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 runnomore:


Yes it was and the rain gauge that recorded that was at FM 528 and the Clear Creek Bridge. Less than a mile from the house I lived in at the time. Clear Creek went out of its banks for over a mile. I remember walking thru 5’ of water in the street. Or in my case more like bobbing I was only 8 years old at the time.

It was far worse than Allison I don’t care what anybody says I lived thru both of them. Our house flooded in ’79 and did not even come close in Allison.
Your last sentence nailed it. The only difference is Claudette's rain fell in the country, Allison in the city. If Houston had received Claudette's rain I hate to think how much worse things could have been.
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Quoting TexasHurricane:


That is what I was thinking...they both (6 & 12) tend to play down storms..


Yeah. Seems that way to me too.
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Thank you Kori! Have a great evening....what is left of it.
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Quoting homelesswanderer:


Hi. yep I got the email you sent tonight. It's been raining real hard but off and on here. Hoping it's just rain. And like you say not too much of it. You may get some up there too. Greg said not everyone has gotten any yet. But 90% coverage for this weekend. Gonna be a wet one no matter what.


homeless - you have mail. :)
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting FloridaDweller:
Huh? I have not checked in a few days as I thought Fred was going north.....???? Is it really now expected to go west? Can someone explain.....what is this thing supposed to do? Thank you in advance!


The W turn is because it will become a shallow system and consequently, be steered by the low-level trade winds, which are easterly.
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Whens the next NHC tropical cyclone activity's map coming out?
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Quoting Gumluvr:
Homeless, thanks for posting that. I received your mail and sent one to you. It is really a wait and see situation. Hope you don't get too much rain or anyone for that matter. Some parts of my town flood but my area hasn't so far. Keeping fingers crossed for us all.


Hi. yep I got the email you sent tonight. It's been raining real hard but off and on here. Hoping it's just rain. And like you say not too much of it. You may get some up there too. Greg said not everyone has gotten any yet. But 90% coverage for this weekend. Gonna be a wet one no matter what.
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1353. centex
About time we got official AOI. They are 24 late from 48hr potential. You can't wait that long in hot water. This is not CV.
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http://radar.weather.gov/radar.php?rid=BRO&product=NCR&overlay=11101111&loop=yes
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Quoting hydrus:
T.S.Claudette-79?


Yes it was and the rain gauge that recorded that was at FM 528 and the Clear Creek Bridge. Less than a mile from the house I lived in at the time. Clear Creek went out of its banks for over a mile. I remember walking thru 5’ of water in the street. Or in my case more like bobbing I was only 8 years old at the time.

It was far worse than Allison I don’t care what anybody says I lived thru both of them. Our house flooded in ’79 and did not even come close in Allison.
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1350. hydrus
Quoting mossyhead:
thats why i like you, you make it real easy to understand, thanks, for the info.
That is Storm.W,s work, I accidentally hit the quote button to soon.
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Link

Put a check in the "NCEP Fronts" box. The convection, for the given amount of shear, is pretty organized near the center. What the heck? :O

Right now on Long Island (~Port Jefferson-ish), there's no rain but there's rain-bearing clouds and winds gusting 30-35 mph.

I wonder if there's a defined LLC. TO THE BUOYS!!
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Quoting winter123:
radar of unnamed Tropical Storm approaching land.



You've named it.
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Quoting homelesswanderer:


Actually under reacting but its just another opinion. We'll see in the end. Who knows?


That is what I was thinking...they both (6 & 12) tend to play down storms..
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting Tazmanian:



in fac it would be a STS its too far N too be name a TS if it was too be name


thats the NHC's attitude also. But remember hurricane vince? Also, there was a storm in late may this year, 92l, near the azores... but before it was declared an invest there was data to support it was warm core. Madness, but it was a subtropical or tropical storm, and they refused to name it just because it was unusual circumstances and location. Same will happen with NE gale.
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1345. Gumluvr
Homeless, thanks for posting that. I received your mail and sent one to you. It is really a wait and see situation. Hope you don't get too much rain or anyone for that matter. Some parts of my town flood but my area hasn't so far. Keeping fingers crossed for us all.
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Quoting F4PHANTOM:
Different from Houston forecast, but Ch 12 has been overreacting ever since Rita.


Actually under reacting but its just another opinion. We'll see in the end. Who knows?
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Quoting mossyhead:
thats why i like you, you make it real easy to understand, thanks, for the info.
i meant stormw explaining the mjo.
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Huh? I have not checked in a few days as I thought Fred was going north.....???? Is it really now expected to go west? Can someone explain.....what is this thing supposed to do? Thank you in advance!
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Post #1322. Love that avatar. Funny. Sick, but funny.
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oh *#$( where did this thing come from! Between this and the NE gale, the east coast is in for a deluge.

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Quoting Weathermandan:
I thoroughly appreciate this blossoming coastal low of the Mid-Atlantic Coast. Any shot at it becoming a sub-tropical depression? Or will it be too weak/short-lived? It certainly doesn't look purely non-tropical..but regardless, the effects are the same. It's just cooler if it has a name. :D


I thought so too. But nobody listens to me. Lol.
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Quoting hydrus:
thats why i like you, you make it real easy to understand, thanks, for the info.
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Quoting rainraingoaway:



It was an amazing feat of Mother Nature. I live around here and was well, younger then, lol. We have pictures still. Lots of places completely underwater that people who live there now have no idea.
I lived in Hitchcock on a bayou and we never flooded before Claudette. Got 6" of water in the house. Got flood insurance after that and thank goodness, because 4 years later we got 18" of water in our house from Hurricane Alicia.
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Quoting spathy:
TexasH
If you look at the blue circles the table at the bottom shows the pressure. Blue is lower pressure. Low pressure in a swirly thing = STORM
Now look at all the blue swirly things. Blog would go nutz:)


ohhhhhh, ok. Ughhhh
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting winter123:
radar of unnamed Tropical Storm approaching land.




in fac it would be a STS its too far N too be name a TS if it was too be name
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I thoroughly appreciate this blossoming coastal low of the Mid-Atlantic Coast. Any shot at it becoming a sub-tropical depression? Or will it be too weak/short-lived? It certainly doesn't look purely non-tropical..but regardless, the effects are the same. It's just cooler if it has a name. :D
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Quoting hydrus:
T.S.Claudette-79?
Yes.
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Quoting homelesswanderer:
Channel 12 changing its tune...a little. :)

The National Hurricane Center is monitoring the following Tropical Lows and Waves in the Atlantic:

A low level circulation is beginning to develop just off the coast of Brownsville.

Models all week have been developing a low in this location and at this point models continue to be on track to move this area of low pressure up the Texas coast into Southeast Texas.

One aspect of this low still remains unknown and that is the intensity of it. As of 6p.m. we are unable to determine if this low will be a tropical or non-tropical low. Atmospheric conditions are not very favorable to create a tropical low however, some models do turn this into a Tropical Depression by Friday afternoon.

The NHC has labeled the western Gulf low with a 30% chance of developing into a Tropical Depression between now and Saturday night.

As the low moves to the north-northeast it is likely to bring SETX an abundance of rain, possibly more than 8 inches. In addition, it is likely there will be some gusty winds up to 20mph at times on Saturday and overnight into Sunday.

At this time the area of low pressure is developing off the coast and may be considered an "investigation" low later tonight. After the low is investigated by the NHC it may be upgraded to a Tropical Depression. A Depression has winds sustained less than 39mph.

Stay tuned to KBMT 12 News, online, on Twitter, on Facebook and on our phone line for additional information as it becomes available.

References to the term NHC stand for National Hurricane Center located in Miami, Florida.

KBMT 12 Storm Team Meteorologist Bryan Rupp.



Yep, they have....next few days ought to be interesting.
Member Since: July 2, 2009 Posts: 0 Comments: 2811

Quoting AllBoardedUp:
That was the local National Weather Station located right in Alvin. I don't think it is located in the same spot. Alvin is located about 25 miles south of downtown Houston. Their was flooding in places that no one ever saw flood. Their were unoffical reports as high as 44 to 48 inches.


It was an amazing feat of Mother Nature. I live around here and was well, younger then, lol. We have pictures still. Lots of places completely underwater that people who live there now have no idea.
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1326. hydrus
Quoting AllBoardedUp:
That was the local National Weather Station located right in Alvin. I don't think it is located in the same spot. Alvin is located about 25 miles south of downtown Houston. Their was flooding in places that no one ever saw flood. Their were unoffical reports as high as 44 to 48 inches.
T.S.Claudette-79?
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radar of unnamed Tropical Storm approaching land.

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So Fred is beginning to make a western turn. It will remain stationary for a bit, then begin a more western track...correct so far?

Fred's longitudal position (SST) remains favorable for reintensification on this heading also, correct?

Next question, what's the long range forecast for Fred?

The GOMEX GFS posted a threads back is quite impressive. Thoughts

Thanks, Herb
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Channel 12 changing its tune...a little. :)

The National Hurricane Center is monitoring the following Tropical Lows and Waves in the Atlantic:

A low level circulation is beginning to develop just off the coast of Brownsville.

Models all week have been developing a low in this location and at this point models continue to be on track to move this area of low pressure up the Texas coast into Southeast Texas.

One aspect of this low still remains unknown and that is the intensity of it. As of 6p.m. we are unable to determine if this low will be a tropical or non-tropical low. Atmospheric conditions are not very favorable to create a tropical low however, some models do turn this into a Tropical Depression by Friday afternoon.

The NHC has labeled the western Gulf low with a 30% chance of developing into a Tropical Depression between now and Saturday night.

As the low moves to the north-northeast it is likely to bring SETX an abundance of rain, possibly more than 8 inches. In addition, it is likely there will be some gusty winds up to 20mph at times on Saturday and overnight into Sunday.

At this time the area of low pressure is developing off the coast and may be considered an "investigation" low later tonight. After the low is investigated by the NHC it may be upgraded to a Tropical Depression. A Depression has winds sustained less than 39mph.

Stay tuned to KBMT 12 News, online, on Twitter, on Facebook and on our phone line for additional information as it becomes available.

References to the term NHC stand for National Hurricane Center located in Miami, Florida.

KBMT 12 Storm Team Meteorologist Bryan Rupp.

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Quoting btwntx08:

it says it there lp mm5-fsu gfs lol


well thx.. that means nothing.. i meant like nam,gfs,gfdl.... ya know
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1319. hydrus
I apologize for that quote Storm> W-I was going to say that was easy to understand.
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Well, howdy y'all. For the GOM AOI, wind shear is still rather high, and it will be close to land the whole time. The low should be ashore by early Sunday, so it doesn't have much time. It is currently disorganized, and will likely stay so with the shear. I wouldn't put the odds of development very high, but the system will still brings windy conditions and heavy rains to Texas and Louisiana this weekend.
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Quoting redwagon:
I guess I meant non-cyclonic source of rain.

Four feet of rain in one day.... wow. Over what size area?
That was the local National Weather Station located right in Alvin. I don't think it is located in the same spot. Alvin is located about 25 miles south of downtown Houston. Their was flooding in places that no one ever saw flood. Their were unoffical reports as high as 44 to 48 inches.
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1315. hydrus
Quoting StormW:


If the question was IRT the MJO map...the brown contours you see over the Atlantic indicate downward motion, or downward vertical velocity, indicating sinking air. Sinking air will warm at the DAR (Dry Adiabaric Rate) of 5.5F/1,000 FT. This has a tendency to dry the air out, and is where most of the dry air we are seeing has been coming from. When you dry out the air, it's very hard to get convection going.

The green contours are the opposite. They indicate upward motion, or rising air. Rising air aids in instability, lift, and moisture in the atmosphere...great for forming clouds. Warm air rised at the DAR of 5.5F/1, 000 ft.

Once it reaches the LCL (Lifted Condesation Level) you start to get clouds (hence condensation). Then the air rises at the WAR (Wet Adiabatic Rate) at 3.0F/1,000ft.

Look at the contours sort of like pressure areas. On high and low pressure, the closer the isobars, the stronger the wind. For the MJO map, the closer the contours, the stronger the upward or downward motion.
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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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