Hurricane Season Approaches....

By: Levi32 , 1:51 AM GMT on April 26, 2007

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As June rushes closer, conditions and patterns for the upcoming season are beginning to reveal themselves. Not surprisingly, some of the changes so far are different than what we expected a month ago. The La Nina which we thought would be so strong this summer may not end up as potent. As I stated in a blog a month and a half ago, several key factors were and still are not present to support a strong La Nina. A big one is the SOI, which instead of going positive, which is the normal case during a positive ENSO, is tanking negative, which we normally see during El Nino conditions. This is altering precipitation patterns across the equatorial Pacific regions, causing the ENSO Precipitation Index (ESPI) to rise (now nearing zero again). Here is a look at the latest SST anomalies:



Back in February, cold anomalies showed up in the central Pacific, where the ENSO is thought to make its strongest impression on the SSTs. However, these anomalies have been replaced by normal to warmer than normal waters, and the cooler anomalies reappeared in the eastern Pacific close to South America a month ago. This is not indicative of a coming strong La Nina to me. If there were, the central Pacific would be cold and not warm. To me, this looks more like a neutral pattern with a cold bias factor in the ENSO. This could be both a good and a bad thing for the upcoming hurricane season. On the good side, neutral to El Nino conditions generally increase wind shear and the number of upper-level lows and troughs in the Atlantic. We saw this last year, when the jet stream consistently dipped south and ripped apart many a potential storm during the entire season. The bad news is that a neutral pattern usually produces the most named storms on average in the Atlantic. The classic example of this was of course 2005, when we had 28 named storms. The ENSO was neutral that year. So, the key will be how the upper pattern sets up over the Northern Hemisphere over the next couple months. The position of the Bermuda High will be closely watched, as well as wind shear anomalies, which have been fluctuating up and down over the last several weeks. Another factor has been the ESPI, which moistened up the bone-dry Atlantic quite nicely last month when it went negative. But the ESPI has been trending back up for 2 weeks now, and the results are clear on the water vapor imagery. The Atlantic is bone dry again in most areas.

All these factors will come together during May and June to give us a picture of what the hurricane season could be like. Right now nothing much is certain. I don't believe we will have a strong La Nina this year, and as I said I think a more neutral pattern with a cold bias is likely. I'm sticking with my season predictions that I posted 2 weeks ago until I see a need to change them.

We shall see what happens!

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23. Raysfan70
11:15 AM GMT on April 26, 2007
{{Levi}}


Have a Great Thursday! :-)
Member Since: July 28, 2005 Posts: 138 Comments: 57354
22. TheCaneWhisperer
3:19 AM GMT on April 26, 2007
Night Levi!
21. TheCaneWhisperer
3:17 AM GMT on April 26, 2007
Zonal Wind Anomalies in the EPAC and 3/4 are going to be lower than 05 this year!
20. Levi32
3:13 AM GMT on April 26, 2007
Exactly, the whole basin makes a difference. I always look at other key regions such as the Gulf of Alaska, and the waters off Japan as well.

Michael, yes there were fluctuations, but overall it was a fairly swift and smooth change from El Nino to La Nina in 1998. Also, if you look at the SOI numbers for that year, you will see a smooth and rapid transition as well. This year, the SOI is not cooperating, and right now is going the complete opposite direction it should be. That and all the other upper patterns over North America are sort of messed up this winter and spring. We'll see how it all turns out, but nothing is by the text book the last 2 years that's for sure.

I'm off for the night guys. See you all later!
Member Since: November 24, 2005 Posts: 635 Comments: 26684
18. TheCaneWhisperer
2:45 AM GMT on April 26, 2007
One thing I notice is how much colder the waters are off South America, the whole coast! 98 seemed much warmer up and down the coast of South America! Granted the Central Pacific is colder in 98 but, that is also where the cold pool developed! Cool water at the coast this year, that is where the cold pool is at. The pacific is a huge mess right now, doesn't know how to act! Cold, Warm, Cold and Warm. My assumptions from the maps posted are that the SST's in the EPAC, Central Pacific and South America, as a whole, are much less than they were in 98! Almost seems like the Pacific is normalizing in temperature, notice the stark difference in patterns from 98 till now!
16. HadesGodWyvern (Mod)
2:08 AM GMT on April 26, 2007
okay later Levi
Member Since: May 24, 2006 Posts: 51 Comments: 46173
15. Levi32
2:07 AM GMT on April 26, 2007
Oh I see Hades. I'll stop by soon and see how it's going. Great seeing you again :)
Member Since: November 24, 2005 Posts: 635 Comments: 26684
14. HadesGodWyvern (Mod)
2:07 AM GMT on April 26, 2007
one basin that is getting hot.. The North Indian Ocean.
Member Since: May 24, 2006 Posts: 51 Comments: 46173
13. Levi32
2:06 AM GMT on April 26, 2007
Aww gotta go for dinner. I don't have much time anyway before going over limits. Have a wonderful evening everyone!
Member Since: November 24, 2005 Posts: 635 Comments: 26684
12. HadesGodWyvern (Mod)
2:05 AM GMT on April 26, 2007
ya my blog is near the middle of the page.. the tropics are free of warnings so it's not updated as much.
Member Since: May 24, 2006 Posts: 51 Comments: 46173
11. Levi32
2:05 AM GMT on April 26, 2007
Ok Michael, I see what you're getting at, but see the CENTRAL pacific? Look at how cold it is. Now look at today:



The central Pacific isn't cold at all like it was in 1998. Also the eastern pacific is a sort of "mix" of cold and warm. Really weird, but cold to the south and warmer to the north.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
10. Tazmanian
2:03 AM GMT on April 26, 2007
well any way the Bermuda High was be more W this year
Member Since: May 21, 2006 Posts: 5091 Comments: 115362
9. Levi32
2:03 AM GMT on April 26, 2007
Thanks Bob. I'll keep reading Joe B's posts throughout the season though :)

I'm a faithful reader LOL.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
7. weatherguy03
2:00 AM GMT on April 26, 2007
Smart young man. Keep listening to yourself and not Joe B and you will do just fine. Great stuff.
Member Since: July 5, 2005 Posts: 592 Comments: 29707
6. Levi32
1:59 AM GMT on April 26, 2007
Hey Hades! Long time no see! I haven't seen your blog up there lately. Should have visited but I haven't had much time as of late :(
Member Since: November 24, 2005 Posts: 635 Comments: 26684
5. HadesGodWyvern (Mod)
1:58 AM GMT on April 26, 2007
Good Evening Levi
Member Since: May 24, 2006 Posts: 51 Comments: 46173
4. Levi32
1:57 AM GMT on April 26, 2007
Thanks Ryan!

LOL David what now about the Bermuda High? I didn't quite get it.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
3. ryang
1:56 AM GMT on April 26, 2007
Dang Taz...Oh well....LOL
Member Since: August 25, 2006 Posts: 329 Comments: 12452
2. ryang
1:56 AM GMT on April 26, 2007
1st!!!

Good blog Levi...
Member Since: August 25, 2006 Posts: 329 Comments: 12452
1. Tazmanian
1:55 AM GMT on April 26, 2007
1st


whats talk about the Bermuda High
Member Since: May 21, 2006 Posts: 5091 Comments: 115362

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Levi Cowan has been tracking tropical systems since 2002, and is currently working on his bachelor's degree in physics at UAF.

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