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El Niño Tracker Update - December 2014

Friday, December 19, 2014

From the Dec 18, 2014 - Southwest Climate Outlook - 

We are still waiting for a decisive signal, but conditions indicate we are near, or possibly already into, at least a weak El Niño event. Sea surface temperatures (SSTs) are elevated across the equatorial Pacific Ocean (Fig. 1), and the measurements in the Niño 3.4 region are indicative of El Niño having already started (Fig. 2).

There remains a distinct lack of cooperation on the part of the atmosphere. This lack of coupling between ocean and atmosphere (demonstrated by near-normal wind and rainfall anomalies), along with a lack of temperature gradient along the equatorial Pacific and little in the way of El Niño wind patterns, means that while we are likely already experiencing El Niño-like conditions in the Southwest (e.g. some of the recent wet weather), it may be a little longer before a formal declaration occurs, even if retroactively.  

On Dec. 4, the NOAA-Climate Prediction Center (CPC) issued another El Niño Watch, with a 65 percent probability of a weak El Niño event occurring.  Anomalous SSTs alone were probably enough to suggest a weak El Niño event, but the lack of atmospheric coupling kept the current assessment at ENSO-neutral.  On Dec. 10, the Japan Meteorological Agency declared that an El Niño started in late summer and that it would continue through early 2015. This was based on favorable El Niño conditions and elevated SSTs, even while other more robust criteria were not yet met. On Dec. 16, the Australian Government’s Bureau of Meteorology maintained its El Niño tracker status at El Niño Alert status, despite a lack of atmospheric conditions to complement the anomalous SSTs. That outlook assigned a 70 percent probability of a weak El Niño event developing in winter 2014–2015. The Dec. 18 International Research Institute for Climate and Society (IRI) and CPC upped the probability of El Niño conditions developing to more than 80 percent in the next three months and more than 70 percent through spring and into summer (Fig. 3).

The North American multi-model ensemble shows a weak event that extends well into spring (Fig. 4). The extended period of above-average SSTs appears to be increasing confidence in the formation of El Niño this winter into spring.

Seasonal precipitation forecasts still indicate an enhanced chance of above-average precipitation over the upcoming winter, but confidence in this forecast is partially contingent on the strength of the emerging El Niño event. The impacts associated with weak El Niño events are generally less certain than those of a moderate or strong event, with past weak events bringing both dry and wet conditions to the Southwest U.S. during the winter. Ultimately, the above-average tropical storm season and the humidity that has remained in the region may be indicative of the effect of El Niño-like conditions, and we may be seeing the emergent effects of El Niño impacts on the climate of the Southwest, despite the absence of a formal definition identifying the start of a bounded El Niño event.

Southwest Climate Outlook Dec 2014

Thursday, December 18, 2014

Taken from the Dec 18, 2014 - Southwest Climate Outlook - 


Precipitation: November was particularly dry in Arizona and New Mexico, with many locations recording no measureable precipitation (Fig. 1). A few events in December brought widespread moisture to the region, but actual measureable precipitation was still relatively low despite these incursions. The dew point remains well above seasonal averages, likely related to the persistent tropical activity and the conditions that favor the formation of an El Niño event. 

Source: High Plains Regional Climate Center - HPRCC

Temperature: Arizona and New Mexico were warmer than average over the past 30 days (Fig. 2), continuing a yearlong trend, and Arizona is on track for the warmest year on record. The persistently high dew point is also related to observed temperature, as we have yet to see an extended cool/dry period that brings lower nighttime temperatures to the region.

Source: High Plains Regional Climate Center - HPRCC

Snowpack & Water Supply: Snow water equivalent (SWE) is low across Arizona and New Mexico, ranging from 0 to 50 percent of average in Arizona and 0 to 90 percent of average in New Mexico (Fig. 3). Despite a few widespread snowfall events, high temperatures and below-average precipitation have led to lower-than-average snowpack levels across the region. In October, total reservoir storage was 45 percent in Arizona (compared to 47 percent last year) and 22 percent in New Mexico (compared to 22 percent last year). 

Source: Natural Resources Conservation Service - NRCS

Drought: The monsoon and tropical storm season brought seasonal rainfall totals close to or above average across Arizona and New Mexico, but these intense storms provided limited long-term drought relief, with widespread areas well below-average over the past 12 to 36 months (Fig. 4). The Four Corners region, northeast New Mexico, and portions of southern Arizona experienced the largest deficits in the past 12 months. The likelihood of an El Niño event continues to offer hope for additional drought relief. There is hope that regular precipitation over the winter may still help saturate soils in the region, which could lead to higher reservoir storage during springtime snowmelt runoff events, even if temperatures stay above average and snowpack is below average, 

Source: High Plains Regional Climate Center - HPRCC

ENSO: Forecast projections range from 65 percent to more than 80 percent probability that an El Niño will occur, with several outlooks indicating an El Niño event is imminent, if not already underway.  The Southwest is experiencing El Niño-like weather patterns and should continue to do so into the spring, especially if the El Niño event is moderate in strength.

Precipitation Forecasts: The Dec. 18 NOAA-Climate Prediction Center seasonal outlook continues to predict above-average precipitation through the winter and into early spring (Fig. 5). This forecast is tied to the ongoing conditions favorable to an El Niño event and the impact of the Pacific Decadal Oscillation.

Temperature Forecasts: The Dec. 18 NOAA-Climate Prediction Center temperature forecasts remain split across the region, with elevated chances for above-average temperatures along the West Coast, extending eastward into Arizona, and with increased chances for below-average temperatures along the Gulf Coast into New Mexico (Fig. 5). This pattern is projected through the winter and into the spring.

Source: NOAA-Climate Prediction Center

Nov 2014 SW Climate Podcast: A Warm End to Autumn and Waiting for ENSO

Wednesday, December 10, 2014

In the November Southwest Climate Podcast, Ben McMahan and Mike Crimmins discuss the warm autumn weather in the southwest, the transition to winter weather patterns, the ongoing uncertainty of El Niño forecasts, a recap of El Niño conditions and definitions, and the possibility of interaction between El Niño conditions and weather patterns in the southwest looking forward.

Intro 0:00
A Wet and Warm Autumn: Warmer than average temps, higher than average humidity, and a recent "cold" snap 1:00
Recap of 2014 Tropical Storm Season: A more active season in the E Pacific 7:30
El Niño Forecast Models: More on how El Niño is defined, models that go into them, and the current state of "now-casting" 13:44
El Niño Definition: Revisiting a more precise definition of El Niño and the conditions we might expect (if it ever arrives) 22:00
Looking toward the Future: Impact of El Niño conditions on the SW, and looking forward into 2015  27:00
Recap on Long Term Forecasts & Looking Forward 34:00

If you have a question you'd like answered, you can email Zack Guido (zguido@email.arizona.edu) or Ben McMahan (bmcmahan@email.arizona.edu) with "CLIMAS Podcast Question" in the subject line. You can also tweet us @CLIMAS_UA or post a question on facebook

Also, as we mentioned last month, we have a new podcast feature: video mini-segments from the podcast.  We have four segments posted from previous podcasts, including:

And we have decided to release approximate transcripts of the podcast.  

Suggested Source/Citation:

CLIMAS: Climate Assessment for the Southwest, (2014). A Warm End to Autumn and Waiting for ENSO. [podcast] CLIMAS Southwest Climate Podcast. Available at: climas.arizona.edu/podcast/nov-2014-sw-climate-podcast-warm-end-autumn-and-waiting-enso [Date Accessed]

Notes from an Applied Climatologist - Nov 2014 Rainlog Climate Summary

Monday, December 1, 2014

A pesky ridge of high pressure over the east Pacific dominated the weather for much of November.  This steered storms well to our north and east, leaving Arizona with unusually warm and dry conditions.

The month started off with promise, as a strong and relatively cold low pressure system dropped down the West Coast, clipping northern Arizona as the storm turned east. This system was largely starved of moisture, but managed to bring some light precipitation (and even some snow) to parts of northern Arizona. Rainloggers in Flagstaff reported precipitation amounts of 0.1 to 0.5” inches on the 1st and 2nd of the month. Other parts of the state, including the area along the Mogollon Rim near Show Low and down into southeast Arizona, saw limited precipitation over the next several days as the low pressure system became a closed low and wandered to the south and into Mexico.

This bit of weather and moisture was short lived. A strong ridge of high pressure quickly built over the east Pacific and desert Southwest causing temperatures to rise well above average and the persistence of a dry weather pattern through the middle of the month. Strong storm systems entering through the Pacific Northwest started to weaken and flatten the ridge towards the middle of the month causing temperatures to moderate to near-average levels across Arizona, but brought very little in the way of precipitation. Northeast Arizona was clipped by a weak system on the 15th and 16th that brought very light precipitation to mostly high elevation areas along the Mogollon Rim. A handful of Rainloggers in the Show Low and Springerville areas reported precipitation amounts of 0.1 to 0.3 inches over this period.

The end of November was again at the mercy of the strong east Pacific ridge as it built quickly again over the last week of the month. Temperatures were at record or near-record levels across the state on the Thanksgiving holiday. The Tucson National Weather Service reported that the high temperature of 83F was the 6th warmest Thanksgiving on record for Tucson.

All of the state observed below-average precipitation with much of the west and central parts of Arizona observing no precipitation at all, and short-term drought conditions remain firmly entrenched across all of the state. El Nino still appears to be on its way and may still bring some relief in the form of average to above-average precipitation over the next several months.

 

What is El Niño? - From the SW Climate Podcast

Monday, December 1, 2014

This mini-segment was taken from the November 2014 Southwest Climate Podcast


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