Convergence and divergence are features that are pretty much just like they say: things coming into an area and things going out of an area, respectively. You can use it to talk about any quantity that you like, but it is usually done with regards to winds.

Convergence is a sign or a by-product of cyclonic shear or circulation; it can be associated with either a low-level or upper-level low. Divergence is a sign or a by-product of anticyclonic shear or circulation; it can be associated with either a low-level or upper-level high. An example of divergent flow is given by the occasional massive blowups of convection (that usually die out with time) over the Caribbean.

It is possible that divergent flow from an upper-level high pressure system could be helping to push Emily southward, but the more likely culprit (in my estimation) is reorganization of the storm.

Another aside: 10:30p TWO suggests the potential for 99L to become a tropical depression in the next day or so as it moves westward (also near 20mph). It does look better organized on satellite this evening, but still needs some time to consolidate the broader overall circulation. Nevertheless, we might see TD 6 late tomorrow, continuing the most active start to a season in recorded history.