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: 471 - 421

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 Clearwater1:


Quoting Jedkins01:



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

*****
SE FL wasn't in the cone as Wilma Approached either.
*****

Exactly. Nice we have long range radar, out of Tampa and Key west to watch it's progress off shore. See if it is indeed heading nw as it gets closer.
I believe S. FL was in the five day cone. They were pretty accurate on that one.
Member Since: Posts: Comments:
Quoting UWalkTheMall:


Peeling????

it's a joke
Member Since: Posts: Comments:
Quoting washingtonian115:
In the location Isaac will be making landfall it reminds me of Ivan.

nahhh, further east
Member Since: Posts: Comments:
Quoting weatherh98:


EYES PEELING


Peeling????
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting weatherh98:


Moving slow

oh no
Member Since: Posts: Comments:
In the location Isaac will be making landfall it reminds me of Ivan.
Member Since: Posts: Comments:
Quoting stormpetrol:
To my eye the center of Isaac looks to half on shore , half offshore on the SE coast of around 19.9/20N 74.9/75W , barely moving at all.

more like the ne coast to me
Member Since: Posts: Comments:


Moving slow
Member Since: Posts: Comments:
tropical storm watch all the way up to daytona on the east coast..see its a huge storm..in area
Member Since: Posts: Comments:
Quoting JasonRE:


Yeah, guess I'm just tired of this storm showing models that flip flop from night to day. Last night I started thinking about sand bags bc we flooded after 3 hours of rain 2 weeks ago, and this morning I'm thinking not so much.

I would assume this is because Isaac has changed from day to night. Blah during the day and partying it up at night. LOL!
Member Since: Posts: Comments:
Quoting presslord:



you'll be glad to know: Stormjunkie is about to drive me insane pestering me about making sure we have plenty of bug spray when we deploy....my guess is he put you up to posting this....


LOL, I posted something about it last night and he plussed my comment..I guess I put the idea out there for him
Member Since: Posts: Comments:
Quoting weatherh98:


EYES PEELING

nooooooooooooooooooooooo
Member Since: Posts: Comments:
To my eye the center of Isaac looks to half on shore , half offshore on the SE coast of around 19.9/20N 74.9/75W , barely moving at all.
Member Since: Posts: Comments:
Quoting JasonRE:


Yeah, guess I'm just tired of this storm showing models that flip flop from night to day. Last night I started thinking about sand bags bc we flooded after 3 hours of rain 2 weeks ago, and this morning I'm thinking not so much.

watch 18z later on
Member Since: Posts: Comments:
Quoting TomballTXPride:

Further west, slower, and more intense.


EYES PEELING
Member Since: Posts: Comments:
GFS came in even further south. Seems like ridge is going to be building in fairly well. I wonder if Isaac may slide south of key west.
Member Since: Posts: Comments:
Quoting flcanes:

hey now, this would really get it retired
yeah maybe, with its unusuall track it may make the history books..storms this late in season usually go to texas and LA area..not up the west coast of florida all the way up
Member Since: Posts: Comments:
Northeastern/central Gulf coast should be preparing for a category 3 to 4 major hurricane making landfall this week.

Member Since: December 31, 1969 Posts: Comments:
Quoting weatherbro:
The center is located just wnw of the eastern tip of Cuba so it being ripped apart is totally out of the question.

Since the Bermuda ST Ridge is displaced well to the east, why do some models still insist it entering the Gulf???

Because the high is building in, which will gradually curve it west-northwest.
Member Since: Posts: Comments:
Quoting WeatherNerdPR:

He's probably crying because they discontinued the TS Watch for the Caymans. :P


It was still in effect at 10.58 AM EST today
Member Since: Posts: Comments:
Quoting barotropic:


Low level circulation appears to be over eastern tip of cuba....seems to be actually moving slower last couple of hours

Link

that's a mixed bag
it's good that isaac will get weakened by mountains but...
it's bad once it gets over the straights
Member Since: Posts: Comments:
Quoting SELAliveforthetropic:


Houma here.... We all should know that you never ever take your eye off of any that may get in the gulf....


Yeah, guess I'm just tired of this storm showing models that flip flop from night to day. Last night I started thinking about sand bags bc we flooded after 3 hours of rain 2 weeks ago, and this morning I'm thinking not so much.
Member Since: Posts: Comments:
66 hrs.

Member Since: Posts: Comments:
West
Member Since: Posts: Comments:
Quoting Grothar:
I've got the runs again.


You know they make something for that...
Member Since: Posts: Comments:
Quoting Grothar:
I've got the runs again.



Need some Bitters ?
Member Since: Posts: Comments:
Quoting presslord:



you'll be glad to know: Stormjunkie is about to drive me insane pestering me about making sure we have plenty of bug spray when we deploy....my guess is he put you up to posting this....


lol, well i know he didn't put me up to posting this, but boy oh boy is it one of the first and most important things i keep stocked in my supply kit!!!!!
Member Since: Posts: Comments:
The center is located just wnw of the eastern tip of Cuba so it being ripped apart is totally out of the question.

Since the Bermuda ST Ridge is displaced well to the east, why do some models still insist it entering the Gulf???
Member Since: Posts: Comments:
60 hrs.

Member Since: Posts: Comments:
Quoting LargoFl:
hmmm the storm is 250 miles wide someone posted..from tampa to daytona is only 132 miles..if it comes within 50 to 100 miles of tampa..daytona will be getting its winds and rains as well...huge storm folks in area, most of florida will indeed get something out of this ..and tampa eastward..all on the Bad side of this storm..it could throw off tornado's up and down the east coast of florida..as the melbourne nws said a few days ago..everyone prepare and stay safe

hey now, this would really get it retired
Member Since: Posts: Comments:
Quoting E46Pilot:
Are you guys seeing a very prominent NNW movement like I am?


Low level circulation appears to be over eastern tip of cuba....seems to be actually moving slower last couple of hours

Link
Member Since: Posts: Comments:
Please put info along with maps/images so we know what we are looking at. I come to this blog to learn about dangerous weather and I have learned allot. It would sure help my education to understand the illustrations posted. Thank you to all of you that are here for our safety & well being. We sure appreciate it.
Member Since: Posts: Comments:
Hey all....

Either including or not including this current (what looks to be a legitimate landfall in Cuba) landfall/strike, how many landfalls/strikes has Isaac had thus far? Was trying to read back for a "at 0600 UTC Isaac made landfall on the island of"... but haven't seen that wording yet... anyone know?
Member Since: Posts: Comments:
GFS at hour 54 even more west
Member Since: Posts: Comments:
Quoting ncstorm:
If you are in the future impact zones, please get some mosquito repellant as one of your supply item..with the flooding expected from Isaac and standing water around for some days will tend to bring out the mosquitos in full force..the west nile virus is at epidemic levels and you dont need to chance it without having some protection to fight them off



you'll be glad to know: Stormjunkie is about to drive me insane pestering me about making sure we have plenty of bug spray when we deploy....my guess is he put you up to posting this....
Member Since: Posts: Comments:
Quoting wpb:
looking weak shear from nw carb mountains put him on one knee

nope, isaac hasn't weakened in 6 hrs, bad sign of things to come
Member Since: Posts: Comments:
hmmm the storm is 250 miles wide someone posted..from tampa to daytona is only 132 miles..if it comes within 50 to 100 miles of tampa..daytona will be getting its winds and rains as well...huge storm folks in area, most of florida will indeed get something out of this ..and tampa eastward..all on the Bad side of this storm..it could throw off tornado's up and down the east coast of florida..as the melbourne nws said a few days ago..everyone prepare and stay safe
Member Since: Posts: Comments:
Quoting Grothar:

Very heavy convection entering Hispaniola right now.

Not good at all.
Member Since: Posts: Comments:
Quoting flcanes:

ri alert



Not rewlly
Member Since: Posts: Comments:
Quoting MarcoIslandCat5:
So what kind of surge can we expect here? Getting worried now


Check out the Collier County Storm Surge page for projected surge for different areas:

Link
Member Since: Posts: Comments:
Quoting RTSplayer:

So what's gonna happen when that upper level anticyclone in the NWGOM meets up with that low coming into the GOM from the East later on today?
Member Since: Posts: Comments:
I've got the runs again.


Member Since: Posts: Comments:
Quoting Grothar:


Isaac's saying, 'gimme some a dat!'

Quoting wpb:
looking weak shear from nw carb mountains put him on one knee

Isaac would like a piece of that trough to its north. not funny
Member Since: Posts: Comments:
I'm tired of the media getting it wrong with the storms. IT'S A TROPICAL STORM, not Hurricane Isaac... jesus.
Member Since: Posts: Comments:
Quoting 892mb:


Only "free" to subscribers - HA!!

bastardi is almost always wrong lol
Member Since: Posts: Comments:
422. wpb
looking weak shear from nw carb mountains put him on one knee
Member Since: Posts: Comments:
Quoting GTcooliebai:
48 hrs.


ri alert
Member Since: Posts: Comments:

Viewing: 471 - 421

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