This module starts with a forecast scenario that occurs along the California coast. The module then proceeds to describe the structure and climatology of these disturbances, as well as their synoptic and mesoscale evolution. The instruction concludes with a section on forecasting coastally trapped wind reversals. The module also includes a concise summary for quick reference and a final exam to test your knowledge. Like other modules in the Mesoscale Meteorology Primer, this module comes with audio narration, rich graphics, and a companion print version.
At the end of the module you should be able to do the following things:
With regard to characteristics of CTWRs
• Describe how pressure, temperature, and wind change with passage of a coastally trapped wind reversal (CTWR)
• Recall how quickly CTWRs propagate up the U.S. West Coast
• Recall why SLP rises after passage of a CTWR
• Locate areas likely to experience CTWRs on a physical map of the world
• Recall the frequency of CTWRs along the California coast
• Explain why CTWRs are best explained as a Kelvin wave, rather than a gravity wave
With regard to the structure of CTWRs
• Describe how the MBL changes with passage of a CTWR
• Recognize how a cross-coast profile of the MBL changes during a CTWR
• Recognize a CTWR on a wind profiler record
• Recall the height at which wind first reverses direction as a CTWR propagates
• Recall the association of stratus formation with CTWRs
With regard to the synoptic evolution of CTWRs
• Describe how MSLP, 850-mb heights, and 500-mb heights depart from climatologic norms during a CTWR
• Describe how changes in MSLP and 850-mb pressure force low-level offshore winds, and how this affects sensible weather along the coast
• Describe how variations in MSLP affect along-shore pressure gradients
With regard to the mesoscale evolution of CTWRs
• Recall how the synoptic setup forces the mesoscale offshore low
• Recall how the offshore low moves during a CTWR
• Describe how coastal mountains force ageostrophic flow
• Recall how coastal mountains contribute to warming of offshore winds
• Describe how and why a mesoscale high forms along the coast
• Recall the factors that cause northward propagation of the CTWR
With regard to forecasting CTWRs
• Recall the 3 best synoptic clues for forecasting a CTWR
• Recall where the offshore low forms with respect to the low-level offshore flow
• Recall where the stratus surge initiates with respect to the offshore low
• Describe the use and limitations of mesoscale NWP models in predicting CTWRs
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