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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Have a good night all. Here are some interesting weather vids I ran across while looking for the lighting item. That Atlantic system sure does look to be in good health. Be well and prayers to those on the plane.

Link

Link

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Quoting Levi32:


Tropical Storms rarely have a uniform wind field. Even most hurricanes don't.

This is a very impressive system.


I trust what you have to say, Levi.
Do you see why this is not a TD/TS/STS/Anything more than it is now?

Thanks.
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Go to irc.hurricanehollow.org for a special 3 hour HUrricane hollow eye on the storm broadcast starting at 8. Should be a very informative show

this is straight from website:

I will have special guests, a giveaway of an AquaPod Kit, and we will be part of a Guiness World Record. You can listen live and watch the Studio Cam in Storm Chat!
My guests include:
Dan Brown, Senior Hurricane Specialist at the National Hurricane Center.
Hilary Stockdon from the USGS to discuss Coastal Erosion and Storm Surge.
Will Shaffer from the NWS in Silver Springs, MD to discuss Storm Surge and Modeling.
We will be streaming Live Video and will be in Storm Chat. Follow the Real Player link to download if you don't have it on your computer to watch the video.
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Final comment maybe, there are no words to explain the sorrow the people that are left behind by the airplane tragedy feel but I wish them peace sometime in the future. I would say at that altitude if there was a catastrophic failure of the airplanes frame massive decompression would explain the silence.
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Quoting HurricaneGeek:


Ok, and if you compare this to the previous pass, you see that this one has purple bars indicating >40 knots which is roughly 46 mph.
But then you notice that on the West side there is yellow which is indicative of 20-25 knots which is roughly 23 to 29 mph.


Tropical Storms rarely have a uniform wind field. Even most hurricanes don't.

This is a very impressive system.
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This system has a well define tight circulation with the strongest winds near the center. I am surprisingly impressed. For comparision reasons:

Td 1



Vince

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
Its sad, if the plane did crash near the ITCZ, they have been bad lucky this spring, with 49 dead across twelve states due to flooding from the ITCZ, along with other factors.


Last I had heard, they were stated to be 60 miles off of Cape Verde and had auto transmission data of an electrical problem. There was also conjecture of lighting being the cause and due to the fact the planes now days are made of composite material to save weight, and not aluminum, that indeed could have had a serious impact on the electronics. Ofcourse, there is always the issue of terror attacks. No radio communication from the pilot seems very strange.

Here is a video showing how lightning passes through a traditional aircraft. The composite craft would provide much more resistance and problems with the flow and perhaps impact the cabin pressure also via puncture. Note, these videos are at low altitude and not at 35,000'

Link

Link
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so its a lopsided storm basically.
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Sorry I was just speaking for the general public. I guess if they made it the lead story there must be a lot of people asleep like me. Sorry to upset the enlightened.I'll go back to watching the experts sorry for the redundant info.
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Final comment: They are looking for any satellites that were in the position that they believe the plane went down in, to see if they can recover any data as to what happened. I would not be surprised to see the US get involved, as we had American citizens on board, and I know that there are navy ships within the area that can lend a hand, even the Coast Guard as well..
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Quoting Levi32:


That should settle any debates on whether it has TS-force winds. That's a very nice tight well-defined circulation and secondary wind core there.


Ok, and if you compare this to the previous pass, you see that this one has purple bars indicating >40 knots which is roughly 46 mph.
But then you notice that on the West side there is yellow which is indicative of 20-25 knots which is roughly 23 to 29 mph.
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maybe that explains whey there was no mayday call made, stsimon. they must have all passed out. they keep saying something had to have happened quickly to keep the pilots from a mayday call.
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Quoting StSimonsIslandGAGuy:
If the Air France flight lost cabin pressure anywhere near its 35,000 foot cruising altitude, everyone would pass out very quickly, and in a few minutes, some would be dead. I suppose there is still a chance, but I strongly suspect they are all dead.


Unfortunately we may never get to recover the remains because of the 15,000 ft seafloor. Also the plane would have been crushed at that depth.
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read my post Gordy
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electrical events in the sky and fly-by-wire are a tough set of circumstances. Still and all, flying is a very safe mode of transportation. Its a wonder there are not a lot more of this type of loss. Peace to the missing.
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Gordy, if you had read what Master's and other forecasters said in the past. You would have seen the predictions of a below average CV season and a greater chance for storms to develop closer to home. Its become the norm for hurricane season for a system to form closer to home.
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Quoting Weather456:
New QuikSCAT



Are those 50knot wind vectors? That would definitely warrant an upgrade.
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No but the fact that they are saying it maybe a major shift away from the Cape Verde traditional threat to a new more quick developing threat is interesting I know this is a dirty word but are they trying to bring in GW sorry for the capitals.
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Quoting Weather456:
New QuikSCAT



That should settle any debates on whether it has TS-force winds. That's a very nice tight well-defined circulation and secondary wind core there.
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New QuikSCAT

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting gordydunnot:
So, none of you guys or gals want to comment on the main story on the home page for yahoo. Maybe we need the doctor to make that call.


It has been said numerous times this year that storms would develop close to the US. Nothing new.
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456, The latest thinking is that the plane was hit by lightning and thus went down. There are recordings of pressure alarms present, so its to suffice that the plane at some point or another lost altitude and cabin pressure.
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So, none of you guys or gals want to comment on the main story on the home page for yahoo. Maybe we need the doctor to make that call.
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Its sad, if the plane did crash near the ITCZ, they have been bad lucky this spring, with 49 dead across twelve states due to flooding from the ITCZ, along with other factors.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
hurricane hollow 3 hr barometer bob show at 8 pm

Link
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Quoting KEEPEROFTHEGATE:
no broke apart on impact sunk soon after ward what got out got sucked down with the sinking pieces what was left if shock did not get em exposure did

may there be mercy for there souls


Hopefully they didn't suffer.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting CaneWarning:


This is one of the most advanced airplanes available. I am sure there is some type of tracking device. My thoughts are that the plane is at the bottom of the ocean along with its passengers.
no broke apart on impact sunk soon after ward what got out got sucked down with the sinking pieces what was left if shock did not get em exposure did

may there be mercy for there souls
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well, i think there are survivors. too bad they can't find them. good point about the weather, however.

sorry to get y'all off topic.
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GFS develops the low into a full blown GOM TS.

372 hours:

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I don't think the water temperature would be a concern. The problem is, even if you survive the impact which is very unlikely, you are probably knocked out. Someone knocked out can't swim... Not to mention did the plane explode or break apart before impact? There's no way to know right now.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting hurricanemaniac123:


Way to think positive...


The waters there are near 15,000 feet deep. Water temperatures are somewhat bearable but weather conditions wouldnt help (High waves and cold winds). Especially if they crashed near the ITCZ. Even if some survived the initial crash, survival looks futile with those conditions.
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Quoting truecajun:
it just seems like even though they went through a storm near the equator, there would still be a way to track it somehow.

how cold is the water in that area?


Probably in the 80's.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting CaneWarning:


It's been almost 24 hours. They would first have to survive the crash, then somehow stay afloat. It's not likely. Even the experts are saying that. Remember TWA 800?


Sorry about that, I just read that they think nobody survived or that there's a 'minimal chance' anybody survived.
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it just seems like even though they went through a storm near the equator, there would still be a way to track it somehow.

how cold is the water in that area?
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The 18z GFS still has its southern Caribbean system. You can see the disturbance with the surface low at 180 hours.
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Quoting hurricanemaniac123:


Way to think positive...


It's been almost 24 hours. They would first have to survive the crash, then somehow stay afloat. It's not likely. Even the experts are saying that. Remember TWA 800?
Member Since: April 26, 2009 Posts: 3 Comments: 3667
.
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Quoting truecajun:
no they still don't know anything. it all seems really strange to me. you'd think that there would be GPS reporting exact location in the year 2009. are French airliners not as advanced as american?


This is one of the most advanced airplanes available. I am sure there is some type of tracking device. My thoughts are that the plane is at the bottom of the ocean along with its passengers.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting truecajun:
no they still don't know anything. it all seems really strange to me. you'd think that there would be GPS reporting exact location in the year 2009. are French airliners not as advanced as american?


They think that they flew through a thunderstorm off of Brazil and had their GPS knocked out.
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
no they still don't know anything. it all seems really strange to me. you'd think that there would be GPS reporting exact location in the year 2009. are French airliners not as advanced as american?
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Good Evening all!

Looks like everyone's eyes are turned to the eastern Atlantic at the Subtropical Low. Looks pretty good for where it is at.

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Quoting Weather456:


Give it within the next hr


Alright.
Thank you.
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Quoting HurricaneGeek:

A couple of minutes or a couple of hours?


Give it within the next hr
Member Since: July 24, 2005 Posts: 407 Comments: 19076
.
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Quoting Weather456:


soon

A couple of minutes or a couple of hours?
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Quoting truecajun:
what is the temp of the waters that the plane went down in?


Did they find where it went down? I really haven't been listening to the news today. All I know is that the depths around the "presumed crash area" are extremely deep.
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Quoting HurricaneGeek:


Hi Levi,
when will that new QuikSCAT pass be?


soon
Member Since: July 24, 2005 Posts: 407 Comments: 19076
what is the temp of the waters that the plane went down in?
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Quoting Levi32:


1001mb pressure is squarely in the middle of the range of a typical minimal tropical storm, and the winds are right there near TS threshold. What we need is a new QuikSCAT pass, then we'll see what it looks like.


Hi Levi,
when will that new QuikSCAT pass be?
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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.