast to reach
minimal hurricane strength just prior to landfall (keep in mind she was forecast
to be a hurricane several days ago too...).  Landfall is expected midday Tuesday
near the Mexico/Texas border; if you recall the forecasts from last week, the
track forecast has been very accurate, just the intensity has been off.  A
Hurricane Watch is in effect for the extreme northern Mexico coast up to Port
O'Connor, TX.

The shear should lessen a bit before landfall as she pulls away from a strong
anticyclone aloft over the Bay of Campeche, and the ocean's heat content
(combination of SST and depth of warm water) increases slightly toward the west
as well.

Elsewhere, there is a tropical wave east of the Lesser Antilles at about 18N 40W
moving W at 15kts.  This will be monitored over the next few days for
development.  It's certainly noteworthy how active the deep tropics have been
this season.  In June and July, the action is typically more in the northern
Gulf and off the eastern seaboard, not from tropical waves rolling off of
Africa.  It seems somewhat analogous to 1996 so far.

Please visit my tropical Atlantic headquarters.

11 July 2003

Claudette over the Gulf of Mexico...

Just to prove that nature still has the upper hand, Claudette went
against all forecasts yesterday and weakened dramatically in the
afternoon.  The MSLP rose 15mb in just a few hours and it appeared that
shear would be victorious over the tropical storm.

Early Friday morning, she passed very near Cozumel, Mexico and crossed
over the extreme northeast tip of the Yucatan Peninsula.  Her appearance
has changed from banded to more "blobby" (i.e., a classic CDO... with
cloud top temps nearly -80C).  This new structure should prove
beneficial to her development, because the outflow has become more
symmetric and all the latent heating and spinning up of vorticity is
occuring where it needs to.  Furthermore, the Gulf is amply warm and the
environmental winds are such that vertical wind shear will be low.

At 15Z today, TS Claudette was located at 21.6N 87.4W and heading NW at
12kts.  Maximum sustained winds are 50kts and the MSLP is 1008mb, but
gradual intensification is expected as she slowly traverses the Gulf
over the next few days.  Tropical Storm Warnings are still in effect for
the northern Yucatan Peninsula.  The forecast track has changed little
since yesterday, with the northern Mexican coast up to the central TX
coast being the most likely landfall target area on Tuesday.  Hurricane
Watches may be issued for these areas later in the weekend.

Please visit my tropical Atlantic headquarters.

10 July 2003

Claudette nearly a hurricane...

Wednesday evening, Claudette was strongly sheared by the TUTT to her
west... it also restricted outflow and exposed the low-level
circulation.  However, as the TUTT moved over the Yucatan Peninsula, it
filled and weakened slightly, allowing the tropical storm to "breathe"
much better.  In rapid response to this, Claudette's MSLP dropped 11mb
in 9 hours and maximum sustained winds increased 10kts in that same
time.  She is also over the western Caribbean Sea, which has a large
heat content (very warm SST to a substantial depth).

As of 18Z, TS Claudette was located at 18.3N 83.6W and tracking WNW at
12kts.  Intensity is 60kts and 993mb, with rather large fluctuations
found by aircraft, so the wind and pressure values are somewhat
ephemeral it seems.  A large-scale flight is planned for later today to
probe the Gulf of Mexico and gather a lot of data about the dynamic and
thermodynamic environment so the computer models can be initialized very
accurately.  (that's no guarantee the output will be "correct", but it's
better than starting with garbage!)

Tropical Storm Warnings are in effect for the Cayman Islands, northern
Belize, and the northern side of the Yucatan Peninsula.  A Hurricane
Warning is in effect for the eastern side of the Yucatan Peninsula.  She
is expected to hit the Yucatan as a strong CAT1 hurricane late Thursday
night, then weaken slightly as she crosses the Yucatan on Friday, then
enter the Gulf, where conditions should be favorable for
re-development.  Right now, it appears that the northern Mexican coast
to central TX coast is the favored location for second landfall on
Tuesday.  Gulf coast residents should be watching Claudette very

Please visit my tropical Atlantic headquarters.

09 July 2003

Claudette forms in central Caribbean...

As you probably gathered from my intermediate update later on the 8th,
the tropical disturbance I had been talking about was named once an
aircraft was able to find not only a closed circulation, but
tropical-storm-force winds.  Claudette's first advisory was at 21Z
yesterday.  Later that night, the IR satellite presentation was
incredible, with symmetric outflow, cold CDO, and classic banding
features.  During the night however, the TUTT (Tropical
Upper-Tropospheric Trough) to her west induced unfavorable shear across
the system and the appearance became much more ragged and lopsided. 
Furthermore, the storm was due north of the Venezuelan highlands, a
climatologically brutal location for tropical cyclones because of the
accelerated trade winds there (increased shear).

In the past few hours, centralized deep convection is making a comeback,
but strong vertical shear is still quite evident.  At 15Z, TS Claudette
was located at 15.5N 77.6W and tracking W at 21kts.  Intensity is 55kts
and 1004mb (there was a short-lived peak of 1000mb at 03Z).  Forward
motion should continue to slow over the next few days and the track
should take her over the Yucatan, then into the Gulf, with weak steering
winds, warm SSTs, and an anticyclone aloft.  This means that although
she's struggling to stay intact now, the weekend could paint a very
different picture.

A Tropical Storm Warning is in effect for Jamaica and the Cayman
Islands, and a Hurricane Watch is in effect for the eastern Yucatan
Peninsula, down to the Belize border.

Please visit my tropical Atlantic headquarters.

08 July 2003

TS Claudette forms...

210 PM EDT TUE JUL 8 2003



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Organization in the central Caribbean...

Over the past few days, I've been watching a tropical wave move across
the central tropical Atlantic, and just recently it has taken on a much
more organized appearance, including a spiral band and cooling CDO.

Presently located at about 15N 69W, it's racing westward at 26kts.  The
steering flow leaves it few options but to continue heading west, then
perhaps bending slightly north as it nears the Mexico/Texas coast. 
Despite the impressive satellite presentation, aircraft recon into the
storm was unable to find a closed circulation.  Keep in mind the forward
motion of 26kts would require at least 26kt winds around the Low in
order to close the circulation.

The environment is favorable for development in terms of shear and SST,
but there is a very dry Saharan Air Layer just to its west that's been
tailgating it for a while.  It if can avoid ingesting that air,
development should be quick to occur.

Check out http://www.mcwar.org/gallery/tropics/tropics.html for the
latest satellite imagery and updates on this disturbance.  It would
become TD4 or TS Claudette.

Please visit my tropical Atlantic headquarters.