Hurricane Hunters find tropical storm winds in TD 9

By: Dr. Jeff Masters , 7:51 PM GMT on August 21, 2012

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The Air Force Hurricane Hunters are in Tropical Depression Nine, and have discovered a region of 40 - 45 mph winds at the surface, using their SFMR instrument. Flight level winds at their 1000 foot altitude spiked as high as 49 mph. The surface pressure was 1005 mb, a typical one for a weak tropical storm. Based on these measurements, it is highly likely that NHC will name this Tropical Storm Isaac at 5 pm EDT. A large area of dry air lies just to the north of the storm, as seen on water vapor satellite loops, and this dry air is interfering with development, allowing only a few clumps of heavy thunderstorms to fire up near TD 9's center, as seen on visible satellite loops. These loops also show some arc-shaped low clouds expanding away from the heavy thunderstorm area on the south side of the center, showing that TD 9 is ingesting dry air that is creating strong thunderstorm downdrafts, robbing the storm of moisture and energy. An analysis of upper level winds from the University of Wisconsin CIMSS shows that an upper level outflow channel has opened to the southwest, and another channel is attempting to open up to the north. A large clump of heavy thunderstorms several hundred miles to the southeast of TD 9 continues to compete for moisture, and is interfering with the low level inflow and upper level outflow of the storm. The center of TD 9 will pass about 50 miles to the north of buoy 41101 near midnight tonight. The next hurricane hunter mission into TD 9 is scheduled for 2 am Wednesday, and there will be a new mission launched every six hours. The NOAA jet is first scheduled to fly into the storm on Thursday afternoon, to do a large-scale dropsonde mission to aid model forecasts.


Figure 1. Satellite image of TD 9 and 96L taken at 10:45 am EDT August 21, 2012. The two storms are connected by a thin line of low clouds. Image credit: NOAA Environmental Visualization Lab.

Intensity forecast for TD 9
The latest 2 pm EDT run of the SHIPS model predicts that wind shear will be low to moderate, 5 - 15 knots, for the next five days. Ocean temperatures will warm from 28°C today to 29°C by Wednesday afternoon, and the total heat content of the ocean will increase sharply during that period. The low wind shear and warm waters will favor strengthening. The main impediment to development through Wednesday will be dry air to the north, though the storm will also have trouble separating from the clump of thunderstorms to its southeast. I expect that TD 9 will continue to struggle with dry air through Wednesday. The official NHC forecast is of a 60 mph tropical storm moving through the Lesser Antilles on Wednesday evening; I put the most likely range of strengths for TD 9 Wednesday evening at 50 - 60 mph. Once TD 9 enters the Eastern Caribbean, wind shear will be low, oceanic heat content high, and the storm should have had enough time to moisten the atmosphere to allow steady strengthening to a hurricane. Intensity forecasts 4 - 5 days out are low in skill, though, and it would not be a surprise at all to see TD 9 struggle like so many other storms have over the past two years, and remain a tropical storm over the next five days. Conversely, rapid intensification into a Category 2 hurricane five days from now, as the official NHC is suggesting may happen, would also not be a surprise.


Figure 2. Daily Oceanic Heat Content or Tropical Cyclone Heat Potential (TCHP) for TD 9. The forecast points are from the 11 am EDT NHC advisory, and the 24 hour forecast point shown here is for 8 pm EDT Wednesday. For tropical cyclones in favorable environmental conditions for intensification (i.e., vertical wind shear less than 15 kt, mid-level relative humidity >50 %, and warm SSTs [i.e., >28.5C]) and with intensities less than 80kt, values of ocean heat content greater than 50 kJ/cm^2 (yellow and warmer colors) have been shown to promote greater rates of intensity change. TD 9 will be crossing into such a region early Wednesday morning, and will enter a region of very high TCHP south of Hispaniola on Friday morning (the 72 hour forecast point.) Image credit: NOAA/RAMMB.

Latest model runs for TD 9
The latest set of 12Z (8 am EDT) model runs for TD 9 are fairly unified for the coming three days, showing a west to west-northwest track to a point just south of Hispaniola. Most of the models then predict a more west-northwest track across Southwest Haiti and into eastern Cuba, as TD 9 responds to a small trough of low pressure over the Southeast U.S. A notable exception is our best-performing model, the ECMWF, which keeps TD 9 south of Hispaniola, and takes the storm more to the west over Jamaica by Saturday, and then into the Yucatan Channel between Mexico and Cuba by next Tuesday. We'll have to wait another day to see where the center of TD 9 consolidates before judging which model solution is likely to be correct; reformations of the center closer to bursts of heavy thunderstorm often cause the center point to shift around in the early stages of development, leading to large changes in the forecast track many days later. TD 9 is a threat to affect Tampa during the Republican National Convention, August 27 - 30. I blogged about the climatological chances of a hurricane causing an evacuation of Tampa during the convention in a post last week, putting the odds at 0.2%. The odds in the current situation are higher, probably near 2%. It would take a "perfect storm" sort of conditions to all fall in place to bring TD 9 to the doorstep of Tampa as a hurricane during the convention, but that is one of the possibilities the models have been suggesting could happen.

Disturbance 96L off the coast of Africa
A large tropical wave in the eastern Atlantic about 550 miles southwest of the Cape Verde Islands (Invest 96L) is headed west at 15 mph. This disturbance has an impressive amount of spin, as seen on visible satellite loops, and a respectable amount of heavy thunderstorm activity that is increasing. The storm is under a light 5 - 10 knots of wind shear. Given that TD 9 has moistened up the atmosphere ahead of 96L, this disturbance should have less of a problem with dry air. In their 2 pm EDT Tropical Weather Outlook, NHC gave 96L a 60% chance of developing into a tropical cyclone by Thursday afternoon. This disturbance will track nearly due west the next three days, then is expected to turn more to the west-northwest late this week, bringing it close to the northern Lesser Antilles Islands by Sunday.

Disturbance 95L in the Gulf of Mexico near the Texas/Mexico border
A region of disturbed weather (Invest 95L) is in the Gulf of Mexico, just northeast of Tampico, Mexico. In their 2 pm EDT Tropical Weather Outlook, NHC downgraded the chances of 95L developing to 20%. The Air Force hurricane hunter aircraft scheduled to investigate 95L this afternoon was cancelled. Radar out of Altamira, Mexico does not show any organization to the precipitation echoes and visible satellite loops show that 95L is small and disorganized. The computer models show that 95L should drift westwards, and may move over Mexico on Wednesday.

I'll have a new post in the morning.

Jeff Masters

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Yup. More east on this run. 114 HR:

Member Since: August 1, 2011 Posts: 28 Comments: 8041
Quoting JLPR2:


Deep...
Worthy of a Facebook post. XD


You know, I think you're right. I haven't posted anything quite so provocative in awhile.

I think you've suddenly reawakened the controversial person within me. :P
Member Since: March 7, 2007 Posts: 597 Comments: 21099
Quoting Bluestorm5:
orrrr not.



It looked like it would track over the spine of cuba...looks to be okay now
Member Since: August 29, 2006 Posts: 22 Comments: 1352
2081. Gearsts
Quoting JLPR2:


Basically crosses PR's south coast. :\

Has to be the brother of Irene.
Member Since: Posts: Comments:
2080. NCSCguy
Any chance this guy could be like Irene was last year?
Member Since: Posts: Comments:
New blog on Isaac Link
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Quoting JLPR2:


I'll repeat, no such thing is happening.



Station 41101
Meteo France
Location: 14.600N 56.201W

Wind Direction (WDIR): SSW ( 210 deg true )
Wind Speed (WSPD): 17.1 kts


this bouy is not really trusted so well because it is not keeped with the NDBC so says NDBC

anyway this may be happening and recon should gives us a better picture they liftoff in about an hour or less

shoud keep an eye on that bouy wind could change
Member Since: Posts: Comments:
Quoting 954FtLCane:


This looks like a large storm so there is a good possibility it will. It'll obviously be affected if it's the case though.


I think the last storm I saw attempt to cross those mountains had its convection completely separated and it was left with a naked swirl.
Member Since: Posts: Comments:
2076. wxhatt
oh no, looks like the GFS trending NORTH!
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Quoting KoritheMan:


As long as I'm not wrong by hundreds of miles, I think I'll survive. :P

That's happened to me before, not fun.
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2074. scott39
Now since the GFS has went back to the right a little....Everyones track changes??? Come on, we all know that the the 5 day cone can be off a by 250 miles. I bet the EURO sticks to the eastern GOM.
Member Since: Posts: Comments:
Quoting louisianaboy444:
GFS might kill it this run
orrrr not.

Member Since: August 1, 2011 Posts: 28 Comments: 8041
2072. Levi32
Quoting thelmores:


Hey Levi...... how long till the fix, guesstimated?


90 minutes, ish.
Member Since: November 24, 2005 Posts: 635 Comments: 26684
2071. JLPR2
Also, lets not forget good ol 96L, looking really good right now, If it keeps this up I expect an increase in its % and probably a renumber for 5am.
Member Since: Posts: Comments:
2070. Skyepony (Mod)
Quoting westpalmer:

Tried it and it worked once then froze up IE.  New computer, high end, Windows 7,  Not sure what the problem is.  But is this satellite data or what exactly? Thanks.


You need may need to download quicktime. Or maybe try the smaller movie. That very large can take me near a minute sometimes. It's like a moving side slice of the precipitation. It's satellite data.. Helps with rain rates & how tall a storm is to determine steering heights to use. More here.
Member Since: August 10, 2005 Posts: 193 Comments: 38679
Quoting thelmores:
The FIM model, which is experimental, shows an east coast hit for Isaac, missing Florida all together.....

Looks around Savannah....

Link


The FIM7, which uses the lowest resolution of the FIM models, takes it east of FL. It is not a very accurate version. FIM 9 would probably be the best.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting wunderkidcayman:


I totaly agree

sue looks like it from all satellite loop

Recon is to takeoff in about an hour if this is so hopefully it will be put in the models

and if this is (which I highly think it is) expect the Track to shift S and W and should be stronger due to less land interaction due to it being further S and W


people thought the wobble to north today meant a long-term west northwest track. cyclones tend to wobble north from to time due to nature of the storm. does not mean it has veered off its overall westward component.
Member Since: September 6, 2008 Posts: 0 Comments: 127
Quoting Levi32:
Here we go. I'll be staying up for the first fix.

how far west and east do you think isaac will go?
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Quoting KEEPEROFTHEGATE:

Doesn't look like he is in any hurry to get out of the Windward Passage...
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2065. Grothar





This looks like a storm that want to go through the Windward Passage.

Member Since: July 17, 2009 Posts: 71 Comments: 26878
2064. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 175 Comments: 54858
2063. Buhdog
Quoting justsouthofnola:
look at the convection forming much further to the south.... looks like a center relocate to me.
Link
\

I don't think so, Maybe shear is letting up because it seems to be tightening up. looks due west.
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2061. HrDelta
Quoting DVG:


It could be which version of internet explorer you are using. Look to see if you ae in the 64 bit or 32 bit mode. Many things won't run in the 64 bit version.


Or use Chrome. It is quick as a flash, even on a 4 year old Vista Laptop.
Member Since: October 4, 2007 Posts: 0 Comments: 451
2060. JLPR2
Quoting KoritheMan:


Amazing how irrationality deludes the mind and perverts the senses, isn't it?

(Agree with you btw)


Deep...
Worthy of a Facebook post. XD
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Quoting PalmBeachWeatherBoy:
I don't think Isaac can survive going over the highest mountains of Hispaniola.


This looks like a large storm so there is a good possibility it will. It'll obviously be affected if it's the case though.
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Quoting 1900hurricane:

I wouldn't worry about it. The GFS has been wiggling around that general area for a while now. I haven't put out an official forecast, but I think yours looks good and is along my vein of thinking.

And if you're wrong, oh well. :P


As long as I'm not wrong by hundreds of miles, I think I'll survive. :P
Member Since: March 7, 2007 Posts: 597 Comments: 21099

Quoting DVG:


It could be which version of internet explorer you are using. Look to see if you ae in the 64 bit or 32 bit mode. Many things won't run in the 64 bit version.


Yes, I am using 64 bit.  Can you change the mode in settings or do you need to use a different browser?  Does Firefox work better?  Thanks.
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Quoting Levi32:
Here we go. I'll be staying up for the first fix.



Hey Levi...... how long till the fix, guesstimated?
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Quoting ecupirate:


It is comical at this point how far off you are. This storm could be landfalling in Nova Scotia and you would still be calling for a SW turn.
Well it's is not all that farfetch'd early in a Tropical Storms life for center relocations, actually around this time last year Irene made a major jump northwards and threw all the models off.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Doesn't look like it's going north anytime soon.
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The FIM model, which is experimental, shows an east coast hit for Isaac, missing Florida all together.....

Looks around Savannah....

Link
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Quoting JLPR2:


I'll repeat, no such thing is happening.



Station 41101
Meteo France
Location: 14.600N 56.201W

Wind Direction (WDIR): SSW ( 210 deg true )
Wind Speed (WSPD): 17.1 kts


Amazing how irrationality deludes the mind and perverts the senses, isn't it?

(Agree with you btw)
Member Since: March 7, 2007 Posts: 597 Comments: 21099
GFS might kill it this run
Member Since: August 29, 2006 Posts: 22 Comments: 1352
Quoting SunriseSteeda:


There is a decent chance we played with or against each other at some point then :) My corporate coed teams were based there, and my men's tournament teams were as well (DuckSoup/Ecometry/Accelerated Rehab). I played there from 92 until... Wilma! (coincided with the spine injury that shut me down) I still visit now and then to watch and drink some brews :)




I wouldn't be surprised if we played on the same team or against each other either. I played a lot... sunday ball was probably my favorite ;-), both sun sentinel league and SFAAA (a league of our own), also co-ed and mens during the week from 95-07. Got to the point I was playing 4-5 days a week for a couple of years. Blew knee out and got hitched and that was the end of that. Way too many sponsors during that time to remember names. You know the typical realtors, bars,etc....
Heck I live real close to what used to be the old "duck soup" now area 51.
Wilma changed the park a bit but still a good venue!!! Great tourney held on Thanksgiving weekend.

Sorry bout the blah blah everyone.... heck atleast it wasnt politics


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2048. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 175 Comments: 54858
one run of the GFS isnt going to change my mind on the track. if the euro changes ill change my track. right now i still have it south of cuba
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Pico Duarte; 10,100 ft high, tallest mountain in all Caribbean islands VS TS Isaac
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Quoting KoritheMan:
Based on the 0z GFS, the forecast track I made tonight may be a little too far south, heh. Name of the game.

I wouldn't worry about it. The GFS has been wiggling around that general area for a while now. I haven't put out an official forecast, but I think yours looks good and is along my vein of thinking.

And if you're wrong, oh well. :P
Member Since: Posts: Comments:
2044. DVG
Quoting westpalmer:

Tried it and it worked once then froze up IE.  New computer, high end, Windows 7,  Not sure what the problem is.  But is this satellite data or what exactly? Thanks.


It could be which version of internet explorer you are using. Look to see if you ae in the 64 bit or 32 bit mode. Many things won't run in the 64 bit version.
Member Since: Posts: Comments:
2043. Levi32
Here we go. I'll be staying up for the first fix.

Member Since: November 24, 2005 Posts: 635 Comments: 26684
look at the convection forming much further to the south.... looks like a center relocate to me.
Link
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Quoting Levi32:
There's nothing like an ice cold Sprite while tracking a storm. Nothing.
Agreed. Though an iced Goombay Punch is better, IMO.... lol

Quoting Chiggy:
This shows (..surprisingly)how few storms have hit FL from the current position of Issac! I count only 4 storms; more storms either curve eastwards past FL or go straight West! I am really surprised about this statistics - this also shows how it's almost impossible for storms to hit Tampa dead on - last time I believe was about 60 years ago...
I like these maps; in fact it was this very feature that drew me to the Wunderground.

However, u have to be careful as you interpret them. For example, this particular map only includes storms that were TSs at this point. Cat 1-5 storms and TDs at this point don't show up. Additionally, it only shows August storms. Storms in July or September, for instance, are not shown.

Basically what I'm highlighting is that this map presents a specific subset of the storms passing this point.

Nevertheless, it does a very good job of highlighting something I discovered about hurricane strikes on the Bahamas a couple of seasons ago; 8/10 CV storms recurve before reaching our area, and though Florida gets hit relatively often, strikes from storms originating in the deep tropical Atlantic are not as common as we may think.

Member Since: October 25, 2005 Posts: 19 Comments: 22576
Member Since: July 12, 2007 Posts: 0 Comments: 6065
though I am keeping an eye on the bouy for change in wind but recon should give us a better picture and they take off in an hour
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Isaac survives Haiti just fine... at 90 HR

Member Since: August 1, 2011 Posts: 28 Comments: 8041
2037. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 175 Comments: 54858
2036. JLPR2
Quoting wunderkidcayman:


I totaly agree

sue looks like it from all satellite loop

Recon is to takeoff in about an hour if this is so hopefully it will be put in the models

and if this is (which I highly think it is) expect the Track to shift S and W and should be stronger due to less land interaction due to it being further S and W


I'll repeat, no such thing is happening.



Station 41101
Meteo France
Location: 14.600N 56.201W

Wind Direction (WDIR): SSW ( 210 deg true )
Wind Speed (WSPD): 17.1 kts
Member Since: Posts: Comments:
Quoting wunderkidcayman:


I totaly agree

sue looks like it from all satellite loop

Recon is to takeoff in about an hour if this is so hopefully it will be put in the models

and if this is (which I highly think it is) expect the Track to shift S and W and should be stronger due to less land interaction due to it being further S and W


It is comical at this point how far off you are. This storm could be landfalling in Nova Scotia and you would still be calling for a SW turn.
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Quoting ChaseyChasinStorms:
Good evening. Just in case anyone wants to know a lurkers opinion, I think the forecast cone for tropical storm isaac is placed too far east. Jim cantore just said on the weather channel that he feels the storm will take the southern track. My question is why is he the only person saying that? But yet all the models are still more easterly...???


don't quote me, but 96 L as the poster Mississippi has alluded too earlier on this blog picking up speed and intensity behind Issac and busting through the ridging, creating the high over Issac to strengthen and bring it farther south. Levi says the models might not of caught of this bit of info yet...I'm not sold either yet either on a track over Haiti, as it may just graze/sneak under the chain.
Member Since: September 6, 2008 Posts: 0 Comments: 127

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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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