Isaac pounding Haiti and the Dominican Republic with torrential rains

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

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


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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Quoting Chiggy:
GFDL, CMC and now GFS moved WEST of 87.5W, If 12Z EURO shows something similar then NHC probably has no choice BUT to move the cone WEST....


Yep. But it will then move back east again...and so forth....haha!

At some point, the models have to quit flip flopping.
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770. wpb
p3 off today flying out of tampa sunday
noaa jet out thee working
af recon nothing flying now
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Quoting mynameispaul:


Seems to reason if Isaac strengthens the more chance of an easterly track within the cone? Just guessing.


I hope so. I absolutely don't want to be on the east quadrant of Isaac at landfall. Just FYI, I am located just east of Pensacola.
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harder.to.turn.a.heavy.storm?
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Quoting barotropic:


This is what your seeing...LOL

Link



I see what you're talking about. But I am not sure that is the exact center. His center is so broad that it is hard to tell. I think he's still over the coast of NEastern Cuba - moving W/NW.
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Quoting yoboi:


how low did wilma get???



882mb
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GFDL, CMC and now GFS moved WEST of 87.5W, If 12Z EURO shows something similar then NHC probably has no choice BUT to move the cone WEST....
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Quoting Maineweatherguy20023:

Katrinia was 902 and isaac is NOT going down to 918...





you dont no that
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Quoting wolftribe2009:


I think you mean "Kyle"

I pray you will not see a direct hit. I have a friend who used to live in Mississippi and the images from there were horrible. I know a lot think of NOLA when Katrina is mentioned but I remember the images portrayed for those in your area. I can't say that it will hit your area for certain since anything can happen but I don't think it would hurt to move a few things you might really want protected just in case. I wouldn't freak out though and try to remain calm. I know that is going to be hard to do but I do wish for the best for you. I am in South West Georgia. They are predicting a CAT 1 hurricane here. The last storm to do that here caused 6 twisters in my town. I saw one of them pass across the parking lot of the grocery store I worked at in 2004.


Katrina was awful. I got lost trying to get to my home, because every single landmark was substituted by rubble. I am grateful to God because we left the area before it hit and the whole entire family made it well, but Rebuilding can be a very traumatic experience. Thank you for your prayers, and I think your advise is wise I will start moving a few things and keep an eye on things. This will be a sleepless weekend. I just hope it dissipates I do not wish this on no one and wishing it moves to the east makes me feel like an awful person, so I will wish it dissipates.
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Isaac's center does appear to be nearing the northern coast of Cuba already. Right now visible satellite is a better tracking device than the primitive Guantanamo Bay radar.

Rapid-scan Visible Loop
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Well I guess it's time to get to work. I need to sandbag my rental cottage which is flood prone. Ive have those clamshell shutters which are easy to put down and better off down in windy weather anyway....so here goes nothing.
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Link

3 Killed
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Regardless Of the exact path I think all of Florida is going to feel this thing before its over...The wind field is a big one and if it ramps up its gonna be spinning well after land interaction.
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Quoting HurricaneDean07:

If NHC is predicting 100 Mph now...
You should expect borderline 2/3 at landfall... Very BIG situation.
A major is seeming more and more likely.Especially since Isaac will not tangle as much with Cuba like the previous thought was.We had some really close calls these last few years.Will Isaac be the one?.
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Srry if already posted but so far death count in Haiti stands at 3 and Florida is under a state of emergency
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Quoting maeko:
The more I listen to y'all and the more I watch these maps, I am certain the track is going to shift to the East :(


Seems to reason if Isaac strengthens the more chance of an easterly track within the cone? Just guessing.
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Quoting yonzabam:


I'm in the UK and haven't had a problem. Try a different browser? The address is correct.


Thanks That U.K. origin and success at getting on the site are useful to know.
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Quoting 900MB:


Wow! 918MB, that is low!!!!!!

Andrew was 922Mb
Camille 909
Katrina 904

Katrinia was 902 and isaac is NOT going down to 918...
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750. amd
Quoting MiamiHurricanes09:
First time that I get a real good look at the surface circulation: Link.

Correct me if I'm wrong, but am I the only one that is seeing the circulation move from Imias, Cuba in in the southeastern tip, and jog due north to near Baracoa, Cuba, on the northeastern tip over the past 90 minutes? If you speed up the loop sufficiently, you'll see a tight surface circulation executing that motion. Thoughts?


I have seen the same thing as well, and by looking at the GOES-14 One Minute Imagery one can clearly see a slghtly elongated LLC that is just about to leave the coast of Cuba.

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Quoting misscoast:


You must have missed this mornings model runs. I thought there were two that had the storm hitting Louisiana this morning. The HWRF definitely had it on this run.
http://moe.met.fsu.edu/cgi-bin/hwrftc2.cgi?time=2 012082418-isaac09l&field=Sea Level Pressure&am p;hour=A nimation


Outliers. The model clusters are between Mobile, Al. and Panama City, Fl. Latest NHC model is showing Cat 2 at landfall. La. / Ms. is on the far west side of the cone. Could it shift further west? I really don't think so. There are no - I repeat, no - meteorological wild cards that could punch Isaac much further west than Mobile.

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748. etxwx
A reminder for folks new to coastal and inland areas : pay attention to your local warnings – especially surge and flooding potential. Wind is bad but water can be deadly. Wind, heavy rain, flooding and even tornado threats can extend far beyond the landfall area and last for a long time. It’s not like a fast moving thunderstorm: strong winds and heavy rain can last for hours. Never take a tropical storm lightly. Power goes out, water and sewer lines can be compromised; streets can be flooded and littered with debris. It’s not like a movie where it’s all over in 90 minutes, folks. Seriously. Wherever Isaac goes, folks will be dealing with after effects for quite a while. (Example: I live 100 miles north of the Texas coast…Hurricane Ike winds and rain lasted several hours, took out lots of trees, flooded roads, lost power for 5 days, and it was “only” a tropical storm by the time it reached here.)
Don’t dismiss Isaac as “only” a tropical storm or minimal hurricane.
Be prudent, be informed, and be prepared. Take care and I hope everyone stays safe!
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Quoting Articuno:

I disagree.


Whether the naysayers like it or not, Isaac is still at 60 mph. per the 11 a.m., not a weak storm or depression. Should have no problem regaining strength to Hurricane status later tonight as it drifts a bit more north of Cuba. Anyone remember how fast Rita strengthened in the straits?
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Quoting washingtonian115:
Will the U.S go on another year without a major?.Sure will be interesting to see these next few days.

If NHC is predicting 100 Mph now...
You should expect borderline 2/3 at landfall... Very BIG situation.
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12 hours
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Quoting FLWaterFront:


Jedkins, you are mistaken on this one. Punta Gorda was in the cone of uncertainty as Charley approached. However, it was never on the forecast track (that infamous "black line" which the NHC insists upon continuing to use but then warns everyone to "pay no attention to that black line" because it means nothing) and that may be where the confusion comes in.

I remember very clearly that in the immediate aftermath of Charley hitting Punta Gorda, Max Mayfield at the NHC and other forecasters protested that even though the exact forecast track, with Charley making landfall in Tampa, was erroneous but that they had put most of SW Florida including Punta Gorda in the cone of uncertainty. This was suggesting that if people were unprepared it was because they weren't using the forecast products correctly. Also, the whole of the Florida West Coast was in a hurricane warning or watch for more than a day before Charley's arrival.

I have not been able to find it as of yet but just the other day someone here posted the forecast graphics from the NHC for Charley, including the 3 day and 5 day warning maps which show where the cone of uncertainty was. And Punta Gorda was in that cone, just not on the dreaded black line. That black line should be eliminated altogether (as TWC has done) if they don't want people to be mislead by it.



Alright, I don't really remember the cone that well, and I didn't feel like digging out of archives, so you got me, lol.

Anyways though, I agree about the cone issue. I can also see why the NHC uses the center piece of the cone as well. Maybe it would be better to use the black center line in the cone only for meteorologists for symmetry, and for a consensus point, and just remove the black line for the general public because despite how many times people are noted not to focus on the center line, many of them do.

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Quoting BoroDad17:
From what I can see the LLC is right on the N Cuba coastline, and traveling at an angle just slightly North of parallel to the coast line, and will ever so slowly pull away from Cuba. NHC is spot on with their track, at least for the short term.


For a storm where Isaac is the coastline of Cuba goes WNW or NW so he will need some northern motion to escape it.
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741. maeko
The more I listen to y'all and the more I watch these maps, I am certain the track is going to shift to the East :(
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....................GFS at 51 hours
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It appears Isaac is only going to clip Eastern Cuba, and then will be right back out over water in about 6 hours or less. This means much more time over water, and much more time to regorganize and strengthen... I see that the NHC bumped up in the Intensity to what Im forecasting to Hit the Gulf Coast -Category 2- and the Eastern Gulf Coast needs to be on HIGH ALERT as Isaac could intensify further, if given the time to do so.
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Will the U.S go on another year without a major?.Sure will be interesting to see these next few days.
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Quoting MiamiHurricanes09:
I wish I could show you exactly what I'm seeing, but right around the time the advisory was initiated, the circulation seemed to be coming onshore at WNW heading (which the coordinates, as well as the discussion reflected), but if you continue to monitor that same circulation, you can see it heading due north over the past 90 minutes, basically emerging off of the northeastern coast as we speak.


This is what your seeing...LOL

Link

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Quoting MiamiHurricanes09:
First time that I get a real good look at the surface circulation: Link.

Correct me if I'm wrong, but am I the only one that is seeing the circulation move from Imias, Cuba in in the southeastern tip, and jog due north to near Baracoa, Cuba, on the northeastern tip over the past 90 minutes? If you speed up the loop sufficiently, you'll see a tight surface circulation executing that motion. Thoughts?


Yes, it does look like Isaac took a jog more toward the N. We'll see how long this continues.
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HWRF starting to run also.
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Quoting HCW:
I have wood this morning . It's good thing cause some of the stores this morning in the Mobile area are running low if not out of most stuff and forget about finding a generator . Good luck to everybody in the path of this storm :)


I just got on i am right outside of Mobile, Al in Satsuma, has things changed to where it could come this way?

sheri
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Is the 12z GFS out yet?
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Quoting MiamiHurricanes09:
First time that I get a real good look at the surface circulation: Link.

Correct me if I'm wrong, but am I the only one that is seeing the circulation move from Imias, Cuba in in the southeastern tip, and jog due north to near Baracoa, Cuba, on the northeastern tip over the past 90 minutes? If you speed up the loop sufficiently, you'll see a tight surface circulation executing that motion. Thoughts?

That's one heck of a link, lol.
I agree with you though, looks like a northward jog.
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Quoting HCW:
I have wood this morning .


Alllllrighty then.

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Quoting NICycloneChaser:


I was thinking exactly the same thing. I think he's emerging off of Cuba.
I wish I could show you exactly what I'm seeing, but right around the time the advisory was initiated, the circulation seemed to be coming onshore at WNW heading (which the coordinates, as well as the discussion reflected), but if you continue to monitor that same circulation, you can see it heading due north over the past 90 minutes, basically emerging off of the northeastern coast as we speak.
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Quoting MiamiHurricanes09:
First time that I get a real good look at the surface circulation: NRLMRY Visible Loop.

Correct me if I'm wrong, but am I the only one that is seeing the circulation move from Imias, Cuba in in the southeastern tip, and jog due north to near Baracoa, Cuba, on the northeastern tip over the past 90 minutes? If you speed up the loop sufficiently, you'll see a tight surface circulation executing that motion. Thoughts?


I agree is right at the coast with deeper convection trying to build to the East.

Here's the Rapid Scan Sat Image.
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Quoting wpb:
a recon would have trouble finding 40 mph winds now


Guantanamo radar would disagree. There are severe thunderstorms much stronger than 40mph in the bands on the radar.



While some of the bands have lost a bit of reflectivity over the past half-hour, the band just NE of the CoC is re-intensifying now.

Note:

On this radar, yellow is more powerful than orange. The color scale is reversed to avoid your eye mixing up boundaries of red and orange.
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Quoting Grothar:
I've got the runs again.


STAWP it! [as Press would say... lol]
Quoting weatherh98:


Moving slow
This is the scenario that caused the problems w/ Debbie...
Quoting flcanes:

that spells tampa under water
This has always been the biggest concern for Tampa with this storm, IMO...
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Quoting MiamiHurricanes09:
First time that I get a real good look at the surface circulation: Link.

Correct me if I'm wrong, but am I the only one that is seeing the circulation move from Imias, Cuba in in the southeastern tip, and jog due north to near Baracoa, Cuba, on the northeastern tip over the past 90 minutes? If you speed up the loop sufficiently, you'll see a tight surface circulation executing that motion. Thoughts?



your spot on he prolly wont refrom north he will just not hug the coast as tight
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isacc.twin.brother..yikes
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Quoting LargoFl:
yes and traveled all along the northern gulf into texas geez..i sure hope THAT model is wrong


WOW. Ok, it wasn't just my imagination. With the path this storm has taken, I thought I was maybe just loosing my mind haha
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather