A series of strong Pacific storm systems hit the Bay Area Monday night in what National Weather Service officials say is the beginning of the much-anticipated El Nino.
Bay Area residents can expect about an inch of rainfall in the lower elevations and more than three inches possible in coastal and mountain ranges, according to weather service forecaster Bob Benjamin.
The beginning of the system came through this morning but has since dissipated, Benjamin said.
Commuters in the Bay Area should be advised that the majority of the rainfall is expected to occur during the peak morning commute hours today and Wednesday. People should expect delays and possible flooding in areas with poor drainage, according to Benjamin.
The storms appear to signal the start of El Nino conditions, Benjamin said, which the National Oceanic and Atmospheric Administration described as unusually warm equatorial sea temperatures across the Pacific Ocean.
“The previous systems we saw had a lot of cold air, with temperatures at freezing or near freezing. In this system, we’ll see the temperatures remain about the same through the day and night with the clouds remaining low,” Benjamin said.
Passengers at San Francisco International Airport can expect some flight delays as a ground delay program was put into effect this morning, SFO spokesman Doug Yakel said.
Ground delay programs, which reduce the flow of aircraft into the airport, are often triggered by weather conditions such as rain or heavy fog at SFO, Yakel said.
Passengers are encouraged to check with their airlines prior to arriving at the airport for any delays or updated information regarding their flights.
The rain is expected to let up by the weekend, but is likely to be back at the beginning of next week, weather service officials said.
I’m glad that this needed drenching is happening during a waning moon.
Hmmm – how does the waning moon matter? Thanks
Tides
“Tides”
Not much to be glad about there. A dark moon means the moon is on the sun side of earth, where its gravity augments the sun’s gravity and makes for extra high tides. Also, we are at perihelion, so the sun’s gravitational effects are at max.
Fortunately, our storms are being relatively tame.
Yup, prediction is for a high tide of +8.7 feet at 9:38AM tomorrow.
High tides 6 inches higher with New Moon this weekend.
Though not much rain forecast.
Curious – the tidal basin around here impacts flooding, as do the tidal creeks. All tidal forces this time of year dovetailing with heavy rains are something to keep an eye on.
An Engineer – the perihelion occurred before this week’s rains commenced, so something to be glad about, actually. We are still due for some high tides, but this week I was concerned about the rain’s impact on the creek and the moon phase since the high tides + rain are occurring post-perihelion and pre-new moon this month. Hard to know what’s ahead this month and next, though.
Musical – exactly – which is why I commented as I did. Am I recalling correctly that in the big flood it was a new moon and high tides? I’m noticing a difference on the creek monitor this week vs the rains during the waxing moon and high tides before Christmas, when the creek was much higher during the high tides.
“An Engineer – the perihelion occurred before this week’s rains commenced, so something to be glad about, actually.”
Well, although the almanacs mark an instant of perihelion, the earth’s orbit is fairly circular so our distance from the sun has not changed very much. We are still in a period of enhanced solar tide effect.
Perihelion and lunar apogee occurred the same day, resulting in fairly even keel (pun intended) tides for a few days. Since the solar tides don’t influence as much as lunar tides, and the rain started a few days after, we caught a break this week. I hope it’s not the only break we will get this winter. Next week could be interesting.
“Perihelion and lunar apogee occurred the same day, resulting in fairly even keel (pun intended) tides for a few days.”
We’ll take it.
Aphelion-perihelion distances are pretty consistent, about a 3.4% swing every year. The moon orbit is surprisingly more variable, anywhere from 6% to 14% difference between apogee and perigee month to month in any given year.
I haven’t found much regarding the effect of how far the moon is north or south of the equator (“declination”), which goes as high as 28 degrees in an 18-year cycle. Complicated motions but predictable centuries ahead.
On top of this will be rainfall, wind, and barometric pressure.
Beware the perfect storm.
Check this out https://www.uwgb.edu/dutchs/Graphics-Geol/Animations/TideNodes0.gif . Keyword: amphidromic points
From a Santa Clara Valley Water District webpage:
“More than 90% of the actual observed tides are higher than the predicted tides with 3% more than a foot higher. The National Ocean Survey prepares the tide tables based on astronomic conditions, which account for only 70% of the influence on tidal action. Other factors are meteorological conditions such as barometric pressure or wind speed and direction. A drop of 0.1 inch in barometric pressure will increase the tide height by 0.1 feet.”
“Other factors are meteorological conditions such as barometric pressure or wind speed and direction.”
Plus inflows from nearby watercourses.