La Niña Is Gone - El Niño To Return This Spring?
2017 Starting Off Warmer & Wetter Than Normal.
(January 1st - February 17th).
U.S. Year-To-Date Daily Average High Temperature Anomaly.
(January 1st - February 17th).
U.S. Year-To-Date Daily Average Low Temperature Anomaly.
(January 1st - February 17th).
U.S. February Average Temperature Anomaly.
(February 1st - February 17th).
U.S. February Daily High Temperature Anomaly.
(February 1st - February 17th).
U.S. February Daily Low Temperature Anomaly.
(February 1st - February 17th).
U.S. 2017 Precipitation Totals.
(January 5th - February 17th).
U.S. February 2017 Precipitation Totals.
(February 1st - February 17th).
California 2017 Year-To-Date Precipitation Totals.
(January 5th - February 17th).
California 2017 February Precipitation Totals.
(February 1st - February 17th).
New Mexico & Texas 2017 Year-To-Date Precipitation Totals.
(January 5th - February 17th).
New Mexico & Texas 2017 February Precipitation Totals.
(February 1st - February 17th).
So far this year is starting out warmer to much warmer than normal across the nation. This can be in part be blamed for the above average sea surface temperatures in the Pacific Ocean, and the Gulf of Mexico. And to a somewhat lesser degree the Eastern Atlantic Ocean. La Niña conditions over the Pacific Ocean have dissipated leaving the Ocean in a near neutral condition. There are increasing signs that El Niño conditions will return later this spring or early this summer.
The MJO has had a huge short term impact on this winter's temperatures and precipitation. Also playing a role in this winters pattern was the early and deep snowpack and cold across Northern Asia, which helped produce a strong jet stream that cooled the waters of the Central Pacific Ocean.
So instead of Climate Change once again its the planet's natural cycling of the its Oceans (in this case the Warm PDO Phase) that has been a driving force in how this winter has turned out so far. These factors have helped to form "The Atmospheric River Events" that have produced record to near record rainfall totals across California and parts of the Western U.S. this winter. Click on this link to view some of the more recent significant AR Events.
Sadly the worst of this winter's onslaught may yet to occur in California. Long range computer forecast models and climatology suggest that yet more storms will line up and take aim at California and the Western U.S. as we transition out of winter and into spring. This will be bad news for them as temperatures warm and the record to near record snowpack in the mountains begin to melt and fill already swollen lakes, rivers, and creeks.
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More Heavy Rain & Snow For California Today Into Tuesday!
Area Forecast Discussion National Weather Service San Francisco Bay Area 955 AM PST Sun Feb 19 2017 .SYNOPSIS...High impact event set to unfold during the next 24 to 36 hours as a potent Pacific storm system and atmospheric river brings widespread rainfall and strong winds to the region. Periods of heavy rainfall are likely from late this evening through Monday evening, potentially resulting in flooding across portions of the region. In addition, southerly winds will increase late today and be locally strong and gusty through Monday evening. Widespread rainfall will then taper off late Monday night into Tuesday. Cooler and somewhat drier weather conditions are expected late in upcoming week. && .DISCUSSION...as of 10:00 AM PST Sunday... The next wet and windy storm system is nearly at our doorstep, with KMUX radar already showing scattered rain showers moving inland from offshore. These precursor rain showers are associated with the initial push of a 1-1.5" TPW plume originating from the tropics and extending to the California coastline. Precipitation accumulations from these early rain showers have already brought over half of an inch of rain to some portions of the coastal North Bay, including at the Venado and Oak Ridge observation stations. Additional weak to moderate rain showers are expected to continue through midday and into the early afternoon hours. Meanwhile, south-southeast winds will gradually ramp up in strength through the same time period, especially along the coast and over higher peaks and ridges. By late this afternoon into early this evening, the deeper moisture surge will begin to advect inland and bring heavy rainfall. Models continue to disagree on where this initial surge of moisture will arrive, however, there has been a noticeable model trend to nudge the main precipitable water plume northward from Big Sur towards the Santa Cruz/San Mateo coastal mountains over the last 24 hours. As such, have modified the QPF forecast grids to reflect this, with lesser amounts for Big Sur and other portions of Monterey/San Benito county as the most noticeable change. The remainder of the overnight package appears on track at this time, so see previous discussion for details on the current forecast. .PREVIOUS DISCUSSION...as of 03:29 AM PST Sunday...Light precipitation being reported this morning mainly across the North Bay and down through the San Mateo coast inland into portions of the East Bay. This precipitation is associated with increased moisture advection across the region along with a weak mid/upper level system approaching from the west. Rainfall will generally remain light through the early morning and begin to increase in coverage and intensity later in the day as warm air advection spreads across the region. By late this afternoon and evening, an atmospheric river (AR) with PWAT values forecast to exceed 1.35" will take aim at the Central Coast and further increased rainfall rates, especially along the coastal ranges as onshore surface winds also increase. Breezy to locally gusty winds greater than 45 MPH will be possible, especially along the coast and in the higher elevations. By late tonight, the heaviest rainfall will likely become more narrow in focus along a frontal boundary that is forecast to lift northward somewhere between the Santa Cruz Mountains and the greater North Bay region. Rainfall will likely further intensify and the threat for flash flooding, flooding of area creeks, streams and low lying, poorly drained areas will significantly increase. With that said, the forecast models continue to struggle on exactly if/when the AR will stall and where this might occur. Regardless, considerable rainfall will be possible from late tonight into Monday across portions of the region. With super saturated soils across just about the entire region, downed trees and isolated power outages along with rock/ mud slides, shallow landslides and debris flows across recent burn scar areas remain of great concern. The heavier band of precipitation is then forecast to slowly sag southward from Monday morning through the afternoon and evening hours. However, some of the forecast models, such as the NAM show the boundary stalling over the North Bay and not progressing southward until late Monday into Monday night. This event will have to be closely monitored and folks in flood prone areas are urged to remain vigilant, stay up to date on the latest forecast information and take necessary precautions to protect life and property. Rainfall amounts of 4 to 7 inches will be possible along the coastal ranges with the potential for some locations to see upwards of 10 inches. Meanwhile, North Bay valley locations, coastal areas in and around the San Francisco Bay Area and areas around Santa Cruz have the potential to receive 2 to 5 inches of rainfall through Monday night. Further south and inland, rainfall totals will range from 1 to 2 inches with lesser amounts possible in inland valley locations from the Santa Clara Valley southward through the Salinas Valley due to rain shadowing effects. Given the antecedent conditions from a very wet winter so far, a Wind Advisory and Flood Watch remain in effect from this afternoon through early Tuesday morning. By late Monday into Tuesday, the forecast models indicate the deeper plume of moisture will finally shift southward as an upper level trough approaches the Pacific Northwest. This should result in the more organized rainfall to shift south of the region as well with lingering showers likely from Tuesday into Wednesday as the parent mid/upper level trough shifts inland across northern California. While any additional rainfall after the AR event will only exacerbate any ongoing flooding, widespread heavy rainfall is not currently forecast from Tuesday into Wednesday. Dry weather conditions are then expected from late Wednesday into early Friday as a short-wave ridge builds across the region in wake of the exiting trough. Forecast model solutions diverge from late in the week into next weekend, however the GFS and ECMWF now show the potential for additional unsettled weather conditions late in the forecast period, mainly Friday night into Saturday as a cold, mid/upper level low drops southward down the West Coast. Stay tuned as forecast confidence remains low beyond early next week. &&
Area Forecast Discussion National Weather Service Sacramento CA 524 AM PST Sun Feb 19 2017 .Synopsis... Wet weather with renewed flooding concerns into the middle of next week with wettest storm of the bunch expected for Monday through Tuesday. Gusty winds likely again Monday. Mountain travel will also be impacted at times due to heavy snow. Valley thunderstorms possible Tuesday and Wednesday. && . Discussion... Large upper level trough in the northeast Pacific will continue to impact norcal weather over the next several days. A shortwave disturbance pivoting through central California this morning in southwest flow ahead of the trough is bringing light rain to the Sacramento and Delta area this morning. A 6 mb surface gradient from Redding to Sacramento is bringing breezy winds to the northern Sacramento valley this morning with sustained winds between 20 and 25 mph north of about Chico. Have issued wind advisory through today for this area as model guidance keeps this level of winds going through the day. Snow levels this morning range from about 3500 feet northern Shasta county to 5000 feet over the northern Sierra. Snowfall amounts should be relatively light today although chain controls are still in affect for the major Sierra passes. More light showers expected this afternoon as another shortwave disturbance pivots through...this time a little farther north. Things begin to ramp up this evening as a much stronger and wetter Pacific storm system moves onshore. Widespread moderate to heavy rain and snow are expected with gusty winds as this atmospheric river weather system moves through. The blended total precipitable water satellite product shows PW values of and inch and a half within the river with locally even higher values. This is a return interval in the 5-10 year range. Precipitation amounts max out during the day on Monday. Between tonight and Monday night...1 1/2 to 2 1/2 inches of rain are forecast for the valley and orographically favored areas of the Sierra west slopes could see up to 8 inches of rainfall during this time. Snow levels during this time will climb to about 7000 feet but are still likely to be low enough to continue to impact pass level travel over the Sierra. Rainfall will likely create even more flood issues during and after Monday. A flood warning will remain in place for interior Norcal through much of the week. Winter storm warnings have been issued for the Sierra Cascade range. As if this is not enough...evening stronger winds are expected Monday evening as the main frontal band shifts through with 925 nb progs from the NAM showing over 55 mph winds. This will likely produce another round of power outages as soggy ground allows even more trees to topple on powerlines. Focus of heaviest rainfall continues to shift southward. Heaviest rainfall still likely over the American river basin and now southward so needed to increase QPF south of the 80 corridor from previous forecasts. Precipitation drops off on Tuesday behind the main front as do winds but snow levels drop as colder air filters in so a larger area of Sierra will be impacted by snowfall. Have extended the winter storm warning through Tuesday evening. Main upper trough shifts through on Wednesday keeping the showers going and bringing down snow levels even farther but precip amounts should be relatively light. Snow levels could be down to 3000 feet by Wednesday evening. Cold air aloft that brings down the snow levels will also destabilize the atmosphere so it is likely that the valley will see isolated afternoon and evening thunderstorms Tuesday and Wednesday. && .EXTENDED DISCUSSION (Thursday THROUGH Sunday) Thursday into Friday is expected to be mainly dry as short wave high pressure ridging moves in, with just some lingering mountain and foothill showers. Any precipitation is expected to be light. Northerly winds should limit fog formation, moist low level conditions could allow some fog/mist to develop in sheltered areas. Extended models are trending towards a wetter scenario for late Friday through Saturday night. Models previously were showing a less wet scenario, and disagree on the track of a low which is dropping down from western Canada. If the latest GFS is correct, this cold be a rather wet system, though quite a bit less than the early week system. If the ECMWF and GEM are correct, there could be some precipitation, but not a large amount. Sunday there is a relative lull in the wet weather, with mainly mountain precipitation. This may a brief lull, with yet another system expected on Monday, showing no significant break in the wet pattern. EK &&
Why So Much Rain & Snow This Winter In California?
Atmospheric Rivers (ARs) are relatively narrow regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics. While ARs come in many shapes and sizes, those that contain the largest amounts of water vapor, the strongest winds, and stall over watersheds vulnerable to flooding, can create extreme rainfall and floods. These events can disrupt travel, induce mud slides, and cause catastrophic damage to life and property. However, not all ARs cause damage – most are weak, and simply provide beneficial rain or snow that is crucial to water supply.
On average, about 30-50% of annual precipitation in the west coast states occurs in just a few AR events, thus contributing to water supply. In the strongest cases ARs can create major flooding when they make land-fall and stall over an area.On average, about 30-50% of annual precipitation in the west coast states occurs in just a few AR events, thus contributing to water supply.In the strongest cases ARs can create major flooding when they make land-fall and stall over an area.ARs are a primary feature in the entire global water cycle, and are tied closely to both water supply and flood risks, particularly in the Western U.S.A well-known example of a type of strong AR that can hit the U.S. west coast is the "Pineapple Express," due to their apparent ability to bring moisture from the tropics near Hawaii to the U.S. west coast.A strong AR transports an amount of water vapor roughly equivalent to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River. ARs move with the weather and are present somewhere on the earth at any given time.
What are atmospheric rivers, in more scientific terms?
ARs are the water-vapor rich part of the broader warm conveyor belt (e.g., Browning, 1990; Carlson, 1991), that is found in extratropical cyclones ("storms"). They result from the action of winds associated with the storm drawing together moisture into a narrow region just ahead of the cold front where low-level winds can sometimes exceed hurricane strength. The term atmospheric river was coined in a seminal scientific paper published in 1998 by researchers Zhu and Newell at MIT (Zhu and Newell 1998). Because they found that most of the water vapor was transported in relatively narrow regions of the atmosphere (90% of the transport occurred typically in 4-5 long, narrow regions roughly 400 km wide), the term atmospheric river was used. A number of formal scientific papers have since been published building on this concept (see the publication list), and forecasters and climate researchers are beginning to apply the ideas and methods to their fields.
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Examples of AR events.
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The satellite images at left show strong ARs as seen by satellite. The advent of these specialized satellite observations have revealed ARs over the oceans and have revolutionized understanding of the global importance of ARs (more traditional satellite data available in the past could not clearly detect AR conditions). The interpretation of these satellite images, which represent only water vapor, not winds, was confirmed using NOAA research aircraft data over the Eastern Pacific Ocean and wind profilers along the coast (Ralph et al. 2004). The event shown in the bottom-left image was documented by Ralph et al. (2006), which concluded this AR produced roughly 10 inches of rain in 2 days and caused a flood on the Russian River of northern California. It was also shown that all floods on the Russian River in the 7-year period of study were associated with AR conditions. As of late 2010 there have been a number of papers published on major west coast storms where the presence and importance of AR conditions have been documented. These are provided in an informal list of the "Top Ten ARs" of the last several years on the U.S. West Coast. It is now recognized that the well-known "Pineapple express," storms (a term that has been used on the U.S. West Coast for many years) correspond to a subset of ARs, i.e., those that have a connection to the tropics near Hawaii. In some of the most extreme ARs, the water vapor transport is enhanced by the fact that they entrain (draw in) water vapor directly from the tropics (e.g., Bao et al 2006, Ralph et al. 2011).
The Truth Is Stranger Than Fiction!
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