Isaac bearing down on Haiti

By: Dr. Jeff Masters , 8:40 PM GMT on August 24, 2012

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Tropical Storm Isaac has remained approximately level in intensity this afternoon. An Air Force Reserve hurricane hunter aircraft measured surface winds of 65 mph at 3:55 pm EDT, with winds at the aircraft's flight level of 5,000 feet of hurricane force, 80 mph. The surface pressure is falling, and is down to 994 mb. Tropical cyclones have a warm core, and the Hurricane Hunters typically find that a storm's lowest pressure is also where the warmest temperature are. That was not the case this morning, but is the case this afternoon. The Hurricane Hunters found a modest 4°C increase in temperature as they penetrated Isaac's core at 2:43 pm EDT (that difference fell to just 1°C by 3:55 pm, though.) A ship located about 100 miles southwest of Santo Domingo in the Dominican Republic measured sustained winds of 58 mph early this afternoon, and wind gusts of 46 mph have been measured on the south coast of the D.R. at Barahona this afternoon. Infrared and visible satellite loops show that Isaac is starting to close off a center, and eyewall formation will likely begin early this evening. An analysis of upper level winds from the University of Wisconsin CIMSS shows that upper-level outflow has improved considerably since this morning.


Figure 1. True-color MODIS satellite image of Isaac taken at 11:10 am EDT August 24, 2012. At the time, Isaac had top sustained winds of 60 mph. Image credit: NASA.

Latest model runs for Isaac
The latest set of 12Z (8 am EDT) model runs is similar in spread to the previous set of runs. Final landfall locations range from Alabama (ECMWF model) to the Florida Panhandle south of Tallahassee (GFS model.) It is possible that the trough of low pressure pulling Isaac to the north may not be strong enough to pull Isaac all the way to the northeast and out to sea, and the ECMWF model indicates that Isaac could stall out after landfall, and spend several days over the Tennessee Valley.

Impact on South Florida, Cuba, Jamaica, and the Bahamas
Residents of South Florida, Cuba, Jamaica, and the Bahamas should not focus overly much of the exact track of the center of Isaac, because the storm's heaviest winds and rain will be spread out over a large area, and will not be focused near the core of the storm. Tropical storm-force winds currently extend outwards 185 miles to the right of Isaac's center, and will continue to extend outwards about this far as the storm passes by the Bahamas and South Florida. Heavy rains of 4 - 8 inches will be common along this swath. I recommend using the latest wind probability forecast from NHC to see your odds of receiving tropical storm-force winds of 39 mph or higher.


Figure 2. Daily Oceanic Heat Content or Tropical Cyclone Heat Potential (TCHP) for Issac. The forecast points are from the 11 am EDT NHC advisory; the 24 hour forecast point shown here is for 8 am EDT Saturday, and the 72 hour forecast point is for 8 am Monday. 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. Isaac will be in such a region when it is over water between its current location and the Florida Keys. Once Isaac goes beyond the Keys, total ocean heat content will fall to levels not as conducive for rapid intensification. Image credit: NOAA/RAMMB.

Intensity forecast for Isaac in the Gulf of Mexico
Isaac will likely be a 50 - 55 mph tropical storm on Saturday and Sunday as it moves over Cuba, but once the storm pops off the coast of Cuba into the Florida Straits, it will likely intensify. Isaac will be over very warm waters of 31 - 32°C (88 - 90°F) in the Florida Straits, wind shear will be light to moderate, and the upper-level wind pattern will feature an upper-level anticyclone over the storm, aiding its upper-level outflow. If Isaac makes landfall near the tip of South Florida, as the latest 12Z (8 am EDT) runs of the GFS, HWRF, and GFDL models are suggesting, the 24 hours it has over water before landfall will probably allow it to intensify by 15 - 20 mph. I think the storm is too large for it to increase its winds more than that in just 24 hours. If Isaac spends a full two days over water after passing the Florida Keys, it is possible that it will have enough time to develop a full eyewall and undergo rapid intensification into a Category 2 or 3 hurricane, though none of the models are currently calling for this to happen. The 5 pm EDT NHC wind probability forecast gave Isaac an 11% chance of becoming a Category 2 or 3 hurricane in the Gulf. While the surface waters in the Gulf of Mexico are very warm, near 30 - 31°C, the total heat content of these waters is unusually low for this time of year. We got lucky with the Gulf of Mexico Loop Current this summer, as it did not shed a big warm eddy during the height of hurricane season, like happened in 2005 (I discuss this in my Gulf of Mexico Loop Current Tutorial.) Without the type of super-high heat energy we had in 2005 in the Gulf of Mexico, I doubt we can get a Category 5 hurricane in the Gulf in 2012.

Invest 97L off the coast of Africa
A tropical wave that moved off the coast of Africa on Thursday has been designated Invest 97L by NHC this morning. The storm has a modest amount of spin and heavy thunderstorms, and is under moderate wind shear of 10 - 20 knots. In their 2 pm EDT Tropical Weather Outlook, NHC gave 97L a 30% chance of developing by Sunday afternoon. The 2 pm EDT SHIPS model forecast predicts that 97L will track west-northwest over the next few days, and now predicts moderate shear for the next 5 days over 97L. However, the storm will have trouble with dry air, and none of the reliable models currently foresee that 97L will develop over the next five days.

I'll have a new post sometime 10 am - 1pm Saturday.

Jeff Masters

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1494. unknowncomic
3:02 PM GMT on August 25, 2012
Quoting Grothar:
The season's a bust.
Are you joking?
Member Since: August 2, 2011 Posts: 0 Comments: 2107
1493. Maineweatherguy20023
10:30 AM GMT on August 25, 2012
Quoting AussieStorm:

That is classified as a Major Hurricane. I don't think Isaac will get that strong, even though the SST's and OHC could become rocket fuel once he's in the GOM if he makes it. Without a defined LLC, he could get ripped apart by land interaction.

OHC is LOW
Member Since: August 1, 2012 Posts: 0 Comments: 269
1492. TX2FL
4:31 AM GMT on August 25, 2012
Just read Bastardi's tweet about a "Billion dollar disaster cat 2-3 in the Keys".

What is he smoking?
Member Since: July 14, 2008 Posts: 0 Comments: 117
1491. Tazmanian
3:00 AM GMT on August 25, 2012
ouch


it went up from 185 mils to 230 miles


TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 230 MILES...
370 KM...MAINLY NORTHWEST AND NORTHEAST OF THE CENTER.
Member Since: May 21, 2006 Posts: 5091 Comments: 115359
1490. code1
2:38 AM GMT on August 25, 2012
And a long term blog post, from before most of current posters here? Go West young man!!!
Member Since: September 18, 2005 Posts: 66 Comments: 13872
1489. SSideBrac
2:10 AM GMT on August 25, 2012
Quoting RTSplayer:
Look at that...

The main one that matters isn't picking up anything...is it broken, or is Isaac become that dry?!



Said it earlier -check out time in top right hand corner - they are old recorded loops - always seems to have been the way for a while now
Member Since: September 21, 2008 Posts: 0 Comments: 311
1488. redwagon
2:07 AM GMT on August 25, 2012
Quoting GeoffreyWPB:


Takes someone smarter than me to figure that out.


Member Since: August 4, 2007 Posts: 0 Comments: 3278
1487. icmoore
2:03 AM GMT on August 25, 2012
Quoting Grothar:
The season's a bust.


Wishful thinking...see y'all in the morning.
Member Since: July 18, 2005 Posts: 9 Comments: 4146
1486. cirrocumulus
1:54 AM GMT on August 25, 2012
Quoting stormhank:
anyone think Isaac will track as far west as La. or Texas??


It could. Right now it is scheduled to hit the Ms./Ala. border according to the best model that is the EURO!
Member Since: September 30, 2005 Posts: 0 Comments: 1606
1485. WXGulfBreeze
1:49 AM GMT on August 25, 2012
Quoting gulfbreeze:
Did I see that right it just sits north of Mobile ?


Check out the 96 and 120 hour positions on the latest NHC advisory. Basically, Isaac rolls in somewhere around Ft. Walton Beach, and then sits on Montgomery for awhile. He could be a big rainmaker in interior Alabama - and of course, his reach to the Gulf shores will continue.
Member Since: March 9, 2012 Posts: 0 Comments: 150
1484. aspectre
1:49 AM GMT on August 25, 2012
23Aug.06pmGMT: 15.9n66.4w (288.1*WNW@16.2knots) 35knots, 1004millibars, TS
24Aug.12amGMT: 16.5n68.0w (291.4*WNW@16.5knots) 40knots, 1002millibars, TS
24Aug.06amGMT: 16.2n69.6w (259.2* West@15.7knots) 40knots, 1000millibars, TS
24Aug.12pmGMT: 15.9n70.4w (248.9* WSW @ 8.3knots) 50knots, 1000millibars, TS
24Aug.06pmGMT's numbers are below, before 25Aug.12amGMT's
Derived from NHC_ATCF data for TropicalStormIsaac for 25August12amGMT
MinimumPressure decreased from 995millibars to 992millibars
MaxSusWinds held to 55knots(63mph)102km/h
Vector changed from 313.1*NWest@15.1mph(24.3km/h) to 311.0*NWest@8.8mph(14.1km/h)

HOG-Holguin :: ICR-Nicaro :: NBW-Guantanamo :: CYA-LesCayes :: JAK-Jacmel :: CBJ-CaboRojo

The southeasternmost dot on the longest line is TS.Isaac's most recent position

The longest line is a straightline projection through TS.Isaac's 2 most recent positions to its closest approach (within 18miles or 29kilometres) to a coastline
23Aug.6pmGMT: TS.Isaac had been headed for passage ~2.2miles(3.6kilometres)SSWest of AltoVeloIsland (left,nearCBJdumbbell)
24Aug.12amGMT: TS.Isaac had been headed for passage over southern LagoDeOviedo (right,nearCBJdumbbell)
24Aug.6amGMT: TS.Isaac had been headed for passage 13.2miles(21.3kilometres)NNWest of Providencia
24Aug.12pmGMT: TS.Isaac had been headed for passage 6.3miles(10.2kilometres)SSEast of Tortuguero
24Aug.6pmGMT: TS.Isaac was had been headed for passage over Cotes-de-Fer, 28.9miles(46.5kilometres)West of Jacmel
25Aug.12amGMT: TS.Isaac was heading for passage over MouillageFouquet, 18miles(29kilometres)South of Miragoane in ~9hours from now (when this was posted)

Copy&paste iga, xsc, hog, icr, nbw, cya, 18.167n72.951w, jak, 17.439n71.647w-17.706n71.363w, cbj, 15.9n66.4w-16.5n68.0w, 16.5n68.0w-16.2n69.6w, 16.2n69.6w-15.9n70.4w, 15.9n70.4w-16.8n71.4w, 16.8n71.4w-17.3n72.0w, 16.8n71.4w-18.186n73.076w, 18.446n73.09w-18.186n73.076w into the GreatCircleMapper for a larger map and other information
The previous mapping for comparison
Member Since: August 21, 2007 Posts: 0 Comments: 4860
1482. VirginIslandsVisitor
1:36 AM GMT on August 25, 2012
Don't know if anyone's interested but some pretty amazing pics coming out from the Dominican Republic...

And Haiti is reporting in when he can..

See the list of the islands on the right.

www.stormcarib.com

-L

Member Since: July 30, 2011 Posts: 3 Comments: 679
1481. LightningCharmer
1:34 AM GMT on August 25, 2012


More rough weather for the Keys and south peninsular Florida.
Member Since: September 1, 2007 Posts: 0 Comments: 1344
1480. westpalmer
1:33 AM GMT on August 25, 2012


Yes, we are having some nice storms kicked up from Isacc's bands.


Member Since: September 20, 2005 Posts: 0 Comments: 42
1479. dsenecal2009
1:29 AM GMT on August 25, 2012
One thing is for sure - that G-IV dropsonde operator earns his keep. He must look like a one-man mortar squad up in there.
Member Since: September 25, 2009 Posts: 0 Comments: 119
1478. 7544
1:28 AM GMT on August 25, 2012
Quoting TropicalAnalystwx13:
Isaac may be up to 60 knots (70 mph) at 11 p.m. EDT.


yeap hes starting to wind up at this hour
Member Since: May 6, 2007 Posts: 0 Comments: 6872
1477. stormhank
1:27 AM GMT on August 25, 2012
anyone think Isaac will track as far west as La. or Texas??
Member Since: September 8, 2005 Posts: 0 Comments: 1386
1476. IceCoast
1:27 AM GMT on August 25, 2012
Bolavens outflow extends from about 15N to 30N, a massive system. He's been an amazing storm to watch, but he still doesn't rival Typhoon Tip. Also to note, there are much smaller typhoons to the west of both these massive storms .

Bolaven


Tip
Member Since: October 17, 2010 Posts: 0 Comments: 1267
1475. Stormbugn
1:26 AM GMT on August 25, 2012
Quoting BlueSkiesAbove:
hey all..long time reader ~ infrequent poster...

I like how this blog ALWAYS ''predicts'' pretty darn accurately and in addition to this, it is predicted BEFORE it is reported on TV...always! I come here every year and ive learned so much. i have a new respect for these storms. there are a lot of talented people here who know what they are talking about. and that brings me to my question:

what would a cat 2 do to a motorhome [not a mobile home but an actual motorhome for road travel ..?] I live in one in Daytona beach about 20 mi or so inland from the coast. this storm is looking downright scary at this moment..


We rode out Gustav in one for work. All I can say about it is...think Wizard Of Oz..."Toto...I don't think we are in LA anymore!". Seriously...DO NOT DO IT!!! I opened the door to check some gear at one point and was sucked out of the thing and was bashed repeatedly against the side. It was a wild couple of days...then Ike hit and it was round two. I wish you the best of luck, hope for your safety, and the safety of everyone in Florida.
Member Since: May 15, 2012 Posts: 0 Comments: 52
1474. scott39
1:26 AM GMT on August 25, 2012
Quoting Grothar:
The season's a bust.
bustin a move!
Member Since: June 13, 2009 Posts: 0 Comments: 6888
1473. WxLogic
1:25 AM GMT on August 25, 2012
Quoting StormJunkie:


Much of that data will be in the 00z runs, and nrti noted that 10 dropsondes from it got in to the 18z runs.


I agree the 18Z got some, but not quite sure 00Z will get all, but should definitely get more than what 18Z had. I'll keep fingers cross that all made it to the 00Z then. :)
Member Since: August 14, 2008 Posts: 4 Comments: 5029
1472. yoboi
1:25 AM GMT on August 25, 2012
Quoting Dakster:


What is your avatar of, an Armadillo on its back??


yep look at what it's drinking....
Member Since: August 25, 2010 Posts: 7 Comments: 2402
1471. gulfbreeze
1:25 AM GMT on August 25, 2012
Quoting Chicklit:

Yes, he is. Cancun, I believe.
Anyway, GFS is showing a Mobile landfall.
Also something else (HINT look east).
Did I see that right it just sits north of Mobile ?
Member Since: June 13, 2010 Posts: 0 Comments: 925
1470. Grothar
1:24 AM GMT on August 25, 2012
The season's a bust.
Member Since: July 17, 2009 Posts: 71 Comments: 26865
1469. nrtiwlnvragn
1:24 AM GMT on August 25, 2012
Member Since: September 23, 2005 Posts: 14 Comments: 11274
1468. scott39
1:23 AM GMT on August 25, 2012
Fredrick shot off of Cuba as a TD and became a Cat 4 in the GOM. Dont underestimate the GOM potential to develope TCs quickly
Member Since: June 13, 2009 Posts: 0 Comments: 6888
1467. caneswatch
1:23 AM GMT on August 25, 2012
His outflow is where he's headed. South Florida, prepare for a 85+ mph Category 1 Sunday into Monday.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
1466. A4Guy
1:23 AM GMT on August 25, 2012
Quoting newportrinative:


Same here in Ft Lauderdale. Made a run to Publix and it was quiet. Got a few things missing to last us if we are homebound for a few days. Better today instead of tomorrow if the track changes and hysteria hits. I'll be sitting back and watching the madness.


I didn't go. Not overly prepared, unfortunatel.y I have batteries..and SOME water..but not much.
After Wilma, I had no power for 8 days (thank god it was cool for much of it), but we only lost water for a day (not even)...so I am keeping fingers corssed. I have a pool if I need water for flushing. :)
Going to freeze empty containers of water so I have ice blocks depending on how things look in the a.m. Have been slowly clearing out food fromthe freezer all week...will make a few more things tomorrow that will do OK in a "cool" refrig for a day or two.
I need some bread, but that's about it - always have cans, granola, etc. in the house...and have a gas side burner for my grill for cooking.
Member Since: June 23, 2006 Posts: 0 Comments: 668
1465. muddertracker
1:23 AM GMT on August 25, 2012
Quoting AussieStorm:

I've just had a cuppa tea. To early to start drinking.


Aussie time? What...that's like...what? Hawaii is 7 hours from me...so you'd be another 5? It's like 8 am?
Member Since: August 16, 2007 Posts: 1 Comments: 2351
1464. LargoFl
1:22 AM GMT on August 25, 2012
Quoting AtHomeInTX:
CAT 1 Humberto damage



Humberto damage on Bolivar exactly a year before Ike

yeah people say..oh..its only a cat-1 huh...i remember people scoffing at TS Debby also..people are still suffering from her today
Member Since: August 6, 2011 Posts: 4 Comments: 40965
1463. NativeSun
1:22 AM GMT on August 25, 2012
The storms over SE Florida are indirectky related to Isaac and this will be the track the storm takes.
Member Since: July 17, 2008 Posts: 0 Comments: 278
1462. weatherh98
1:22 AM GMT on August 25, 2012
Quoting TropicalAnalystwx13:
Both the GIV mission and the investigation through Isaac are done.


What was the final verdict
Member Since: June 17, 2011 Posts: 11 Comments: 6539
1461. avthunder
1:22 AM GMT on August 25, 2012
Quoting newportrinative:


Same here in Ft Lauderdale. Made a run to Publix and it was quiet. Got a few things missing to last us if we are homebound for a few days. Better today instead of tomorrow if the track changes and hysteria hits. I'll be sitting back and watching the madness.
Same here. We are prepared in North Broward in case Isaac changes his mind. Had a hard time convincing folks at work that the cone is about only the eye and the storm is 600 miles big and we are gonna get some weather. They saw we were out of the cone this morning and wrote it off.
Member Since: August 30, 2010 Posts: 0 Comments: 339
1460. JDSmith
1:22 AM GMT on August 25, 2012
Expect a boom soon. Hot towers are firing around the COC. Probably an indication that it's becoming better stacked. Those of you watching tonight are in for a treat during Dmin if land interaction doesn't hinder Isaac too much...
Member Since: August 15, 2008 Posts: 0 Comments: 103
1459. GeoffreyWPB
1:21 AM GMT on August 25, 2012
Have to see how Isacc handles Cuba. That will be the key.
Member Since: September 10, 2007 Posts: 0 Comments: 11427
1458. muddertracker
1:21 AM GMT on August 25, 2012
Quoting RTSplayer:
Would be nice if the Cubans would help people out with their radars, but their site seems to be broken or something...


It's been broken for like ten years or something...some storm took it out and it was never replaced, I think..I remember some bloggers talking about that a few years back.
Member Since: August 16, 2007 Posts: 1 Comments: 2351
1457. wunderkidcayman
1:21 AM GMT on August 25, 2012
hey guys a little bit of history

Gustav was located at 17.5N 72.0W moving NW at 9mph
not too far off from Isaac
Member Since: June 13, 2009 Posts: 2 Comments: 12473
1456. TropicalAnalystwx13
1:21 AM GMT on August 25, 2012
Quoting charlottefl:
That's where the center is at....


I overlaid satellite imaery on the recon data, and it lines up almost perfectly with the clear slot (a.k.a eye).
Member Since: July 6, 2010 Posts: 113 Comments: 32527
1455. jonelu
1:21 AM GMT on August 25, 2012
We just got a nice gusty thunder storm here in W. Palm Beach...Im guessing more to come.
Member Since: October 31, 2007 Posts: 2 Comments: 884
1454. DataNerd
1:21 AM GMT on August 25, 2012
Quoting TropicalAnalystwx13:
Isaac may be up to 60 knots (70 mph) at 11 p.m. EDT.



Should be, recon was finding 76mph on the se side.
Member Since: June 24, 2012 Posts: 0 Comments: 1546
1453. WunderAlertBot (Admin)
1:20 AM GMT on August 25, 2012
JeffMasters has created a new entry.
1452. DataNerd
1:20 AM GMT on August 25, 2012
Quoting LargoFl:
that may be whats coming from africa now




No according to this its a combination of an existing T wave in the mid atlantic and left over disturbed air from Isaac.

At least I think that's what I am seeing here.
Member Since: June 24, 2012 Posts: 0 Comments: 1546
1451. TropicalAnalystwx13
1:20 AM GMT on August 25, 2012
Isaac may be up to 60 knots (70 mph) at 11 p.m. EDT.
Member Since: July 6, 2010 Posts: 113 Comments: 32527
1450. oiltr8er
1:20 AM GMT on August 25, 2012
Does anyone know of a link to any radar stations in Cuba?
Member Since: June 24, 2010 Posts: 0 Comments: 1
1449. LargoFl
1:20 AM GMT on August 25, 2012
Quoting PalmBeachWeatherBoy:
Some crazy convection going on in the bahamas and over Florida. Didn't even know what was going on and my lights just turned off and on. Fast moving thunderstorm going into North palm beach county.
in the next couple of days alot of us will be experiencing things like that
Member Since: August 6, 2011 Posts: 4 Comments: 40965
1448. RTSplayer
1:20 AM GMT on August 25, 2012
Look at that...

The main one that matters isn't picking up anything...is it broken, or is Isaac become that dry?!

Member Since: January 25, 2012 Posts: 33 Comments: 1520
1447. StormJunkie
1:19 AM GMT on August 25, 2012
Quoting yoboi:


MD 20/20 here, trying to get my vision right...


Are you 16 years old? That's the only excuse to pick up the Mad Dog!!!
Member Since: August 17, 2005 Posts: 26 Comments: 16874
1446. Chicklit
1:19 AM GMT on August 25, 2012

discomblobulated mess on water vapor


the anticyclone all over the place

Interesting that NHC has it going over Central Cuba after hitting eastern cuba. The big picture is very confusing for someone who hasn't seen this system all day.
Member Since: July 11, 2006 Posts: 14 Comments: 11390
1445. WhereIsTheStorm
1:19 AM GMT on August 25, 2012
Quoting 12george1:
These thunderstorms here in West Palm Beach aren't from Isaac, are they?


Watch the loop:Link
Member Since: August 14, 2006 Posts: 0 Comments: 443
1444. Hurricanes101
1:19 AM GMT on August 25, 2012
Quoting redwagon:

I'm still dealing with the shock of Isaac going fish... which means yet another dual storm, one center runs off NE, the other heads due W. Suddenly I have a migraine.


?????
Member Since: March 10, 2010 Posts: 1 Comments: 7874

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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.