Hurricane season begins today; normal June activity expected

By: Dr. Jeff Masters , 1:38 PM GMT on June 01, 2009

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Hurricane season is upon us, and it's time to take a look at the prevailing conditions and 2-week forecast for tropical cyclone activity in the Atlantic. June is typically the quietest month of the Atlantic hurricane season. On average, we see only one named storm every two years in June. Only one major hurricane has made landfall in June--Category 4 Hurricane Audrey of 1957, which struck the Texas/Louisiana border area on June 27 of that year, killing 550. The highest number of named storms for the month is three, which occurred in 1936 and 1968. In the fourteen years since the current active hurricane period began in 1995, there have been eleven June named storms (if we include last year's Tropical Storm Arthur, which really formed on May 31). Five tropical storms have formed in the first half of June in that 14-year period, giving a historical 36% chance of a first-half-of-June named storm.


Figure 1. Tracks of all June tropical storms and hurricanes, 1851 - 2007.

Sea Surface Temperatures
Sea Surface Temperatures (SSTs) are close to average over the tropical Atlantic between Africa and Central America this year (Figure 2). These temperatures are some of the coolest we've seen since 1995, when the current active hurricane period began. This year's cool SSTs should prevent a repeat of the unforgettable Hurricane Season of 2005, which had the highest SSTs on record in the tropical Atlantic. Note also that SSTs along the Equatorial Pacific off the coast of South America are quite a bit above average, signaling the possible start of an El Niño episode. As I discussed in Friday's post, odds are increasing for a weak El Niño to form in time for hurricane season, and this should cut down on the number and intensity of Atlantic tropical storms and hurricanes this year. However, if an El Niño is developing, it shouldn't start affecting Atlantic hurricane activity until August.

Typically, June storms only form over the Gulf of Mexico, Western Caribbean, and Gulf Stream waters just offshore Florida, where water temperatures are warmest. SSTs are 26 - 28°C in these regions, which is about 0.5°C above average for this time of year. June storms typically form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance. African tropical waves, which serve as the instigators of about 85% of all major hurricanes, are usually too far south in June to trigger tropical storm formation. Every so often, a tropical wave coming off the coast of Africa moves far enough north to act as a seed for a June tropical storm. This was the case for Arthur of 2008 (which also had major help from the spinning remnants of the Eastern Pacific's Tropical Storm Alma). Another way to get Atlantic June storms is for a disturbed weather area in the Eastern Pacific Intertropical Convergence Zone (ITCZ) to push north into the Western Caribbean and spawn a storm there. This was the case for Tropical Storm Alberto of 2006 (which may have also had help from an African wave). SSTs are too cold in June to allow storms to develop between the coast of Africa and the Lesser Antilles Islands--there has only been once such development in the historical record--Ana of 1979, which coincidentally will be the name given to this year's first storm.


Figure 2. Sea Surface Temperature (SST) departure from average for June 1, 2009. SSTs were near average over the tropical Atlantic. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, signaling the possible start of an El Niño episode. Image credit: NOAA/NESDIS.

Tropical Cyclone Heat Potential
It's not just the SSTs that are important for hurricanes, it's also the total amount of heat in the ocean to a depth of about 150 meters. Hurricanes stir up water from down deep due to their high winds, so a shallow layer of warm water isn't as beneficial to a hurricane as a deep one. The Tropical Cyclone Heat Potential (TCHP, Figure 3) is a measure of this total heat content. A high TCHP over 80 is very beneficial to rapid intensification. As we can see, the heat energy available in the tropical Atlantic has declined considerably since 2005, when the highest SSTs ever measured in the tropical Atlantic occurred. TCHP this year is similar to last year's levels, which were high enough to support five major hurricanes.


Figure 3. Tropical Cyclone Heat Potential (TCHP) for May 31 2005 (top), May 31 of last year (middle) and May 30 2009 (bottom). TCHP is a measure of the total heat energy available in the ocean. Record high values of TCHP were observed in 2005. TCHP this year is much lower, and similar to last year. Image credit: NOAA/AOML.

Wind shear
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream's band of strong high-altitude winds is the main source of wind shear in June over the Atlantic hurricane breeding grounds, since the jet is very active and located quite far south this time of year.

The jet stream over the past few weeks has been locked into a pattern where a southern branch (the subtropical jet stream) brings high wind shear over the Caribbean, and a northern branch (the polar jet stream) brings high wind shear offshore of New England. This leaves a "hole" of low shear between the two branches off the coast of North Carolina, which is where Tropical Depression One formed. The low shear "hole" has dipped down into the northern Gulf of Mexico a few times. Disturbance 90L, which almost developed into a tropical storm before it came ashore in Mississippi/Alabama on May 23, took advantage of one of these low-shear areas.

The jet stream is forecast to maintain this two-branch pattern over the coming ten days. This means that the waters offshore of the Carolinas are the most likely place for a tropical storm to form during this period, though the northern Gulf of Mexico will at times have shear low enough to allow tropical storm formation. The latest 16-day forecast by the GFS model (Figure 4) predicts that the subtropical jet will weaken and retreat northwards by the middle of June, creating low-shear conditions over the Caribbean. This is a typical occurrence for mid-June, and we need to start watching the Western Caribbean for tropical storm formation by the middle of the month.


Figure 4. Wind shear forecast from the 00Z GMT June 1, 2009 run of the GFS model for June 1 (left panel) and June 17 (right panel). Currently, the polar jet stream is bringing high wind shear to the waters offshore New England, and the subtropical jet is bringing high wind shear to the Caribbean. This leaves the waters off the coast of North Carolina under low shear, making this area the most favored region for tropical storm formation over the next 7 - 10 days. By June 17, the subtropical jet is expected to weaken and move northwards, leaving the Caribbean under low shear, and favoring that region for tropical storm formation. Wind speeds are given in m/s; multiply by two to get a rough conversion to knots. Thus, the red regions of low shear range from 0 - 16 knots.

Dry air and African dust
It's too early to concern ourselves with dry air and dust coming off the coast of Africa, since these dust outbreaks don't make it all the way to the June tropical cyclone breeding grounds in the Western Caribbean and the Gulf of Mexico. Developing storms do have to contend with dry air from Canada moving off the U.S. coast; this was a key reason why 2007's Subtropical Storm Andrea never became a tropical storm. Dr. Amato Evan of the University of Wisconsin will issue his dust forecast for the coming hurricane season later this week, and I'll be discussing his forecast in an upcoming post.

Steering currents
The steering current pattern over the past few weeks has been typical for June, with an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs are frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3-5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. At present, it appears that the coming two weeks will maintain the typical June pattern, bringing many troughs of low pressure off the East Coast capable of recurving any June storms that might form. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2006 steering current pattern that recurved every storm out to sea--or the unfavorable 2008 pattern, that steered Ike and Gustav into the Gulf of Mexico.

Summary
Recent history suggests a 36% chance of a named storm occurring in the first half of June. The current conditions in the atmosphere and ocean are near average, so expect about a 1/3 chance of a named storm between now and June 15. The computer models are currently not forecasting development of any tropical storms over the next seven days.

I'll have an update Tuesday afternoon, when I'll discuss the Colorado State University June Atlantic Hurricane season forecast by Dr. Phil Klotzbach and Dr. Bill Gray, which will be issued Tuesday morning.

My next analysis and 2-week outlook for hurricane season is scheduled for June 13.

Jeff Masters

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I'll be on chat too if anyone wants to be on.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting Thundercloud01221991:


what are they waiting for
Have you looked at the SSD floaters? It may look ok on the visible, but the infrared images show it's very disorganized.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
They said you to click a link or refresh the page.
Member Since: July 24, 2005 Posts: 407 Comments: 19076


what are they waiting for
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690. IKE
Okay, I see it now.

Thanks ya'll:)
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for some reason it is not showing up on the list of storms IKE but it is on the Navy site just click 90E invest and then you will see the link to 92L invest under Atlantic basin
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Invest 92L Link
Member Since: July 31, 2006 Posts: 56 Comments: 8112
687. IKE
Quoting winter123:


not yet... click the link i posted.

also... heres future ANA?
ha i doubt it but its possible
Link


Your link didn't post. I've got the Navy site bookmarked. There's no 92L on it.
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Quoting IKE:
After looking at what's left of it....bye-bye.


not yet... click the link i posted.

also... heres future ANA?
ha i doubt it but its possible
Link
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685. IKE
After looking at what's left of it....bye-bye.
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684. IKE
Navy doesn't have 92L up yet. Neither does WU.

Is this really an invest?
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Secure Connection Failed













www.nemoc.navy.mil uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown.

(Error code: sec_error_unknown_issuer)
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My analysis of the SSD 92L floaters:

Visible - Looking somewhat good, nice spin, covection looking OK.

Shortwave (IR channel 2) - Pretty disorganized, not looking very good at all.

Water Vapor (IR channel 3) - No dry air in the area, but not a lot of wetness.

IR channel 4 enhancements:

IR channel 4 (plain) - Convection disorganized, barely a center of circulation.

AVN - Very disorganized convection.

Dvorak - Still disorganized.

JSL - A little better, but mainly convection on the east side.

RGB - Still ragged, but better, probably because of the visible loop.

Funktop - Some good convection on the NE side, but still ragged.

Rainbow - Same as Funktop.

Summary: Looks bad, better than last night, but bad. Don't expect this to be anything more than Invest 92L.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
the e. pac to my surprise has not popped yet. have a good day with some happy weather
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Good morning
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Morning! 7am here 92L actually looks more tropical today however less organized. I think its chances of being named at least till the post season just went down the toilet overnight.

but here's a great loop if people want it (very nice Europe satellite loop, takes a while to load)
Link

And if anyone is interested... I'm going to have a potentially huge entry on subtropical storms, NHC naming issues, bla bla after work (in about 8 hours) and after some research.. and also an analysis of this storm based on what i've learned. Bookmark my page if interested :)
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Quoting Weather456:


Would like to but have get ready for work, maybe later.

Ok, thanks.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting cg2916:

Thanks. Do you want to go on chat?


Would like to but have get ready for work, maybe later.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
Tropical Update

Thanks. Do you want to go on chat?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Tropical Update
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good morning. I see Invest is now officially 92L. Unless this thing does a TD1 (rapidly strengthens from an invest to a td overnight). This should be nothing.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Quoting keywestbrat:
hey char ware are you at :)


Sorry was at work couldn't respond right away. Grew up in Port Charlotte just moved again 4th time in a year Cape Coral
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Quoting charlottefl:
Good morning/ Evening everyone. Nice breeze out there tonight. Reminds me of the night b4 a cane rolls through...Have this feeling this season is gonna be interesting...

Agreed. Same kinda feeling tonight here in Wilmington, NC, and this year marks the 10th year anniversary of Hurricane Floyd in 1999. Ominous memories for alot of North Carolinans.. Hopefully not a repeat of that season.(Dennis, Floyd, Irene)
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670. TX2FL
Good evening..

Just thinking about hurricane prep because I'll probably be moving back to FL from TX in Aug-Sep..I was in Big Lots today and they had Borden milk in the paper container that keeps until 4/2010..for 1.00 was thinking of getting about 10 of them and bringing them with..for that price.
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I well never forget Camille was never close too s. fl. .But if they make a stronger storm I dont want to see it, much less here about it.The intensification of this storm until recent times was truly unprecedented. My god bless anyone that face any such creature.
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hey char ware are you at :)
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Good morning/ Evening everyone. Nice breeze out there tonight. Reminds me of the night b4 a cane rolls through...Have this feeling this season is gonna be interesting...
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orca, burning the after midnight oil
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any aussies awake
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well I am off for now gotta catch my beauty sleep... god knows I need a ton of that... Catch you guys tomorrow..
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Oh wow! no wonder your always mentioning hockey...hehe! Man I bet it is beautiful up there... I have always wanted to drive to Alaska and spend plenty on the scenic routes in Canada.

One of these days when I have plenty of bandwidth left I am going to check out your critter cam or pond cam... whatever it is.
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Quoting SomeRandomTexan:
oh you must be on the west coast... For some reason I thought you were in Florida... my bad big fish


Victoria BC, Canada
BRB checking the pond
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oh you must be on the west coast... For some reason I thought you were in Florida... my bad big fish
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Quoting SomeRandomTexan:
Wow! ORca your up late tonight


Umm its 932 pm
I'm not that old :)
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Wow! ORca your up late tonight
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AOI #1

AOI #2

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Quoting EDTEXAN:
Hello. I thought I was going to post a link to a website dedicated to the tracking of tropical systems which potentially threaten Texas, since it's June 1st today. (I was going to do it earlier while Tropical Depression #1 was active but was unable).

The address is www.explosivedeepening.net. Click here to go to the Storm Updates page.


Thanks Ed :)
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For the hottie looking for Weather Radios
http://www.midlandradio.com/Desktops-Weather.OCS/WR-300

http://www.reecominc.com/r1630.htm

I bodysurfed 10'-12' in Hurricane David off New Smyrna. Probably wouldn't try it now.
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Storm, good to see you. We're never online at the same time anymore. Will the dissipating low north of 92L affect it at all? maybe with steering? Just wondering...
Member Since: September 3, 2007 Posts: 3 Comments: 1519
What is the progression of an invest? I thought the first official designation was the Navy site.
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I'm off for the night. I'll be back tomorrow to watch for little blobs.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
...from the past:

522. kmanislander 1:04 AM GMT on July 02, 2008
Hi Keeper

I think 92L will be an early season oddity but not for too long.
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Quoting CatastrophicDL:
Severe, thank you. That was just what I was looking for! I lost my link and the one I googled didn't work either.

CaneWAOI = area of interest. My AOI is now 92L. There is a 1008mb dissipating low just north of 92L. I was wondering if it would affect 92L at all?


No Problem DL. :)
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I wonder what this Atlantic hurricane season will bring. I expect it to feature above-average activity. (Around 15 named storms).
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Quoting EDTEXAN:
Hello. I thought I was going to post a link to a website dedicated to the tracking of tropical systems which potentially threaten Texas, since it's June 1st today. (I was going to do it earlier while Tropical Depression #1 was active but was unable).

The address is www.explosivedeepening.net. Click here to go to the Storm Updates page.


I don't think you are allowed to do that. I also got an email from someone else advertising another site.
Member Since: April 26, 2009 Posts: 3 Comments: 3667

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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