30 June 2003

Bill makes landfall...

Shortly after yesterday's update, Hurricane Watches were posted in
addition to the Tropical Storm Warnings, as TS Bill was showing signs of
better organization and a possibility of reaching hurricane strength
prior to landfall.  Although he did not attain hurricane strength, the
presentation on radar and satellite imagery was very impressive.  During
the mid-morning hours today, a radar in southeast LA showed a very
obvious eyewall, while such a feature was not so apparent from the cloud
tops.  The MSLP fell 13mb in 24 hours ending 21Z today, or more
impressively, it fell 10mb in 9 hours ending at 21Z.  It was definitely
on the intensifying trend, but landfall occurred just as it was getting
better organized.

Landfall occured at roughly 21Z at Terrebonne Bay in Terrebonne Parish,
LA.  Intensity at landfall was 55kts and 997mb.  There is major flash
flooding occurring, and radar has indicated over 12" has fallen at
places, and as of this writing, 4 tornadoes have been reported
associated with Bill.  Rapid disspiation is expected as he travels
inland over MS, AL, TN, and VA during the next few days.

Please visit my tropical Atlantic headquarters.

29 June 2003

Tropical Storm Bill forms in the Gulf of Mexico...

An area of persistent deep convection in the central Gulf of Mexico finally got
better organized and achieved a closed circulation at 15Z today.  As of 21Z, TS
Bill was located at 24.8N 91.1W and heading NNW at 11kts.  Maximum sustained
winds are 40kts and it has a 1010mb MSLP.  A Tropical Storm Warning has been
issued for all of the MS and LA coasts, and the extreme eastern TX coast.  The
greatest threat will be flash flooding as the storm moves ashore.

Conditions are favorable for futher intensification... Bill is over 29C water
and embedded in 15kts of southerly shear.  The CDO has maintained -70C cloud
tops nearly all day, but of course the outflow aloft is restricted on the south
side.  It is forecast to reach 55kts at landfall on Monday afternoon.  The exact
landfall location isn't critical because there's not an intense eyewall, but it
looks like central LA will see the circulation center.

Please visit my tropical Atlantic headquarters.

12 June 2003

TD2 is no more...

At 03Z today, TD2 degenerated back to a tropical wave, losing the battle
against marginal SSTs and increasing shear... and climatology.  But even
so, it's uncommon to see such activity from a Cape Verde disturbance so
early in the season.

It's still moving west at 15kts and is presently located about 500 miles
east of the Lesser Antilles.

Please visit my tropical Atlantic headquarters.

11 June 2003

Disturbance becomes TD2, and still organizing...

At 03Z today, the tropical disturbance I had been mentioning in the deep
tropics was upgraded to Tropical Depression 2 based on satellite
intensity estimates.  Although still fairly disorganized, the
persistence of the circulation and convection is impressive for this
time of year at that location.  Quoting NHC's bulletin, "THIS IS THE

As of 09Z, TD2 was located at 9.9N 43.3W and tracking W at 17kts.  The
forecast is first for a slight intensification, marginally reaching
Tropical Storm status, then for increasing shear and gradual weakening
as it drifts WNW toward the northern Lesser Antilles.  It's in 10kts of
westerly vertical wind shear, and over 25-26C SSTs.  As it moves
westward, the SSTs will warm into the 26-27C range.  Recall that if TD2
gets named, it will be Bill.

Please visit my tropical Atlantic headquarters.

10 June 2003

The Low in the deep tropics continues to organize as it heads west...

Although still not a Tropical Depression, the 1009mb Low has a very
obvious mid-level circulation and convection has maintained the cloud
tops at -70C or colder.  It's presently at about 10N 39W and tracking
WNW at 15-20 kts.  

The SSTs are marginal at 26C, and this will not improve unless it makes
it to west of 50W where the ocean is warmer at higher latitudes. 
However, it remains in a very favorable low-shear environment.

This is quite early in the season for a Cape Verde storm to develop.  In
recent memory, there was Bertha '96 who formed on July 5 at 34W.  Then
going all the way back to 1976, Ana formed on June 19 at 45W.  I didn't
search beyond 35 years ago, but the point is, it would be very rare if
this developed to a named storm!

As an aside, the disturbance is embedded in a SAL, or Saharan Air
Layer.  This is still a very active area of research in the tropical
meteorology community, but basically, it's a dry layer of air, traceable
by fine dust and sand particles, that originates from the Sahara Desert
and blows out over the tropical Atlantic with the easterlies.  The dry
layer of air is unhealthy for convection, and sometimes you'll notice a
diminished intensity in convection despite amply warm SSTs... look for
this dust as a possible culprit!  Today, the SAL reaches to the Lesser
Antilles.  On a technical note for those who are curious, you can
typically see the SAL much better in the morning's visible imagery... it
appears to almost vanish by afternoon/evening.  This is the effect of
forward scattering.  You can see an example of the SAL at
which is from today at 1145Z.

Please visit my tropical Atlantic headquarters.

09 June 2003

Deep tropics looking interesting...

Last Friday afternoon, a large cluster of thunderstorms moved off the
African coast at about 6N.  During the weekend, the cluster got better
organized and now has a 1010mb Low associated with it, which is now
located at 7N 33W and tracking W at 20kts.  It's embedded in light
southeasterly shear, and the SSTs are marginal for intensification (if
it can stay south of 10N until it gets to about 50W, SSTs will remain
marginally favorable, otherwise, they get too cool).

In the satellite imagery, one can clearly see a low-level circulation,
an anticyclone aloft, and sustained cloud tops colder than -70C (these
are all healthy for a developing storm).

It's climatologically unfavorable to have a "Cape Verde" storm develop
this early, but certainly not impossible.  This name refers to the Cape
Verde Islands at about 15N 25W, or a few hundred kilometers west of the
African coast.

It's something worth monitoring, and should it reach Tropical Storm
strength, it's name will be Bill.

Please visit my tropical Atlantic headquarters.