| Humidity
levels at about 9,000-11,000 ft MSL are important for monsoon tracking because
summer thunderstorm cloud bases in Arizona and Nevada usually develop near that level.
Rather than using a constant height, meteorologists usually look at the
specific levels in the atmosphere that have a constant pressure. The 700mb
layer conveniently corresponds to 9,000-11,000 ft MSL. Past research indicates
that when the 700mb dewpoint increases above 0°C, the chance of thunderstorms
increases. When the 700mb dewpoint is above +5°C, the resulting thunderstorms
are more likely to produce heavy rains and possibly flash flooding.
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