Outlook for the remainder of hurricane season

By: Dr. Jeff Masters , 11. syyskuuta 2009 klo 13:57 (GMT)

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Hurricane Fred continues its slow decline, as wind shear of 25 knots tilts and stretches the storm, allowing dry air to penetrate into the hurricane core from the southwest side. With sea surface temperatures down near the threshold needed to support a tropical cyclone and wind shear expected to increase to 30 knots Saturday, Fred should continue to weaken the next few days. The storm's very slow motion will hasten this decay, since the storm will stir up cold waters from the depths that it will not be able to move away from. Fred will likely die by Tuesday.


Figure 1. Hurricane Fred (upper left) and a new tropical disturbance (right), newly emerged from the coast of Africa. At the time, Fred was a Category 1 hurricane with 85 mph winds.

Elsewhere in the tropics
A large tropical wave emerged from the coast of Africa last night and has a well-organized surface circulation, as seen on this morning's QuikSCAT pass. The wave as yet does not have much in the way of heavy thunderstorm activity associated with it, and wind shear is relatively high, about 20 knots. By Sunday, the shear will drop below 20 knots, and the wave may begin to develop. The GFS model predicts this will be a tropical depression by early next week.

A low pressure system is over eastern Texas and the adjoining waters along the Texas Gulf of Mexico coast. This low is under high shear, about 25 knots, and is not tropical. Shear is expected to remain high, 20 - 30 knots, over the next five days. The low should remain non-tropical during this time, but will bring much-needed heavy rains to drought-stricken south Texas. Flooding problems may also occur, and flash flood watches have been posted for six counties in extreme South Texas.

Early next week, we should be alert for tropical storm development along an old frontal zone stretching from the Florida Keys across the Florida Peninsula to the waters between the Bahamas and North Carolina. The NOGAPS model predicts development could occur on the Gulf side of Florida, and the GFS model forecasts that development is more likely on the east side of Florida.


Figure 2. Departure of Sea Surface Temperature (SST) from average for September 10, 2009, shows that SSTs were 0.5 - 1.0°C above average over most of the Main Development Region (MDR) for hurricanes in the Atlantic, from the coast of Africa to Central America, between 10°N and 20°N. Image credit: NOAA/NESDIS.

Outlook for the remainder of hurricane season
September 10 marks the halfway point of the Atlantic hurricane season, and the season has thus far been average to a bit below average. What, then, can we expect for the remainder of the season? First, let's take a look at Sea Surface Temperatures (Figure 2). SSTs are 0.5 - 1.0°C above average over most of the Main Development Region (MDR) for hurricanes in the Atlantic, from the coast of Africa to Central America, between 10°N and 20°N. This means that the ocean will be capable of supporting the development of major hurricanes well into the middle of October. Approximately 85% of all major hurricanes form in the Main Development Region.

Wind shear and El Niño
The current weak El Niño conditions in the tropical Eastern Pacific show no signs of weakening, and these El Niño conditions are likely contributing to the enhanced levels of wind shear observed over the Caribbean over the past month (Figure 3). However, wind shear has been near average over the remainder of the Main Development Region, which allowed two major hurricanes (Bill and Fred) to form in the region between Africa and the Lesser Antilles Islands. The latest 16-day forecast from the GFS model projects near-average wind shear levels across the Main Development Region for the remainder of September. The latest long range wind shear forecast from NOAA's CFS model predicts high levels of wind shear for the entire tropical Atlantic for the remainder of hurricane season--the typical pattern for an El Niño year. This model's September wind shear forecast doesn't look very accurate, so I mistrust the model's call for high wind shear for the remainder of hurricane season. It does not appear that this year's El Niño conditions are resulting in as much wind shear as a typical El Niño event generates over the tropical Atlantic. This may be because this year's El Niño conditions have some characteristics of a modiki El Niño. These "modiki" El Niños tend to have warming concentrated in the Central Pacific, instead of the Eastern Pacific. This year, the warming is greatest in the Eastern Pacific (see Figure 2), but there is also quite a bit of warming in the Central Pacific.


Figure 3. Departure of wind shear from average for the 31-day period August 9 - September 8, 2009. Wind shear has been above average over the Caribbean and Gulf of Mexico, and much below average over the Eastern Pacific--a typical pattern observed during El Niño years. Image credit: NOAA Climate Prediction Center.

Steering Currents
We've been lucky this year that the steering currents have aligned to keep our two major hurricanes, Bill and Fred, out to sea. This year's hurricane season has featured a very favorable steering current pattern, with an abnormal number of intense troughs of low pressure over the U.S. East Coast. These troughs have brought westerly winds far to the south, which have acted to recurve to the north all the tropical storms that have formed from African tropical waves. The latest 16-day forecast from the GFS model shows no change to this steering current pattern. It will remain difficult for tropical storms spawned from African tropical waves to make the long crossing of the Atlantic and impact the Caribbean, Bahamas, or Florida. The land areas at greatest risk of receiving strikes from hurricanes that develop from African tropical waves will continue to be Bermuda, North Carolina, New England, and the Canadian Maritime provinces.

Only one hurricane has made landfall this season--Category 1 Hurricane Bill, which did minimal damage to Newfoundland, Canada. Although it is an El Niño year, and the steering current pattern will continue to be favorable for keeping most of our storms out to sea, I expect we will get a hurricane strike somewhere in the Atlantic this season that will require a disaster response.

Twenty years ago on this date
On September 11, 1989, Tropical Depression Twelve continued to grow more organized, building a large region of heavy thunderstorms near its center. Two hooking spiral bands formed, prompting the National Hurricane Center to upgrade the depression to a tropical storm in their 11 am advisory. The new storm's name: Hugo. Tropical Storm Hugo continued to trek westward across the open Atlantic at 20 mph, still four days from the Lesser Antilles Islands.

That day at NOAA's Miami-based Office of Aircraft Operations--the hurricane hunting division of NOAA--we joked about the fearsome new storm with the same name as the director of NOAA's Atlantic Oceanographic and Marine Laboratory (AOML), Hugo Bezdek. AOML housed the offices of NOAA's Hurricane Research Division, whose scientists would decide whether or not our hurricane hunting group would intercept the new storm once it got close enough to the Lesser Antilles Islands. Even if Hugo was a dud, we figured we'd be flying the storm for sure, since it shared the same first name as the big boss of the hurricane research scientists.

After work that evening, I celebrated my 29th birthday by biking through the sun-dappled shaded streets of Coconut Grove. As I stopped to watch a perfect tropical fuchsia-red sunset, my thoughts roamed out over the eastern horizon. What kind of birthday present had the weather gods delivered me today? I was first on the list of flight meteorologists that would deploy to meet Hugo, should we fly the storm.


Figure 4. AVHRR visible satellite image of Tropical Storm Hugo taken on September 11, 1989. Image credit: Google Earth rendition of the NOAA HURSAT data base.

Jeff Masters

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1563. TexasHurricane
12. syyskuuta 2009 klo 20:33 (GMT)
Quoting homelesswanderer:


Hello to you Sir! Lol. I'm fine. Hope you are too.;) Yes I read 810. Think Barbra wrote a song about the good ol' days. Hee hee. There also is a lot of weather to discuss. I know I've been concentrating on the gulf but we may not have heard the last of Fred or the wave off Africa. So much for no CV season.


Hi Homeless...how do you like our torrential rainfall? :)
Member Since: 2.07.2009 Posts: 0 Comments: 2811
1562. LovingTX
12. syyskuuta 2009 klo 14:20 (GMT)
Quoting P451:
NEW BLOG

NEW BLOG

NEW BLOG

NEW BLOG

NEW BLOG

NEW BLOG


Seizure activity?
1561. reedzone
12. syyskuuta 2009 klo 13:31 (GMT)
Tampa, this also backs your claim. Look just south of NOLA





Conditions are MARGINALLY favorable for development in that particular area if you go by CIMMS


Member Since: 1.07.2008 Posts: 13 Comments: 7334
1559. Drakoen
12. syyskuuta 2009 klo 13:27 (GMT)
Showers and thunderstorms in the GOM are disorganized and upper level winds are not favorable for development.
Member Since: 28.10.2006 Posts: 57 Comments: 29714
1558. Dakster
12. syyskuuta 2009 klo 13:26 (GMT)
As long as we don't end up in a 2005 - La Chinga event, err. I mean La Nina...

I'll take a weak, moderate, or strong El Nino event.
Member Since: 10.03.2006 Posts: 0 Comments: 9765
1557. hurricanehanna
12. syyskuuta 2009 klo 13:26 (GMT)
Gooood morning!
Okay, WHY is the yellow crayon circle so big in the GOM? Still no clue where the possible LLC could be?
ANd what the heck is with new track on Fred?

I think I'll just go back to bed...
Member Since: 5.09.2007 Posts: 0 Comments: 3480
1556. TampaSpin
12. syyskuuta 2009 klo 13:24 (GMT)
I think the BOC is going to be the likely spot for something to truely develop!
Member Since: 2.09.2007 Posts: 177 Comments: 20430
1555. Dakster
12. syyskuuta 2009 klo 13:23 (GMT)
Quoting vince1966:
Wow, Long range forecasting. This site gets more amazing by the hour.


He's just using the new super extended long range GFS forecasting model. It goes 3 years out.
Member Since: 10.03.2006 Posts: 0 Comments: 9765
1554. Cavin Rawlins
12. syyskuuta 2009 klo 13:22 (GMT)
Quoting TampaSpin:
I think its easy to find a possibly developing Low



take a look at this, it backs ur claim. Look just sse of NO, LA. Look how the winds are veering.
Member Since: 24.07.2005 Posts: 407 Comments: 19076
1553. reedzone
12. syyskuuta 2009 klo 13:22 (GMT)
Quoting Weather456:
Ur right, this year's El Nino is not as strong as 2006 - It's stronger.

as of August 31

2009 - 0.7
2006 -0.3


That is interesting, but still not as powerful as 1997. I don't expect a "shut down" on the season in mid September. Maybe mid October, but I'd like to see some Subtropical systems form in the open Atlantic around November.
Member Since: 1.07.2008 Posts: 13 Comments: 7334
1552. TampaSpin
12. syyskuuta 2009 klo 13:20 (GMT)
I think its easy to find a possibly developing Low

Member Since: 2.09.2007 Posts: 177 Comments: 20430
1551. Orcasystems
12. syyskuuta 2009 klo 13:18 (GMT)
Blog Update
Reflector site for those at work, includes Dr. Masters & Weather456, daily update.


AOI

AOI

AOI

AOI
Member Since: 1.10.2007 Posts: 81 Comments: 26493
1550. Brillig
12. syyskuuta 2009 klo 13:18 (GMT)
14.33 inches in 24 hours reported in Williamson County.
http://www.cocorahs.org/Maps/ViewMap.aspx
Member Since: 23.06.2006 Posts: 20 Comments: 407
1549. Cavin Rawlins
12. syyskuuta 2009 klo 13:16 (GMT)
Ur right, this year's El Nino is not as strong as 2006 - It's stronger.

as of August 31

2009 - 0.7
2006 -0.3
Member Since: 24.07.2005 Posts: 407 Comments: 19076
1548. cyclonekid
12. syyskuuta 2009 klo 13:15 (GMT)
Quoting futuremet:


No...I do not have much time lately. I might update it this afternoon if time permits.


That's ok...take your time...I ALWAYS enjoy your blogs...they are really informative. :D
Member Since: 14.07.2009 Posts: 51 Comments: 1715
1547. TampaSpin
12. syyskuuta 2009 klo 13:13 (GMT)
Quoting reedzone:
Hmm the NHC isn't looking at the shear map close enough.. There is 10 knots of wind shear in the middle of this whole thing. Conditions to me are SOMEWHAT favorable, you go west, conditions are marginal to hostile.


yep......and dropping

Member Since: 2.09.2007 Posts: 177 Comments: 20430
1546. cyclonekid
12. syyskuuta 2009 klo 13:13 (GMT)
Quoting reedzone:
Pointing out here that this years El Nino is still not as strong as 2006s' and not nearly as powerful as 1997s'. It is a weak to near moderate El Nino and indications showing that it will weaken during the winter and we could be talking about an active year next year. Maybe like 2007 or 1998. No this El Nino probably won't "shut down" the Atlantic, you'll see a few storms and Subtropical systems spin in in the open Atlantic and Caribbean before the year is up.


You have to realize too, 2004 was an El Nino year and after that, 2005 was EXPLOSIVE!!! Could we have another 2005 just EXTRA EXPLOSIVE??? Nothing is etched in stone. =) JMO
Member Since: 14.07.2009 Posts: 51 Comments: 1715
1545. futuremet
12. syyskuuta 2009 klo 13:12 (GMT)
Quoting cyclonekid:


Good Morning, futuremet...Have you updated ur blog since the one you talked about the potential for something to happen in GOMEX??


No...I do not have much time lately. I might update it this afternoon if time permits.
Member Since: 19.07.2008 Posts: 43 Comments: 4051
1544. AllStar17
12. syyskuuta 2009 klo 13:12 (GMT)
Quoting reedzone:
Pointing out here that this years El Nino is still not as strong as 2006s' and not nearly as powerful as 1997s'. It is a weak to near moderate El Nino and indications showing that it will weaken during the winter and we could be talking about an active year next year. Maybe like 2007 or 1998. No this El Nino probably won't "shut down" the Atlantic, you'll see a few storms and Subtropical systems spin in in the open Atlantic and Caribbean before the year is up.


We should remain vigilant through mid-October. We should expect....oh....another month plus a few days of activity (until mid Oct.)

It is important to remember, it only takes one bad one to make a season disastrous.
Member Since: 29.06.2009 Posts: 13 Comments: 5238
1543. AllStar17
12. syyskuuta 2009 klo 13:10 (GMT)
WPAC is bursting with activity right now.

Nobody is talking about the Cape Verde wave.....but this could slowly develop over the next few days, and it should trek west or west-northwestward under the influence of the building ridge.
Member Since: 29.06.2009 Posts: 13 Comments: 5238
1542. surfmom
12. syyskuuta 2009 klo 13:10 (GMT)
strangely eerie indeed !!!- feeling like I'm in Tropical Soup -- all the ingredients
Rain w/no Name is what I'd like to see on the menu
Not sure MotherNature has that in mind...what is she cooking up?
Member Since: 18.07.2007 Posts: 30 Comments: 26536
1541. Orcasystems
12. syyskuuta 2009 klo 13:10 (GMT)
Member Since: 1.10.2007 Posts: 81 Comments: 26493
1540. reedzone
12. syyskuuta 2009 klo 13:09 (GMT)
Pointing out here that this years El Nino is still not as strong as 2006s' and not nearly as powerful as 1997s'. It is a weak to near moderate El Nino and indications showing that it will weaken during the winter and we could be talking about an active year next year. Maybe like 2007 or 1998. No this El Nino probably won't "shut down" the Atlantic, you'll see a few storms and Subtropical systems spin in in the open Atlantic and Caribbean before the year is up.
Member Since: 1.07.2008 Posts: 13 Comments: 7334
1539. cyclonekid
12. syyskuuta 2009 klo 13:09 (GMT)
Quoting futuremet:
It is becoming more likely that Fred will degenerate into an open wave. It looks extremely asymmetrical and shear has helped dry air to erode the western semi circle.



Good Morning, futuremet...Have you updated ur blog since the one you talked about the potential for something to happen in GOMEX??
Member Since: 14.07.2009 Posts: 51 Comments: 1715
1538. vortextrance
12. syyskuuta 2009 klo 13:08 (GMT)
Right now shear and dry air are impeding the tx coast low. The shear may relax leaving mid level dry air to contend with. Should keep any development slow. A lot more rain for TX regardless.
Member Since: 5.10.2005 Posts: 0 Comments: 700
1537. vince1966
12. syyskuuta 2009 klo 13:07 (GMT)
Quoting K8eCane:


true but from what im reading there could be somethin later
So, share what your reading, because from all the data and modles and not to mention, the forecasters who get paid to read the weather don't see anything in the Gulf. What do you have?
Member Since: 28.07.2009 Posts: 0 Comments: 59
1536. cyclonekid
12. syyskuuta 2009 klo 13:06 (GMT)
Good Morning WU!!!!

TD 15W (1st pic) is less impressive then our invest (2nd pic)


Member Since: 14.07.2009 Posts: 51 Comments: 1715
1535. vince1966
12. syyskuuta 2009 klo 13:06 (GMT)
Quoting leftovers:
guaranteed things pick up in a couple yrs 2011-12 looks like a dousey. el nino has to a bit stronger now than back in july.
Wow, Long range forecasting. This site gets more amazing by the hour.
Member Since: 28.07.2009 Posts: 0 Comments: 59
1534. futuremet
12. syyskuuta 2009 klo 13:05 (GMT)
It is becoming more likely that Fred will degenerate into an open wave. It looks extremely asymmetrical and shear has helped dry air to erode the western semi circle.



Member Since: 19.07.2008 Posts: 43 Comments: 4051
1533. TexasHoosier
12. syyskuuta 2009 klo 13:04 (GMT)
Texas Hoosier here. Fair amount of rain last night in SW Fort Worth. The real interesting weather is going to be that system coming down off the Rockies into the 4-Corner's region and running smack into the low pressure system over North Texas which is rotating from SE to NW, with the heaviest rain right now, a serious line of Thunderstorms headed to the NW.

Playing football in Raiderland (Texas Tech)in Lubbock tonight and watching it from the student section (my daughter) is going to be one wet event.

Anybody have any update on the potential sub-tropical system that might form off the Texas-Louisiana coastline? the pressure drop along the coast, this very wet airmass, and just the way it feels here in North Texas, makes for a strangly eerie environment right now in this neck of the woods.....
Member Since: 3.12.2002 Posts: 0 Comments: 113
1531. Orcasystems
12. syyskuuta 2009 klo 13:01 (GMT)
Quoting reedzone:
Hmm the NHC isn't looking at the shear map close enough.. There is 10 knots of wind shear in the middle of this whole thing. Conditions to me are SOMEWHAT favorable, you go west, conditions are marginal to hostile.




Disregard.. the one in Google earth is wrong.
Member Since: 1.10.2007 Posts: 81 Comments: 26493
1530. reedzone
12. syyskuuta 2009 klo 12:59 (GMT)
Hmm the NHC isn't looking at the shear map close enough.. There is 10 knots of wind shear in the middle of this whole thing. Conditions to me are SOMEWHAT favorable, you go west, conditions are marginal to hostile.
Member Since: 1.07.2008 Posts: 13 Comments: 7334
1529. surfmom
12. syyskuuta 2009 klo 12:55 (GMT)
BANDIT Chickens usually enjoy the rain... they're looking rather cranky this morning
Member Since: 18.07.2007 Posts: 30 Comments: 26536
1528. surfmom
12. syyskuuta 2009 klo 12:53 (GMT)
Oh yes WEATHER456 -- I'm sitting in it right now.....might be a bit of a longboard wave.... but too much Lightening potential to dip the foot in the waters.

one of those wrap the IPOD up in baggies and run in the rain day.... ALL GOOD BTW... I'm a real time weather girl
Member Since: 18.07.2007 Posts: 30 Comments: 26536
1527. surfmom
12. syyskuuta 2009 klo 12:52 (GMT)
Quoting leftovers:
nothing in the gulf to worry about yet


you never waste words.... i noticed the word yet
barometer SRQ 29.92
Member Since: 18.07.2007 Posts: 30 Comments: 26536
1526. Cavin Rawlins
12. syyskuuta 2009 klo 12:51 (GMT)
An area of low pressure near Tampa is sparking some heavy showers over Florida.



Member Since: 24.07.2005 Posts: 407 Comments: 19076
1525. beeleeva
12. syyskuuta 2009 klo 12:51 (GMT)
Barometer here in Katy, TX this morning lower than its been in a while...29.74in,,no rain overnight...
Member Since: 22.07.2008 Posts: 0 Comments: 82
1524. TheDawnAwakening
12. syyskuuta 2009 klo 12:48 (GMT)
Wow that WV imagery shows three low pressure systems over the United States. Amazing.
Member Since: 21.10.2008 Posts: 243 Comments: 3564
1523. A4Guy
12. syyskuuta 2009 klo 12:48 (GMT)
boy...the vis loops of Fred really show a beautiful surface circulation. Don't get to see the remnants of a major hurricane like that very often.
Member Since: 23.06.2006 Posts: 0 Comments: 655
1522. vortextrance
12. syyskuuta 2009 klo 12:44 (GMT)
Corpus Surface pressure
today 6 am- 1007
Friday 6am- 1012

Pressure are all way down this morning along the tx coast.
Member Since: 5.10.2005 Posts: 0 Comments: 700
1521. weatherman874
12. syyskuuta 2009 klo 12:42 (GMT)
Quoting Weather456:


it could be an area of low pressure. Satellite imagery with surface obs show the wind veering as the feature you observed passed.


pressure has dropped significantly at my house in new orleans. Was about 30.02 last night and now is 29.82
Member Since: 25.05.2008 Posts: 0 Comments: 250
1520. Cavin Rawlins
12. syyskuuta 2009 klo 12:41 (GMT)
Quoting weatherman874:
someone tell me what the spin is right by st bernard parish near new orleans??


it could be an area of low pressure. Satellite imagery with surface obs show the wind veering as the feature you observed passed.
Member Since: 24.07.2005 Posts: 407 Comments: 19076
1519. weatherman874
12. syyskuuta 2009 klo 12:35 (GMT)
someone tell me what the spin is right by st bernard parish near new orleans??
Member Since: 25.05.2008 Posts: 0 Comments: 250
1518. Cavin Rawlins
12. syyskuuta 2009 klo 12:34 (GMT)
Updated it, forgot to post the section on the African wave

Good Morning all;

Did the NHC drop the ball on Subtropical Storm Grace?

Tropical Update


Member Since: 24.07.2005 Posts: 407 Comments: 19076
1517. pearlandaggie
12. syyskuuta 2009 klo 12:31 (GMT)
Member Since: 14.09.2007 Posts: 3 Comments: 3963
1516. tharpgomex
12. syyskuuta 2009 klo 12:30 (GMT)
everytime I get on here that yellow blog in the gulf gets bigger and bigger....Good Morning!
Member Since: 11.07.2008 Posts: 0 Comments: 0
1515. Cavin Rawlins
12. syyskuuta 2009 klo 12:31 (GMT)
.
Member Since: 24.07.2005 Posts: 407 Comments: 19076
1513. Dakster
12. syyskuuta 2009 klo 12:24 (GMT)
Good morning everyone... So is Fred, Yabba Dabba DONE?
Member Since: 10.03.2006 Posts: 0 Comments: 9765

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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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