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#487588 03/07/14 03:45 AM
Joined: Oct 1999
Posts: 84,400
Marty Offline OP
OP Offline

NOAA has issued an El Ni�o Watch for the summer and fall of 2014, giving a 50% chance that an El Ni�o event will occur. The March 6 El Ni�o discussion from NOAA's Climate Prediction Center noted that "While all models predict warming in the tropical Pacific, there is considerable uncertainty as to whether El Ni�o will develop during the summer or fall. If westerly winds continue to emerge in the western equatorial Pacific, the development of El Ni�o would become more likely. However, the lower forecast skill during the spring and overall propensity for cooler conditions over the last decade still justify significant probabilities for ENSO-neutral. The consensus forecast is for ENSO-neutral to continue through the Northern Hemisphere spring 2014, with about a 50% chance of El Ni�o developing during the summer or fall."

None of the El Ni�o models predict La Ni�a conditions for peak hurricane season, August-September-October 2014, and 8 of 18 predict El Ni�o conditions. Temperatures in the equatorial Eastern Pacific need to be 0.5°C above average or warmer for three consecutive months for an El Ni�o episode to be declared; sea surface temperatures were -0.6°C from average as of March 3, and have been +0.1 to -0.7°C from average since April 1, 2013. El Ni�o conditions tend to make quieter than average Atlantic hurricane seasons, due to an increase in upper-level winds that create strong wind shear over the Tropical Atlantic.

Figure 1. Depth-longitude section of the departure of ocean temperature from average over the equatorial Pacific upper ocean between 0 - 300 meters between 5°S and 5°N during the period February 25 - March 1, 2014. Averages are taken from a 1981 - 2010 base period. While surface temperatures in the Eastern Pacific were near average to cooler than average, a strong eastwards-propagating Kelvin wave with temperatures up to 6°C (11°F) above average at a depth of about 160 meters was headed towards the Eastern Pacific. If unusually strong westerly winds continue over the equatorial Western Pacific during March and April, this Kelvin wave has the potential to trigger a strong El Nin�o event over the Eastern Pacific later this year. Image credit: NOAA/CPC.

An impressive westerly wind burst over the Equatorial Pacific
The potential El Ni�o event has been made more likely over the past month due to the intensification of a strong "Westerly Wind Burst" (WWB) along the equatorial Pacific west of the Date Line. As of March 6, 2014, westerly winds that were more than 10 m/s (22 mph) stronger than average had developed between 140 - 150°E, just north of New Guinea. These unusually strong westerly winds were acting to push warm water piled up to the east of the Philippines eastwards towards South America. The "Westerly Wind Burst" was due, in part, to the counter-clockwise circulation of wind around Typhoon Faxai, which became a tropical storm on February 28 near 9°N, 149°E, and later intensified into a Category 1 typhoon. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, was also likely involved in amplifying the WWB. In order to keep the momentum of this WWB going and trigger a full-fledged El Ni�o event, some additional west-to-east push of winds is likely needed during March and April. Some extra push may come from a tropical disturbance (96P) that has developed this week south of the Equator near 13°S 153°E, to the northeast of Australia. The clockwise circulation of air around this storm is bringing increased westerly winds to the Equator in the region of the WWB, and the Joint Typhoon Warning Center is giving this disturbance a "medium" chance of developing into a tropical depression or tropical storm by Friday. The GFS and European models predict that this storm will move southwards and bring heavy rain to the Queensland province of Australia over the weekend.

Figure 2. Departure of the 5-day average west-to-east blowing wind (the "zonal" wind) from average, averaged along the Equator, between 2°S and 2°N. A strong "Westerly Wind Burst" (WWB) formed in January 2014 near 140°E, and has intensified and propagated eastwards along the Equator. As of March 6, 2014, westerly winds that were more than 10 m/s (22 mph) stronger than average had developed. Image credit: NOAA/PMEL.

Additional links
An El Ni�o Coming in 2014? Guest blog post by Dr. Michael Ventrice on February 21, 2014.

Dr. Jeff Masters

Joined: Oct 1999
Posts: 84,400
Marty Offline OP
OP Offline

Record-Warm Subsurface Pacific Waters May Bring Moderate to Strong El Ni�o Event

Today's guest blog post is by Dr. Michael Ventrice, an operational scientist for the Energy team at Weather Services International (WSI). This is a follow-up post to the one he did on February 21 on the progress of El Ni�o. Today's post is very technical! - Jeff Masters

There have been tremendous changes in the Pacific Ocean over the past two months which continue to favor a moderate to strong El Ni�o event later this spring and summer. Since my previous post on February 21, NOAA's Climate Prediction Center (CPC) has issued an El Ni�o watch.

To begin, we are currently observing what looks to be the strongest downwelling oceanic Kelvin wave event since satellite records began in the 1970s. This still needs to be verified in reanalysis, but a large swath of 6°C (11°F) ocean temperature anomalies at a depth of 100 - 200 meters (Figure 1) clearly illustrates the significance of this event. To review, oceanic Kelvin waves travel only from west to east at extremely slow speeds (2-3 m/s). These waves have been alluded to as the facilitators of El Ni�o. There are two phases of an oceanic Kelvin wave, the "Upwelling" phase and the "Downwelling" phase. The Upwelling phase of an oceanic Kelvin wave pushes colder water from the sub-surface towards the surface, resulting in cooling at the surface. The Downwelling phase is the opposite, where warmer waters at the surface of the West Pacific warm pool are forced to sink, resulting a deepening of the thermocline and net warming in the sub-surface.

Figure 1. Departure of ocean temperature from average along the Equator in the Pacific Ocean on March 29, 2014 (top), shows a large area of 6°C (11°F) ocean temperature anomalies at a depth of 100 - 200 meters. A time lapse is available here. Image credit: NOAA/CPC.

In the West Pacific, the thermocline is rising in response to strong upwelling (cold ocean temperature anomalies near the surface). In the central and eastern Pacific, the thermocline is deepening as the warm pool has begun to rapidly shift towards the Date Line. An enlightening time lapse can be found on the NOAA/CPC webpage. Note the lens of colder than average ocean temperature anomalies at the surface in the far eastern Pacific. This can be attributed to a surge in the Easterly trade winds over the eastern equatorial Pacific, which pushes water away from the coast, resulting in some upwelling off the west coast of South America. The surge in the trade winds is just an expression of atmospheric processes occurring in the tropics at intra-seasonal (weekly) timescales. Nevertheless, it is evident that the entire West Pacific Warm Pool has begun to shift eastward, and there is a large adjustment in the Pacific Ocean currently underway.

That being said, we still need to see some favorable atmospheric forcing this month to continue the forward advancement of a full-basin El Ni�o. In particular, west-to-east blowing winds along the Equator are needed to keep pushing warm water eastwards towards South America. Keeping this in mind, there are some signs of an upcoming period of westerly wind bursts along the equatorial Central Pacific in the next few weeks.

Figure 2. Rainfalls rates over the Indian Ocean (shaded colors), departure of the winds at 200 mb from average (arrows), and Kelvin filtered velocity potential at 200 mb (VP200, contours.) Image credit: Michael Ventrice.

An exceptionally strong atmospheric convectively coupled Kelvin wave (CCKW) is currently propagating across the equatorial Indian Ocean. IMPORTANT: An atmospheric CCKW is DIFFERENT than an oceanic Kelvin wave since atmospheric CCKWs are stratospheric waves in the *atmosphere* that are confined to just the equatorial band. Thus we cannot experience a CCKW passage in North America. CCKWs often couple with thunderstorm activity within the troposphere in the tropics. In addition, CCKWs in the atmosphere are non-dispersive in theory, so they can make many circuits around the globe before attenuating from external forcing such as friction; oceanic Kelvin waves can only travel the distance of whatever basin they are in (in this case, the Pacific). However, *both* atmospheric CCKWs and oceanic Kelvin waves propagate from west to east only.

Figure 3. A time-longitude plot of unfiltered VP200 anomalies (shaded) with Kelvin filtered VP200 anomalies (contours; dashed contours represent the upper-level divergent phase of the CCKW or its convectively active phase) illustrates the non-dispersive nature of this CCKW, as it makes a complete circuit around the globe. Image credit: Michael Ventrice.

Figure 4. GFS model forecast for April 6, 2014. Six-hour precipitation rates are shaded. Often during and up to a few days after the passage of a strong CCKW, tropical cyclones can develop on either side of the Equator, depending on the season. An example can be seen over the Southern Indian Ocean this week, where the GFS model is forecasting the development of a tropical "gyre" that could become a tropical depression. Note the equatorial westerlies are a component of the anatomy of the CCKW circulation itself.

The forecast calls for this Indian Ocean CCKW to push across the Date Line during mid-April. This would be a time when we might see another period of westerly winds develop across the equatorial Central Pacific--favorable atmospheric conditions for a full-basin El Ni�o to emerge. The anticipated westerly wind burst in mid-April may be composed of individual tropical cyclones, or extra-tropical waves intruding the tropics.

In addition to the CCKW itself, there are higher than average probabilities of another developing Madden Julian Oscillation (MJO) to emerge over the West Pacific following the passage of this strong CCKW, in mid-to-late April. A great deal of my graduate study work focused on CCKW-MJO interactions and the plot below is from Ventrice et al. (2012), which is of a time-longitude composite plot of unfiltered VP200 anomalies (shaded), Kelvin filtered outgoing long wave radiation (OLR) anomalies (black contours), and MJO filtered OLR anomalies (orange contours). From selecting only dates where a strong CCKW passed the eastern tropical Atlantic, a lagged composite approach from these dates reveal a remarkable picture. Once the CCKW passes across Africa to over the Indian Ocean, we often observe a developing MJO event over the Indian Ocean that then propagates eastward across the Pacific region thereafter. There are increased chances of a similar scenario to play out over the next few weeks.

Why does this matter for El Ni�o? Well, within and following the passage the convectively active phase of the MJO, we often observe an increased number of West Pacific typhoons and low-level westerly wind flow. This is what is likely needed to continue the eastward advancement of the West Pacific Warm Pool this spring, and provides more evidence for a full-basin El Ni�o event to emerge later this spring in through summer. Furthermore, it is important to note that the latest climate model forecasts are now more aggressive with the amplitude of the potential emerging El Ni�o. This can be seen in both the ECMWF and CFSv2 Ni�o3.4 forecasts. For the purpose of illustration, below is the CFSv2 model forecast from mid-February 2014:

And here is the CFSv2 model forecast from Early April 2014:

Nearly a +0.5°C adjustment has been made in just one month for the June-July-August period and beyond, indicating that the model is even more bullish on the El Ni�o this spring in through summer.

Bottom Line: The Pacific Ocean continues to show signs of a developing moderate to strong El Ni�o event. During strong full-basin El Ni�o's, we often observe cooler than average temperatures in summer across the eastern two thirds of the U.S., and lower than average Atlantic hurricane activity.

Michael Ventrice

Dr. Michael Ventrice is an operational scientist for the Energy team at Weather Services International (WSI), who provide market-moving weather forecasts and cutting-edge meteorological analysis to hundreds of energy-trading clients worldwide. Follow the WSI Energy Team on Twitter at @WSI_Energy and @WSI_EuroEnergy.

Jeff Masters

Joined: Dec 2006
Posts: 13,675
This is a lot of techno talk but I'm interpreting it as Good News for us here in the Caribbean.

White Sands Dive Shop
Joined: Oct 2001
Posts: 6,267
Gotta love the first line of the forecast --- a 50% chance of an El Nino.
Safe bet, that.

Joined: Oct 2003
Posts: 2,461
Mas or menos, I guess

Belize based travel specialist
[email protected]
Joined: Jul 2009
Posts: 66
Once again some smart weather prophets and every year they start a bit earlier and if I read about a chance of 50% of this and that I cannot help myself but think that I have some idiots in front of me, some guys with personality problems who just want to seem very important (at least for the next few weeks) - sorry for my words but my stomache is turning when I read such a crab!

Marty - it is not about your post - it is about these guys who are always wrong - always - and still do not shut up! They're incapable to predict even one week in advance but permanently open their mouth to spit this carb over us!

I remember one year when even I could have predicted more acurate: it was in 2006 or 2007; the weather was pretty cool in spring and the real summer heat started in May instead of April and you could feel that the ocean was much cooler than all the years before. They then predicted a hurricane season 85% above average and every person with a bit of brain in the head could guess that this could not be true as tropical cyclones need warm water temperature - the water was colder than all the years before. 4 months later they admittedd that they were wrong and it was a season so very much below average!!!!

Last year on October 23 Mr. Bob Lightbown warned from a forthcoming hurricane and a chance of 30 to 40% blablabla . wow: what a great chance - 30 to 40% - that sounds like real danger and in the end nothing happened even if he claimed that this could happen anywhere in the Caribbean but maybe West of 70 West Longitude. NOTHING happened but we might perhaps have convinced some possible tourists to change idea from coming to us and rather go to the Rockies! Every year the same crab!

Well guys, I realize that every time when my big toe has a slightly greenish color and the small hair in my nose itch more than 5 times a day then we're going to have a 10 to 42.456% chance of a heavy hurricane season. Please take your measurments and prepare for the worst!

...if not I might perhaps have to wash my feet more frequently????

Again another beautiful day in paradise - just smile and be happy :-)
Joined: Dec 2006
Posts: 13,675
Ya know I really understand how you feel. It makes me angry also that the forecast can actually have me giving back money on canceled reservations from tourist reading this crap. They don't read it like us they just pick up on key words like Hurricane + Caribbean + Chance and go hysterical.

White Sands Dive Shop

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