A Case Study of the Onset of the North American Monsoon 16-17 July 2002

The importance of this study was to research the intensity and effects of El Nino in the year of 2002 both regionally and globally. The record-breaking 1997-1998 El Nino attracted global attention which affected global weather conditions. The focus of this study was the North American Monsoon (NAM) and the effects on the global circulation cycle. The North American Monsoon (NAM) is a type of meteorological phenomena that occurs in the desert southwest region of the United States (Adams and Comrie 1997). The meteorological setup for the North American Monsoon is highly dependent on the position of a high-pressure system located within the Mexican Plateau. This strong high-pressure ridge progressively moves north into the Southwestern United States and eventually positions itself near the ‘Four Corners’ region of the country (this region geographically describes the borders of the states of Utah, Colorado, New Mexico, and Arizona) (U.S. Department of Commerce, NOAA 2016). The location of this high pressure, combined with the effects of El Nino/La Nina (ENSO) cycle will be examined for the year of 2002. A case study of the dates of July 16-17 was examined to determine these dates as the onset of the monsoon in Las Vegas, Nevada. Temperature data was collected from Las Vegas, Nevada using METAR data from Harry Reid International Airport using the months of July through August. Reanalysis data for the METAR data from Las Vegas was evaluated with a 75% correlation. This indicated a moderate accuracy in the data collected from Las Vegas. The data errors were because of observational data when compared to reanalysis data obtained from ECMWF Reanalysis v5 (ERA5). Future studies will include a timeline of weather observations leading up to the onset of the NAM in the Southwestern United States to include the precise location of the high pressure in the Mexican Plateau, precipitation data, and wind circulation patterns in relation to the thermal low. Global, synoptic, and mesoscale circulation patterns will also be analyzed to provide an enhanced comprehension of the NAM.