Other Climate Patterns and Winter 2010-2011

Since I looked at La Nina and its effects on winter weather. Now, you wonder, does La Nina solely play a role for winter? Of course not and it is a major piece of the puzzle. Other atmospheric and oceanic patterns that play a role are North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Pacific-North American (PNA). Here is a glossary that explains those atmospheric and oceanic patterns.

Here is the forecast and trends for all those atmospheric and ocean patterns. They are based on indices and I multiplied by 10 for simplicity. For example, the ENSO original value is -1.5, it is multiplied by 10, so the result is -15. Data is from Climate Prediction Center-Daily Indices during last 120 days in Ascii format using GDAS.

2010 (As of December 3, 2010)
ENSO=-15 (Based on all El Nino region temperature and averaged out)Trending towards negative
NAO=-16.521 Trending towards negative
AO=+0.42 Trending towards negative
PNA=-9.08 Trending towards negative

Let’s look at the value of those atmospheric patterns at the time of the La Nina winters. For some winters, the data is not available. The indices for those patterns are seasonal average from December to February of the year.

1916-1917
NAO=-24 Extremely Strong Negative
AO=N/A
PNA=N/A

1949-1950
NAO=+6.333 Weak Positive
AO=+2.835 Neutral
PNA=-16.9 Strong Negative

1955-1956
NAO=-12.667 Moderate Negative
AO=-12.257 Moderate Negative
PNA=-14.767 Moderate Negative

1973-1974
NAO=+11 Moderate Positive
AO=-1.46 Neutral
PNA=-3.533 Neutral

1975-1976
NAO=+4.333 Neutral
AO=+9.933 Weak Positive
PNA=-3.7 Neutral

1988-1989
NAO=+20.333 Extremely Strong Positive
AO=+26.88 Extremely Strong Positive
PNA=-3.833 Neutral

1998-1999
NAO=+17.333 Strong Positive
AO=+6.483 Weak Positive
PNA=-0.167 Neutral

1999-2000
NAO=+16.333 Strong Positive
AO=+11.297 Moderate Positive
PNA=+1.7 Neutral

Here is a divisional map and scatter plot with correlation value of climate patterns and winter precipitation and temperature. They were generated at US Climate Division Dataset Seasonal Correlation Page.

NAO
Divisional Maps

NAO is not strongly correlated with winter precipitation in the Upper Texas Coast. Interestingly, it is more correlated in the Midwest region. On the other hand, NAO is strongly correlated with winter temperature in the Upper Texas Coast. A positive NAO means a warmer winter, while a negative NAO means a cooler winter.

AO
Divisional Maps

Like NAO, AO is not strongly correlated with winter precipitation in the Upper Texas Coast. Like, NAO, a positive AO means a warmer winter, while negative AO means cooler winter.

PNA
Divisional Maps

PNA is correlated with winter precipitation in the Upper Texas Coast. A positive PNA means a wetter winter for the Upper Texas Coast. On the other hand, PNA is strongly correlated with temperature. It is a negative correlation, in which a negative PNA means warmer winter. A positive PNA means cooler winters for the Upper Texas Coast.

Here are scatter plot charts of NAO, AO, and PNA effects on Upper Texas Coast climatology. All data goes back to 1950 with the exception of NAO, which goes back to 1895. A word of caution, correlation does not equate causation, but they can give us a good idea of what is likely to happen.

NAO
Scatter Plot

The scatter plot shows that winter precipitation and NAO either could be wet or dry. On the other hand, a negative NAO means a cooler winter, while a positive NAO means a warmer winter.

AO
Scatter Plot

The scatter plot is similar to NAO in terms of precipitation. It could either be wet or dry. No correlation between AO and precipitation. On the other hand, a more negative AO means a cooler winter, while a more positive AO means a warmer winter.

PNA
Scatter Plot

PNA and winter precipitation is correlated, the more positive PNA is, the wetter Upper Texas Coast is. On the other hand, a negative PNA means a warmer winter, while a positive PNA means a cooler winter. So, if the PNA is in positive territory, we would see a cold and rainy winter because PNA often pushes cold fronts southward.

From those scatter plots of NAO, AO, and PNA, I could forecast that this winter will likely be a warmer and drier winter. However, do not be surprised if we see Arctic outbreaks in Texas this coming winter. I would not rule out an icestorm or even a snowstorm this winter. The reason is that NAO and AO are in negative territory and as mentioned the more negative NAO and AO are, the cooler it is. On the other hand, PNA is trending into negative territory and would favor a warmer winter. As I mentioned, a positive PNA would allow cold Arctic/Siberian Air to go south into the Lower 48. A negative NAO puts the low pressure west of Greenland, which pushes cold air southward. NAO, AO, and especially PNA can change suddenly, which can lead to changes in the weather. 

The closest analog for this upcoming winter in term so El Nino are 1973-1974, 1988-1989, and 1998-1999. The winter of 2009-2010 was an El Nino winter and has transisted into La Nina. I think the closest analog for 2010-2011 winter in terms of non-ENSO is 1955-1956 because NAO, AO, and PNA were mostly negative, which the trends we are seeing right now. Also, 1955-1956 had a strong La Nina, which I discussed previously, which was persistent. This winter may see a freeze or two. I think we are likely to have a milder and drier winter, a far cry from last winter, which was cooler and wetter for the Upper Texas Coast. NAO, AO, and PNA can change quickly and is unpredictable.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s