I missed the beggining of the last explanation that Dave read about the cold conveyor belt. Is there someone who can write it here?
Thanks!
Julie
Cold conveyor belt flows sely relative to the reference frame moving with the storm. Since the storm is moving relative to the ground, the observed direction will be different. For example, if the storm system is advancing eastward, and the CCB flows sely relative to the storm system, the resultant direction will be deflected to swly.
I can't believe I didn't think about it...
Thanks
An supercell develops in a high shear environment, more importantly in a high shear environment that is storm relative. Such as system is said to be ... baroclinic. Essentially, supercells develop in baroclinic zones.
Why shouldn't other storms behave the same way? The answer is, there's no reason they shouldn't, and that was the central thesis of much of the late Jim Moore's research; he was a frequent contributor to the MSC Winter Weather Course by the way. He spent many years investigating the role of storm-relative flows as they applied to synoptic storm systems prior to his death.
I bring this up, because this case that Elena presented, seems to be yet another case where the storm-relative flow leads to insights that the ground-relative flow doesn't show, or doesn't show easily.
Why shouldn't other storms behave the same way? The answer is, there's no reason they shouldn't, and that was the central thesis of much of the late Jim Moore's research; he was a frequent contributor to the MSC Winter Weather Course by the way. He spent many years investigating the role of storm-relative flows as they applied to synoptic storm systems prior to his death.
I bring this up, because this case that Elena presented, seems to be yet another case where the storm-relative flow leads to insights that the ground-relative flow doesn't show, or doesn't show easily.
Very good explanation. As you saw my conveyor belt image was from comet and there is more material about it - I wonder if Dave could link it here.
There are two kinds changes we see: changes in time and changes with height. I understood Julie also asked why we see the change more clearly in velocity than in direction, and part of that explanation lies within averaging over cylinder (remember the CDs in the pre-reading material ?)
Another comment to Ka's first question about the reflectivity to amount of rainfall-conversion: yes we see more reflectivity in snowfall in warmer temperatures, but the larger snowflakes also contain more water. However, the reflectivity grows with 6th power of diameter, while the amount of water grows only with 3rd power of diameter. All dbZ-to-mm equations assume some particle size distribution, this is always a default, and in snowfall the assumption is worse than is liquid rain. Also on the liquid rain, some people use different dBZ-to-mm equation for convection (large drops) than for stratiform rain (small drops).
What is more, the density of snow varies: fluffiest snowflakes contain 90% air, whle the heavily rimed almost graupels are 40% ice, 60% air. Knowing the density of snow is a subject of intensive research, especially with polarimetric radars.
Thank you for active participation, good luck with continueation of the class
Elena
There are two kinds changes we see: changes in time and changes with height. I understood Julie also asked why we see the change more clearly in velocity than in direction, and part of that explanation lies within averaging over cylinder (remember the CDs in the pre-reading material ?)
Another comment to Ka's first question about the reflectivity to amount of rainfall-conversion: yes we see more reflectivity in snowfall in warmer temperatures, but the larger snowflakes also contain more water. However, the reflectivity grows with 6th power of diameter, while the amount of water grows only with 3rd power of diameter. All dbZ-to-mm equations assume some particle size distribution, this is always a default, and in snowfall the assumption is worse than is liquid rain. Also on the liquid rain, some people use different dBZ-to-mm equation for convection (large drops) than for stratiform rain (small drops).
What is more, the density of snow varies: fluffiest snowflakes contain 90% air, whle the heavily rimed almost graupels are 40% ice, 60% air. Knowing the density of snow is a subject of intensive research, especially with polarimetric radars.
Thank you for active participation, good luck with continueation of the class
Elena