Dan's Wild Wild Science Journal

From NOAA- The El Nino is fading away in the Pacific but Atlantic sea surface temps. are near record levels. Both of these factors argue for an active hurricane season in the Atlantic.

Hurricane season begins June 1st and NOAA’s hurricane experts will release their 2010 season forecast Friday 28 May. It’s not much of a secret among meteorologists what it will be.

Likely BAD.

Actually Daffy, it's HURRICANE Season. (Warner Bros.)

Forecasting the number of hurricanes we will see each year is a very tricky project. There is some skill but changes in the sea surface temperatures and in the upper level wind shear during the summer months make any forecast iffy.

So, that said here is why NOAA will forecast an increased number of hurricanes this year.

THE AMO:

The Atlantic Multi-Decadal Oscillation is an ocean atmosphere oscillation that runs in 10-30 year cycles. It causes warmer than normal waters in the main development region and favorable winds for more hurricanes. (On top of changes caused by increasing greenhouse gases). The AMO cycle has been favorable for above average hurricane seasons since the mid 1990′s.

Models are forecasting El Nino to quickly die and an increasing possibility of a La Nina. La Nina's cause more hurricanes. Just the opposite of El Nino's.

EL NINO:

Last winter’s El Nino is now rapidly disappearing. The warmer than normal waters in the Equatorial Pacific have almost disappeared and virtually all of the models are forecasting a return to either neutral or even La Nina conditions by the end of summer.

El Nino’s in the Pacific produce a weather pattern in the Atlantic that causes increased wind shear. This usually means fewer hurricanes. La Nina’s produce lower wind shear in the Atlantic and are associated with more active seasons.

SEA SURFACE TEMPS:

The oceans worldwide are the warmest ever measured right now. There are very strong indications this is due to the increasing greenhouse gases in the atmosphere. The record warmth in the Atlantic is likely caused the AMO discussed above and the Arctic Oscillation.

This is the same pattern of atmospheric pressure that was responsible for the cold and snowy winter in the UK and the Eastern USA. It also causes warm waters to spread over the main development region for hurricanes in the Atlantic.

You add up all of this and you get very good odds for an active season. Keep in mind that the Arctic Oscillation may change and sea water temps could cool. El Nino may hang on longer than expected too. If this happens we could see a normal season, or even below.

The odds however say otherwise.

Dan

PS There is some fascinating new science in one of the great questions of meteorology. Will we see more or fewer hurricanes in the warmer World of the late 21st century?? I will have that post soon. I’m still reading the papers…

The 1997-1998 El Nono was the strongest on record. The combination of this, and rising greenhouse gases made it the warmest year on record.

NASA GISS has the Summer global temp. data online now. August 2009 was the Second warmest on record globally. The Northern Hemisphere meteorological summer of 2009 was the third warmest on record. Only 1998 was warmer. The reason 1998 was so warm is easily explained. The Pacific ocean was incredibly warm that year. The reason?  The greatest El Nino event on record.

August Temp. Anomalies. from NCDC (NOAA). The larger the red dot, the warmer it was above average.

That much warm water heated the surface temperature of the entire planet. The warmth over the tropical pacific, caused the jet stream to blow faster from west to east. This, in turn, slowed the rotation of the planet! The days were actually a few thousands of a second longer in 1998!

Some of these junk science sites use 1998 to claim that the planet is cooling. They start their graphs in 1998 and yell global cooling. Doctor Mark Serreze of NOAA’s National Snow and Ice Data Center (NSIDC) said it best. Amazing ignorance. I wrote about El Nino earlier in the summer in this space.

One more picture. The great melt in the Arctic. I spotted it on the One Blue Marble blog. It was taken by Michael Nolan a well known environmental speaker.

If a picture paints a thousand words...

Later,

Dan

El Nino has returned.

The NOAA scientists, who monitor the tropical Pacific, sent out the notice this week. Temperatures in what is called the NINO 3.4 region of the Equatorial tropical Pacific, have increased to the point that we can say an El Nino has begun. (The threshold is an anomaly of .5 C) The official definition is a bit more technical and you can find it on this more technical summary for Meteorologists put put by the Climate Prediction Center. If you want to really understand how El Nino’s begin and end, then Taichiro Sakagami has made it easy. His videos are highly recommended.

El Nino’s CAN have a major impact on the climate around the world. Each one is different, however and we do not know yet how strong this particular event will be. Most of the effects happen in the Northern Hemisphere winter months.

One aspect of El Nino that does show up well in Summer is the effects it has on tropical cyclones in the Atlantic Basin. The increased wind shear caused by all that warm water tends to reduce the number of named storms.

It’s important to remember that El Nino is a natural oscillation. It was first noticed by a Meteorologist named Gilbert Walker. He was asked to look into why the Indian Monsoon had failed and to see of such failures were predictable. He collected weather observations, and noticed that when the average pressure at Darwin, in Australia, was close to the pressures much farther east in the Pacific, that the Monsoon would fail.  Australia would suffer severe droughts and other changes were noted as well. In normal years, the pressure would be much lower in Darwin, and higher to the East of Tahiti.

He named his affect the Southern Oscillation.

The atmospheric affects of this were first shown by Jacob Bjerknes. He is the son of one of the greatest Meteorologists ever, William Bjerknes. (Father was the first to give a name to cold fronts). Jacob realized that the pressure oscillations were actually the sloshing of warm water in the Western Pacific back to the East. It would later be realized that this had a profound affect on the atmosphere.

In “normal” years the Northeast trade winds blow the warm surface water in the Pacific westward toward Asia. The warm water piles up and seal level there is actually about half a meter higher than it is off the coast of Central America! The depth of this warm water is nearly 300 meters in the West, but the thermocline in the Pacific is much shallower near the Americas.

All this warm water in the Pacific, adds incredible amounts of moisture to the atmosphere, and keeps Indonesia very wet. When the warmth moves eastward, the rains follow. This warm air changes the pressures in the upper atmosphere and these cause changes in the storm tracks. El Ninos usually push the jet stream to the north in the Pacific. This causes a trough to develop many times near California, that brings intense winter storms. These changes don’t just show up in the Pacific, but around the world. Think of the atmosphere as a water bed. Jump on one side and what happens on the other? Now you get the idea!

Temperature anomalies in the Nino 3.4 region over last 12 months. From NOAA NCEP

Bjerknes named this entire process of ocean atmosphere interaction the Walker Circulation in honor of Gilbert Walker who discovered it in the 1930′s, by pouring over pressure records of thousands of stations. Meteorologists tend to call it ENSO for El Nino Southern Oscillation.

The strongest known El Nino, of modern times, was in 1997. This event was a monster, with affects felt around the world. The warm waters transferred an incredible amount of heat to the atmosphere. The jet stream sped up so much that it actually slowed the Earths rotation by a measurable amount! (The jet stream flows from West to East and since every action has an EQUAL and opposite reaction, the Earth slowed a tiny bit. The days were a few thousandths of a second longer!).

Sea Surface Temps. Ctsy NOAA CPC

Because of the El Nino of 1997, the global temperature was very warm. 1997 is among the warmest years ever measured. Because of differences in how the calculations are done, NASA ranks 97 and 2007 as tied for the warmest year, where the Hadley Center folks in the UK have it as 1998. The last few years have been slightly cooler because of the La Nina which brings large areas of colder than normal water across the Pacific. (The temperatures have still been well above those of the past because of increasing greenhouse gases).

The 1997 El Nino has been responsible for much of the silliness among climate skeptics. (Who claim that global warming stopped in 1998.) Now you know why this stuff is so silly. Many climate scientists believe that with greenhouse gases steadily increasing, the next strong el nino will bring yet another all time record global temperature (instrumental record dating to the 1880′s).

Image courtesy NOAA

They are very likely right, but there are other oscillations that have to be considered as well. The Pacific Decadal Oscillation is just one. Another is the North Atlantic Oscillation. I pay close attention to that in the winter, because it can be a harbinger of polar air deep into the southeast United States.

Claiming that climate change has stopped because this year is not as hot as last year is like saying that spring has stopped because the temperature on April 14th is not as warm as it was from April 10th through April 12th. If you look at the average temperature from the first week of April and compare it to the last week of may, you will see that this of course is ridiculous.

You would be shocked at how many emails and twitter messages I get from people who make this claim.  I cannot give them the science education they never had. Sad, still the same.

Dan

Note: A great fact sheet, with a much more detailed explanation, of the Walker Circulation has been written by my friend Bob Henson at the National Centers for Atmospheric Research (NCAR). He and Kevin Trenberth put together one of the best written pieces I have seen. I used it heavily in writing this post. The other information is from the NOAA- CPC El Nino page, and the COMET program modules on ENSO.

Looking at the satellite imagery this evening is a scary prospect. Hannah is now a hurricane east of the Bahamas. The numerical weather prediction (NWP) guidance brings it into Savannah or S. Carolina as a minimal hurricane by Friday afternoon.

A new tropical storm has formed in the middle of the Tropical Atlantic. This system looks very healthy, and is now named Tropical Storm Ike. I suspect it will become a hurricane and approach the Bahamas and perhaps the USA in 7-10 days.

Looks like a busy September, with a lot of tropical troubles….

Later,
Dan

I have a screencast update on Hurricane Gustav. It was recorded at 12:30 am (0530Z). I’m still getting used to this software, and it will get better.

This is a chance for you to get an in depth look at what I am seeing in the maps as I go through the forecast process.

Video is here: GUSTAV UPDATE

On the brighter side of things. Meteorological Summer ended at midnight!!

Dan

ps: You will need the Quicktime movie player to view it. It will play much fast if you are on a mac. I recorded it on my Imac at home. If you are on Windows PC, download the file to your desktop before playing. File is 23 megbytes, so broadband is needed.