16 July 2008

Bertha persists, new depression ready to form...

Bertha is still a strong 60kt tropical storm, now around for 13 days.  It's located about 400 miles northeast of Bermuda.  The forecast is to maintain this intensity, and continue heading generally eastward, then northeastward.

An interesting feature deserves to be pointed out... a cold SST wake left by Bertha.  As a storm passes over a patch of ocean, it churns it up, and upwells cooler water from below.  In some regions and times of the year, the "mixed layer" is very deep and it's hard to upwell cool water because it lies so deep.  Other times, the sea surface temperature might be very warm, but the warmth doesn't extend very deep.  It's in these cases that we typically see a dramatic cold wake.  The wake can be exaggerated by slow storm motion (longer time to act), an intense storm (more vigorous churning), or a combination.  Anyway, with that background in mind, check out this 2-week SST loop:
(areas of persistent cloud-cover as shown as gray because SSTs couldn't be retrieved that day)
Also take note of the beautiful eddies and vorticies formed along the Gulf Stream.  Some eddies are warm, some are cold... some rotate cyclonically, some rotate anticyclonically.

Elsewhere, the easterly wave I've been discussing each day is now located near 57W and is getting much better organized... it's about 100 miles east of the Windward Islands and moving W at 20kts.  There is a broad mid-level circulation, and scattered deep convection with cloud tops hitting -70C.  It's in weak-moderate northwesterly vertical wind shear, and SSTs are in the 28C ballpark.  This is forecast to keep tracking W-WNW through the Caribbean and perhaps enter the Gulf of Mexico  by early next week.
You can find a radar loop of pre-TD3 (?) from Martinique at http://einstein.atmos.colostate.edu/~mcnoldy/tropics/cristobal08/Cristobal_16Jul08.gif
(I took the liberty of naming the loop after its likely future name...)

There's also a fairly well-organized wave south of Jamaica, heading toward Nicaragua.  This system will also be watched closely for development, as it's in a favorable environment as well.

Please visit my tropical Atlantic headquarters.

No comments:

Post a Comment