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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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Tuesday, September 20th, with Video
Good afternoon to everyone, Levi, I think 98L is moving slower than any other CV storm this season, where its located now. I also have seen a further Southern trend in the GFS and Euro, with 98L over the last few days. They do curve it, but the trend seems to be further S. Now I see the GFDL has 98L in the central Caribbean. Can we look for more of this?
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Comment re: Southern Plains heat/drought/rainfall removed.
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159. JLPR2
98L seems very close to TD status and if the exposed circulation is actually the main one then it is moving NW/WNW.

A little more distance from the ITCZ is what this system needs.

*The more I look at Visible Sat loops, the more I get convinced that the exposed swirl is not the main LLC and is probably spinning around it. With the main LLC to the SW of it.
Member Since: September 4, 2007 Posts: 7 Comments: 8669
Quoting JLPR2:


Yeah, no deep convection, so cold core.
But it's eye candy. :)
lol Facepalm
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Good afternoon, everyone. Just checking in to see what's up for this weekend. I can tell you that we are getting sick and tired of all the rain we've had for what seems like weeks now!

Also wanted to thank those of you who post here for the information you give us. We honestly do pay attention!

Thanks again....J&L
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156. JLPR2
Quoting GTcooliebai:
Thanks for the image, a cold-core, non-tropical low, probably too far north, to be classified as a sub-tropical system.


Yeah, no deep convection, so cold core.
But it's eye candy. :)
Member Since: September 4, 2007 Posts: 7 Comments: 8669
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Quoting JLPR2:


Maria is long gone, that's a nontropical system that looks incredibly interesting.
Thanks for the image, a cold-core, non-tropical low, probably too far north to be classified as a sub-tropical system.
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Quoting AussieStorm:

Isn't that Maria???


Very extended CFS loop.
IDK, unless I'm having a nostalgic moment, I thought Maria was gone since last week. Btw nice link.
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152. JLPR2
Quoting AussieStorm:

Isn't that Maria???


Very extended CFS loop.


Maria is long gone, that's a nontropical system that looks incredibly interesting.
Member Since: September 4, 2007 Posts: 7 Comments: 8669
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Quoting GTcooliebai:
Look at the system south of Newfoundland, it has an eye like feature.


Isn't that Maria???


Very extended CFS loop.

3am here, I'm out. Goodnight all.
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting ackee:
which model solution do u buy for 98L

A GFS
B ECMWF
C NOSAPS
D GFDL
E HWRF
F CMC


D
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Look at the system south of Newfoundland, it has an eye like feature.

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Quoting wxmobilejim:

But in reality we do not know if it is an all time record. Now do we? We don't have records from 400 years ago do we? I love it when someone says it is the hottest day in the last 40 years. Well what about the 1 million+ years before that are you really sure that day is the hottest all time?


We also have to determine just how accurate the old LIG (liquid-in-glass) thermometers were 120 years ago, compared to today's solid state thermistors (which can display in fractions of a degree).
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Member Since: September 30, 2007 Posts: 9 Comments: 15935
144. DVG
Quoting ColdInFL:
You guys just can't get a break

Link


Amen.
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Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Tuesday, September 20th, with Video



thanks Levi very imformative as always
Member Since: September 19, 2005 Posts: 2 Comments: 4154
Good morning.

Blog update:

Tropical Tidbit for Tuesday, September 20th, with Video
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Obvious that the center is exposed.

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I'd say that this gets a 90% at 2pm, and becomes a TD at 5pm.

Impressive Invest:


Also, the center is much farther north than the NHC thinks.
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last frame 384 hours

Member Since: August 19, 2006 Posts: 13 Comments: 15225
Quoting will40:
if i remember correctly Maria was very shallow when approaching the islands but got picked up by a weakness when she was N of the Bahamas
That's true, if it's a deep layer trough then it will be picked up. We'll have to see if the GFDL picks up on this scenario.
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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 hearing about weather events from around the world. thanks Aussie, although I am sad about fires.
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Good morning

Just a post or two for now.

The models are little or no guidance now as to where 98L may go, assuming it develops which it appears to be doing. It has been essentially sitting in one area for over 24 hours and while quasi stationary or just crawling the rest of the upper air dynamics have been changing to its North and West which affect steering and intensity down the road. For that reason, every time the models run with an initializng position at or close to the same coordinates the extrapolated position out in time will change, sometimes dramatically, from run to run. We see this even when systems are on the move but it is more pronounced when one is going nowehere and everything else is changing around it.

For now the steering is West to just North of West, assuming it starts to head off at an appreciable speed if it is classified later today which seems to be a distinct possibility.

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if i remember correctly Maria was very shallow when approaching the islands but got picked up by a weakness when she was N of the Bahamas
Member Since: September 19, 2005 Posts: 2 Comments: 4154
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.

uncertainty is a recipe for blog angst.
will check back at 2.
regarding people who annoy you, just iggy and move on. you can only control yourself.
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Quoting daddyjames:


Totally agree with you Nea. The statements posted regarding any causation inferred from the information you and Dr. JM's provided were completely unwarranted (see #94) and uncalled for.


Nobody said Nea started anything..I myself was talking about the GW discussion period..its not the topic of the blog today..I specifically said Dr. Masters posted about temperature and then here come people who run with it and posts about climate change and whatever..did Nea posts about climate change or GW..no he didnt but his fellow bloggers did and thats who I was pointing at.
Member Since: August 19, 2006 Posts: 13 Comments: 15225
Dry air??? That will inhibit Roke. which is what I am wishing for.

Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting Neapolitan:
For the record, I didn't "drag AGW" into this. In the final paragraph of today's blog entry, Dr. Masters commented on the "...lopsided ratio of high temperature to low temperature records..." in the United States this past summer, and I expanded on that comment by posting some accurate temperature data from a valid source. Period. I mentioned neither agendas, nor AGW, nor climate change, nor Al Gore, nor some government takeover of everything. Just temperature statistics. That's all. 'Twas others who picked up the non-existent football and ran wild with it.

Seriously, methinks some doth protest too much... ;-)


Totally agree with you Nea. The statements posted regarding any causation inferred from the information you and Dr. JM's provided were completely unwarranted (see #94) and uncalled for.
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its funny that the lost post in ricky rood's blog is over 22 minutes ago..go figure??..maybe we should just post tropical weather discussion in that blog since nobody is in there posting..

236. PurpleDrank 4:07 PM GMT on September 20, 2011
Member Since: August 19, 2006 Posts: 13 Comments: 15225
Quoting Tango01:
Things are not looking good for Japan... Most of the towns in the Sanriku coast lost their seawalls from the tsunami and the coast sunk from the earthquake in March so any little storm surge will flood large portions of those coastal towns fighting to recover since March.

I am surprised Dr. Masters have not commented much about Typhoon Roke.

agree. it's going to be a mess. although, it is forecast to weaken as it interacts with land and moves north, am wondering about how much nuclear material will get dispersed as it travels past fukushima.
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You guys just can't get a break

Link
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Quoting cmahan:


Dude, who brought it up? Dr. Masters posted about temperature records. Neapolitan added more data about temperature records.

Then hysterics descended across the blog...


The nastiness started with Post 17.
Member Since: September 18, 2008 Posts: 0 Comments: 615
Quoting wxmobilejim:

That is like comparing apples to oranges of course you will most likely see more high temp. records broken than low temp. records in the summer because it is supposed to be hot. WOW some people amaze me in their trying to twist data to form into their own agendas.
This is a very wrong assumption, but a few others have already explained that. Surpassing previous records (high or low) can happen in all seasons and usually cancel each other out if there are no significant deviations over a long period of time.
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Quoting jpsb:
I enjoy reading your posts about things going on down under. Please continue to do so. I was just saying .... ;)

well. preliminary obs are pointing to another active cyclone season for Qld, and very active fire season for NSW. Today we got a taste of that. Sadly, 3 fires have been confirmed to of been lit deliberately. Btw, thanks.
Member Since: September 30, 2007 Posts: 9 Comments: 15935
For the record, I didn't "drag AGW" into this. In the final paragraph of today's blog entry, Dr. Masters commented on the "...lopsided ratio of high temperature to low temperature records..." in the United States this past summer, and I expanded on that comment by posting some accurate temperature data from a valid source. Period. I mentioned neither agendas, nor AGW, nor climate change, nor Al Gore, nor some government takeover of everything. Just temperature statistics. That's all. 'Twas others who picked up the non-existent football and ran wild with it.

Seriously, methinks some doth protest too much... ;-)
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Quoting WeatherfanPR:
The 12z GFS model shows a track north of Puerto Rico for 98L "Ophelia"


I would think if 98L does not become Tropical Storm before reaching the Islands then it heads South into the Caribbean. Just my take tho.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Quoting ncstorm:


yall cant have it both ways..when we object to GW talk when Dr. Masters post it, then you scream its the topic of the blog but when he clearly didnt state GW in the blog topic today, you want to twist it and say its related to weather..


Dude, who brought it up? Dr. Masters posted about temperature records. Neapolitan added more data about temperature records.

Then hysterics descended across the blog...
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Hi, everybody.... 2 second look in.... gotta give a whistle and a wow to Roke.... now THAT's a cyclone.....

Back later if time permits.

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111. jpsb
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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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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