A diagnostic study of rapidly developing cyclones using surface-based Q vectors

• Main Author: Titley, David W.
• Other Authors: Nuss, Wendell A.
• Language: en_US
• Published: Monterey, California. Naval Postgraduate School 2013
• Online Access: http://hdl.handle.net/10945/25850

Approved for public release; distribution is unlimited === Accurate short term (0-6 h) forecasts of rapid cyclogenesis are important to both civilian and military maritime interests. Because upper-air observations over the ocean are sparse, the relatively plentiful surface synoptic data must be used for diagnostic analysis. Surface pressure and temperature data for two Intensive Observation Period (IOPs) that occurred during the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA) are objectively analyzed and Q vectors--a measure of the low-level ageostrophic flow required to restore geostrophic balance--are calculated. Areas of Q vector convergence, which imply upward vertical motion, were compared to satellite imagery and to the future 3-h and 6-h pressure tendencies. When the storms were intensifying most rapidly, satellite imagery showed cold-topped stratiform clouds over areas of Q vector convergence. Areas of strong Q vector convergence (divergence)) showed significant (95% confidence level) pressure falls (rises) 3 h and 6 h in the future. Surface Q vectors are shown to have qualitative value in short-range forecasts of the location of the storm, but do not forecast storm intensity. The surface Q vector interpretations are lee useful near landmasses, as the surface temperature field becomes less representative of the mean tropospheric temperature.