DENVER — The satellite image on Thursday showed a bit of a swirl in the clouds over the Four Corners. That's what’s left over from Tropical Storm Harold— meteorologists call it tropical remnants.
Harold made landfall near South Padre Island, Texas on Tuesday, but quickly broke apart over Mexico about 620 miles south of Colorado.
But the storm’s remnants— the moisture that’s still associated with the original system— blended into the monsoon flow, boosting the rainfall probabilities.
There is an excessive rainfall risk for one to four inches of rain for parts of northeast Colorado all day Friday into Saturday morning. Only a few areas are likely to get over two inches, but many more spots will likely get a half inch to an inch of rain over 36 hours.
These scenarios of tropical infusions are not common, but there have been a few examples in the state.
The highest known rainfall total was from an unnamed tropical cyclone that came out of the Pacific Ocean in October of 1911. It dissipated in Arizona, but the remnants brought more than eight inches (8.16”) of rain to Colorado.
In 1992, Hurricane Lester dissipated in New Mexico near Albuquerque, but the remnants from that storm went on to drop more than five inches (5.35”) of rain on Wolf Creek Pass in Colorado.
Here are the most recent examples, before Harold.
- 2021 Hurricane Nora (Pacific)
- 2016 Hurricane Newton (Pacific)
- 2015 Hurricane Blanca (Pacific)
- 2008 Hurricane Dolly (Atlantic)
- 2004 Hurricane Javier (Pacific)
- 1997 Hurricane Nora (Pacific)
When Colorado gets tropical remnants, the storms usually come from the Pacific Ocean— Harold is coming from the Atlantic side. The last time moisture came to our state from an Atlantic-born tropical cyclone was Hurricane Dolly in 2008.
The only other tropical system known to come to Colorado from the Atlantic side was Hurricane Debra back in 1959.
The large dome of high pressure that is causing the surge in monsoon moisture is also responsible for pressing Tropical Storm Harold straight west and bringing the moisture from its remnants around the side of the ridge.
70s return Friday with possible storms and showers
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