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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1163. Dakster
When is the next QuickScat of the Gulf?
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Quoting btwntx08:
gracie is forming radar lol


Lol. She's an exhibitionist. :)
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1161. KEEPEROFTHEGATE (Mod)
Link

barometer bob show live
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1159. Patrap
Quoting IKE:


Is that a pinhole eye on radar?


Yeppars IKE,..LOL "Vary" interesting..


Maybe even a RI cycle beginning..snicker,ack,,..coff
Member Since: July 3, 2005 Posts: 419 Comments: 127355
Quoting Weather456:
development is not a sure think so dont get the hopes up about development. Just a watch and see.


Hate to let ya down but my hopes go down with development.
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development is not a sure thing so dont get ur hopes up and ahead of urselves. Just a watch and see.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1154. IKE
Quoting Patrap:


Is that a pinhole eye on radar?
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1153. KEEPEROFTHEGATE (Mod)


AOI/XX/XX
MARK
24.1N/95.4W
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Quoting TexasHurricane:


Your welcome! Channel 6


Ah ok. Bout what he said earlier without the Freeport. :)
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...
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1149. docrod
1137. Cool link - lets watch
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1148. Dakster
Quoting tropics21:
The next thunderstorm sub tropical you track One Katrina was enough


I feel the same way about Andrew...
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Quoting OneDay:
I know better than this, but it's kind of like seeing the Virgin Mary in a grilled cheese sandwich....

Is this the eye of Grace??? ;-)

Link


Well crap. Looks to me that this s spinning up quick.
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1145. OneDay
Looks like I'm not the only one.
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1144. Patrap
Looks to be Heading for TAMPA...
Member Since: July 3, 2005 Posts: 419 Comments: 127355
Quoting btwntx08:
ok heres a good question why is the nhc saying its gonna stationary for a couple of days when everybody else is saying going to move nne to se tx who telling the truth here? lol


Think of how long this mess has been festering over the Cent Gulf for at least a week, might be over us for that long, unless the cold front comes thru quickly. Frontal timing is up for debate since trof paralleling coast in Gulf may lift north and stall along the coast next week causing extended rain chances.
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1142. dis1322
well all i got to say was thank god for the rain.. In brownsville we went from drought to flooding ... i know its not even enough rain, but i am still thankful. Hopefully we get rain tomorrow !!!
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1141. Dakster
I see a little rotate on the radar..and it's heading into the Gulf.

But yes, I trust the NHC and some key ppl here.
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1140. OneDay
I know better than this, but it's kind of like seeing the Virgin Mary in a grilled cheese sandwich....

Is this the eye of Grace??? ;-)

Link
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Quoting btwntx08:
if this going to develop i would look east to ese of brownsville cause it look suspcious there

Good call, I believe your local weather folks called it;

Local Update:

Watching Low Near Brownsville....

Low pressure is slowly becoming better organized near Brownsville this evening. This low will likely move slowly to the north-northeast and has some potential for some development. It is possible that it could become a tropical depression or tropical storm in the next 24-36 hours. The low should move inland near Freeport Saturday with widespread heavy rains spreading into our area. In fact through Sunday, rainfall totals to near 10 inches will be possible in isolated spots. With plenty of clouds, temperatures will be below normal for afternoon highs.


Member Since: August 25, 2009 Posts: 20 Comments: 6785
My public advisory on Mujigae at 5PM
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting btwntx08:
ok heres a good question why is the nhc saying its gonna stationary for a couple of days when everybody else is saying going to move nne to se tx who telling the truth here? lol


Lol. Like I said earlier, take your pick.
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1135. Patrap
Quoting btwntx08:
ok heres a good question why is the nhc saying its gonna stationary for a couple of days when everybody else is saying going to move nne to se tx who telling the truth here? lol



The Radar

Member Since: July 3, 2005 Posts: 419 Comments: 127355
1133. Patrap
Member Since: July 3, 2005 Posts: 419 Comments: 127355
Fred appears to be hold its own

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


Thanks Tex. Which one was that from?


Your welcome! Channel 6
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting cajunmoma:


Thanks!!

No prob! If you go to the Tropical/Hurricane section, in the upper left hand corner in the "features", there is all sorts of good links!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting TexasHurricane:
Local Update:

Watching Low Near Brownsville....

Low pressure is slowly becoming better organized near Brownsville this evening. This low will likely move slowly to the north-northeast and has some potential for some development. It is possible that it could become a tropical depression or tropical storm in the next 24-36 hours. The low should move inland near Freeport Saturday with widespread heavy rains spreading into our area. In fact through Sunday, rainfall totals to near 10 inches will be possible in isolated spots. With plenty of clouds, temperatures will be below normal for afternoon highs.



Thanks Tex. Which one was that from?
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Tampa...You killin me here. You got 3 of you lil area's of interest pointing in my direction. Enjoy your game!!
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Quoting Dakster:
The next Katrina in the making....?

OR the next thunderstorm we track?
The next thunderstorm sub tropical you track One Katrina was enough
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Local Update:

Watching Low Near Brownsville....

Low pressure is slowly becoming better organized near Brownsville this evening. This low will likely move slowly to the north-northeast and has some potential for some development. It is possible that it could become a tropical depression or tropical storm in the next 24-36 hours. The low should move inland near Freeport Saturday with widespread heavy rains spreading into our area. In fact through Sunday, rainfall totals to near 10 inches will be possible in isolated spots. With plenty of clouds, temperatures will be below normal for afternoon highs.

Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting Bordonaro:
Link
Link to CIMSS Shear Maps :)


Thanks!!
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1122. amd
Quoting btwntx08:

and decreasing


correct. I didn't notice that the shear has decreased by at least 10 knots over where the low may be trying to form. Good call
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1121. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #14
TROPICAL STORM MUJIGAE (T0913)
9:00 AM JST September 11 2009
=========================================

SUBJECT: Category One Typhoon Overland Hainan Island

At 0:00 AM UTC, Tropical Storm Mujigae (994 hPa) located at 19.8N 109.7E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The storm is reported as moving west at 15 knots

RSMC Dvorak Intensity: T2.0

Gale-Force Winds
================
120 NM from the center in north quadrant
90 NM from the center in south quadrant

Forecast and Intensity
=======================
24 HRS: 19.6N 106.0E - 35 knots (CAT 1/Tropical Storm)
48 HRS: 20.1N 102.6E - Tropical Depression
Member Since: May 24, 2006 Posts: 50 Comments: 44437
Quoting laflastormtracker:
The models were consistent this week about developing a "strong low" off southeast TX moving NE to Southern Louisiana. This was the forecast the whole wk. Track to TX within the last 24 hrs.


What I've been seeing all week a low develops off Brownsville rides the coast to Louisiana.
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What a mess
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My non-expert opinion is that the models expect a low to form very close to the Texas coast, if not that, over land.

However, the Brownsville NEXRAD radar may be telling a different story. A low pressure is trying to develop about 50 miles offshore, and it is drifting to the east. But, upper level winds are still unfavorable, at about 20 to 25 knots.

Thanks for this great info
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Quoting cajunmoma:
I would love to view shear charts for the gulf...unfortunately I have lost my contacts and quiet honestly cant see anything. So can someone tell me what the chances are the AOI develops?
Link
Link to CIMSS Shear Maps :)
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting LPStormspotter:


456, do you think there is a chance for that blob to develop in the GOM?


it has a window of 72 hrs to do so. Shear is expected to increase after said time and the low drifts ashore. Basically watch and see situation.
Member Since: July 24, 2005 Posts: 407 Comments: 19076

Areas of Interest (AOI)
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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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