Geopotential heights are contoured black every 60 gpm. Isotherms are contoured
red every 3 °C.The main feature is a strong closed Low centered over southern IA. This is WNW of its 850 mb location. Contours are much smoother on this chart than for 850 mb, which are smoother than for the surface. Hints of fronts can be seen, though much less defined. 500 mb is well above the ABL and most of the weather action, such that friction should be minimal and the gradient wind a good approximation. Thus the analysis rules discussed should be remembered and used where possible. Data is abundant enough though that linear interpolation of contours would definitely not be bad. Typically upper air data is not so abundant at many places, such as over oceans; so that the rules and aids can be quite helpful for making sense of sparse observations.
I can discuss many of the small features & perhaps bore you if you already aren't. Contour spacing generally corresponds with winds and latitude as supposed - e.g., no contours in the stagnant area NNW of the cyclone center, closely-spaced contours in the jet stream SSE of it. A broad but weak trof extends from S MO to MS & the Gulf of Mexico. I drew this because it corresponds well with geopotential height readings and the turning winds to its E. A front may be analyzed here if desired. The data also supports ridging E of the cyclone. The Wward bulge of the 534 contour N of the cyclone and curving of the 552 & 558 contours over W NY to SW ON justify the bulge in the 546 & 540 contours drawn between. Geopotential height data over TX and turning of winds between there & S NM supports the gentle shortwave trof drawn over TX. Perhaps the 558 contour should be nearer the 5560 gpm observation over NE TX, but that could be 5555 gpm even if the data is correct. I think the single digits should be reported in radiosonde data !
As I also mention in the article, perhaps I analyzed this chart a little like a klutz, with
my preference for linear interpolation and smooth contours; but I don't believe an analyst
should suppose too many shortwaves or microridges exist if the data does not clearly support
them. The general pattern is imperative. Some analysts might want the contours nearer at some
places where winds are strongest and vice-versa, but please remember that the gradient wind is
only theoretical, (geostrophic) adjustment processes are always occurring, and weather phenomena
constantly disturbs the theoretical balance the atmosphere tends to achieve.
Text and embedded image are copyright of Joseph Bartlo, though may be used with proper crediting.