“Streamer” is the name given to a cloud roll that develops near the majority of the Caribbean islands. The dynamics and other possible factors involved in the formation and development of this mesoscale feature are still not well understood, especially for the streamer that develops over northeastern Puerto Rico. In an attempt to understand the dynamics and physical processes involved in the streamers' formation and development, our research involved the meteorological in situ measurements analysis for Puerto Rico, as well as high-resolution numerical simulations. The main goals of this research were: 1) to establish a database that contains streamers activities in terms of soundings, high-resolution visible satellite imagery, Doppler radar reflectivity and storm total imagery and rain-gauge datasets for June, July and August 2006 over the Caribbean area; 2) to characterize streamer's life cycle under different weather regimes as well as topography effects; and 3) to conduct numerical simulations using the Weather Research and Forecasting model (i.e. WRF) for a domain over the Puerto Rico region centered at San Juan, PR. The validation will be confined to comparing the in situ measurements to those fields calculated by the model.

Currently, eighteen streamer cases were identified using 1 km resolution visible satellite imagery and Doppler's radar reflectivity imagery. For each case, the rain-gauge and Doppler's storm totals datasets were used to characterize each streamer case as wet or dry condition. Atmospheric variables such as the mixing ratio, wind direction and speed, temperature inversion height and the lifted condensation level were analyzed using San Juan, PR's atmospheric soundings. A light easterly or south-easterly surface wind was present for each streamer day at 12Z, with velocities from 5-10 knots. A wind direction change was not observed below 820 hPa. There were 55% of the streamer cases occurred during August, where the mixing ratio at low levels (i.e., 925 hPa) was the highest compared to June and July's cases. Additionally, 66% of the cases showed a temperature inversion height near or below 700 hPa, where the mixing ratio was low (~ 4-6 g/kg). These cases were considered “wet streamers” as the precipitation estimates ranged between 1-5 inches of rain in a 12-hr period. Further study is needed to validate our preliminary results and develop better understanding of these mesoscale systems. Our findings will help in the short term forecast done by the National Weather Service in Puerto Rico.