Hurricane season begins today; normal June activity expected

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

Share this Blog
2
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 144 - 94

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18Blog Index

Accuweather now forecasting weather for pirates- Link
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Okay this is a weather related subject, just not specific to forecasting. Thanks to Ike, I once again find myself in the market for window coverings for my homes windows. Since Florida has been much more of a "test zone" over the last couple of years I am hoping someone on the blog might have some experience with any of the new window protection systems.

After my near death experience last year (almost fell off a ladder on the second floor)
My critera is pretty simple, light weight, easy to install, and effective. I have looked at the polycarbonate clear panels (screw mount, no hook and loop fastener), another system that looks like tennis court wind screen and finally a coated fabric that mounts in a similar fashion (all are Miami/Dade county approved). Does anyone have any real world observations of these systems in use? I am interested in hearing good or bad comments, before I go and invest a small fortune in one of these systems. I would really like to know how they actually performed in a storm.

Roll down shutters and permanent shutters are not an option due to house design and cost constraints, besides I have picked up more than one of those systems out of my yard before.
Member Since: Posts: Comments:
Quoting Levi32:
134.

Lol whatever I don't care about all the hate propaganda spread about Accuweather.

That "invest" looks like an awesome subtropical storm to me =).

Looks like a result of a warm-seclusion extratropical storm.





That's what I was thinking.
Member Since: Posts: Comments:
134.

Lol whatever I don't care about all the hate propaganda spread about Accuweather.

That "invest" looks like an awesome subtropical storm to me =).

Looks like a result of a warm-seclusion extratropical storm.



Member Since: Posts: Comments:
Quoting Stormchaser2007:
T-number is around 1.5.

01/1745 UTC 39.9N 24.7W TX.X/1.5 INVEST


The t number is low because of the weak convection brought on by the cold waters. If this storm was in warmer water the t numbers would match the winds.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting HurricaneKing:


On visible you can see the upper level eye is a little to the right of the lower level eye. Other than that it looks like hurricane vince.


Its a pretty impressive system. It has a very nice wind filed as depicted by QUICKSCAT.

Member Since: Posts: Comments:
T-number is around 1.5.

01/1745 UTC 39.9N 24.7W TX.X/1.5 INVEST
Member Since: Posts: Comments:
Quoting Stormchaser2007:
An INVEST has been tagged on the SSD site. Interesting.

Oh and it has an eye.



On visible you can see the upper level eye is a little to the right of the lower level eye. Other than that it looks like hurricane vince.
Member Since: Posts: Comments:
Quoting Levi32:


They are absolutely right. The NWS is pretty unclear about it.


It does not matter whether they are right or wrong.They are insane and have no right to do that. AccuWeather does not issue the warnings, watches, or advisories. All they do is Hype and make forecasts that are based off biased opinions by a person that is missing the Pecan from the Shell.Accuweather is just a group of Biased Arm Chair Met's and that's why I have completely disowned them.
Member Since: Posts: Comments:
An INVEST has been tagged on the SSD site. Interesting.

Oh and it has an eye.

Member Since: Posts: Comments:
That north atlantic storm is an invest on the ssd site.
Member Since: Posts: Comments:
130. beell
Good look at the "Rex Block" over the west coast. A factor in the present trajectory of the sub-tropical jet.

Photobucket

Haby Hints-Rex Block
RAMSDIS 16KM GOES-EAST IR/WV Loop
Member Since: September 11, 2007 Posts: 143 Comments: 16652
Quoting SevereHurricane:
LOL,
AccuWeather has some nerve to criticize the NWS...

Link


They are absolutely right. The NWS is pretty unclear about it.
Member Since: Posts: Comments:
Quoting SevereHurricane:
LOL,
AccuWeather has some nerve to criticize the NWS...

Link

Sounds like our friends at accuweather feel a bit bruised by the NWS.

Personally, I would prefer a bit overzealous and vague hurriacne forecast, rather than a very specific one that is more likely to be wrong than it is to be right. Weather forecasting is far from an exact science. Anyone who thinks they can exactly predict something like the weather is just deluding themselves.
Member Since: August 3, 2008 Posts: 16 Comments: 5882
w00t! Theres a Teresa this year! :)
Member Since: Posts: Comments:
We talk about the ITCZ all the time on this Blog, and how it needs to "rise" above 10 Degrees North later in July and August for the Coreolis effect to spin up tropical disturbances.....Enclosing an exceprt from an article on the possibility of the ITCZ playing a role in the downed airliner...Not sure about the science of it from the standpoint of this journalist (41,000 foot high T-Storms) but gives me food for thought, and pause, in light of this tragedy............

It was a dark and stormy night - in a place that is home to the world%u2019s worst thunderstorms. Just as it disappeared, the Airbus A330-203 was flying into a thick band of convective activity that rose to 41,000 feet. This equatorial region is known as the Intertropical Convergence Zone %u2013 it is where Northeast and Southeast Trade Winds meet - forcing a lot of warm, moist air upward - which condenses %u2013 an efficient thunderstorm producing machine.
Member Since: August 8, 2006 Posts: 0 Comments: 9134
Time to go burn some calories....off for my Run......BBL!
Member Since: Posts: Comments:
LOL,
AccuWeather has some nerve to criticize the NWS...

Link
Member Since: Posts: Comments:
Quoting stillwaiting:
as it moves wnw in the next 24hrs it could start to be effected vort,

The more north it pulls, the more hostile the environment in terms of shear.

Keep in mind it is very rare for a storm to be able to spin up south of 10N. It will sometimes happen, but I have yet to see it happen in the last 5 years I've been watching the tropics south of 8N.

Looking at the map I posted, it is solid red along 10N from Africa all the way to Central America. Red on this map = 40 kt shear.
Member Since: August 3, 2008 Posts: 16 Comments: 5882
Quoting presslord:
Volusia Flood...

OK...this is admittedly somewhat premature, as we still have some details to work out over the next couple of days...but will give y'all an overview of how we're progressing....

we have a disability community contact who is assessing medical equipment needs...when we get the "Wish List" we will arrange shipment...

SJ is putting together a team ...or teams...to go there and help with clean up on one or more homes....

we are working to get insect repellant and face masks to those on scene engaged in clean up....

Thanks!

www.portlight.org


You guys are doing great work.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting stillwaiting:
as it moves wnw in the next 24hrs it could start to be effected vort,

looks like we might actually get some storms around sunset tonight here along the west coast of FL,some may get strong,IMO.....


NOAA gives the Tampa area 0% chance of rain today. It would be interesting if we got some though. It's hot here, so it would be nice to cool off.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting stillwaiting:
that wave in the ITCZ is looking darn healthy and IMO w/be worthy of an invest if it persists for another 24hrs,is there a slight anti over the area???...


StillWaiting if you are going to want an invest with everything with a blob of clouds this year...Its gonna be a long season of over Hype for ya...LOL...enjoy your day.
Member Since: Posts: Comments:
Quoting Vortex95:
This is the worst rain ive had since Fay was in north florida and dropped rain bands in on south Fl my area was the worst hit with 5 inches in a little over two hours. luckly it ended there.


Vortex- you got that right. We just had some very heavy rain in Fort Lauderdale.
Member Since: Posts: Comments:
Volusia Flood...

OK...this is admittedly somewhat premature, as we still have some details to work out over the next couple of days...but will give y'all an overview of how we're progressing....

we have a disability community contact who is assessing medical equipment needs...when we get the "Wish List" we will arrange shipment...

SJ is putting together a team ...or teams...to go there and help with clean up on one or more homes....

we are working to get insect repellant and face masks to those on scene engaged in clean up....

Thanks!

www.portlight.org
Member Since: Posts: Comments:
as it moves wnw in the next 24hrs it could start to be effected vort,

looks like we might actually get some storms around sunset tonight here along the west coast of FL,some may get strong,IMO.....
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Quoting stillwaiting:
shear is 5-10kts over the area,there's vortcity at the surface look at the visible loop and you can see it....

The far eastern wave is under marginal shear (varies from 5-30 kts), and it does have a weak anti-cyclone above it. However, SSTs in the area aren't exactly toasty (26-28C), there is a heavy SAL nearby, it is mighty far south (5 deg N), and most importantly, it has a very hostile road ahead of it.
Member Since: August 3, 2008 Posts: 16 Comments: 5882
I have family up near you in ft walton,Iv'e never been up there,I live on siesta key,how's it up there????
Member Since: October 5, 2007 Posts: 20 Comments: 4970
yepper dj!!!,lol....2 diff area's...
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Howdy all, please find the attached for your use this hurricane season. It is free and well worth a look. This tool can help.

www.onestorm.org
Member Since: June 12, 2005 Posts: 6 Comments: 8186
shear is 5-10kts over the area,there's some vorticity at the surface look at the visible loop and you can see it....
Member Since: October 5, 2007 Posts: 20 Comments: 4970
that wave in the ITCZ is looking darn healthy and IMO w/be worthy of an invest if it persists for another 24hrs,is there a slight anti over the area???...
Member Since: October 5, 2007 Posts: 20 Comments: 4970
105. bcn
(sorry, wrong link, try again)
Closed Azores loop:
Member Since: Posts: Comments:
Quoting lakeEFX:


Now I'm REALLY laughing because MY name is Claudia!! (close enough) LOL!!


ROFLMAO!!!!!
Member Since: August 30, 2007 Posts: 0 Comments: 1857
101. bcn
Closed Azores loop:



East Atlantic
Member Since: Posts: Comments:
Quoting MNTornado:


That is very disturbing. Now I see what all the hub bub is about. New weather trend or has this pattern been here for a while?


It's just for June, and yes it's been around for as long as records have been kept! lol. It's nothing new, conditions out in the middle of the Atlantic are never conducive enough for developments yet in the month of June. Therefore most developments are close to home caused by trough splits or old fronts.
Member Since: Posts: Comments:
June Outlook

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting SomeRandomTexan:


UH OH!!!! don't tell me that...lol!

Oh and Claudette just sounds like its going to be a booger...haha


Now I'm REALLY laughing because MY name is Claudia!! (close enough) LOL!!
Member Since: Posts: Comments:
Quoting Levi32:
Thanks Dr. Masters!!



LOL....yeah it does look like it. What you're supposed to get out of it is that the spagetti was only thrown at one part of the map, the Caribbean, GOM, and off the Southeast US coast. Notice how only one storm in 150 years has formed out in the middle of the Atlantic. The point is most early storms form close to home and not form African tropical waves.


That is very disturbing. Now I see what all the hub bub is about. New weather trend or has this pattern been here for a while?
Member Since: Posts: Comments:
that is the paths of all the june storms
Member Since: August 30, 2007 Posts: 0 Comments: 1857
Quoting MNTornado:
Please excuse my ignorance, but what the heck am I supposed to get out of this mess? It looks like somebody had a food war with the spaghetti!



Those are the tracks of storms that formed in June previously. It shows you what to expect if a storm does form now.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Thanks Dr. Masters!!

Quoting MNTornado:
Please excuse my ignorance, but what the heck am I supposed to get out of this mess? It looks like somebody had a food war with the spaghetti!



LOL....yeah it does look like it. What you're supposed to get out of it is that the spagetti was only thrown at one part of the map, the Caribbean, GOM, and off the Southeast US coast. Notice how only one storm in June in 150 years has formed out in the middle of the Atlantic. The point is most early storms form close to home and not from African tropical waves.
Member Since: Posts: Comments:

Viewing: 144 - 94

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18Blog Index

Top of Page

About

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