I'm not very good with graphics, but I'll give this a layman's version of a shot.
I've cropped some of the upper air maps from NHC to show the upper air cuurents at 850mb (5000ft) and 200mb (38000ft).

The first two are from the area around Tropical Storm Bertha. And the latter two are from the GOM and NW Caribbean area.
The links will take you to the latest upper air charts of the Atlantic and Eastern Pacific Oceans.
The contour lines indicate clockwise ( High pressure) circulation and counter-clockwise (Low pressure) circulation. The numbers are the wind speeds at that altitude at the time of the map.
Anti-cyclonic circulation at 200mb, over cyclonic circulation at 850mb would normally be favorable for strengthing. SSTs and other parameters would also have to be in place.
070408 1800Z or 2 PM EDT today.

200mb-38000ft

850mb-5000ft

Gulf of Mexico and NW Caribbean Sea

200mb-38000ft

30-50 knots of wind shear present in W. GOM

850mb-5000ft

NHC links to the 850mb and 200mb charts.
http://www.nhc.noaa.gov/tafb/QUNA00.jpg
http://www.nhc.noaa.gov/tafb/QHQA17.jpg

Trropical Storm Bertha, appears to be slightly increasing in intensity. Due mainly to the indication of higher, colder cloud tops near the center. The 'rainbow' enhancement would seem to indicate some type of wind shear or dry air on the western side of the system. Notice the difference in the low and mid level blue-grey clouds on the left side of the storm.
The lower larger circular area underneath the storm appears to be tilted somewhat to the upper right side of the photo, or to the northeast.