Extratropical Cyclones, Windstorms, and Fronts

• Supervisors: Prof David Schultz
  Prof Geraint Vaughan
  
  
  
• External Supervisors:
  
  
• Contact:

  Prof David Schultz David.Schultz@manchester.ac.uk

• CASE Partner: No

Application deadline: 3 February 2017

In the 1920s, Norwegian meteorologists working with a dense network of surface stations developed a conceptual model of extratropical cyclone structure and evolution that revolutionized and modernized meteorology.  Ninety years later, this model is still being taught and is the primary way by which meteorologists conceptualize cyclones and fronts.  Recently, we have made important advances in addressing the weaknesses of the Norwegian cyclone model of occluded fronts and rebuilding it in a modern framework (Schultz and Vaughan 2011; Schultz et al. 2014).  Yet, more work remains.  Our previous work has changed textbooks.  Can you contribute to further advances in our understanding?

Strong windstorms associated with cyclones crossing the Atlantic can cause billions of euros of damage.  The occurrence of these cyclones is typically well forecasted, yet the predictability and reasons for the strong winds remains uncertain.  After the discovery of the sting jet (a particular mesoscale region of strong winds) in 2004, our group's work has focused on understanding the physical processes that cause the acceleration of the air (Schultz and Sienkiewicz 2013; Slater et al. 2015).  But, are our simple models applicable to all cyclones around the globe?  Satellite observations could be used to understand the global distribution of strong winds and their interactions with the ocean.  Do different ocean basins yield cyclones with different life cycles?  Preliminary research suggests yes, but a student could make great progress on this topic as part of their PhD.

Questions about whether cold fronts fit the Norwegian cyclone model have been raised (Schultz 2008).  For example, do fronts represent the material boundaries between air masses, do they represent transition zones between air masses, or do they represent a transitory process with little relation to airmass boundaries?  Some cyclones have multiple cold fronts, multiple warm fronts, or both (Lawson et al. 2011; Mulqueen and Schultz 2015).  What controls the structure and evolution of fronts within extratropical cyclones?  What is the relationship between the jet stream and the structure and evolution of extratropical cyclones?  Are there regional or seasonal variations?

New observational tools are being employed to understand the distribution of organized regions of precipitation within extratropical cyclones.  We have been involved in the analysis of heavy snow bands from such storms using polarimetric radar (e.g., Picca et al. 2014).  We have also modelled organized precipitation features within idealised extratropical cyclones (Norris et al. 2014).  Yet, more work needs to be done to understand why precipitation organises on these space and time scales.  What is the best way to observe them with these new tools and how can we improve the prediction of these mesoscale bands of precipitation?

We draw inspiration from the daily weather.  One way we do that is through looking at our real-time modelling of the weather over the UK and Europe.  Check out our real-time web-based weather forecasting portal and Apple mobile app: http://www.manunicast.com

Ideally, students would have a previous background in meteorology, atmospheric science, ocean science, physics, math, or a related discipline.  The project can be largely observationally based (using satellites, wind profiler data, or surface station data), heavily numerically based (using mesoscale or cloud-resolving model simulations based on real or idealized cyclones or fronts), or a combination.  The student has much say about the direction of this project, and we hope that the possibilities described here motivate the successful applicant to develop their own project based on their own interests.  

Potential research projects could include: 

• determination of the factors that affect the location, intensity, and organization of precipitation-producing bands associated with fronts and cyclones,

• understanding the causes of the variety of cyclone structures and evolutions,

• creating a global climatology of strong windstorms associated with extratropical cyclones,

• modeling the strong winds in extratropical cyclones and fronts,

• understanding how the ocean and the atmosphere interact in regions of strong winds,

• exploring whether changes in sea surface temperature or ocean heat content affect weather,

• exploring the variety of frontal structures in model data (e.g., occluded fronts, cold fronts, warm fronts),

• interpreting conceptual models such as split fronts and cold-fronts aloft using dynamical concepts such as the Sawyer–Eliassen equation, frontogenesis, and potential vorticity,

• using surface-based remote-sensing instrumentation (vertically pointing radars, lidars)  to understand frontal and cyclone structure. 

Students are also encouraged to suggest their own research project within the broad topic of extratropical cyclones and fronts.  Please contact Profs Schultz and Vaughan to discuss your ideas.

Slater, T. P., D. M. Schultz, and G. Vaughan, 2015: Acceleration of near-surface strong winds in a dry, idealised extratropical cyclone. Quart. J. Roy. Meteor. Soc., 141, 1004–1016, doi: 10.1002/qj.2417.

Mulqueen, K. C., and D. M. Schultz, 2015: Non-classic extratropical cyclones on Met Office sea-level pressure charts: Double cold and warm fronts.  Weather, 70, 100–105, doi:10.1002/wea.2463.

Picca, J. C., D. M. Schultz, B. A. Colle, S. A. Ganetis, D. R. Novak, and M. J. Sienkiewicz, 2014: The value of dual-polarization radar in diagnosing the complex microphysical evolution of an intense snowband.  Bull. Amer. Meteor. Soc., 95, 1825–1834, doi: 10.1175/BAMS-D-13-00258.1.

Norris, J., G. Vaughan, and D. M. Schultz, 2014: Precipitation banding in idealized baroclinic waves. Mon. Wea. Rev., 142, 3081–3099, doi: 10.1175/MWR-D-13-00343.1.

Schultz, D. M., B. Antonescu, and A. Chiariello, 2014: Searching for the elusive cold-type occluded front. Mon. Wea. Rev., 142, 2565–2570, doi: 10.1175/MWR-D-14-00003.1.

Schultz, D. M., and J. M. Sienkiewicz, 2013: Using frontogenesis to identify sting jets in extratropical cyclones.  Wea. Forecasting, 28, 603–613.

Schultz, D. M., and G. Vaughan, 2011: Occluded fronts and the occlusion process: A fresh look at conventional wisdom. Bull. Amer. Meteor. Soc., 92, 443–466, ES19–ES20.

Lawson, J., G. Vaughan, and D. M. Schultz, 2011: Classifying fronts in data from a VHF wind-profiling radar.  Atmos. Sci. Lett., 12, 375–380.

Schultz, D. M., 2008: Perspectives on Fred Sanders' research on cold fronts. Synoptic–Dynamic Meteorology and Weather Analysis and Forecasting: A Tribute to Fred Sanders, Meteor. Monogr., No. 55, Amer. Meteor. Soc., 109–126.

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