Isaac pounding Haiti and the Dominican Republic with torrential rains

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

Share this Blog
48
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

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

Viewing: 1521 - 1471

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 cchsweatherman:


Channel 10 News' website is reporting breaking news that schools have been closed for both Broward and Miami Dade counties, but have seen no confirmation whatsoever on the official Broward Schools website.
Confirmed; press conference by the superintendent just finished right now.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
1520. robj144
Random comment: I don't know if anyone was watching CNN a few years ago, but Chad Myers called the Cone of Uncertainty, the Cone of Unsurednessness. :) That guy's a straight up idiot, I'm sorry to say.
Member Since: Posts: Comments:
the weather CH needs new tv ads
Member Since: May 21, 2006 Posts: 5091 Comments: 114917
1517. maeko
Quoting chrisdscane:


what?


The coordinates changed .7 degrees North and .7 degrees W since the 11am posting. Equally North and West...I thought there would be a slightly greater northward movement.
Member Since: Posts: Comments:
Quoting seflagamma:
I just checked again and NO MarcoIslandCat5

Broward County schools are still scheduled to be OPEN on Monday...

it may change later but as of now that is the official word...

unless you have a link that has not gone public yet.




Just announced closed monday for broward schools.
Member Since: Posts: Comments:
1514. dmh1026
Just goes to show that you can't trust models....
Quoting Drakoen:
wow on the ECMWF lol. Interesting to see the ECMWF come this far east after it had been hanging on to a western solution.
Member Since: Posts: Comments:
1513. scott39
Quoting Michfan:


Yeah that's why i posted that. I know that you know but some people don't understand why they tend to flip flop like that.
Gotcha:)
Member Since: June 13, 2009 Posts: 0 Comments: 6750
Quoting Levi32:
And look at the recurve into the Carolinas. The pattern and history strongly support this track. Nothing is guaranteed though.

Usually once the ECMWF corrects within 3 days of landfall it has corrected the "correct" way.



I put so much stock in the ECMWF, I really wasn't too concerned until now. We have been pounded with rain for the last 3 weeks on the Georgia coast, and if this verifies it could mean a major flooding event. It doesn't help that Isaac will be passing by during large spring tides.

And I had just been content with lurking like I always do...
Member Since: Posts: Comments:
Quoting MississippiWx:


Cuba is holding onto Isaac for now.
Isaac is leaving the coast now
Member Since: Posts: Comments:
Quoting Tazmanian:



its all ready back in too open water



looks like nnw
Member Since: July 21, 2010 Posts: 0 Comments: 1118
1509. Michfan
Not good. Looks like the SMFR broke. Hope they get it working again. Last few points have it blank.
Member Since: Posts: Comments:
1508. wpb
not sure how close recon can get to cuban north coast
Member Since: Posts: Comments:
Quoting cchsweatherman:


Channel 10 News' website is reporting breaking news that schools have been closed for both Broward and Miami Dade counties, but have seen no confirmation whatsoever on the official Broward Schools website.
looking at the RGB? visible the center is starting to get going with convection forming on the NE side. how do you see things currently
Member Since: Posts: Comments:
It is very unsettling that the models have still not come into better agreement - and we are only 3-4 days out from a possible landfall on the Northern gulf coast.

The GFS is known for picking up on troughs the best. I think the latest run (12Z) may be a little suspect...but if the GFS still shows west on the next run then we can bet that the trough is not eroding the ridge much and should push Isaac more westward.

At some point, something's gotta give. These models have to come into agreement at some point.
Member Since: Posts: Comments:
For those who are wondering if they are "out of the woods" due to the change in the Euro, ask yourself this...."are you still in the cone of uncertainty?". If you are, you are not in the clear. These things will change from run to run.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting MississippiWx:


Cuba is holding onto Isaac for now.



its all ready back in too open water
Member Since: May 21, 2006 Posts: 5091 Comments: 114917
1502. robj144
Regardless of the intensity and how close the closest approach to FLA will be, south FLA is going to get a huge amount of flooding from this storm. It's not going to be pretty.
Member Since: Posts: Comments:
Quoting charlottefl:
Can see it even better here:



Cuba is holding onto Isaac for now.
Member Since: Posts: Comments:
1500. Michfan
Quoting scott39:
I know its nothing new. I made my point very clear in my post. Whatever model is more E of the NHC will be the crowned king for that run. But if it changes on the next one.... it all of a sudden sucks!


Yeah that's why i posted that. I know that you know but some people don't understand why they tend to flip flop like that.
Member Since: Posts: Comments:
Quoting seflagamma:
I just checked again and NO MarcoIslandCat5

Broward County schools are still scheduled to be OPEN on Monday...

it may change later but as of now that is the official word...

unless you have a link that has not gone public yet.




Channel 10 News' website is reporting breaking news that schools have been closed for both Broward and Miami Dade counties, but have seen no confirmation whatsoever on the official Broward Schools website.
Member Since: Posts: Comments:
Did SFMR break on HH?
Member Since: Posts: Comments:
1497. Bielle
Quoting Seastep:


Now THAT is premature.


Schools are often also shelters. Shelters are difficult to get up to operating speed on short notice. So, schools have to be closed in ample time for people to know what is coming and to get organized and out to them.
Member Since: Posts: Comments:
1496. scott39
Quoting Michfan:


00Z and 12Z are almost always more poleward than the 18Z and 06Z are because the 18Z and 06Z are extrapolated where the other two are not. We've seen this happen with them flip flopping many times over the years. Its nothing new. Get used to it. Intensity of the storms is a huge factor as to where they will go and models do not predict intensity well at all. The HWRF is probably the best at it.
I know its nothing new. I made my point very clear in my post. Whatever model is more E of the NHC will be the crowned king for that run. But if it changes on the next one.... it all of a sudden sucks! Lol
Member Since: June 13, 2009 Posts: 0 Comments: 6750
Quoting maeko:
Equal N and W movement since 11am...how long will that keep up?


what?
Member Since: July 21, 2010 Posts: 0 Comments: 1118
Quoting washingtonian115:
Can you post the run?.


I will as soon as it's finished updating.

It's only on 168 hours right now, and should go to 240.
Member Since: Posts: Comments:
Can see it even better here:

Member Since: Posts: Comments:
Quoting tennisgirl08:


Agreed. I believe Isaac is a huge panhandle threat...mostly Destin/FWB/Panama City area.

I am sticking with that for now.

Despite climatology, I am not buying the Euro's far east movement now.


Well Euro has landfall right in the area you just mentioned, just recurves east instead of straight north as the other iterations have shown.
Member Since: Posts: Comments:
Well this is interesting huh. On one hand, the GFS and Euro have swapped solutions and that has got to be making the NHC scratch their heads a little. On the other, that makes it 4 consecutive runs with the model consensus being to the west of my track reasoning, and the general middle point of the guidance continues to be an impact on the Florida Keys, offshore of the W-ern coast of Florida with a final landfall between Mobile Bay and Panama City.

I will lean towards the eastern guidance for now (blend of GFDL and latest ECMWF), but any major center jogs or contrasting data from the G-IV planes could throw another wrench into it. But at this point, I'll go with a track around 50-75 miles offshore of Cuba paralleling the coast (moderate TS intensity), on through the Upper Keys (reaching Category 1 strength) and grazing SW Florida, before gradually turning NNW and N over the extreme E-ern Gulf of Mexico (intensifying to a Category 2 or 3 hurricane) and making a final landfall between Panama City and Apalachicola as a Category 2 storm.
Member Since: Posts: Comments:
1490. JLPR2
Quoting SLU:
25/1800 UTC 14.7N 32.2W T1.5/1.5 97L -- Atlantic


SHOWERS AND THUNDERSTORMS REMAIN DISORGANIZED IN ASSOCIATION WITH A
BROAD AREA OF LOW PRESSURE
LOCATED ABOUT 400 MILES WEST-SOUTHWEST
OF THE CAPE VERDE ISLANDS. SLOW DEVELOPMENT OF THIS SYSTEM IS
POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE
WEST-NORTHWEST AT 10 TO 15 MPH. THIS SYSTEM HAS A MEDIUM
CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

This system is better developed than the NHC thinks ....




Agreed, but it seems the problem lies on where the NHC thinks the center is.

AL, 97, 2012082518, , BEST, 0, 134N, 315W, 25, 1006, DB
Member Since: Posts: Comments:
I wonder if there is any other news From Haiti Hispanola, thats alot of rain in a very short period of time.If anyone has a link or news on there dire situation pst me.
Member Since: Posts: Comments:
1488. Hhunter
Quoting StormSurgeon:


Absolutely not. Keep a close eye on this storm.
bama not out of woods. In fact direct hit still possible...
Member Since: Posts: Comments:
97L looks good


Member Since: May 21, 2006 Posts: 5091 Comments: 114917
Quoting Drakoen:
Indeed, we are in the range that the ECMWF is know for. Still thinking that Issac will be a panhandle landfall.


Agreed. I believe Isaac is a huge panhandle threat...mostly Destin/FWB/Panama City area.

I am sticking with that for now.

Despite climatology, I am not buying the Euro's far east movement now.
Member Since: Posts: Comments:
I don´t wanna be alarmist..but people of florida please get ready for the worst just in case...Isaac COC passed 50 mile of my country Dominican Republic and just passed like a strong TS... this storm is large and WINDS EXTEND OUTWARD UP TO 205 MILES!!!

Member Since: Posts: Comments:
Quoting MississippiWx:


European is Central Panhandle, not GFS. Lol. GFS went to MS/AL for some reason.
Dammit, y'all confusing me with the models. hahaa
Member Since: September 2, 2009 Posts: 130 Comments: 21109
THERE IS RECON AF303 HEADING INTO ISAAC...THEY ARE ABOUT 95 MILES AWAY FROM THE CENTER
Member Since: Posts: Comments:
It's funny how all the FLorida people bad mouthing the EURO model


Ya probably shouldn't speak in absolutes, unless you're an absolute moron.
Member Since: Posts: Comments:
1481. maeko
Equal N and W movement since 11am...how long will that keep up?
Member Since: Posts: Comments:
Quoting RTSplayer:
Euro makes "K" and "L" within 6 days, though "K" looks fishy for now, and "L" looks like a redo of Isaac...

CAn you post that please? my flash player thingy is not working :( all imagry Ive gotten has been from here. And I REALLY don't want an isaac redo bad for Haiti
Member Since: August 1, 2012 Posts: 0 Comments: 252
.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting RTSplayer:
Euro makes "K" and "L" within 6 days, though "K" looks fishy for now, and "L" looks like a redo of Isaac...
Can you post the run?.
Member Since: August 14, 2010 Posts: 10 Comments: 16756
I just checked again and NO MarcoIslandCat5

Broward County schools are still scheduled to be OPEN on Monday...

it may change later but as of now that is the official word...

unless you have a link that has not gone public yet.


Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
So now the GFS is thinking central Florida panhandle. Nice.

Give up the crown to the GFS, Europe. ;)


European is Central Panhandle, not GFS. Lol. GFS went to MS/AL for some reason.
Member Since: Posts: Comments:
Alabama is definnitely no in the clear. We are in the cone and therefor I am getting my ducks in a row just in case.
Member Since: Posts: Comments:
Quoting catastropheadjuster:
So can Alabama breathe a sigh of relief know, since everything is pointing to Florida. I don't wish no harm to Florida. Just trying to figure out what we need to do. We have 2 boats off the trailors on stands in the air working on them and if by chance it might come this way we need to get them down and batten down the shop and tell folks to come get there boats.


sheri


Remember the size of the storm. If Isaac is still 500+ miles across at landfall, then Alabama is still very much in the risk zone.
Member Since: Posts: Comments:
Quoting bigeasystormcaster:
You are right! Also I am a NOLA Lender!


Nola here too.
Member Since: Posts: Comments:
Euro makes "K" and "L" within 6 days, though "K" looks fishy for now, and "L" looks like a redo of Isaac...
Member Since: Posts: Comments:
They're just using the inputs that are on the ground so to speak.  They're not sentient.
Quoting louisianaweatherguy:
GFS and the GFDL/EURO have swapped places on this model run... THEY REALLY HAVE NO CLUE AT THIS POINT.... we need 2-3 consistent runs!!!!!

Member Since: Posts: Comments:

Viewing: 1521 - 1471

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

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.