February 20, 2021 Weather Impacts On Economic Activity – Major Storm And New Insights

Written by Sig Silber

We had a major storm and there is new information on how our climate may be changing. I have not completed my analysis of the new information but I am presenting what I have as Part I and providing information on the recent storm as well as an update on the Spring runoff situation and the status of major reservoirs. There is also a new drought forecast. As usual, we include a lot of other information including an intermediate-term weather forecast.

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I want to attempt to present a paper that explains why we have more La Ninas than El Ninos. I think you can read the full paper here. I am not positive of that because I am registered with ResearchGate but they did not ask me to log in so I think you can access the full article but hopefully I will present enough for readers to understand the concept.

The rest of the discussion is later on in the article. And consider this an introduction because some of my readers may be familiar with this but for me, it is uncharted territory. So I need to do a lot more research. But what caught my interest was the part of the discussion not shown here but in the slides that are presented later in this article which suggests that the Pacific Decadal Oscillation or PDO does not explain as much about weather cycles (what I call low-frequency weather cycles) as I have assumed and that there are other factors now that need to be included in the analysis. One of the two is the Pacific Meridional Model or PMM mentioned in the Abstract. If that is the case, and I can come across some other references to this it is very important – let me just say it that way.

I have moved the other slides I made to somewhere close to the end of this article. I will be coming back to this topic very soon. I am not sure yet if this theory if you want to call it that explains why we may have a two-year La Nina this time around. It is not clear that we will but some of the models suggest it. Not all La Nina’s are dry for the Southwest but most are. So if the ratio of two-year La Ninas to one-year La Ninas is increasing, that is very important. I could have held back all this information until was read to fully discuss it but that did not seem to be proper. Some of my readers may know more about this and can leave me messages in the comment section that follows every article I publish.

I also see the possible connection of what is discussed in this paper with the storm we just had. In the article I posted last night on the NOAA four-season forecast I provided some snapshots of the Equatorial Pacific which showed a lack of movement of the cool and warm anomalies. I showed four snapshots which basically covered three months but I could have gone back many more months and it would have looked similar. You can see that set of graphics here. The importance of that is this La Nina is not decaying rapidly. So it could last into next winter or fade for a short period of time and later regain La Nina Status. I am not making any predictions here but I am raising the question of has something fundamentally changed?

I am certainly familiar with the deliveries to Elephant Butte the major reservoir on the Rio Grande and I am familiar with the deliveries to the three beneficiaries of that project namely an irrigation district in New Mexico, a similar irritation district in El Paso County Texas, and Mexico. Shortly after the MegaNino of 1997 and the subsequent La Nina of 1998 deliveries declined to Elephant Butte Reservoir and to the three (there is actually a fourth in good years when there is surplus water available to Hudspeth County Tx under a Warren Act Contract). I concluded that this was a normal change of phase of the PDO but perhaps there is more to it. So that explains my interest in the topic and although I frame the issue in a New Mexico context it impacts essentially all of the U.S.

I was not going to publish tonight but due to the storm, I have some interesting information on the storm so I did not want to hold that back for a week. So I am presenting what I have on the Double-Dip La Nina even with my presentation being Part I rather than the full presentation and I am presenting most of the usual information that is in this Weather Economics article. I did not include any NASS reports although there are a few but I can include them next week.

The rest of what I have appears later in this article.

Let’s now discuss the recent and ongoing Major Winter Storm.

This is a more up-to-date map of snow coverage.

Where Things Stand in terms of Spring Runoff

Reservoir Status

Let us focus a bit on California

Let’s look at the current drought situation.

And the week to week change

Here we look at four-time periods: one week, one month, six months, and a full year.

The result is very dry soil conditions

February Drought Outlook

Intermediate-Term Weather Forecast

Showing from left to right, Days 1- 5, 6 – 10, 8 – 14, and Weeks 3 – 4 You can click on these maps to have them enlarge. Also, the discussions that go with these forecast maps can be found here (first two weeks) and here (Weeks 3 and 4).

First Temperature

And then Precipitation

The Week 3-4 Discussion is always interesting.

Week 3-4 Forecast Discussion Valid Sat Mar 06 2021-Fri Mar 19 2021

In the tropics, the La Nina pattern continues to maintain a strong presence over the equatorial Pacific while the Madden Julian Oscillation (MJO) signal across the west Pacific has weakened over the last several days. The RMM index, which appears to be influenced by other tropical waves and the current La Nina state, is forecast to continue weakening during the next week. There is some indication that a weak MJO may re-emerge prior to the start of the forecast period, but multimember ensembles from the GEFS and ECMWF are uncertain on the timing and location. In the extratropics, the Arctic Oscillation (AO) has undergone a transition from a strong negative phase to a slightly positive phase and is forecast to stay neutral/positive throughout the Week-2 period. With these factors in mind, this week’s forecast is primarily based on a blend of dynamical model guidance with additional influences from La Nina.

The anomalous 500-hPa height patterns are in good agreement among the dynamical models (CFS, ECMWF, JMA and the SubX multi-model ensemble). Models consistently feature positive height anomalies over the North Pacific and off the coast of Newfoundland with below normal heights across Alaska. This pattern bears some similarity to the positive phase of the AO. The most relevant inconsistency among the dynamical models is the extent to which the troughing over Alaska extends down to the western coast of CONUS, with the CFS favoring a more southward extension compared to the ECMWF and JMA.

As a result of the widespread positive height anomalies over much of CONUS, the temperature forecast tilts broadly toward above-normal probabilities from the Southwest to the eastern US. The highest probabilities are forecast throughout the Upper Midwest and the Northeast. The troughing over Alaska favors colder than normal conditions across the southern part of the state. The aforementioned uncertainty regarding the extent to which that troughing will extend south is further manifested in uncertainty in anomalous temperature conditions. As such, equal chances are carved out for the western and northwestern portions of CONUS.

Consistent with La Nina conditions and dynamical model guidance, the precipitation forecast for the outlook period favors below-normal precipitation across the southern tier and along the east coast with highest probabilities in the Southeast. Dynamical model guidance is less consistent with regard to an anomalous precipitation signal across the northern tier and thus equal chances are forecast. Elevated probabilities for anomalously wet conditions are forecast over western Alaska with equal chances favored over the rest of the state.

Sea surface temperature anomalies surrounding Hawaii are slightly above normal, elevating the chances of above normal temperatures throughout the forecast period. Dynamical model guidance also shows equal chances across the region tilting toward slightly below normal precipitation over the southeastern islands.

Double Dip La Nina Continued

Just what is the Pacific Meridional Mode?

This may help a bit. It is a second reference to the issue and this time an NOAA article. BTW, the fish are never wrong. We create indices on observed fish behavior. If their behavior deviates from what our indices suggest their behavior should be, it is not because the fish are confused it is because our indices or models no longer are accurate.

This graphic also might help

4 | DISCUSSION AND SUMMARY

From the present study, it is necessary to discuss two possible factors responsible for modulating La Niña persistence. The first is the preceding El Niño amplitude. From a linear perspective, the discharging amount is proportional to the El Niño amplitude. With strong discharging, significant SSTA cooling could last more than 2 years. The preceding El Niño amplitude also affects the intensity of the interbasin SSTA gradient by influencing the adjustment time of the Indian and tropical Atlantic Oceans to the Pacific SSTA (Wu et al., 2019). More specifically, the delayed response of SST cooling over the Indian and tropical Atlantic Oceans, in comparison with the Pacific cooling, allows the easterly wind anomaly over the western Pacific to be dominated even after the La Niña decaying phase. This initiates a La Niña that tends to persist up to 2 years. However, the role of the Indian Ocean capacitor effect on western Pacific wind anomalies has been questioned by Chen et al. (2016). Using data analysis and numerical experiment, the authors claim that the Indian Ocean basin warming during mature El Niño wintertime events has little effect on the easterly anomalies in the equatorial western Pacific, and the local process over the western Pacific has more influence over the Indian Ocean capacitor effect. Further numerical experiments may provide quantitative insight in to the importance of these factors, which is beyond the scope of this study. The second factor is a recharging/discharging efficiency with respect to anomalous wind-stress/WSC relevant to SSTA patterns, which contributes to ENSO phase transition. This was the focus of this study. An EP-type El Niño preceding a La Niña leads to strong discharge by positive WSC (0 – 15N) that is widely spread over the Pacific basin, which induces a strong and long-lasting La Niña. When a La Niña develops through the mid-latitude connection (PMM or NPO), SSTA cooling and a tropical easterly wind anomaly expand to the North Pacific. In this case, an anomalous negative WSC is weak and, thus, the recharging efficiency by equatorial Rossby waves is low. Consequently, to understand La Niña persistence, it is reasonable to consider both the preceding El Niño amplitude and recharging/discharging efficiency by anomalous SST/wind-stress patterns as the La Niña evolves. In this study, we investigated how the evolution of single- and multi-year La Niña events differs from their onset phase by analysing both observational and climate model data sets. Our analyses showed that there was a significant difference in the evolution between the two types of La Niña events, even from their initial development associated with a mid-latitude connection. These differences are described as follows (Figure 10).

1. A weak CP-type (Niño-4 > Niño-3) El Niño tends to exist one year prior to a single-year La Niña event, whereas a strong EP-type (Niño-3 > Niño-4) El Niño tends to exist prior to a multi-year La Niña event.

2. For single-year La Niña events, negative WSC, associated with CP-type El Niño and confined to the western Pacific, induces weak discharge that leads to a weak La Niña. In contrast, a widely extended negative WSC of a multi-year La Niña in the Pacific basin causes efficient discharge, resulting in a strong La Niña.

3. From the decay of an El Niño to a La Niña developing period, SSTA cooling is initiated by anomalous easterly wind in the eastern Pacific for single-year La Niña. However, for multi-year La Niña events, SSTA cooling is triggered by a mid-latitudinal influence (i.e., PMM/NPO). Such a difference in initiation of a La Niña explains why the meridional width of multi-year La Niña events exceeds that of single-year La Niña events.

4. During a La Niña peak period, single-year La Niña events have an equatorially confined SST cooling structure; however, multi-year La Niña events have intensified SSTA cooling and meridionally expanded easterly wind anomalies. In addition, the overall structure of multi-year La Niña events is shifted westward. Comprehensively, the SST structure of multi-year La Niña events is similar to Mega-ENSO. Thus, the recharging process of a singleyear La Niña is strong due to equatorially confined SST cooling/strong WSC, whereas that of a multi-year La Niña is relatively weak due to meridionally expanded SST cooling/weak WSC.

5. During a La Niña decaying period, the SSTA cooling of a single-year La Niña disappears with strong recharging, resulting in the termination of the La Niña. For multi-year La Niña, the SSTA cooling persists with a weak recharge. Because of the insufficient recharge, the surface cooling in the equatorial Pacific persists until the following summer. Bjerknes feedback is then initiated, resulting in the development of a second La Niña in boreal winter (Chen et al. 2016).

6. The iteration of processes 3 through 5 for a multiyear La Niña may lead to the development of another La Niña in the subsequent winter.

In summary, by analysing the statistically significant differences in precursory signals between single- and multi-year La Niña events, we observed that a midlatitude connection associated with the PMM/NPO, such as the meridional expansion of anomalous SST and wind stress fields, is critical for La Niña persistence. This indicates that there is similar dynamics operating during mega-ENSO and multi-year La Niña events. These results have important implications for improved ENSO prediction and provide an appropriate alternative interpretation to the state-of-the-art climate models in predicting multiyear La Niña events.

International

This week we have a map.

In the box are shown the major resources we use. We will not be using them all each week but the reader is welcome to refer to these resources.

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