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

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 671 - 621

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Quoting flcanes:

there are millions of lives in the balance
by the way, how many dead in haiti yet

I think the count now is 3. Might seem low but that's still horrible.
Not sure I could be wrong.
Member Since: Posts: Comments:
Quoting tennisgirl08:


Nice update, Levi.

Your track seems further east than latest GFS and even NHC track. Can you explain your reasoning behind this? I tend to agree with your track, although a little farther west closer to Panama City.

Thanks!


I'm pretty close to the consensus now (at least before the 12z GFS), just a tad to the east. A track like the 12z GFS still looks fishy to me, as it hasn't happened in 170 years since track records began, but you can't really say never with the weather.

The track has had to shift east in bits for the last couple of days, and we just saw the models flop on the 24-hour forecast due to the Caribbean mountains, so some things can still happen to the forecast in a span of 3 days. We'll see.
Member Since: December 31, 1969 Posts: Comments:
Quoting WPBHurricane05:
Looks like Isaac is about to exit Cuba. Still traveling NW.


I think its moving btw 315 and 320 maybe like 318 JMO
Member Since: Posts: Comments:
Quoting cabice:
Hard to follow and help me if I'm wrong, but it looks like it's headed north or NNW.



According to NHC at last report, Isaac was moving NW. Some on this board have it hugging the Cuban coastline which is dead wrong. Isaac may be reorganizing more to the north and east giving an appearance of a northerly movement, in my opinion.
Member Since: Posts: Comments:
this is from 2am this run..but did you see what happened?
Member Since: December 31, 1969 Posts: Comments:
Quoting GTcooliebai:
150 hrs. and Isaac is inland and flooding will be a major problem. Also here comes Kirk, so coffee will remain in the pot for the late nighters.



With that setup... the future disturbance will surely end up in the W / NW Carib.
Member Since: Posts: Comments:
nw.it.seems..dang
Member Since: Posts: Comments:
664. wpb
big guy looking weak not sure he can regain.
Member Since: December 31, 1969 Posts: Comments:
Please someone correct me. Did the GFS changed to the west? Seriously I need lost everything during Katrina and I am getting sick of my stomach now. Is this thing going to hit Mississippi. I just cannot go tru this again. Someone give me an educated guess so I can start moving the few things I do not want destroyed.
Member Since: Posts: Comments:
Quoting allancalderini:
And the last veteran of the I.
Yep.Seems it don't wanna be on the list anymore.
Member Since: Posts: Comments:
Quoting AllyBama:


smart professor! do you study at South? if so, you may have come into the bank to see me a time or two.



I use to come into your bank all the time till i moved. Use to bring my little girl in with me. Moved over to west mobile though earlier this year.


I think the models are having trouble figuring out how strong the trough will be to lift the storm north. A weaker trough means more towards MS/AL. A stronger one takes it further east towards Panama City
Member Since: December 31, 1969 Posts: Comments:
Quoting Grothar:


Grothar, we are wet here on Broward! Seems like the storm started hitting us last night..
oh I forgot , it did! Lo)


Wonder how bad our winds will get Sunday afternoon with the storm off Key West???
Member Since: Posts: Comments:
Looks like Isaac is about to exit Cuba. Still traveling NW.
Member Since: Posts: Comments:
NRL NEXSAT

Great animation of Issac crossing over Haiti. You can see how disruptive the mountains were to his circulation. I am interested to see how much his wind field will expand as he expands then contracts again.
Member Since: December 31, 1969 Posts: Comments:
150 hrs. and Isaac is inland and flooding will be a major problem. Also here comes Kirk, so coffee will remain in the pot for the late nighters.

Member Since: December 31, 1969 Posts: Comments:
Quoting Levi32:
Good morning.

Blog update:

Tropical Tidbit for Saturday, August 25th, with Video


Ahh your new track forecast is now west of my thinking...which means I might need to re-evaluate things haha. I am concerned that several models have now followed the HWRF in forecasting rapid intensification in the SE-ern Gulf of Mexico.
Member Since: December 31, 1969 Posts: Comments:
Quoting washingtonian115:
If that were to pan out instant retirement off the back and that will be the 3rd year in a row the "I" storm has joined the list.
And the last veteran of the I.
Member Since: Posts: Comments:
Quoting Jedkins01:



Punta Gorda wasn't in the cone as Charley approached.


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.
Member Since: Posts: Comments:
Quoting flcanes:

ehh, maybe a bit west


I would agree with you but the models keep flip flopping back and forth.
Member Since: December 31, 1969 Posts: Comments:
Quoting barotropic:
LLC about to exit NE tip of cuba appears on the move again after just spinning last couple of hours.....pretty visible see link.

Link


j

again, this is ver bad
Member Since: December 31, 1969 Posts: Comments:
The models are performing really poor even still with Isaac, however the chances of it being significant for my area and the RNC are decreasing once again, thanks to the models insistence on the ridge in the Atlantic quickly building back over Florida before it has a chance to curve farther right. I must the pressure gradient over Florida is rather strong right now. Which isn't typically what one would expect from a weakness between a high when a storm is approaching from the direction Isaac is.


While I have insisted on a Central or Eastern Panhandle or eastern panhandle landfall after first striking the keys with tropical storm force winds for the Tampa Bay area. Some of the new guidance like the new GFS suggests this area won't get anything now except breezy winds and showers and thunderstorms from tropical moisture, which is normal weather for this time of year anyway.


However a lot can still change, if I was the NHC, I would have my track further west where they have it for the sake of people, however since i am no weather authority I'm sticking with a central and eastern panhandle landfall for now just because I have doubted the ridge will rebuild in time because there is often a delay in time regarding model tendency for change in pressure systems. Of course that isn't always the case, but it often is.

Member Since: Posts: Comments:
Quoting chrisdscane:



could SE FL still see a direct hit
Not very likely. We'll see how it interacts with the mountains of Cuba throughout the remainder of the day.

Basically a northern Keys landfall seems most likely to me, and if you do live in SE FL, prepare for what I highlighted in my previous post: 40-50mph winds with gusts to 75mph on Sunday evening.
Member Since: Posts: Comments:
Member Since: December 31, 1969 Posts: Comments:
Quoting MiamiHurricanes09:
9mb stronger than the previous run. Major hurricane.



Says at the bottom GFS PMSL, so I wouldn't take it seriously.
Member Since: Posts: Comments:
dont know why NHC see's a western jog doesnt look like it to me
Member Since: Posts: Comments:
Quoting Chiggy:
... just as we thought we had a track consensus! 12Z GFS solution begs me to ask a question - can Issac go even further WEST?


I don't think so. The models seem to like MS/AL all the way to PCB area in Florida.

The GFS hasn't shown a run into LA or MS/LA for several days now.
Member Since: December 31, 1969 Posts: Comments:
Quoting MiamiHurricanes09:
Where's Nrt lol?


LOL yeah
Quoting reedzone:


I don't think he's dissing Levi, might be dissing me cause I made a bold statement that Isaac would not cross 85W.. I'm still in good confidence that the storm will recurve at 85W and not pass it. I don't see how storms bust through a developing ridge. I can see it busting through a banana type ridge where the ridge could split, but not a corner of a developing ridge. Isaac remains moving NW towards the East Coast of Florida for now, and because of the uncertainty in track and the size of the storm, Tropical Storm watches have been issued all the way up to Flagler Beach, which is Northeastern FL.


I have to agree... with Isaac not crossing 85W, but time will tell. :)
Member Since: Posts: Comments:
Quoting tennisgirl08:


Good to hear. I think Panama City, FL will be a good place to be.

ehh, maybe a bit west
Member Since: December 31, 1969 Posts: Comments:
LLC about to exit NE tip of cuba appears on the move again after just spinning last couple of hours.....pretty visible see link.

Link


j
Member Since: December 31, 1969 Posts: Comments:
Quoting hurricane23:
In terms of miami dade and broward thus far iam likeing the 12z model trends which are further south into lower keys. Bamd is now an outlier.
I'm still in the northern Keys camp primarily based on the fact that it shouldn't spend much time over Cuba, thus allowing for some decent intensification between now and then. Could see it going further south though -- regardless, the threat for 40-50mph winds with gusts to 75mph remains across south Florida.
Member Since: Posts: Comments:
Quoting Chiggy:
... just as we thought we had a track consensus! 12Z GFS solution begs me to ask a question - can Issac go even further WEST?


Yes, although I'd say SE LA is probably the farthest it could make it.
Member Since: Posts: Comments:
RECON's Flight later

I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ISAAC
FLIGHT ONE --TEAL 72
A. 25/1800Z,26/0000Z
B. AFXXX 1609A ISAAC
C. 25/1530Z
D. 20.0N 76.3W
E. 25/1730Z TO 26/0000Z
F. SFC TO 10,000 FT

Member Since: Posts: Comments:
Quoting GTcooliebai:
Like I told you last night we wait to see how it looks as it crosses the Keys, but I'm feeling better right now that we will escape the worst Isaac has to offer, based on the trends by the GFS and the Euro.

that though could hurt others
mot to mentio, isaac has an enourmous wind field that will only ballon in the gulf even more
Member Since: December 31, 1969 Posts: Comments:
Quoting StormJunkie:
Just wanted to run a quick update. The Portlight Disaster Relief Team will be pre-deploying to Panama City (tentative location) tomorrow in order to be in position for any response that is needed for potential Hurricane Isaac's landfall along the Gulf Coast. We will be running the live webcam as much as cell coverage permits during our relief efforts starting tomorrow. I will be in out of the blog today since I am pretty busy getting ready, but please look for updates from presslord, myself, and other team members as the day progresses.



Good to hear. I think Panama City, FL will be a good place to be.
Member Since: December 31, 1969 Posts: Comments:
Quoting drs2008:
i keep thinking that since i live in biloxi,we are ok. But i guess thats not true.
everyone needs to watch this storm all around the gulf this week..you just never know
Member Since: December 31, 1969 Posts: Comments:
Quoting LargoFl:
yeah this storm is going to hit very populated area's

there are millions of lives in the balance
by the way, how many dead in haiti yet
Member Since: December 31, 1969 Posts: Comments:
... just as we thought we had a track consensus! 12Z GFS solution begs me to ask a question - can Issac go even further WEST?
Member Since: Posts: Comments:
Quoting LargoFl:
yes tomorrow morning will be the good advisory, especially for tampa
Like I told you last night we wait to see how it looks as it crosses the Keys, but I'm feeling better right now that we will escape the worst Isaac has to offer, based on the trends by the GFS and the Euro.
Member Since: December 31, 1969 Posts: Comments:
Quoting StormJunkie:
Just wanted to run a quick update. The Portlight Disaster Relief Team will be pre-deploying to Panama City (tentative location) tomorrow in order to be in position for any response that is needed for potential Hurricane Isaac's landfall along the Gulf Coast. We will be running the live webcam as much as cell coverage permits during our relief efforts starting tomorrow. I will be in out of the blog today since I am pretty busy getting ready, but please look for updates from presslord, myself, and other team members as the day progresses.



Thanks for the update SJ...becareful and praying that NO ONE needs your help this go around!
Member Since: Posts: Comments:
Member Since: December 31, 1969 Posts: Comments:
Quoting LargoFl:
yes indeed
i keep thinking that since i live in biloxi,we are ok. But i guess thats not true.
Member Since: Posts: Comments:
Quoting schistkicker:
Hmmm... a large, broad, lumbering Cat-2 "I"-storm tracking into the Gulf coast... where have I seen this before?

I sure hope that GFS model run doesn't pan out.


did you mean Hurricane Ivan? I don't remember if it was slow but I know it hit as a CAT 3. It did a number of the florida panhandle.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Where's Nrt lol?



could SE FL still see a direct hit
Member Since: Posts: Comments:
Hard to follow and help me if I'm wrong, but it looks like it's headed north or NNW.
Member Since: Posts: Comments:
Quoting flcanes:
nhc is really worried
yeah this storm is going to hit very populated area's
Member Since: December 31, 1969 Posts: Comments:
In terms of miami dade and broward thus far iam likeing the 12z model trends which are further south into lower keys. Bamd is now an outlier.
Member Since: Posts: Comments:
Quoting reedzone:


I don't think he's dissing Levi, might be dissing me cause I made a bold statement that Isaac would not cross 85W.. I'm still in good confidence that the storm will recurve at 85W and not pass it. I don't see how storms bust through a developing ridge. I can see it busting through a banana type ridge where the ridge could split, but not a corner of a developing ridge. Isaac remains moving NW towards the East Coast of Florida for now, and because of the uncertainty in track and the size of the storm, Tropical Storm watches have been issued all the way up to Flagler Beach, which is Northeastern FL.


Winds so far north are not just because of size of storm....its because of the gradient between the storm and the strong ridge to its north thats likely going to protect and steer Isaac south of florida and even possibly the keys. IMO only of course.
Member Since: December 31, 1969 Posts: Comments:
Quoting MAweatherboy1:
This cannot be stated enough times.


IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.
yes indeed
Member Since: December 31, 1969 Posts: Comments:
levi any clue which way isaac is moveing atm
Member Since: Posts: Comments:
Quoting tennisgirl08:


Well, Debby recurved. But I think Isaac will move further west because of timing.
I meant to say recurve out in the Atlantic. Ernesto and Isaac are examples of waves that came off the coast of Africa and did not recurve east of the US.
Member Since: December 31, 1969 Posts: Comments:

Viewing: 671 - 621

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Top of Page

Category 6™

About

Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather