In May, San Diego got 2.39 inches of rain. It was the second most ever recorded in town during the month. That was weird.
In July, remnants of Hurricane Dolores delivered 1.71 inches to San Diego, the most ever in July. That was very weird.
On Tuesday, Hurricane Linda leftovers, pulled up by a trough that dropped down from the north, dumped 1.24 inches at Lindbergh. Very odd.
But we may be about to encounter the strangest weather we've had all year. The National Weather Service says that this coming week, the precipitable water level, a measure of the moisture in the atmosphere that could fall as rain, could be the highest on record for Southern California in the month of September.
The so-called PW this coming week could surpass the 2.15 inches measured in September 1997, when remnants of former Hurricane Nora drenched the region, and San Diego got 0.76 of an inch. The weather service now projects 0.88 of an inch at Lindbergh Field this week. Mount Laguna stands to get more than 2.5 inches.
And none of this moisture is from a former hurricane or tropical storm. It's coming from a rather odd cut-off low that will be off the coast of Baja. That low will pull up moisture from the south and southwest on Monday. Then the low will pass over Southern California late Monday/early Tuesday.
San Diego could see several rounds of intense rain with thunderstorms likely on Monday and perhaps again on Tuesday. Flash-flood warnings are a good possibility, especially in recent burn areas.
Heavy rain, thunderstorms and the risk of flash flooding will expand from northwestern Mexico and into the southwestern United States into Wednesday.
A surge of tropical moisture from the eastern Pacific will unleash an expanding area of torrential downpours and locally gusty thunderstorms. The downpours could be more widespread and heavier than the typical storms.
While the atmospheric event will bring beneficial rain to some drought-stricken areas and greatly aid firefighting efforts, the same system will threaten lives and property.
The combination of heavy rain and rocky, rugged terrain in the region will lead to the risk of flash flooding and mudslides.
Rainfall in this swath is likely to average 1-2 inches (25-50 mm) with local amounts of 4 inches (100 mm) possible, especially along the southern- and southwestward-facing slopes of the mountains.
Even where rain may seem insignificant at a particular location, a torrential downpour over a nearby mountain or canyon could lead to flash flooding within minutes.