If you've read my blogs or followed my Facebook weather page, you know I'm a believer in repeating patterns, not only for weather, but for climate, and even across the cosmos itself.
Pattern recognition is a very important skill when it comes to weather forecasting. When it comes to weather and climate, these cyclical weather patterns can be months, a few years, decades (as in certain Atlantic and Pacific ocean warming and cooling patterns), or even longer.
Looking back at the 1950's:
The Atlantic Basin was quite active with tropical cyclone activity during the 1950's. part one of this series covered 1954, 1955, and 1960. If you've read part one...you know 1954 and 1955 saw a lot of tropical cyclones strike the U.S. East Coast.
Here are two charts that show the Atlantic Multidecadal Oscillation (AMO) and The Pacific Decadal Oscillation (PDO).
I've talked and explained about the different oscillations many times. So I won't go into a lot of detail about what they do. Those reading this, that don't know about them, you can find Information about them on this blog post. There are other post that go into them. You can find them in the blog archives (found on the left hand side of the blog page).
The current state of the AMO is positive (warm phase) which means warm water temperatures off the East Coast. When the AMO is in a positive phase there is melting of sea ice in the Arctic. The recent news of the Greenland ice sheet and sea ice melting is the result of the AMO being in a warm phase. When the AMO is in a positive phase Greenland blocking is more likely, which means cold air pretty much locks in place, in the East; during last winter the AMO being in a positive phase, in conjunction with the NAO being in a negative phase, was the reason New England saw so many nor'easters, with many seeing near record to record breaking snow amounts.
The PDO is in a negative (cool phase) which means cool water temperatures off the Pacific Northwest coast. When it's in a cool phase Alaska generally see harsher winters. Most of us have seen stories in the news about the harsh winter conditions in Alaska the last few years. The cool phase of the PDO has a lot to do with this. I think the PDO is also part of the reason Colorado and the Northern Plains have been seeing the late season snow.
But basically, when the PDO is in a warming phase, more of a wet pattern is seen. Therefore when it's in a cooling phase, the jet gets stronger and directs the flow toward the Pacific Northwest, air south of the jet is not as dense and tends to not rise as easily, so more of dry pattern is seen.
As you can see in the charts, the two oscillations in the same phase in the 50's, as they are now. This means, the sea surface temps off the west coast of Africa, to the Caribbean, Gulf , off the North American Coast , and most of the North Atlantic, were more or less the same then as they are now.
Ocean temperatures. The ocean temperatures and ocean currents have an important influence on weather. Warmer temperatures will add more moisture to the air. Changes in ocean temperatures will change the wind patterns aloft. Changing the wind pattern will change how moisture is distributed. El Nino and La Nina are examples of how changing ocean temperatures can influence the weather pattern. The PDO and AMO help anchor the jet streams which in turn amplify or de-amplify temperatures and moisture distribution. For example, A warm AMO means less arctic ice and with a cold PDO more Atlantic hurricanes.
When one looks at the temperature and precipitation profiles of the 1950's, things look eerily similar to the current temperature and precipitation profiles across the country. It never ceases to amaze me how many meteorologist fail to look at past weather patterns when making a forecast. I mean if X, Y, and Z produced a certain kind of weather event, then logically those same X,Y, and Z parameters should produce a fairly similar weather event in the same general areas. Oh I know there are a lot of other factors that come into play. But still, basically the same things that happened then should happen again.
Anyway, back to the oscillations. The Atlantic and Pacific oscillations have a major impact on sea surface temperature, ocean current, and have a great deal of influence on the jet stream, which in turn controls the temperature and precipitation patterns across North America. Since the PDO is currently in cool phase and the AMO is currently in a warm phase we're seeing drought across the Midwest and Southeast and to a lesser extent the Northeast. The areas seeing the drought now are the same areas that saw major droughts in the 1950's.
Back in part one, I went into detail about the storms that struck the U.S. East Coast in 1954,1955, and 1960. During those years the PDO and AMO were in the same phases they are now. During the decade of the 1950 the U.S East Coast saw several tropical hits each year. The reason for this is: The AMO was in a warm phase and the PDO was in a cold phase. So as the Pacific cooled down the Atlantic was warming up. Hurricanes thrive on warm water. When surface ocean temps are at 80 degrees (F) they aid in the development of tropical cyclones. So when the Atlantic Basin is warm, we see more tropical cyclone development.
So to answer the question, are we retuning to a the patterns of the 1950's? The answer is a resounding yes. The cold PDO and warm AMO will make a great breeding ground for Atlantic Basin tropical cyclones, for several years to come. The pattern is such that the East Coast can expect more storms like Irene, Lee, and Sandy over the coming years.
A little about Sandy:
The media loves to use terms like extreme when describing major weather events. To quote Greenpeace co-founder Patrick Watson : “It doesn’t matter what is true, it only matters what people believe is true…You are what the media define you to be.”
Here's a chart put together with data from the National Climatic Data Center ( NCDC) . For those who don't know, the NCDC is a NOAA climate research unit. The chart shows the maximum temperature record for each state, going back to 1890 (Interestingly, the NCDC refers to these as 'climate extremes'). But IMO, it would be more accurate to refer to them as just weather extremes.
As can be seen, through 2011, no maximum temperature records have been set since the 1990's. This is simply amazing since all the climate doomsday scientists and pundits have stated that recent global warming was "unprecedented" and that U.S. temperatures were rapidly increasing due to CO2 levels. Per NOAA, 82% of all maximum records were initially set prior to 1960 and prior to the accelerated growth of human CO2 emissions and atmospheric CO2 levels.
One might ask, why show data on CO2 levels? The answer is, because the media and sadly many people in the meteorological field used terms like extreme, one of a kind, unprecedented when it came to describing Sandy back in October of 2012. Even President Obama blamed global warming. But in fact Sandy was just a very powerful storm...Incredible yes....unprecedented no. Remember that quote, “It doesn’t matter what is true, it only matters what people believe is true…You are what the media define you to be.”
Well say something enough times and people will start to believe it. By saying Sandy was extreme, people will start to think the weather has never been as bad as it is now. But this is not a post on global warming. You can find a post I did on the subject here. I've also done several blog post on Sandy including her timeline, you can find the other post in the blog archives.
Sandy was the deadliest and most destructive hurricane of the 2012 Atlantic hurricane season, as well as the second-costliest hurricane in U.S history. last October the media was using terms like Frankenstorm, when describing Sandy. Al Gore said she was extreme and unprecedented. My response to Mr. Gore is that's a bit of a exaggeration, to say the least.
Sandy was born in the western Caribbean Sea, fueled by the warmth of the sea. As far as tropical cyclones go Sandy was fairly typical., as she raged across Haiti and the Dominican Republic, Cuba, Jamaica, Puerto Rico and the Bahamas, causing at least 65 deaths.
As she exited Cuba, her structure became disorganized due to strong shear. But she maintained convection due to the influence from the approaching trough moving east out of North America. By the time October 27th arrived, Sandy was no longer a fully tropical system. The National Hurricane Center (NHC) downgraded her to a tropical storm. But she soon got her act back together and regained hurricane status. However, has she moved north along the U.S East Coast she became more distinctive. She was undergoing a transformation from a tropical type storm into something called an extra-tropical storm (kind of a hybrid).
The difference between a tropical and an extra tropical storm is how the storms get their energy. Tropical cyclones are fueled by warm water evaporating into the air; as I said above, water temperatures 80 degrees (F) or greater will enhance tropical development. Therefore, waters colder than that will inhibit tropical storm development. However, extra-tropical storms get their energy from the battle between warm and cold air masses. Normally a storm like Sandy would lose their power by moving over colder northern waters. But because Sandy was turning extra-tropical she was able to feed off both types of energy. Therefore when she plowed into New Jersey she was still gaining strength and increasing in size and wind coverage.
The 1991 storm nicknamed "The Perfect Storm" was of a similar type when a nor'easter fed by Arctic air absorbed Hurricane Grace. But thankfully that storm never made landfall. Most likely several of New England's major storms in the past, including the great 1938 Long Island Express, the storm that other storms are still measured by today, were extra-tropical. Had Sandy acted more typical of similar systems, she would have gone out to sea, with only some heavy rain, strong gusty winds, and beach erosion to note her passage. However, Mother Nature had other ideas.
So then, what caused Sandy to behave the way she did?
The conditions that lead to her behavior are rare but not unique.
There was a blocking high-pressure centered west of Greenland (remember when the AMO is in positive phase, Greenland blocks are much more likely). There was also a trough of cold air moving eastward across the United States. Behind the wave of cold air was a big arctic storm dropping out of Canada.
Low pressure systems have counter-clockwise winds. High-pressure systems feature clockwise winds. So when Sandy got close enough, those clockwise winds from the blocking high started pushing her to the west. But still this was not enough to cause what happened.
The other player in the setup was that wave of cold air moving eastward. The timing couldn't have been more disastrous. The trough grabbed on to Sandy and pulled her to the west. Because of these two forces acting on Sandy, the stage was set for a catastrophe.
The East Coast is not the only place these hybrid storms can strike. The great Columbus Day Storm of 1962 was a Pacific Northwest windstorm, that struck the Pacific Northwest. This storm also underwent a similar transition from Typhoon Freda to an extra-tropical storm.
Well that's it for part two. I hope you enjoyed reading it, and learned a thing or two. I will close by saying this:
As I've shown in part one and part two, the East Coast of the U.S. has seen years that featured several Sandy type storms. In fact many of these storms made Sandy tame by comparison. The East Coast has seen a huge amount of development since the 1950's, if a Carol or Donna where to hit now, the devastation would be worse than anything we've ever seen. The reason for this is simple, it's not that the storms are anymore extreme, unprecedented, or more powerful. Instead it's our failure to learn from the past that is making the situation so much worse than ever before.
Rebecca