Isaac pounding Haiti and the Dominican Republic with torrential rains

By: Dr. Jeff Masters , 2:24 PM GMT on August 25, 2012

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Tropical Storm Isaac is pounding Haiti and the Dominican Republic with torrential rains that are causing extremely dangerous flooding and landslides. Isaac's center passed over Haiti's southwest peninsula early this morning, tracking about 50 miles west of the capital of Port-au-Prince. As the center pulled away to the northwest, Isaac's heaviest thunderstorms moved ashore over Hispaniola near sunrise, and are now dumping heavy rains with rainfall rates approaching one inch per hour, according to recent microwave satellite estimates. Barahona on the south coast of the Dominican Republic had received 5.14" of rain as of 8 am EDT this morning, and it is probable that some mountainous areas in Haiti and the Dominican Republic have already received up to 10" of rain from Isaac. These rains will continue though much of the day, and have the potential to cause high loss of life in Hispaniola.


Figure 1. A river north of Port-au-Prince, Haiti in flood due to rains from Isaac. Image from Amélie Baron via Twitter.

Latest observations
Isaac built a partial eyewall last night as the storm approached Haiti, but passage over the rough mountains of Haiti has destroyed the inner core, and the surface center of the storm is now fully exposed to view on satellite images. Radar out of Guantanamo Bay, Cuba shows no sign of an organized center, but does reveal some very intense thunderstorms affecting Eastern Cuba, Western Haiti, and nearby islands. Latest data from the Air Force Hurricane Hunters confirm that Isaac has weakened; during their penetration to obtain their 7:08 am EDT center fix, the aircraft reported top surface winds of 55 mph with their SFMR instrument, top flight-level winds at 5,000 feet of 68 mph, and a pressure rise of 3 mb, to 998 mb. Infrared and visible satellite loops show that Isaac remains a large and well-organized storm, though it lacks an inner core. An analysis of upper level winds from the University of Wisconsin CIMSS shows that upper-level outflow is still good to the north, but is lacking elsewhere. An impressive large multi-day satellite animation of Isaac is available from the Navy Research Lab.


Figure 2. Rainfall rates estimated by the NOAA F-17 polar orbiting satellite at 6:21 am EDT August 25, 2012. Rainfall rates of 1 inch per hour (orange colors) were occurring in a large area to the south of Hispaniola, and these heavy rains have now moved onshore. Image credit: Navy Research Laboratory.

Latest model runs for Isaac
The latest set of 0Z and 06Z (8 pm and 2 am EDT) model runs are similar in spread to the previous set of runs. Our two best models, the GFS and ECMWF, are virtually on top of each other, with a landfall location in the Florida Panhandle between Fort Walton Beach and Panama City. It is likely that the trough of low pressure pulling Isaac to the north will not be strong enough to pull Isaac all the way to the northeast and out to sea, and Isaac has the potential to drop torrential rains capable of causing serious flooding over the Southeast U.S. The latest 8-day precipitation forecast from the GFS model (Figure 3) calls for 10 - 15 inches of rain over portions of Georgia and South Carolina from Isaac. The ECMWF model, however, predicts that a ridge of high pressure will build in and force Isaac to the west after landfall, resulting in a slow motion across the Tennessee Valley into Arkansas by Friday. Arkansas is experiencing its worst drought in over 50 years, so the rains would be welcome there.


Figure 3. Predicted precipitation for the 8-day period from 2 am Saturday August 25 to 2 am Sunday September 2, from the 2 am EDT August 25 run of the GFS model. This model is predicting a wide swath of 5 - 10 inches of rain (orange colors) will affect portions of Cuba, Florida, the Bahamas, and the Southeast U.S. Image credit: NOAA/NCEP.

Intensity forecast for Isaac
Isaac survived passage over Hispaniola relatively intact. It's large size aided this, and this will also help it survive passage over Cuba today and Sunday. By the time Isaac pops off the coast of Cuba into the Florida Straits on Sunday, it will likely be a 50 mph tropical storm with a large, intact circulation. Isaac will be over very warm waters of 31°C (88°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. As I discussed in my previous post, Crossing Hispaniola and Cuba: a history, there have been five storms since 1900 with an intensity similar to Isaac, which crossed over both Haiti and Cuba, then emerged into the Florida Straits. These five storms strengthened by 5 - 20 mph in their first 24 hours after coming off the coast of Cuba. Given the relatively intact structure of Isaac so far, and the favorable conditions for intensification, I expect Isaac will intensify by 15 - 20 mph in 24 hours once the center moves off of the north coast of Cuba. 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. The latest 06Z (2 am EDT) run of the GFDL model is calling for Isaac to intensify to Category 2 strength, then weaken to Category 1 at landfall in Mississippi on Tuesday. The 06Z HWRF run is calling for landfall in the Florida Panhandle near Fort Walton Beach as a borderline Category 2 or 3 hurricane. The 5 am EDT NHC wind probability forecast gave Isaac a 19% chance of becoming a Category 2 or stronger hurricane in the Gulf. I expect these odds are too low, and that Isaac has a 40% chance of becoming a Category 2 or stronger hurricane in the Northern Gulf of Mexico. I doubt the storm has much of a chance of hitting Category 4 or 5 status, though. 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, Category 4 and 5 hurricanes in the Gulf of Mexico in 2012 will have difficulty forming.

Invest 97L off the coast of Africa
A tropical wave (Invest 97L) is located about 350 miles west-southwest of the Cape Verde Islands off the coast of Africa. The storm has a modest amount of spin and heavy thunderstorms, and is under moderate wind shear. In their 8 am EDT Tropical Weather Outlook, NHC gave 97L a 30% chance of developing by Monday morning. The 8 am EDT SHIPS model forecast predicts moderate shear for the next 5 days over 97L, so some development is possible if 97L can fend off the dry air to its north. None of the reliable models foresee that 97L will be a threat to the Lesser Antilles Islands. However, both the GFS and ECMWF models predict that a tropical wave that has not yet emerged from the coast of Africa may develop next week, and potentially take a more westward track towards the Lesser Antilles.

The Weather Channel's hurricane expert, Brian Norcross, is now writing a blog on wunderground.com. For those of you unfamiliar with his background, here's an excerpt from his first post, from last night:

"This evening 20 years ago the sun set on the horrendous first day after Hurricane Andrew. I was in downtown Miami at the studios of the NBC station. We knew that there was "total" destruction in South Dade County, but even that didn't describe it. Here's to the people that went through it... and held their families together in a situation that most people can't imagine."

Angela Fritz will have a new post here by 6 pm EDT. For the next few days, I plan to do the morning blog post, and Angela will be doing the late afternoon post.

Jeff Masters

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1321. KEEPEROFTHEGATE (Mod)
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1320. KEEPEROFTHEGATE (Mod)
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1319. LargoFl
Quoting Dakster:
I guess I should expect no power by Sunday night according to the latest model runs.
maybe that might go for all of us..we lost power the other night just from a thunderstorm grrrrr
Member Since: August 6, 2011 Posts: 4 Comments: 38109
1318. KEEPEROFTHEGATE (Mod)
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1316. KEEPEROFTHEGATE (Mod)
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http://www.srh.noaa.gov/mfl/analysis/?type=Wind



very very strong winds off of the key west coast atm
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1314. KEEPEROFTHEGATE (Mod)
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1312. LargoFl
GFS at 48 hours
Member Since: August 6, 2011 Posts: 4 Comments: 38109
Quoting msjayhawk:
Why does the hurricane hunter graphic page on the Isaac page show 995.8mb/105mph??

http://www.wunderground.com/tropical/tracking/at2 01209_hd.html

Glitch??
Member Since: August 1, 2012 Posts: 0 Comments: 254
1310. Dakster
I guess I should expect no power by Sunday night according to the latest model runs.
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Quoting Maineweatherguy20023:

Initialized wrong then it is at the 12 hr mark already (or close)


The model is delayed because it needs time to run, so it's 12 hour point is going to be 6 hours ahead of the storm, on average, for the first point.
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Quoting trHUrrIXC5MMX:

NEAR CAT 4

Small though...
Member Since: August 1, 2012 Posts: 0 Comments: 254
1307. Bielle
Quoting CybrTeddy:
For summary sake for people who can't read as fast or don't have the access to the tools some of us do.

The ECMWF, GFS, CMC, NOGAPS, GFDL, HWRF are all showing a formidable hurricane developing from Isaac in the Gulf as it passes through the Keys. Issac has emerged from Cuba per latest satellite and radar images, but do not expect intensification today as Isaac will be working on rebuilding its elongated core from it's ordeal with Haiti and Cuba. After that, intensification at a fairly decent pace is likely. There is little to stop this storm as dry air is a non factor and shear will lessen once Issac's somewhat displaced Upper Level Anti-Cyclone (ULAC) begins to become stacked over it.


Thank you for thinking of the rest of us. :>)
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1306. KEEPEROFTHEGATE (Mod)
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Where about are you? Anywhere near Isle of Capri?
Quoting Abacosurf:
Still can't believe the amount of people here (Naples)that are taking this storm for granted. They just think it's going to be a little blow comparing this to Wilma. BUT Wilma came in to our south. We had NO surge due to offshore winds. Even if this is a 90 MPH storm and parallels us we will have surge way higher than anything experienced from Wilma. Once this storm is directly west of Naples the naples bay will fill with water due to its north south orientation. The water will pile up in thebay and lead to a 4-6 ft surge. IMO
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When all the models are showing a strong storm..you know we have something on our hands :(.Maybe the U.S will not escape this year major hurricane free.
Member Since: August 14, 2010 Posts: 10 Comments: 16828
Quoting TallyWeather15:
What impact will the Florida big bend get from this storm if it makes landfall near Destin? TS winds in Tallahassee?


Welcome fellow Tally blogger I would say to check www.nws.noaa.gov/tlh they have been really good about keeping us up todate here
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Quoting KeyWestbeachcomber:
I did my Hurricane grocery shop at 11pm last night,beat the crowds who had earlier almost gutted the shelves.I spent 400.American..ALWAYS get sticker shock when I see the total...Well I am ready.I have a BIG bird cage outside that I will cover with a tarp... SO MY CONCERN is STORM SURGE..although I am about 8 ft above sea level here in Old Town.Can anyone give me some input at this time what to expect.Wilma (though a different animal) had the north end of the Island under 5-6 ft of storm surge sea water TWICE during 2 high tides.It was much worse up the keys.Is this likely to happen again? I had never seen it in my 25 years here and really don't want to see it again. Input most appreciated THANK YOU FOR YOUR CONCIDERATION.


From the 2 p.m. update quoted above, SW Florida should expect storm surge of 5 to 7 feet. Also, you should expect heavy rain and winds up to 95 mph.

And of course power outages.
Finally, it's important to try to stay up to date o the latest forecasts and tracks. Good luck! hurricanes can be scarey
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Why does the hurricane hunter graphic page on the Isaac page show 995.8mb/105mph??

http://www.wunderground.com/tropical/tracking/at2 01209_hd.html
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I love Key West, especially Old Town!

Stay safe!
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does anybody find the reposting of NHC advisories and discussions helpful on this blog? is there anybody who doesn't read them on their own? just wondering.
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Quoting justsouthofnola:
48 hours and down to 984 mb

little fast maybe 993 or so in 48 hrs
Member Since: August 1, 2012 Posts: 0 Comments: 254
Quoting KeyWestbeachcomber:
I did my Hurricane grocery shop at 11pm last night,beat the crowds who had earlier almost gutted the shelves.I spent 400.American..ALWAYS get sticker shock when I see the total...Well I am ready.I have a BIG bird cage outside that I will cover with a tarp... SO MY CONCERN is STORM SURGE..although I am about 8 ft above sea level here in Old Town.Can anyone give me some input at this time what to expect.Wilma (though a different animal) had the north end of the Island under 5-6 ft of storm surge sea water TWICE during 2 high tides.It was much worse up the keys.Is this likely to happen again? I had never seen it in my 25 years here and really don't want to see it again. Input most appreciated THANK YOU FOR YOUR CONCIDERATION.


Glad to see you are prepared for this storm; hope your neighbors are also.

I hope someone answers you because I think we need to be discussing this storm's land fall in Key West before we get to excited about it 2nd landfall on the North GOM in 3 days...

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Dbl Post
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1295. LargoFl
Quoting TampaFLUSA:

Look at the previous run, you'll see this run is further east on the GFDL by quite a bit..

i wonder what..is going to cause issac to jump away from the coast of florida? midway up the coast?
Member Since: August 6, 2011 Posts: 4 Comments: 38109
So Euro at 24 hours has Isaac still on the Cuba coastline at 23N 80W. Isaac already N of Cuba coastline. Euro predicting WNW movement, NHC predicting NW movement. Off in the first 24 hours? Can't be good for the rest of the run...
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Quoting Ameister12:
In the WPac, Typhoon Tembin is predicted to hit Taiwan for a second time.

Wow!
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ECMWF has a high-end Category 1 hurricane in 48 hours.
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Quoting TampaFLUSA:

Look at the previous run, you'll see this run is further east on the GFDL by quite a bit..


Improving dosent mean perfect yet though...
Member Since: August 1, 2012 Posts: 0 Comments: 254
For summary sake for people who can't read as fast or don't have the access to the tools some of us do.

The ECMWF, GFS, CMC, NOGAPS, GFDL, HWRF are all showing a formidable hurricane developing from Isaac in the Gulf as it passes through the Keys. Issac has emerged from Cuba per latest satellite and radar images, but do not expect intensification today as Isaac will be working on rebuilding its elongated core from it's ordeal with Haiti and Cuba. After that, intensification at a fairly decent pace is likely. There is little to stop this storm as dry air is a non factor and shear will lessen once Issac's somewhat displaced Upper Level Anti-Cyclone (ULAC) begins to become stacked over it.
Member Since: July 8, 2005 Posts: 259 Comments: 23892
48 hours and down to 984 mb
Member Since: August 6, 2011 Posts: 0 Comments: 226
1287. KEEPEROFTHEGATE (Mod)
531

WHXX04 KWBC 251741

CHGQLM

ATTENTION...NATIONAL HURRICANE CENTER



NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR



TROPICAL STORM ISAAC 09L



INITIAL TIME 12Z AUG 25



DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT

REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD

NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC

OFFICIAL FORECAST.





FORECAST STORM POSITION



HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)



0 19.7 73.9 320./14.9

6 20.6 75.4 302./17.5

12 21.6 76.4 314./13.2

18 22.6 77.8 307./15.8

24 23.5 79.3 301./17.0

30 24.1 80.6 293./13.3

36 24.4 81.6 288./ 9.7

42 24.9 82.6 296./10.0

48 25.6 83.6 309./11.7

54 26.2 84.4 306./ 9.5

60 26.8 85.1 308./ 8.2

66 27.4 85.8 308./ 9.2

72 28.2 86.4 325./ 9.0

78 28.8 86.6 344./ 6.3

84 29.2 86.6 359./ 4.5

90 29.6 86.6 357./ 4.0

96 30.2 86.3 30./ 6.2

102 30.7 85.8 38./ 6.4

108 31.3 85.3 42./ 7.2

114 31.9 85.2 16./ 6.4

120 32.7 85.1 7./ 8.3

126 33.4 85.2 347./ 7.3


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Link
Look here and note the low level clouds spiraling in from all of the WCAR
Member Since: August 1, 2012 Posts: 0 Comments: 254
Euro at 48 HR:

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Quoting muddertracker:


Come on, man. Texas rules. Visit Austin and you won't want to leave.
Yes muddertracker I have visited  Austin a few times and it is a very beautiful and very clean City and I did not want to go back home when I left there. Another town beautiful, clean and fast growing Town in Texas is Katy outside of Houston my brother lives there. Did not want to go back home after visiting Katy too.
Member Since: February 11, 2010 Posts: 0 Comments: 108
Quoting Joshfsu123:
GFDL 12z has already been updated on this map - shifted slightly eastward to landfall near Destin. GFS 12z and HWRF 12z haven't been updated on the map.




And the back and forth continues...
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What impact will the Florida big bend get from this storm if it makes landfall near Destin? TS winds in Tallahassee?
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Quoting Maineweatherguy20023:

A smige west and a tad too strong but otherwise not obscene.

Look at the previous run, you'll see this run is further east on the GFDL by quite a bit..

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In the WPac, Typhoon Tembin is predicted to hit Taiwan a second time.
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Euro passing Tampa off-shore as a 60kts+ storm, with the 50kts sustained radius grazing the shore, but probably not hitting downtown Tampa.
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1278. Dakster
Miami-Dade Schools closed on Monday...
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According to the Associated Press: At least three people were reported dead. A woman and a child died in the Haitian town of Souvenance, Sen. Francisco Delacruz told a local radio station.

A 10-year-old girl died in Thomazeau when a wall fell on her, said Marie Alta Jean-Baptiste, director of Haiti's Civil Protection Office.

She said as many as 5,000 people were evacuated because of flooding, the AP reported.

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Can someone post the link to the EURO? Would be nice to follow.
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Quoting Abacosurf:
Still can't believe the amount of people here (Naples)that are taking this storm for granted. They just think it's going to be a little blow comparing this to Wilma. BUT Wilma came in to our south. We had NO surge due to offshore winds. Even if this is a 90 MPH storm and parallels us we will have surge way higher than anything experienced from Wilma. Once this storm is directly west of Naples the naples bay will fill with water due to its north south orientation. The water will pile up in thebay and lead to a 4-6 ft surge. IMO


NHC website has some areas in SWFL marked for a 9ft surge +/- tides. That's a lot of water...
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1274. robj144
Quoting HurricaneHunterJoe:


Dude, I love your grammar,even better than mine. :)


That's just Taz. By the way, you used a comma instead of a semi-colon. :)
Member Since: August 19, 2008 Posts: 0 Comments: 825
Quoting popartpete:
morning wood??? LOL


I saw this comment and could help but to CRACK UP!!!! LOLOL!!!!!
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NEAR CAT 4
Member Since: April 23, 2011 Posts: 104 Comments: 14873
1271. dader
Quoting Seastep:


TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM FROM THE CENTER.

No buses at 39mph+


I understand. It just seems like they could have waited until tonight/Sunday morning with the uncertainty. Closing schools has an incredible impact- especially for someone who has children in North Dade schools and I am expected to be at work for TS force winds- it's Florida not New England.
Member Since: September 6, 2008 Posts: 0 Comments: 165

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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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