Don closing in on Texas; 91L a potential threat to the Lesser Antilles

By: Dr. Jeff Masters , 3:22 PM GMT on July 29, 2011

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Tropical storm warnings are flying along the coast of Texas from Brownsville to Matagorda as Tropical Storm Don closes in on the Texas coast. Don remains a disorganized, moderate strength tropical storm, and appears unlikely to cause major damage or bring much-needed drought-busting rains to Texas. A hurricane hunter plane is in Don, and found highest surface winds of 55 mph at 11:06am EDT. Don continues to have trouble with moderate wind shear of 10 - 20 knots, which is injecting dry air to the northwest into the storm. Water vapor satellite images show this region of dry air to the northwest of Don. Visible satellite imagery from this morning shows little change to Don so far today, with most of the heavy thunderstorms on Don's south side, and the cloud pattern elongated, the sign of a storm struggling with wind shear. Radar out of Brownsville, Texas shows the main rain areas are on the south of Don's center, and bands of heavy rain are now very close to the Texas/Mexico border.


Figure 1. Morning image of Tropical Storm Don from the Brownsville, Texas radar.


Figure 2. The latest drought map for Texas shows that over 75% of the state is in exceptional drought--the highest category of drought. Image credit: U.S. Drought Monitor.

Forecast for Don
The wind shear and dry air affecting Don will continue until landfall, and it is unlikely Don will intensify to more than a 60 mph tropical storm. With most of the heavy thunderstorms displaced to the south side of the storm, Mexico will be the primary beneficiary of Don's expected rains of 3 - 5 inches. South Texas will see modest rains of 1 - 2 inches over a few isolated areas, but Don is going to do very little to bring drought relief to the state. Most of Don's rains in Texas will be concentrated in the extreme southern portion of the state near Brownsville. This portion of Texas is experiencing only moderate drought, and the extreme to exceptional drought areas of the state will miss the bulk of Don's rains.

For those of you wondering about your odds of experiencing tropical storm force winds, I recommend NHC's wind probability forecast. The 11 am version of this forecast shows that Corpus Christi Texas has the highest chance of tropical storm-force winds (39+ mph): 48%. The primary threat from Don will be heavy rain, which will caused localized flooding problems. An isolated tornado is also a possible concern.


Figure 3. Morning satellite image of 91L.

African wave 91L a potential threat to the Lesser Antilles
A well-organized African wave near 9°N 44°W (Invest 91L) is headed west-northwest at 15 - 20 mph, and could arrive in the vicinity of the Lesser Antilles Islands as early as Monday night. Residents of the Lesser Antilles should pay careful attention to this system, as it has the potential to organize into a tropical storm before reaching the islands. While visible satellite loops currently show only minimal heavy thunderstorm activity and no signs of a surface circulation, there is a pronounced large-scale rotation to the cloud pattern. Water vapor satellite loops show that a large area of dry air from Africa lies just to the north of 91L, and this dry air is inhibiting development. The SHIPS model is diagnosing low shear, 5 - 10 knots, over 91L, but the University of Wisconsin CIMSS analysis shows that moderate shear, 10 - 20 knots, is affecting 91L. Sea surface temperatures are 27.5° - 28°C, which is 1° above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 91L
Low to moderate wind shear of 5 - 15 knots is predicted along 91L's path over the coming three days, which should allow the storm to steadily organize, assuming it can shut out any incursions of dry air that might intrude. The latest 06Z run of the GFS model does show 91L developing into a tropical storm by Monday, but the other three most reliable models for forecasting formation of a tropical storm--the ECMWF, NOGAPS, and UKMET models--show little or no development of 91L in their latest runs. On Monday, when most of the models predict that squalls of rain from 91L will begin affecting the Lesser Antilles, wind shear is expected to rise to the moderate or high range, which should act to interfere with development. The latest runs of the GFDL and HWRF models show 91L developing into a hurricane by Monday, but these models are not to be trusted for systems that have not developed into a tropical depression yet. The long-range path of 91L could take it through the Caribbean or towards the U.S. East Coast; it is too early to know with path might be more probable. NHC is giving a 30% chance that 91L will develop into a tropical depression by Sunday morning.

Iran records its hottest temperature of all-time
Omidieh, Iran and Shoshtar, Iran hit a scorching 52.6°C (126.6°F) on July 27, the hottest temperatures ever recorded in the country. The previous record was 52.5°C (126.5°F) set in Hamidiyeh on August 4, 2001. If confirmed by the Iranian weather service, these readings would rank as the third hottest undisputed temperatures ever measured in Asia. There have been only two Asian readings matching or exceeding Wednesday's new Iranian record of 52.6°C that are undisputed that I am aware of. Both of these occurred last year, and were recognized by their respective country's meteorological services as new official records for their country:

53.5° (128.3°F) in Moenjodaro, Pakistan on May 26, 2010
52.6°C (126.7°F) in Abdaly, Kuwait on June 10, 2010

Iran is the third nation this year to set a new all-time heat record (no nations have set an all-time coldest temperature record this year, or did so in 2010.) The Democratic Republic of the Congo, the world's 12th largest country, set a new all-time extreme heat record on March 8, 2011, when the temperature hit 39.2°C (102.6°F) at M'Pouya. Congo's previous all-time hottest temperature was 39.0°C (102.2°F) at Impfondo on May 14, 2005.

Also this July, a 50.2°C temperature was measured at Aydyngkol Lake, China--the highest temperature on record at any official Chinese weather station. Next week, our weather historian, Christopher C. Burt, will report on this record. Credit for researching these records goes to weather records researcher Maximiliano Herrera, who maintains a comprehensive set of world extreme temperature records on his web site.

Vacation
I'm taking some time off today through August 9 for a family celebration and vacation, and don't plan on blogging again until August 10 unless a major hurricane develops. In my absence, Angela Fritz will be handling most of the blogging duties, and she will have a post on the latest for Don this afternoon. Angela is on Pacific time, so her posts will be later in the day than I make them.

Jeff Masters

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jpsb got the right idea, and when the MOAB was created it was largest ordinance bomb, but like i said earlier times change guns get deadlier, bombs more effective, etc. etc. etc.
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting AtHomeInTX:


True. He went against climatology. No storm had ever come in the gulf from where he was right before he turned around and decided to go that way. Lol.
Call me batty, whatever, but I think that is why the storms get names. For scientists, a numerical designation is sufficient for tracking purposes. But one gets the feeling that by them having names, they also will behave more like a human, difficult to predict, even when forecasters are armed with the most sophisticated technology, a set of avgs, and years of experience.
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Quoting washingtonian115:
Memorial Bridge is full of traffic as well when people get off of work/visiting D.C.it's always in that 12:30-6:00 range.That's when I avoid the bridge when I got to Fort Myers or Cosco.


I have been here a yr and a half and have never driven in the District. Too many streets that are at weird directions and just the parking/traffic in general.

I Metro or walk. Love the Metro!
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Okay I'm going to get back to weather now...
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lol people are silly, a weapon wouldn't stop a hurricane, it might temporarily disrupt a portion of it, but a low pressure area with air wrapping around it at over 100 mph will quickly fill in that little dent that it took millions and millions of dollars to produce. Waste of money, waste of time. Oh and not too mention its just stupid. Hurricanes are there for a reason. This Universe was designed along with the Earth no matter how much people want to deny it. We already have stupidly done enough damage to the nature and the environment, trying to stop hurricanes is just another big step of human pride and foolishness.
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Quoting HimacaneBrees:


Oh yeah? I've never been there, but my Avatar used to live somewhere in the area.
It' in Up town D.C.It's closer to the Maryland line(No really.All I have to do is walk up the street and in a minute I'm in Maryland.)I live by Tokoma station.
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the difference between strip mining and the moab is that the moab is a set amount of explosives, you can pile on the strip mining and make a larger and larger explosion but that would be ineffective because how are you goin to transport that, bigger explosion cause more explosive and more ineffective. the moab is medium amount of explosive, large explosion, easily transportable. Iran and North Korea probably just piled up the explosives.
Member Since: July 25, 2011 Posts: 0 Comments: 453
689. jpsb
Quoting GHOSTY1:
yes and im sure our scientist and explosive experts can keep coming up with something with something bigger and better, we didn't go from a biplane to a f-22 raptor without improvements and thinking outside the box
If you want bigger then an H-Bomb, don't fool around with a carbon or oxygen bomb, go straight for an anti-matter bomb. 100% efficiency and no harmful long lasting radiation :)
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Quoting CanesfanatUT:


I work out in Fairfax. Clarendon is close enough to the night life but not across the dreaded Potomac. What is it about driving across rivers that makes traffice awful? Over the MS in Baton Rouge was always a debacle.
Memorial Bridge is full of traffic as well when people get off of work/visiting D.C.it's always in that 12:30-6:00 range.That's when I avoid the bridge when I got to Fort Myers or Cosco.
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...CENTER OF DON APPROACHING THE COAST OF SOUTH TEXAS...RAINBANDS SPREADING ONSHORE...

4:00 PM CDT Fri Jul 29
Location: 26.9°N 96.2°W
Max sustained: 50 mph
Moving: WNW at 16 mph
Min pressure: 1004 mb
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Quoting washingtonian115:
Yep!!.N.W D.C.Laurel St!!


Oh yeah? I've never been there, but my Avatar used to live somewhere in the area.
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Quoting MrstormX:
Right now 91L is a swirl of clouds, it hasn't even developed and it may never. Fiona & Gaston should ring a bell, CATL waves don't always become hurricanes even when the models say they will.


Gaston's problem was wind shear...91L doesn't have to deal with that. Fiona's problem was Earl, 91L won't have to deal with that.

It has dry air to deal with...that's it.
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Quoting Slamguitar:


Ah, Ike. I was in Michigan when he hit as a depression. Lots of rain...


Yeah he took a while to wind down. Followed us to Longview TX where we evacuated to. Knocked out the lights flooded the 1st floor of the motel. Also put trees on houses up there. But he put about 90% of my county under water so I guess Longview was a good call. :)
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Quoting jasblt:


Your past post and constant use of others graphics and analysis have proven you are nothing short of an idiot...also, please remove the bold from your post.


personal attacks are frowned upon in this forum. Judging on your short tenure here you may not know that so i will not report.

Deep Easterly flow in south florida....waiting for our afternoon storms still.
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682. Tygor
Loving how all the rain coming off Houston is dying before it gets near us in SA. Just another hot sunny day, only more humid than usual.
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Also, MOAB, is an acronym for Massive Ordinance Air Bomb. Mother of all bombs is a nickname for it. It's also not the largest conventional bomb in the world.
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Quoting washingtonian115:
Yay!!.That's one person from the local area.


I work out in Fairfax. Clarendon is close enough to the night life but not across the dreaded Potomac. What is it about driving across rivers that makes traffice awful? Over the MS in Baton Rouge was always a debacle.
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Quoting ElConando:
The last Tropical system to hit the United States was Tropical Storm Bonnie. Quite quite amazing that over 20 named storms in a row didn't hit that US.


And I'm afraid were gonna pay for it now with a vengence
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First time I actually had a chance to look at 91L. That is one large wave. Interested to see what comes out of that.... I think.
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Quoting AtHomeInTX:


True. He went against climatology. No storm had ever come in the gulf from where he was right before he turned around and decided to go that way. Lol.


They have been further north:

Member Since: August 26, 2006 Posts: 16 Comments: 4766
The last Tropical system to hit the United States was Tropical Storm Bonnie. Quite quite amazing that over 20 named storms in a row didn't hit that US.
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Right now 91L is a swirl of clouds, it hasn't even developed and it may never. Fiona & Gaston should ring a bell, CATL waves don't always become hurricanes even when the models say they will.
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Quoting HimacaneBrees:


Oh you live in D.C. Da Capital!!!!!
Yep!!.N.W D.C.Laurel St!!
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Don is going to make landfall soon!!
Member Since: July 12, 2011 Posts: 0 Comments: 1532
Quoting yonzabam:


Whew! Glad I'm not the only one who saw those 'multiple vortices'.

Made me wonder if these large systems with well defined separately rotating areas could actually develope into different storms. Or do they always coalesce into a single system?


It will consolidate into one center. The separate vorts will rotate around a common center until they coalesce into one. This is very common with these huge systems.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting twincomanche:
LOL
Hmmm this is interesting.

You got +8 points just for typing in "LOL". Sounds like someone's cheating the system...
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Quoting AtHomeInTX:


True. He went against climatology. No storm had ever come in the gulf from where he was right before he turned around and decided to go that way. Lol.


That was called super ass ridging, don't think we'll ever see anything like that again
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Quoting Hurricanejer95:

:| any Californian bloggers here
Yeah Taz.
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610 GHOSTY1 "there are some weapons that produce a large modest explosion without the use of radiation it is called a MOAB uniquelly named for Mother Of All Bombs. The largest non-nuclear explosion was produced from this."

Not even close. Strip-mining operations routinely set off explosions MUCH larger than MOAB. Then there are the USmilitary tests called MinorScale.
As well, NorthKorea's "nuclear explosion" and (at least the first) Pakistan's "nuclear explosion" were FAR more likely conventional explosions set off to mask nuclear-bomb tests (which were either being faked through use of conventional explosives or were failures, according to air-born radiation and satellite gamma measurements).
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667. jpsb
Quoting DFWjc:
CBS 11 Weather
Made it to 100 degrees again at DFW. Streak now at 28 days.

Will the streak ever end???
Not anytime soon, hottest summer since 1980, 1980 was a b.
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Quoting washingtonian115:
I'm (as far as I know)the only person from the city of Washington D.C on here.Well what can I say.At least I don't have to share a state with anyone.D.C is the city everyone looooves to hate.


Oh you live in D.C. Da Capital!!!!!
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665. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting GHOSTY1:
yes and im sure our scientist and explosive experts can keep coming up with something with something bigger and better, we didn't go from a biplane to a f-22 raptor without improvements and thinking outside the box


Look a typical hurricane produced about 6 * 10^(19) Joules of energy per day. A megaton of TNT is 4 x 10^(15), so the energy of a hurricane is about 1000x's more than a megaton of TNT in a day. To disrupt you need to build a gigantic weapon... that gigantic weapon would most likely do more harm than the hurricane itself. Also, as I said before, we have hurricanes for a reason - they regulate sea surface temperatures.
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Quoting angiest:


A lot of people here said that that bend to the SW would never happen, that storms so far north couldn't come to the Gulf, let alone Texas.


True. He went against climatology. No storm had ever come in the gulf from where he was right before he turned around and decided to go that way. Lol.
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Quoting Levi32:
Invest 91L has a long way to go yet. It's a massive circulation with multiple vortices which will take time to consolidate. Dry air is also an issue. However, gradual development is likely as it approaches the northeastern Caribbean, and I do have a feeling we will get Emily out of this at some point in that area.


Whew! Glad I'm not the only one who saw those 'multiple vortices'.

Made me wonder if these large systems with well defined separately rotating areas could actually develope into different storms. Or do they always coalesce into a single system?
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Quoting washingtonian115:
Yay!!.That's one person from the local area.

:| any Californian bloggers here
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Quoting RitaEvac:
What the hell is this?? this isn't even a storm anymore, lol

LOL It's got two vortices?
Member Since: August 27, 2009 Posts: 0 Comments: 525
Member Since: August 29, 2010 Posts: 0 Comments: 5236
Quoting AtHomeInTX:
This one here had a strange track. It was supposed to go out to sea a couple times. You never know what they will do. Don't see nothing wrong with discussing the what ifs. That's what we do around here. :)



Ah, Ike. I was in Michigan when he hit as a depression. Lots of rain...
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invest 95E LOOKING BETTER!! maybe up to 30% at 8pm
Member Since: July 12, 2011 Posts: 0 Comments: 1532
Quoting CanesfanatUT:


I live in Arlington. :)
Yay!!.That's one person from the local area.
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Quoting CanesfanatUT:


Believe it and SHIPS were calling for Don to be a bit higher than he actually maxed out, no?


Don't know, didn't really look at the LGEM model.
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yes and im sure our scientist and explosive experts can keep coming up with something with something bigger and better, we didn't go from a biplane to a f-22 raptor without improvements and thinking outside the box
Member Since: July 25, 2011 Posts: 0 Comments: 453
Quoting AtHomeInTX:
This one here had a strange track. It was supposed to go out to sea a couple times. You never know what they will do. Don't see nothing wrong with discussing the what ifs. That's what we do around here. :)



A lot of people here said that that bend to the SW would never happen, that storms so far north couldn't come to the Gulf, let alone Texas.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting AtHomeInTX:
This one here had a strange track. It was supposed to go out to sea a couple times. You never know what they will do. Don't see nothing wrong with discussing the what ifs. That's what we do around here. :)

Ahh yes that damn Ike.Ike just didn't get along with any reporters.He brought misery and devestation to the U.S after when we had to deal with Gustav.What a sneaky snake he was.His name means "he will laugh".But he surley wasn't while coming for Texas and the carribean Islands.
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Quoting stormwatcherCI:


Tropical13 beat you by 2 minutes....you must be getting old...;^)
Member Since: August 29, 2010 Posts: 0 Comments: 5236
Quoting TropicalAnalystwx13:


Think it could achieve TD status by the end of the month?

LGEM has it at hurricane status in five days...very reliable intensity model.


Believe it and SHIPS were calling for Don to be a bit higher than he actually maxed out, no?
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649. DFWjc
Quoting robj144:


Right and those MOAB's have a fraction of the energy of an H bomb which in turn has a fraction of a fraction of the energy of a hurricane.


I've always wondered about that since the first time i sat in a tub and waved my hand to "kill" the funnel in it.
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Quoting RitaEvac:


I dont think so, this is a reality blog

:) Couldn't agree more!
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Quoting ProgressivePulse:



We seem to have missed all those troughs in SFL?


Well, troughs have not dug down that far, but it doesn't matter, South Florida has still been influenced by them, just about every time you have had a deep tropical flow off the gulf of Mexico over the last several weeks, that's been from a the trough influence.

If a trough dug down to the Gulf Coast and North Florida while a tropical cyclone approaches, it would steer any tropical cyclone that gets close enough away from Florida, off to the northeast. That's just how it works.
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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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