With a southeast surface wind, the stronger the wind the better. The stronger the surface wind the more low level wind shear you have, and the better your chances for tornadogenesis.
(Can a moderator perhaps split this off into a different / new thread?)
Not necessarily. Strong surface winds may create strong extremely-near-surface (e.g. 0-10
m) wind shear, but we typically look for wind shear in the 0-1, 0-3, and 0-6 km layers. If 6 km winds are 40 kts from the southwest, then southerly surface winds of 30 kts will create LESS wind shear than southerly surface winds of 5 kts. Think about this in terms of a hodograph -- the "longer" the vector between, for example, the 6 km wind and the surface wind, the stronger the wind shear between those levels. Strong low-level, but above-surface, winds (e.g. at 850 mb) are often desireable, but that's not really the surface wind. Let's look at any example hodograph.
Note that the hodograph below represents that of a VEERING wind profile (i.e. the winds veer from southerly to west-southwesterly at 6 km). This is a
straight-line hodograph despite having winds that veer with height:
The
red line represents a wind profile characterized by a surface wind of 30 kts from the south, a 3km wind of ~40 kts from the southwest, and a 6 km wind of 60 kts from the west-southwest. The
red star represents an approximate storm motion for a right-moving supercell. Now, let's look at the
blue lines... The only difference is that we now have a surface wind of 10 kts from the south, with the 3km and 6 km winds the same as for the red wind profile. Note that the change in the surface wind has had some change in the winds between the sfc and 3 km. Similar to before, the
blue star is an approximate storm motion for a right-moving supercell. Owing to a WEAKER surface wind, the
blue wind profile actually has
more 0-3km SRH! Because the
red wind profile yields a straight-line hodograph, there won't be ANY 0-3km SRH for initial convection; any 0-3km SRH will only arise when storm can split, whereafter the right-moving supercell will take a motion that takes it off the hodograph. In the
blue case, even a storm that does NOT have a storm motion that deviates from the norm will ingest some 0-3km SRH. The blue wind profile does have slightly stronger 0-6 km shear, but they're pretty similar in that regard.
Similarly, let's look at an example of a couple of vertical wind profiles for which a VEERED surface wind will actually resulted in higher 0-3 km SRH than a backed surface wind:
Again, the
red wind profile features southeasterly surface winds at 10 kts, south-southwesterly 3 km winds at 30 kts, and between southwesterly and south-southwesterly 6 km wind. So, the mid-level flow is a bit meridional, but this isn't uncommon sometimes, and often not "bad" given southeasterly surface winds. Yet again, despite both
directional and
speed shear in the
red wind profile, this is a straight-line hodograph. So, unless you get a right-moving supercell (which probably won't happen until after a cell splits), there is actually 0 0-3 km SRH. Now, let's say the surface wind veers to the southwest and remains 10 kts -- this is the
blue wind profile. Now, because there is some curvature of the low-level flow (e.g. no longer a straight-line hodograph), even initial convection (moving with the mean flow) will ingest some 0-3km SRH. If we take a supercell with minor right-moving characteristics, we note that the 0-3km SRH with this
blue wind profile (i.e. veered sfc wind) actually has
more 0-3 km SRH than the
red wind profile. In other words, we would actually want a VEERED surface wind, since it yield better curvature to the low-level hodograph. In this case, the
red wind profile does have marginally greater 0-6km shear.
From the two above idealized example hodographs, all of which feature winds that VEER and increase in speed with height (e.g. all hodographs have directional and speed shear). However, one can see that there are wind profiles for which weaker surface winds are better than strong surface winds. In addition, one can see that there are wind profiles for which a veered / SWrly surface wind yields a better hodograph (and greater 0-3km SRH) than a backed / SErly surface wind. This is not necessarily intuitive, but it brings about the importance of looking at a hodograph.
EDIT: The storm motions above are only eye-balled estimates, but they illustrate the point I think. The storm motion for the blue case in the 1st example may be too fast, but the point remains.
