Image 1 is the surface weather map for 00Z 29 OCT 2012, Sunday evening. At map time Hurricane Sandy was seen off the North Carolina coast. Sandy’s central pressure was reported by the National Hurricane Center as 950 mb. Radar echoes showed precipitation extending from the Mid Atlantic States to New England and westward to the Ohio River Valley. The cold front stretched along the coast with northern and southern sections shown as stationary. An extension of high pressure from Lake Superior to eastern Texas represented the cold air mass that followed the cold front.
Based on station models in the broad arc from Maine to Florida, the winds indicated that the flow about the center of Sandy’s intense low-pressure center was [(clockwise and outward)(counterclockwise and inward)].
Reported surface wind speeds across the coterminous U.S. were generally less than those at New York City, Detroit, MI, Cape Hatteras, NC, and Atlanta GA, which were two full feathers or [(10)(15)(20)] knots.
Image 2 is the 500-mb constant-pressure map for Sunday evening, 00Z 29 OCT 2012, the same time as the Image 1 surface map. The mid-tropospheric flow pattern shown by the contour lines on the 500-mb map, was one of [(a trough across the eastern U.S.)(a ridge across the eastern U.S.)(smoothly zonal west-to-east flow across the U.S.)]
Recall that the heights at which the radiosondes detected 500-mb of pressure are reported in the upper right position of the upper-air station models on the map. Also, the heights are plotted in tens of meters, so that a “0” needs to be added to the digits for the actual height. The height of the 500-mb pressure level plotted at Cape Hatteras, on the eastern tip of North Carolina, was [(5440)(5570)(5620)] m.
Comparing the heights of the 500-mb pressure surface from south to north on the map, as latitude increases (one moves poleward), particularly over the western U.S., the height of the 500-mb surface generally [(increases)(remains constant)(decreases)], but not always when strong storms are present!
The highest wind speeds plotted on the 500-mb map were at several stations including Little Rock, AR, where there were one pennant and one long feather for a total speed of[(30)(60)(100)] kts generally from the northwest, much higher than surface wind speeds.
Image 3 is the 300-mb constant-pressure map for 00Z 29 OCT 2012, the same time as the surface and 500-mb maps. The 300-mb station model heights are also plotted in tens of meters. The heights of the undulating 300-mb pressure surface were within several hundred meters of [(5500)(9300)(12,500)] meters. The 300-mb level occurs in the upper troposphere.
The general 300-mb contour pattern at 00Z on 29 OCT exhibited an upper air flow with [(a trough across the eastern U.S.)(a ridge across the eastern U.S.)(smoothly zonal west-to-east flow across the U.S.)] The curvature of the contour lines on both the 500-mb and 300-mb maps also suggests the existence of a weak ridge over the western U.S.
Comparing the heights of the 300-mb pressure surface from south to north on the map, as latitude increases (one moves poleward), the height of the 300-mb surface generally[(increases)(remains constant)(decreases)], in most cases.
This latitude-height relationship at 300 mb is consistent with the same relationship in Item 5 at 500 mb. Generally, there is also a corresponding change in temperature, confirming that pressure decreases more rapidly in colder columns of air than warmer ones (again recall Investigation 5B).