Get ready for some weather whiplash, SLO County: Hot temps followed by thunderstorms expected

July presented contrasting temperature patterns between San Luis Obispo County and Santa Barbara County.

In San Luis Obispo County, temperatures were nearly record-breaking, while in Santa Barbara County, they were slightly below average.

At Paso Robles Municipal Airport, the mean temperature for July was 78.6 degrees Fahrenheit, just 0.3 degrees shy of the record of 78.9 set in 2006. Meanwhile, the San Luis Obispo County Regional Airport recorded a mean of 70.5, which is 4 degrees above normal and only 0.3 degrees below the record mean of 70.8 for July, set in 1931.

In contrast, Santa Barbara County experienced cooler conditions. The Santa Maria Airport had a mean temperature of 63.6, compared to its historical average of 64.2. The Santa Barbara County Airport reported a mean of 65.2, about 0.7 degrees cooler than normal.

Many readers have inquired about the likelihood of a La Niña condition developing this winter, which could bring below-average rainfall.

Unfortunately, the Climate Prediction Center forecasts that the current neutral condition, known as “El Nothing” or “El Nada,” will transition to a La Niña condition in the central equatorial Pacific Ocean. This region, referred to as Niño 3.4, is the standard for classifying El Niño (warmer-than-normal sea-surface temperature) and La Niña (cooler-than-normal SST) events.

These cycles in the northern Pacific Ocean suggest about a 75% chance of below-average rainfall for the Central Coast this rainfall season.

Meanwhile this week, an upper-level high-pressure system centered over the Four Corners region will continue to produce triple-digit temperatures in the inland valleys (Paso Robles) and mid-80s in the coastal valleys (San Luis Obispo).

The coastal regions will experience night and morning low clouds and fog with pockets of mist and partial afternoon clearing as moderate to fresh (13 to 24 mph) northwesterly winds develop. Temperatures along the beaches will range from the high 50s to the low 60s. This pattern is expected to continue through Wednesday.

Monsoon moisture from Hurricane Carlotta off the Baja Peninsula will bring variable mid- to high-level clouds and a slight chance of rain showers and thunderstorms, primarily in the eastern regions of San Luis Obispo and Santa Barbara counties. This condition will result in lower maximum daytime temperatures but warmer overnight lows with higher humidity levels from Wednesday into Friday. Along the coastline, this subtropical moisture often dissipates the marine layer, leading to sunnier skies.

Another tropical cyclone, which would be named Daniel, is expected to bring another chance of monsoon moisture that could generate thunderstorms the following week.

Surf report

A 3- to 5-foot northwesterly (295-degree deep-water) swell (with an 8- to 11-second period) is forecast along our coastline through Wednesday, decreasing to 2- to 4-feet with the same period on Thursday through next Sunday.

Combined with this northwesterly swell, will be a 1- to 2-foot southern hemisphere (220-degree deep-water) swell (with a 13- to 15-second period) through Wednesday.

Even though Hurricane Carlotta, is not expected to produce any significant waves along the Central Coast, another predicted tropical cyclone, Daniel, is forecast to intensify to hurricane strength levels and move northward off the Baja Peninsula toward Southern California.

If this condition verifies, a 2- to 4-foot hurricane swell (180-degree deep-water) swell (with a 14- to 16-second period) will arrive along the Central Coast beaches on Friday. Note: This swell will be much bigger in Southern California.

Seawater temperatures

Surface seawater temperatures will range between 54 and 56 degrees through Wednesday, warming to 55 to 58 degrees on Thursday through next Sunday.

On this date in weather history (Aug. 4)

1882: A vivid aurora was visible from Oregon to Maine, down the east coast as far as Mayport, Florida, and inland as far as Wellington, Kansas. Observers at Louisville, Kentucky, noted merry dancers across the sky, and observers at Saint Vincent, Minnesota, noted it was probably the most brilliant ever seen at that location. (The Weather Channel)

1980: A record 42 consecutive days of 100-degree heat finally came to an end at the Dallas-Fort Worth Airport. July 1980 proved to be the hottest month of record with a mean temperature of 92 degrees. There was just one day of rain in July, and there was no measurable rain in August. There were 18 more days of 100-degree heat in August, and four in September. Hot weather that summer contributed to the deaths of 1,200 people nationally, and losses from the heat across the country were estimated at twenty billion dollars. (The National Weather Summary)

This week’s temperatures

LOWS AND HIGHS, PASO ROBLES

LOWS AND HIGHS, SAN LUIS OBISPO AND COASTAL VALLEYS

John Lindsey is a retired PG&E marine meteorologist. Email him at JohnLindseyLosOsos@gmail.com or follow him on Twitter @PGE_John.