About right

1. Houze, Robert A., Jr and Peter V. Hobbs Organization And Structure Of Precipitating Cloud Systems , Advances in Geophysics, Vol 24, 1982 p. 225-313. We will only review P. 229-247 “Extratropical Cyclones”

2. Typical model of the organization of precipitation in extratropical cyclones based on the Norwegian cyclone model (note vertical scale is stretched by a factor of 30 from the horizontal) About right

3. Typical evolution of a marine extratropical cyclone from its open wave stage through the occluded stage

4. Classification of rainbands based on studies in the Pacific Northwest • Warm-Frontal Bands • occur within the leading portion • of the frontal system • warm advection occurs through a • deep layer • oriented parallel to warm front • typically about 50 km wide • can be along (1a) or ahead (1b) • of warm front

5. Schematic cross section through warm frontal rainband

6. Classification of rainbands based on studies in the Pacific Northwest • Warm Sector Bands • occur within the leading portion • of the frontal system • warm advection occurs through a • deep layer • oriented parallel to warm front • typically about 50 km wide • can be along (1a) or ahead (1b) • of warm front

7. Schematic cross section through warm sector rainband

8. Classification of rainbands based on studies in the Pacific Northwest • Wide Cold-Frontal Rainbands • parallel to cold front • behind or along cold front • typically about 50 km wide • in case of occlusions, associated • with cold front aloft

9. Schematic cross section through wide cold frontal rainband

10. Classification of rainbands based on studies in the Pacific Northwest • Narrow Cold-Frontal Rainband • coincides with surface cold front • typically about 5 km wide • marked difference in structure • from other band types

11. Schematic structure of narrow cold frontal rainbands

12. Classification of rainbands based on studies in the Pacific Northwest • Pre-frontal cold surge rainbands • associated with surge of cold air • aloft ahead of cold front • otherwise have characteristics of • wide cold frontal bands

13. Schematic structure of pre-frontal cold surge rainbands and wavelike bands

14. Classification of rainbands based on studies in the Pacific Northwest • Post-frontal rainbands • lines of convective clouds forming • well behind cold front • Generally parallel to cold front

15. Example Interaction between rainbands (wide and narrow cold frontal example) WCFR disturbs and overtakes NCFR WCFR disturbs and eliminates NCFR WCFR reaches NCFR and dissipates

16. Statement of understanding in 1982 from HH (82) “Although the full classification of rainbands described above is based on observations in the Pacific Northwest (refs), it is consistent with observations of rainbands in the United Kingdom (refs) and in the northeastern United States (Cunningham 1951, Boucher 1959, Austin and Houze 1972). It is also consistent with observations made in subtropical oceanic cyclones near Japan (Nozumi and Arakawa 1968). There is good reason to believe that the picture in Fig. 4 is representative of the inherent mesoscale organization of precipitation in extratropical cyclones.” Today • Classification is reasonable for marine cyclones. Does not generally apply to continental cyclones over central North America, since • frontal structures do not conform well to Norwegian model and • convective instability is much different from marine cyclones