98L organizing; September temperatures in the U.S. return to normal

By: Dr. Jeff Masters , 1:29 PM GMT on September 20, 2011

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A tropical wave midway between Africa and the Lesser Antilles (Invest 98L) continues to look well-organized on satellite imagery, with a modest amount of heavy thunderstorm activity and excellent spin. An ASCAT pass from 7:47 pm EDT last night showed that 98L had a moderately well-defined surface circulation. Wind shear as diagnosed by the SHIPS model is light, less than 10 knots, and is predicted to stay light to moderate through Friday. Ocean temperatures are 28 - 28.5°C, well above the threshold typically needed for a tropical storm to spin up. Water vapor satellite images show 98L is embedded in a moist environment, but there is dry air to the system's northwest. However, given the light wind shear, this dry air may not pose a hindrance to development at this time. An analysis of upper level winds from the University of Wisconsin CIMMS group shows a pattern favorable for development, with an outflow channel open to both the north and south available to ventilate the storm and allow 98L to efficiently lift plenty of moisture to high levels.


Figure 1. Morning satellite image of 98L.

The models are not very aggressive about developing 98L into a tropical storm, but most of them do show some development. NHC gave the disturbance a 70% chance of developing into a tropical depression by Thursday in their 8 am Tropical Weather Outlook. 98L's westward motion of 5 - 10 mph should bring the storm into the Lesser Antilles Islands by Saturday, though the models are not in strong agreement about the forward speed of the storm. The GFDL model brings 98L into the islands on Friday, while the NOGAPS model keeps the storm east of the islands through Tuesday. If 98L takes a more west-northwesterly path through northern Lesser Antilles, which has been the preferred track for tropical systems this year, the disturbance should encounter high wind shear in excess of 20 knots due to strong upper-level winds out of the west. This shear should make it difficult for 98L to intensify as it moves though the islands. However, if 98L takes a more southerly path across Barbados, as predicted by the GFDL model, the storm will miss seeing the high shear area that lies over the northern islands, and the storm would have more opportunity to strengthen. The most likely scenario I see at this point is for 98L to be a weak tropical storm on Saturday as it moves through the Lesser Antilles--but there is more than the usual amount of uncertainty in both the track and intensity forecast.

September temperatures return to normal over the U.S.
The summer of 2011 was the second hottest in U.S. history, but September of 2011 is so far shaping up to be an average one for temperature. A series of cold fronts and cold-cored low pressure systems have moved southwards out of Canada this month, bringing typical amounts of cool air to the country. If you want to select dates for the start and end of the U.S. heat wave of 2011, the dates to pick would be May 20 - September 4. During the period May 20 - September 4, 2011, the number of daily record high temperatures at the 515 major airports in the U.S. exceeded the number of daily low temperature records every day but one. That's an astonishing 107 out of 108 days! Only July 15 had more record daily lows than highs during that 108-day period. I doubt one could find a similar stretch of days anytime in U.S. weather history where such a lopsided ratio of high temperature to low temperature records existed. For the 3-month summer period of June, July, and August, 2703 daily high temperature records were set, compared to 300 daily low temperature records--a ratio of 9-to-1. Not surprisingly, the summer of 2011 wound up as the hottest summer in 75 years in the U.S., and was only 0.1°F cooler than the all-time record hottest summer, during the Dust Bowl year of 1936. But so far this September, the ratio of high temperature records to low temperature records has been close to 1-to-1. There were 283 daily high temperature records set during the first sixteen days of September, and 246 low temperature records. Eight of the first sixteen days of September have seen the lows outnumber the highs, and eight have seen the highs outnumber the lows. The latest 2-week forecast from the GFS model shows a continuation of pretty normal weather over the U.S. for the rest of the month, and September temperatures will end up close to average.

Jeff Masters

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111. jpsb
4:25 PM GMT on September 20, 2011
Quoting AussieStorm:

Nothing, I was just bringing info to ya'll.

why are people commenting on TYPHOON ROKE? It's not part of this blog but it is tropical. should it be banned?
I enjoy reading your posts about things going on down under. Please continue to do so. I was just saying .... ;)
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110. AussieStorm
4:25 PM GMT on September 20, 2011


Member Since: September 30, 2007 Posts: 9 Comments: 15977
109. ncstorm
4:25 PM GMT on September 20, 2011
NC coast 138 Hours


moves north 144 hours
Member Since: August 19, 2006 Posts: 13 Comments: 16222
108. GTcooliebai
4:25 PM GMT on September 20, 2011
Hi, everyone Good afternoon, or morning, or night wherever you are from. What's the latest on 98L? Anyone think it will become a TD today?
Member Since: August 31, 2009 Posts: 0 Comments: 5628
107. ncstorm
4:22 PM GMT on September 20, 2011
126 Hours


135 hours
Member Since: August 19, 2006 Posts: 13 Comments: 16222
106. AussieStorm
4:22 PM GMT on September 20, 2011
Quoting WatchingThisOne:
Aussie, what is your take on Roke? I'm concerned about prior flood areas, and about passage over Fukushima Daiichi. Do you have a sense as to how reliable the current intensity forecast might be? Info is limited on WU.

98 looks like it may become an impressive storm over the next few days.

Thanks,
WTO

well i could see a EWRC taking place which will bump down Roke's wind speed but will allow it to grow larger.
Member Since: September 30, 2007 Posts: 9 Comments: 15977
105. will40
4:21 PM GMT on September 20, 2011
i could go to the GW blog but would likely be talking to myself because they all are prolly in my iggy list
Member Since: September 19, 2005 Posts: 2 Comments: 4266
104. louisianaboy444
4:21 PM GMT on September 20, 2011
Still sticking with my idea of a hard winter for the Eastern U.S. and that no African-Born storm will make it all the way across this year
Member Since: August 29, 2006 Posts: 22 Comments: 1352
103. WeatherfanPR
4:21 PM GMT on September 20, 2011
The 12z GFS model shows a track north of Puerto Rico for 98L "Ophelia"
Member Since: August 23, 2006 Posts: 0 Comments: 1592
102. CaribBoy
4:20 PM GMT on September 20, 2011
Quoting JLPR2:


I'm going to stay neutral and go with the TVCN, NHC style. xD

GFS changed quite a bit from yesterday.


SURE
Member Since: October 6, 2007 Posts: 0 Comments: 6455
101. louisianaboy444
4:20 PM GMT on September 20, 2011
Quoting CaribBoy:
12Z GFS SHIFTER NORTHWARD....... LOL WHAT A CHANGE FROM YESTERDAY


Yep North and probably out to sea...here we go...
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Very large spread in the BAMS and the BAMD
Member Since: September 2, 2007 Posts: 179 Comments: 20448
12Z GFS SHIFTED NORTHWARD....... LOL WHAT A CHANGE FROM YESTERDAY
Member Since: October 6, 2007 Posts: 0 Comments: 6455
Aussie, what is your take on Roke? I'm concerned about prior flood areas, and about passage over Fukushima Daiichi. Do you have a sense as to how reliable the current intensity forecast might be? Info is limited on WU.

98 looks like it may become an impressive storm over the next few days.

Thanks,
WTO
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GFS 111 Hours
Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting CaribBoy:


Sorry for the caribbean-casters, it's more likely to go north than south..


I'm going to stay neutral and go with the TVCN, NHC style. xD

GFS changed quite a bit from yesterday.
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Quoting jpsb:
And what do fires in Australia have to do with the topic of the day?

Nothing, I was just bringing info to ya'll.

why are people commenting on TYPHOON ROKE? It's not part of this blog but it is tropical. should it be banned?
Member Since: September 30, 2007 Posts: 9 Comments: 15977
Quoting jpsb:
Well if the little girls that some times post here can not stand an adult discussion on one of the most important issues of the day there is always the ignore button.

Funny how we can talk about web browsers, droughts, dancing with the stars, fires, earth quakes, Sarah Palin, etc and no bodies panties get bunched up. But if the topic is AGW or really the lack of it, then it's THIS IS A TROPICAL WEATHER FORUM! Hypocrites.


why would you want to discuss a topic that everyone dosent share your interest of GW..why not go to a blog where the topic is being discussed freely and openly? there are at least two feature blogs on the WU site that discuss climate change and GW but yet, you choose to post in here?? Why is that? Can you not hang in the other blogs?
Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting JLPR2:
Jeez...

It can end up anywhere from: 10N to 25N.


Sorry for the caribbean-casters, it's more likely to go north than south..
Member Since: October 6, 2007 Posts: 0 Comments: 6455
Quoting jpsb:
Well if the little girls that some times post here can not stand an adult discussion on one of the most important issues of the day there is always the ignore button.

Funny how we can talk about web browsers, droughts, dancing with the stars, fires, earth quakes, Sarah Palin, etc and no bodies panties get bunched up. But if the topic is AGW or really the lack of it, then it's THIS IS A TROPICAL WEATHER FORUM! Hypocrites.

The main reason, AGW causes so many problems in here it's not funny.
Member Since: September 30, 2007 Posts: 9 Comments: 15977
Quoting JLPR2:
Jeez...

It can end up anywhere from: 10N to 25N.



Leaning towards the southern route portrayed by the GFDL myself, ATM.



Afternoon All.
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90 Hours GFS

Member Since: August 19, 2006 Posts: 13 Comments: 16222
Jeez...

It can end up anywhere from: 10N to 25N.
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78 Hours GFS

Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting jpsb:
Dr Master frequently posts on the subject of Global Warming. A discussion on that topic is entirely appropriate here.


Admin Notice: When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself. Please do not engage in personal attacks or bickering. Material not conforming to these standards should be flagged with the button and ignored.

AGW/CC is not part of this blog. It's not not relevant to the discussion of tropical weather, or the topic of this individual blog entry.
Member Since: September 30, 2007 Posts: 9 Comments: 15977
link for the Texas wildfires article  http://yubanet.com/usa/Texas-Wildfire-Update---Sep t-20-2011.php#.Tni5pexwulQ
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12z GFS 69 Hours

Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting Chucktown:


Truthfully, I don't care about records. Why even have records, just take what Mother Nature dishes out. Does it really matter? There is no "normal" when it comes to weather. Do you get dressed each morning based on what the temperature is supposed to be or what it is forecast to be that day?
Truthfully,

You have your opinion, I have my opinion, Nea has his opinion. Nea just mad an observation and has every right to state that opinion. He did not try to connect it to CC. You or someone else did that.
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Quoting ncstorm:


no where in the blog did I read GW..only temperature?? you guys take stuff and run with it!! Ricky is waiting on you!


The blog subjects are tropical weather and/or whatever is discussed in today's blog. There is no climate change mentioned in today's blog.
Member Since: September 18, 2008 Posts: 0 Comments: 616
Quoting fireflymom:

Any chance you can send me the link for that info please.
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Quoting floodzonenc:


If you feel the need to debate AGW... here's where you go! Otherwise shut the ... up.


you would think right??
Member Since: August 19, 2006 Posts: 13 Comments: 16222
Quoting jpsb:
Dr Master frequently posts on the subject of Global Warming. A discussion on that topic is entirely appropriate here.


no where in the blog did I read GW..only temperature?? you guys take stuff and run with it!! Ricky is waiting on you!
Member Since: August 19, 2006 Posts: 13 Comments: 16222
Here you go Aussie-sorry to hear you are in the same situation. Some of Texas has had rain this week but not any where near enough. 
By: Texas Forest Service
September 20, 2011 - Yesterday Texas Forest Service responded to 13 new fires for 174 acres.



· In the past seven days Texas Forest Service has responded to 91 fires for 15,405 acres.



· 250 of the 254 Texas counties are reporting burn bans.



· Daily detailed fire information can be found here or at inciweb.org.



New large fires from yesterday (more than 100 acres in timber, 300 acres in lighter fuels; or where homes were lost):



None.



Uncontained fires from previous days (more than 100 acres in timber, 300 acres in lighter fuels):



BASTROP COUNTY COMPLEX, Bastrop County. 34,068 acres, 95 percent
contained. A Type 3 organization took over management of the fire
yesterday afternoon. Crews and equipment continue to protect homes
within the perimeter. There is no fire burning outside the main
containment lines. An assessment team has confirmed 1,554 homes have
been destroyed on the large Bastrop fire and the Union Chapel Fire. Two
civilians were found dead as search crews went through the charred
subdivisions.



101 RANCH, Palo Pinto County. 6,555 acres, 95 percent contained. Crews
and aircraft continue to monitor the fire. Thirty-nine homes and nine
RVs have been reported destroyed. Crews continue to mop up and aircraft
are monitoring.


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Quoting caribbeantracker01:
possible it is kind of indicated on the vort maps


98L tried to eat up the vort of ex-97L but failed and now it seems to be leaving it behind and gaining a bit of latitude, trying to break away from the monsoonal trof and ITCZ where the remnants of 97L are trapped.

Once it finally breaks off it should be able to concentrate its convergence instead of getting the focus stolen by the ITCZ.
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More seriously, 98L please please please DONT ACT LIKE MARIA
Member Since: October 6, 2007 Posts: 0 Comments: 6455
.

Member Since: September 18, 2008 Posts: 0 Comments: 616
98L is trying to make up for it's predecessos and ramp up into a super storm watch out lol
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From Previous blog.

G'day all.
Well fire season has started with a bang. as of today, there is 47 bush fires burning in NSW.
2 are burning the Blue mountains west of Sydney. there is also a bush fire burning in the SW suburbs of Sydney that closed the main highway to Canberra and Melbourne. Today's weather conditions were very ugly and ripe for fire ignition. Sustained wind were 50km/h(31mph) gusting up to 80-100km/h(50-62mph). A almost completed sports Stadium in Woolongong south of Sydney has sustained damage and is on the verge of collapse.









This is what everyone in NSW was dreading, Last year there was only a few bush fires due to the inclement weather, and flooding. This has caused the undergrowth to become a cinder pot waiting to explode.

I will post more info when it comes to hand.


How is Texas and Florida going with there bush fires?
Member Since: September 30, 2007 Posts: 9 Comments: 15977
Quoting Drakoen:
This morning's ASCAT pass reveals that 98L has a large circulation and is gonna need to tighten up a bit before significant development can take place.

Typical story of this season so far.
Member Since: September 30, 2007 Posts: 9 Comments: 15977
Quoting will40:



yes that has been its problem all along
And the longer it takes to pull together, the further into the Caribbbean Sea it will move.
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Quoting hydrus:
It seemed to have two centers there for a while...
possible it is kind of indicated on the vort maps
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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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