This is the change of sea surface temperatures from September 2012 to October 2012, focused in on the north and central portions of the Pacific Ocean. The PNA, the acronym for the Pacific North American index, is based in the northeast Pacific Ocean and has tremendous effects on the weather observed in North America. In above normal SST anomalies, the Pacific North American index tends to favor a positive phase over negative. Graphic showing SST anomalies (shaded) and surface wind patterns (arrows) during the positive phase of the PDO (left image) and the negative phase (right image). In negative SST anomalies, the negative phase of the PNA is supported. If such a warming trend continues through the month of November, the chances of a positive PNA will only continue to increase. What I am showing above appears to bode well for a positive PNA developing. The graphic above takes that information and asserts, based on history, that the positive PDO will result generally in positive 500-millibar height anomalies over the western swath of North America – in other words, a ridge.

Therefore, that ridging off the western coast of North America implies a negative PDO. Similarly, colder colors on this chart mean that if the PDO is in a positive (negative) phase, 500-millibar heights will be lower (higher) in areas with colder-color shading, indicative of troughs (ridges). This means that in a negative PDO, all areas under warmer colors would see lower 500-millibar heights. Indeed, in a positive PDO those coastal waters exhibit positive SSTAs, while a negative PDO typically brings colder waters. There’s one more method I want to look at to determine the state of the PDO. The riparian zones within these communities may be more or less impacted by fire. Two days after the weather finally warmed up in May (in the UK), I was delighted to see tiny wriggly orange larvae appear among the aphid colonies which have exploded in numbers in the past couple of weeks.

To develop iPhone apps, iPhone developer should have knowledge of Objective C or Swift programming language. During the April-through-mid-June time period, we have seen below-normal geopotential heights (stormy weather) south of the Aleutian Islands into Japan. Over the months of April, May, and the first half of June, surface winds were seen flowing from west to east over the waters south of the Aleutian Islands, a prominent mark of the PDO being in the positive phase. Seasonal correlation of 500-millibar geopotential heights with the PDO in the months of April through June. One of the most amusing games to play in the warmer months is “kick the can”. Using the image immediately prior to the one directly above, colder colors are draped over that same area, implying the PDO state is opposite the 500-millibar height anomalies over the northern Pacific. In Figure 44 above (top of the two images), we move up to the stratosphere and examine geopotential height anomalies at the 50-millibar level during the analog winters.

500-millibar geopotential height anomalies from April 1st through mid-June. This seems upside-down, so it’s helpful to also look at the anomalies immediately offshore the western coast of North America. The state of the PDO is identified primarily by the alignment of sea surface temperature anomalies over the Pacific basin. Unfortunately, even this method doesn’t provide much more clarity on the state of the PDO. This would, in turn, lead to more precipitation in states like Colorado and the east central Rockies, as well as the Midwest and Ohio Valley. Much like the SSTA comparison, surface wind patterns seem to be giving us conflicting signals that make it difficult to draw out which phase the PDO is actually in. Let’s take a look at recent surface wind patterns in the Pacific to try and decipher the PDO. In some situations, that’s certainly fine to do, but as was shown extensively in this article, the atmosphere is not totally reflective of a positive PDO state, meaning it would be misleading to just use the index value.

Additionally, performance matters for most hardware (whether that’s absolute performance or performance per dollar or per watt or per other cost), and adding complexity makes hardware slower, which limits performance. In the positive phase, cold air tends to flow south and the storm track is shifted so it favors the Midwest/Great Lakes for precipitation. The Gulf of Mexico is the ‘lighter fluid’ to any severe weather outbreak- it supplies the warm, humid air that is smashed against cold, dry air on the backside of a storm system. The precise track of this system will determine how much rain we could see here in the Midlands. With that will come the rain which will in association with a slow moving front. The rain will be off and on between Monday and Tuesday night totaling between .50 and 1 inch total. Mild air will work its way back into the region later Sunday and into Monday.