Fred fading; halfway point of hurricane season reached

By: Dr. Jeff Masters , 1:40 PM GMT on September 10, 2009

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Hurricane Fred peaked in intensity yesterday afternoon, attaining Category 3 strength with 120 mph winds. It is quite unusual to have such a powerful system so far east in the Atlantic, and Fred is only the third major hurricane to exist east of 35W. Fred is also the strongest hurricane so far south and east in the data record. However, this type of system would have been difficult to document before satellite pictures began in the 1960s.

Fred's glory is past, and the storm is on a downslide now, thanks to moderate wind shear of 15 - 20 knots and dry air eating into the hurricane's southwest side. The shear and the dry air will increase over the next few days, with the shear rising above 40 knots by Monday morning. Sea surface temperatures (SSTs) will also cool to near the 26.5°C threshold needed to sustain a tropical cyclone. The combination of high shear, dry air, and cool SSTs will likely kill Fred by Tuesday.


Figure 1. Hurricane Fred at peak strength, 8:55am EDT UTC 9/9/09. At the time, Fred was a Category 3 hurricane with 120 mph winds. Image credit: NASA.

Elsewhere in the tropics
An upper-level low pressure system has moved over Texas and is expected to spawn a surface low pressure system along the Texas Gulf of Mexico coast on Friday. This low will probably have characteristics of both a tropical and extratropical storm. The surface low is likely to move northeastward and move ashore near the Texas/Louisiana border region on Saturday or Sunday. There will be some high wind shear to the west of the low (shear is currently a high 25 knots), so it is uncertain whether this low will be capable of developing into a tropical cyclone. Regardless, this storm will bring heavy rain capable of causing flooding--and help alleviate the exceptional drought conditions over Southeast Texas.

Early next week, we should be alert for tropical storm development over the waters between the Bahamas and North Carolina, along an old frontal zone. None of the reliable models are forecasting tropical storm development in this area or in the Gulf of Mexico, though.


Figure 2. The climatological halfway point of the Atlantic hurricane season is today, September 10.

Halfway point of hurricane season
September 10 marks the halfway point of the Atlantic hurricane season. Despite a late start (Tropical Storm Ana did not form until August 15, the latest start to a hurricane season since 1992), our number of storms has been near average. An average Atlantic hurricane season has 5 named storms, 3 hurricanes, and 1 intense hurricane by the midpoint of the season. So far this year, we've had 6 named storms, 2 hurricanes, and 2 intense hurricanes. A better measure of hurricane activity that takes into account their destructive power is the Accumulated Cyclone Energy (ACE) index. ACE for an individual storm is computed by squaring the maximum sustained winds of the storm at each 6-hourly advisory, and summing up over the entire lifetime of the storm. As of 5am EDT this morning, the seasonal ACE tally was 37.5. This number should rise to around 40 by the end of the day, thanks to the presence of Hurricane Fred. Over the period 1950 - 2005, the average ACE index for a half-season was 51, so 2009 ranks about 20% below average for the halfway point of the season. But when compared to the hurricane seasons we've been having since the current active hurricane period began in 1995, this year has been quite inactive. Between 1995 and 2008, the average ACE index for the halfway point of the season was 72. Thus, 2009 is about 45% less active than what we've been accustomed to over the past 14 years.

We've been lucky this year that the steering currents have aligned to keep our two major hurricanes, Bill and Fred, out to sea. What will the rest of the season have in store for us? I'll present an analysis on Friday.

Twenty years ago on this date
On September 10, 1989, the strong tropical wave that had moved off the coast of Africa the previous day acquired an organized circulation at the surface and began building a concentrated area of heavy thunderstorms near its center. A new tropical depression, the 12th of the season, was born. Moving westward at 20 mph, the depression brought strong, gusty winds and heavy rain showers to the Cape Verdes Islands as it passed to the south. Forecasters at the National Hurricane Center predicted that the steadily organizing tropical depression would strengthen into a tropical storm within the next day or two. The next name on the list of Atlantic tropical storm names for 1989: Hugo.


Figure 3. AVHRR visible satellite image of Tropical Depression Twelve taken on September 10, 1989. Image credit: Google Earth rendition of the NOAA HURSAT data base.

Jeff Masters

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Quoting mrnicktou:

he was quoting somebody talking about extra-tropical storms and were trying to get a grasp on the storms in the gulf so keep yourself from going off topic because some of us live in SE texas


And some of us live in Nova Scotia...
... Cheers!
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Quoting LPStormspotter:


local station said shear has moved off by FL.


Ok thanks. :) One of my locals said shear might lessen. The other didn't say.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
1009. RJT185
Quoting tpawxguy:
Haha...those were the days!
BTW, we've got a real chance of going undefeated this year. Only real test, is OSU at home. Our schedule is really soft and all the "tough" games at home. Have a great night. I'm off to monitor the Wrf and the Nam. :P


Yup Indeed! Nite!
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Quoting TampaSpin:
DAM that is me......i could state i have a Meteorology degree from PC (Personal Computer).......ROFLMAO


I got one from Life University and majored in PC Wunderground technology, as well! :P
Member Since: August 22, 2006 Posts: 2 Comments: 1988
1006. RJT185
Quoting StormW:
Good evening!

Barometer Bob will be on tonight. Just been IM back and forth.


Evening!
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Genesis starts with a negatively tilt shortwave

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


"on tropic"... get-it? LOL dude


he was quoting somebody talking about extra-tropical storms and were trying to get a grasp on the storms in the gulf so keep yourself from going off topic because some of us live in SE texas
Member Since: July 28, 2009 Posts: 1 Comments: 64
lets not get into the my degree is better game please. PSU is a reputable university though it's course of study is geared for uppergrad stuff ( I plan to go there upon completing my own undergrad) I understand both points and the fact is that the models are an either or not both scenario. If one or two areas form it drastically limits the opportunity for the others to form. That being said I think its fine to label them AOI but at the same time it's all but impossible they all develop and I can definitely see 456's point. Rather than just AIO it would be far more useful if you provided a probability on them. If you are using strictyl model guidance use an x/y format where x is the number of models developing the aoi and y is the number of models under your consideration.
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Quoting JLPR:


Has Fred stalled?
doesn't seem to be moving much


as predicted Weaker steering btw hi fellow puertorican compadre
Member Since: August 22, 2006 Posts: 2 Comments: 1988
Quoting tpawxguy:


And it was WAY before that nice little walkway they've built since then. Where IS the loop??!!!! Nice walk from East halls to Walker.


Uh. Freshman year. Fall semester. METEO 201 ... M W F at 8AM ... my dorm ... Stuart ... HELLISH walk from HELL.
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Quoting mrnicktou:

umm it was dude


"on tropic"... get-it? LOL dude

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Quoting homelesswanderer:


Hi. Ok just watched the locals better post before I forget. :)

Ch 12 said that right now it is just a rainmaker. And if there is development they will let us know because they won awards last year for their Ike coverage. Lol. Tooting his own horn. He said 15 mph winds.

Greg said its still on land. Looks to move east into the gulf. Any development would be slow. Should slowly move up this way. And its going to be a frog strangler. Heck, it just started pouring here again! Anyway he said he'd be very surprised if it got more than 40-45 mph tropical storm.

Lol. I guess take your pick. I'll wumail you Tex if you're not still on. :)


local station said shear has moved off by FL.
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Quoting RJT185:


And not a CATA bus in sight.


And it was WAY before that nice little walkway they've built since then. Where IS the loop??!!!! Nice walk from East halls to Walker.
Member Since: September 18, 2007 Posts: 0 Comments: 24
Quoting TexNowNM:
Tex,

I'm with Homeless on wanting to read your posts concerning SE Texas. Thanks for the updates!



Hi. Ok just watched the locals better post before I forget. :)

Ch 12 said that right now it is just a rainmaker. And if there is development they will let us know because they won awards last year for their Ike coverage. Lol. Tooting his own horn. He said 15 mph winds.

Greg said its still on land. Looks to move east into the gulf. Any development would be slow. Should slowly move up this way. And its going to be a frog strangler. Heck, it just started pouring here again! Anyway he said he'd be very surprised if it got more than 40-45 mph tropical storm.

Lol. I guess take your pick. I'll wumail you Tex if you're not still on. :)
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Quoting Tazmanian:
what a mass in the gulf right now

I big mass... hope all is well Taz... Palmpoint
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Quoting tpawxguy:
Yup...I remember it well. Walker Building in -20 degree Wind Chill. Ugh.


And not a CATA bus in sight.
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991. JLPR


Has Fred stalled?
doesn't seem to be moving much
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Shuttle Discovery Waved-off for last chance to land tonight. Weather doesn't look promising at KSC tomorrow, so we may see a landing out west at Edwards tomorrow.
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GOM, probability of formation

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


Please keep the conversation on tropic...

umm it was dude
Member Since: July 28, 2009 Posts: 1 Comments: 64
Quoting tpawxguy:
Ok, I'll try this again. First of all, I have a degree in Meteorology from Penn State University. Take it for what it's worth. Secondly, go back and look at the NAM and WRF's performance with Katrina. Uh, I BELIEVE that one was pretty tropical. The ONLY model to bring Kat SW across Florida after landfall...it pretty much NAILED her. I am NOT saying the NAM or the WRF is the model of choice in tropical meteorology. In fact, there IS no model of choice. Models get "hot"...just like anything else. Some years the HWRF is awesome, other years, it performs WELL below average. SO, in summation, your honor, Tampa Spin showed several areas of interest. EACH area the WRF or the NAM develops further. Will it happen? Probably not. Is he justified in showing so many?? Why not?? Too many people on this board are SO obsessed with black and white in forecasting the weather. It is one big GREY area, that is constantly changing. That's what makes it fun. Dude.


I think i can take that as a nice compliment coming from a student in the Field. Thank you!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting tpawxguy:
Yup...I remember it well. Walker Building in -20 degree Wind Chill. Ugh.



love it up there! haha
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Yup...I remember it well. Walker Building in -20 degree Wind Chill. Ugh.
Member Since: September 18, 2007 Posts: 0 Comments: 24
Quoting BurnedAfterPosting:


ITs not tropical though, that was the point he was making


exactly, feels like a nor'eastern the rain, just nice presentation on radar.
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Quoting Weather456:


and I got mines from ebay?


dude give me the link to that I want one too LOL
Quoting tpawxguy:
Ok, I'll try this again. First of all, I have a degree in Meteorology from Penn State University. Take it for what it's worth. Secondly, go back and look at the NAM and WRF's performance with Katrina. Uh, I BELIEVE that one was pretty tropical. The ONLY model to bring Kat SW across Florida after landfall...it pretty much NAILED her. I am NOT saying the NAM or the WRF is the model of choice in tropical meteorology. In fact, there IS no model of choice. Models get "hot"...just like anything else. Some years the HWRF is awesome, other years, it performs WELL below average. SO, in summation, your honor, Tampa Spin showed several areas of interest. EACH area the WRF or the NAM develops further. Will it happen? Probably not. Is he justified in showing so many?? Why not?? Too many people on this board are SO obsessed with black and white in forecasting the weather. It is one big GREY area, that is constantly changing. That's what makes it fun. Dude.


and I got mines from ebay? But its ur opinion so I cant really say anything at this point.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting K8eCane:
i dont understand why we get tropical storms? no place in the US is considered tropical except maybe extreme south fla


Coriolis re-curves a hurricane, and Coriolis re-curves the Gulf Stream.
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Quoting Hurricane009:
I tihnk it may be at 11pm, or 5am if condidtions persist.


ITs not tropical though, that was the point he was making
What may be the remnants of Fred may still have to be tracked for as many as 10 days***
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Ok, I'll try this again. First of all, I have a degree in Meteorology from Penn State University. Take it for what it's worth. Secondly, go back and look at the NAM and WRF's performance with Katrina. Uh, I BELIEVE that one was pretty tropical. The ONLY model to bring Kat SW across Florida after landfall...it pretty much NAILED her. I am NOT saying the NAM or the WRF is the model of choice in tropical meteorology. In fact, there IS no model of choice. Models get "hot"...just like anything else. Some years the HWRF is awesome, other years, it performs WELL below average. SO, in summation, your honor, Tampa Spin showed several areas of interest. EACH area the WRF or the NAM develops further. Will it happen? Probably not. Is he justified in showing so many?? Why not?? Too many people on this board are SO obsessed with black and white in forecasting the weather. It is one big GREY area, that is constantly changing. That's what makes it fun. Dude.
Member Since: September 18, 2007 Posts: 0 Comments: 24
Quoting BGMom:


Tropically-challenged.


Please keep the conversation on tropic...
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Quoting tiggeriffic:
bouncin in for just a few...hard to believe that 10 years ago today is when hugo made his first appearance


math fail pal!

not 10, 20 hehe

maybe thats why you found it "hard to believe"! :)
Member Since: August 22, 2006 Posts: 2 Comments: 1988
DAM that is me......i could state i have a Meteorology degree from PC (Personal Computer).......ROFLMAO
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting Hurricane009:
Do you really think this could be a tropical storm?? I think it could become grace, and the GOMEX AOI Henri



as of right now no, but im getting tropical storm conditions, only difference is that its a cold rain.
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Hey Garnsy!
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Quoting tpawxguy:

Hmm...did I know the NAM isn't a "tropical model"?? Well, yes, I believe somewhere in my Penn State Meteorology background they mentioned that! :P I also remember, cyclogenesis doesn't necessarily have to be "tropical". Just look at the Western Gulf right now. My point it...when he mentioned it was an area of interest, there is nothing wrong with that statement. ALL are interesting to me...but I'm a weather geek.



a meteo major from psu that's a weather geek ... it's a prerequ to get into EMS bud...lol
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i dont understand why we get tropical storms? no place in the US is considered tropical except maybe extreme south fla
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Quoting Weather456:


well I respect your point, but I barely use the NAM and it was not recommended to me and i wouldn't to anyone when it comes to hurricane.


Its just another tool to use! That is all it is!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting BGMom:


Tropically-challenged.


LOL..... PC meteorology. :)
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Quoting TexNowNM:
Tex,

I'm with Homeless on wanting to read your posts concerning SE Texas. Thanks for the updates!



Your welcome.. I will post as i get new info...unless you get it first, then you post it.... :)
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting tpawxguy:

Hmm...did I know the NAM isn't a "tropical model"?? Well, yes, I believe somewhere in my Penn State Meteorology background they mentioned that! :P I also remember, cyclogenesis doesn't necessarily have to be "tropical". Just look at the Western Gulf right now. My point it...when he mentioned it was an area of interest, there is nothing wrong with that statement. ALL are interesting to me...but I'm a weather geek.


dude I dont what ur talking about becuz i never said anything about the GOM. All I stated is that the AOIs seems a bit much in his graphic considering the reliable models only picking up on the GOM disturbance and Fred.
Member Since: July 24, 2005 Posts: 407 Comments: 19076


"tropical storm" lol
Highest wind gust: 52mph
Pressure: 1008 and falling
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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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