Ask the Meteorologist: How have we been able to see so much rain without a tropical system?

So far this July, Raleigh has seen more rain than it saw all of January through June. 

In fact, it's been the second-wettest July on record in the Capital City.

WRAL learned Tuesday that water supply levels have improved at both Falls Lake and Jordan Lake.

What's been causing the rain?

We've had a number of fronts come through the area this month.

Cold fronts in the fall, winter and spring often move through the area with now issue. They have more wind support behind them to guide them east, resulting in big temperature and humidity shifts. 

In the summer months, however, that guiding wind is far north.

These fronts move into the area, but no upper-level wind is close enough push the front farther east. 

The front then stalls nearby.

Dr. Gary Lackmann at NC State taught us that new storm systems can form where there's already "pre-existing vorticity." In Layman's terms, that means new storm systems can form where fronts already exist.

As these storms ride in from the west, they draw in more tropical moisture.

Stalled fronts can be big rain makers

Why would a front cause rain?

A front is a boundary between two different airmasses. In the summer time, it's separating tropical moisture south from less humid air north. 

The air converges along the boundary and subsequently rises. It rises to a point where storms form, and they move slowly due to the lack of upper-level wind.

This is a large part as to why we've been able to score on some much-needed rain, while also avoiding any named tropical storms/hurricanes from the Atlantic.