The discussions on the NHC pages are invaluable in forming more accurate assessments of threat. Highly recommended reading for anyone tracking the TD's as they are born in the Atlantic...
w/ regards to TD7 it was in trouble almost immediately...here is their most recent synopsis just to tack a punctuation point to Marty's last post.
...AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION
HAS OBSERVED SHARP WIND SHIFTS AT AN ALTITUDE OF 1000 FT...BUT IT
HAS BEEN UNABLE TO LOCATE A PERSISTENT AND WELL-DEFINED CENTER OF
CIRCULATION. THE DEPRESSION HAS THEREFORE DEGENERATED INTO A
TROPICAL WAVE...AND ADVISORIES ARE BEING DISCONTINUED AT THIS TIME...
NHC runs about a dozen computer models every 6 or so hours as part of their forcasts; each model with its own set of assumptions and data format. Each colored line on the map in Elberts post represents the results of one model run. A projected track does not necessarily mean is what's going to happen, its an indication of what could happen based on the assumptions and data that are "fed" into it...those tracks can be based on worst case, best case conditions and typically updated with data received from a variety of sources such as the Hurricane Hunters and other sensors, like NOAA bouys.
When a new model is being written for use by NHC it is "calibrated" against storm track data from prior storms to see how well the new model "predicts" the track of the historic storm.