A Diagnostic Study of Rapidly Developing Cyclones Using Surface-Based Q Vectors
Abstract
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 Periods (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 less useful near landmasses, as the surface temperature field becomes less representative of the mean tropospheric temperature.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1991
- Accession Number
- ADA246993
Entities
People
- David W. Titley
Organizations
- Naval Postgraduate School