Specific humidity range in tropical lowlands?
Referring to a research article "The Role of Temperature and Humidity on Seasonal Influenza in Tropical Areas: Guatemala, El Salvador and Panama, 2008–2013" by Soebiyanto et al, 2014 DOI: 10.1371/journal.pone.0100659, the authors investigate a few regions in tropical wet and dry (savanna) climates in Central America, some of which are lowland. The authors state that Panama and El Salvador study locations have less varied topography and are at lower elevations than Guatemala. They give the following Specific Humidity values and standard deviation i g/kg:

Lowland Panama province in Panama: 17.66 +/- 1.04 g/kg
Chiriqui province in Panama: 15.38 +/- 1.47 g/kg
West-central departments in El Salvador: 14.29 +/- 2.14 g/kg
San Miguel, El Salvador: 14.84 +/- 2.32 g/kg


So, a specific humidity in the 10-20 g/kg seems like a reasonable range for seasonally dry and humid lowland tropical regions in Central America.