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
THIRD TROPICAL DEPRESSION TO FORM IN THE TROPICAL ATLANTIC EAST OF THE
LESSER ANTILLES IN JUNE SINCE 1967".

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.

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
http://www.nrlmry.navy.mil/archdat/atlantic/tropics/vis/20030610.1145.goes-12.vis.x.trop.x.jpg
which is from today at 1145Z.

Please visit my tropical Atlantic headquarters.

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.