Moisture and Precipitation Evolution during Tropical Cyclone Formation as Revealed by SSMI/SSMIS

The simultaneous precipitation and column water vapor retrievals from the SSM/I and SSMIS passive microwave instruments were used to examine the convective evolution during tropical cyclone evolution. The data were analyzed based on a wave pouch track dataset, and composites were constructed with more than 1,500 satellite passes. It was found that high column water vapor occurs near the pouch center and starts to increase about two days prior to genesis; significant increase in precipitation occurs within 24 hours prior to genesis. These features are consistent with a recently proposed two-stage conceptual model for tropical cyclone formation. On the other hand, the analysis also reveals an unexpected decrease in column water vapor from -18 h to genesis time.