So what does the term 'invest' actually mean?
The National Weather Service defines an invest storm as an area of weather that has gained the interest of a hurricane or tropical storm system forecast organization (like theNational Hurricane Center).
It’s the type of storm that will spur the collection of data for further research by government organizations that help monitor and observe the weather.
A weather system for which a tropical cyclone forecast center (NHC, CPHC, or JTWC) is interested in collecting specialized data sets (e.g., microwave imagery) and/or running model guidance. Once a system has been designated as an invest, data collection and processing is initiated on a number of government and academic web sites, including the Naval Research Laboratory (NRL) and the University of Wisconsin Cooperative Institute for Meteorological Satellite Studies (UW-CIMSS). The designation of a system as an invest does not correspond to any particular likelihood of development of the system into a tropical cyclone; operational products such as the Tropical Weather Outlook or the JTWC/TCFA should be consulted for this purpose. Source