The storm that hit the Central Coast on Tuesday was unlike any other October storm since records have been kept, with many one-day rainfall records for the month broken, especially in the northern part of San Luis Obiso County.
The last time we received over an inch of rain in one day in October occurred on Oct. 19, 2004, when a cold front passed over San Luis Obispo County.
The Diablo Canyon Ocean Lab rain gauge recorded 1.5 inches of precipitation in just six hours.
On Monday, we saw a storm developing in the eastern Pacific; later that day it would further intensify before moving toward British Columbia.
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This low-pressure system produced a steep pressure gradient along the West Coast with the surface charts showing the isobar lines tightly spaced together.
The southerly winds in many locations, especially in the northern part of the county, reached over 50 mph.
And on the newly installed Condor Lookout weather station on Hi Mountain in the Los Padres National Forest — which has an elevation of 3,190 feet — wind gusts reached 85 mph.
The associated warm front arrived on Tuesday morning producing a steady rain.
The rain continued over the next 24 hours as another very-slow-moving weather front from the west passed our area.
It was hard to call this a cold front because there wasn’t really any cold air associated with this system, and there wasn’t much of a wind shift.
Feeding into this weather system were the remnants of former superTyphoon Melor that had slammed into Japan earlier in the month.
The upper-level charts indicated an extremely strong jet stream centered directly over the Big Sur coastline.
This jet acted like a conveyor belt, bringing in tropical moisture from the eastern Pacific.
The south to southwesterly winds pushed air masses higher as they hit the coastal mountains, causing more rain to fall.
Meteorologists call this “orographic enhancement.”
Farther south in the county, the rainfall totals slowly decreased.
The San Luis Obispo County Water Resources rain gauge on the top of Rocky Butte near San Simeon recorded 13.7 inches of rain.
E-mail that I received from readers reported between 7 and 10 inches along Highway 41 between Morro Bay and Atascadero.
I had one report of 10.5 inches in See Canyon.
The SLOweather.com rain gauge in the hills near Los Osos Valley Road and Foothill Boulevard recorded 7.7 inches, while Cal Fire Station 15 — the former South Bay Fire Department in Los Osos —recorded 5.2 inches.
The Diablo Canyon Ocean Lab rain gauge recorded 2.5 inches; further south in Nipomo the San Luis Obispo County Water Resources rain gauges ranged from 1.1 and 2.4 inches.
Nacimiento Lake went from 9 percent of capacity to 18 percent in 24 hours. That’s what I call a rainstorm.
This week’s forecast
Saturday morning’s northeasterly (offshore) winds produced warm and clear weather along the coastline and in the coastal valleys, while fog and mild temperatures developed in the interior.
The winds shifted out of the northwest (onshore) yesterday late morning producing cooler temperatures and giving relief to many soccer players.
A weak cold front will brush Northern California this morning with a few rain showers.
The main effect of this cold front along the Central Coast will be increasing northwesterly (onshore) winds along with variable mid to high-level clouds today.
The onshore flow will bring night and morning coastal low clouds and fog along with cooler temperatures.
Another, stronger weather system will push through Northern California on Monday and will bring rain as far south as the Bay Area.
As this cold front moves down the California coastline on Monday it will produce gentle and variable winds, a deep marine layer, drizzle and mild temperatures throughout our area.
The cold front will be followed by increasing northwesterly winds on Tuesday.
High pressure is expected to develop over the Great Basin late Tuesday producing gentle to moderate (8-18 mph) northeasterly(offshore) winds during the night and morning hours, followed by fresh to strong (19-31 mph) northwesterly winds along the shoreline during the afternoon hours.
This condition will lead to mostly sunny skies and above seasonable temperatures along the beaches and in the coastal valleys, while the interior could see areas of night and morning fog and cooler temperatures, a reversal of what normally transpires between the coastline and interior during spring and summer months.
Surf and sea report
This morning’s 4- to 6-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 11-second period) will become a 4- to 5-foot northwesterly swell (with an 8- to 11-second period) on Monday.
Increasing northwesterly winds will produce a 5- to 6-foot northwesterly (300-degree deep-water) sea and swell (with a 4- to 11-second period) on Tuesday through Wednesday.
A 968 millibar storm is forecast to develop 2,000 miles to the west of Oregon on Monday.
A 2-to-4-foot west-northwesterly (285-degree deep-water) swell (with a 20- to 22-second period) is forecast to arrive along our coastline late Wednesday, building to 10 to 12-feet (with a 16- to 18-second period) on Thursday.
This west-northwesterly swell will decrease to 8 to 10 feet on on Friday, followed by another increase in northwesterly swell next weekend.
Arriving from the southern hemisphere, a 1 foot southern hemisphere (245-degree deep-water) swell (with an 18-20 second period) will arrive along our coastline on Monday, increasing to 1 to 2 feet (with a 16-18 second period) on Tuesday through Wednesday.
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John Lindsey is a media relations and nuclear communications representative for Pacific Gas and Electric Co. He is also a meteorologist who specializes in forecasting for San Luis Obispo County. Send him questions to firstname.lastname@example.org.