Perhaps I can help a little with this one. I'm probably giving away a little meteorological trade secret, but I'm sure that may of you might find it to be a useful piece of info. The NHC coordinates with many other meteorological agencies in this country and with other met organizations in other countries as well. When an area of interest is noted in the Atlantic (and east Pacific) basin, NHC asks NRL to start an Invest on the area of interest and NHC also provides NRL with the centerpoint coordinates (lat/long) for the area. In this case, the area of interest does seem to have a small center of circulation (tropical low) associated with it - which means that it could have some future potential. Remember, many Invest areas don't amount to anything and the Invest is dropped after a day or three. However, if something does eventually develop, the NHC will have an early 'track' record on the system to aid in future projections. Often a tropical low may be so weak that it is not picked up by the more globally oriented models, so the Invest 'track' gives the NHC a head start toward a forecast for future movement. Many tropical meteorologists use this technique (myself included). As the system moves toward the 'edge' of the Invest area, a new set of coordinates are sent to NRL - and this can be annoying when a time-lapse sequence of the system seems to 'jump' to a new location halfway through the loop.

NHC also advises NRL (and other agencies) in advance when they intend to upgrade the Invest to a Tropical Depression (NONAME) or from a TD to a named system (Tropical Storm). Sometimes NRL will upgrade their tropical site to reflect these changes before the NHC has issed the upgrade bulletin - which lets meteorologists know (TWC, Jason, ED, etc.) that a change is forthcoming

There are many other factors which may prompt an Invest, but sometimes its just a desire to take a closer look at an area of interest. Hope this helps.

I also have observed some downtime on both the NHC and NRL sites (especially NRL) in the past couple of days. At 04/00Z the tropical low was near 8.5N 23W. When you enlarge the thumbnail image from NRL, make sure that you look at the timestamp of the image. Often, the enlarged thumbnail will be an image that is more current than the small thumbnail or the full screen enlarged view.
Cheers,
ED