19 September 2011

New disturbance in eastern Atlantic

[This message is the first being sent to both the old and the new email lists.  I apologize for duplicate mailings, but I want to give everyone a chance to migrate and accept the invitation to the new Google Groups list.  If you have not yet accepted the invitation I sent on Friday (there is a link to click in that message... the subject was "Google Groups Invitation: Tropical Atlantic Update"), you will stop receiving these updates once I discontinue the old list.  The old distribution address was tropical@atmos.colostate.edu, and the new address is tropatlan@googlegroups.com.  Please check with me if you have any questions or problems!]

Over the past week or so, 3 easterly waves left the African coast.  But rather than making their way westward one after the other, they have begun to accumulate in a weak-steering region between 35-40W.  There's some evidence of this if you look at the time series of infrared images over the deep tropics: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/hovmoller/atlantic/   In this view, the newest image is on top, and then you look back 12 hours every slice as you go down the page.  This allows you to track persistent features (such as African easterly waves) for many days simply by looking at their convective signature!  The visible satellite below shows the appearance of this disturbance as of this writing, with the surface center location marked by a red dot.  The estimated intensity is 25kts and 1008mb, and it's very close to becoming a Depression (TD16).  The next name on the list is Ophelia.

The plot below shows the past, present, and forecast intensity, track, shear, SST, and mid-level humidity.  The important thing to take away from it is that significant development of this is not expected in the near future, mostly because the vertical shear will be rather high.

Please visit my tropical Atlantic headquarters.

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