Tropical WaveNegatively Tilted (Plan)
This is a chart from the NWS/NCEP Aviation model, August 1998. It is a plot of the 850 hPa winds (barbs/KT). Note the inverted “V” shape of this trough over the Tropical Atlantic. On the plan view, it is hard for the meteorologist to tell is this is a positively or negatively tilted wave by just looking at one chart.