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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1571. dmh1026
Quoting Yelladawg:


Collier Co. has been under a hurricane warning since this AM.

I suspect Lee will as of 5 PM advisory....
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Quoting TomTaylor:
Well ECMWF is now right on top of my track forecast from yesterday, so I'm not going to make any changes to it. But regardless of my exact forecast position, right now the area from the western to central Panhandle is most likely to receive Isaac. That is where the majority of the global models are, as well as the consensus models and the ECMWF. Also, it is interesting to see the CMC, GFS and GEFS make a last minute shift to Louisiana and Mississippi to become the western outliers. Especially since yesterday the GFS and GEFS were so consistent on the central or western Panhandle.


And we're still several days out... It'll be an interesting several days.
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Quoting robj144:


Do you know anything about Palm Beach County schools?


PBC schools will be closed tomorrow!!!!
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I wonder if NOAA was able to get permission for HH to fly over Cuba?
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Quoting washingaway:
Old.
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1566. ncstorm
dannngg..the euro shifted east big time..
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Quoting aislinnpaps:
school websites are generally the last to post. They're run by the local school board and this is Saturday... It will be posted, but generally notice is made, Superintendent starts the calls to admin, who begin the phone tree to teachers and staff. Someone from tech dept. eventually is notified to make the announcement on the webpage.
I usually get a phone call first about the school being cancelled before it's posting on the school's site.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Wish bryan norcoss would inject some light on the current situation

lott guesscasting
Member Since: June 17, 2011 Posts: 11 Comments: 6539
recon decending into the center
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1561. robj144
Quoting guygee:
The MIMIC-TC pretty much tells the tale of landfall in Haiti, a more northerly jog in the Windward Passage, then a more westerly jog into the mountains of eastern Cuba. So far the NHC has done a very good job in forecasting the track of this difficult storm.



Yup, as they always almost do... look at Ernesto. I love how so many here doubt the ability of Ph. D's, sophisticated computer models, and supercomputers. I understand though, this is a blog and it's all in fun, but it still amazes me.
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ASCAT showing an elongated area of low pressure near 9n 38w associated with the tropical wave designated 97L. the NHC has it at 13.4n 31.5w.
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Well ECMWF is now right on top of my track forecast from yesterday, so I'm not going to make any changes to it. But regardless of my exact forecast position, right now the area from the western to central Panhandle is most likely to receive Isaac. That is where the majority of the global models are, as well as the consensus models and the ECMWF. Also, it is interesting to see the CMC, GFS and GEFS make a last minute shift to Louisiana and Mississippi to become the western outliers. Especially since yesterday the GFS and GEFS were so consistent on the central or western Panhandle.
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Link
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Quoting dmh1026:
Lee District Schools closed Monday as well as FGCU, and Edison State College. Hodges University will remain open through any watches, but if officials declare a hurricane warning, operations will cease.


Collier Co. has been under a hurricane warning since this AM.
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Quoting scott39:
When does the updated track come out for Isaac?
Around 5PM.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1555. JLPR2
Quoting RTSplayer:
168




192


116


Triple threat.

I meant "fishy" in the sense of questionable, but near the run, "K" seems to get it's act together, and is coming around a persistent Bermuda High.

One more frame to go.


Dang! Right over me...
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1554. dmh1026
Quoting mahep1911:


Hodges University
With the decision by the National Weather Service to place the Southwestern region of Florida under a hurricane warning in preparation for the arrival of Tropical Storm Isaac, Dr. Terry McMahan, President of Hodges University, has announced that the institution will be closed on Monday, August 27, and will reopen on Tuesday, August 28. This announcement is for both the Fort Myers and Naples campuses, as well as the Learning Site in Immokalee.

For any additiona lquestions, please contact Joe Turner, Publc Relations Coordinator.

Joe Turner
(239) 598-6169 (office)
(239) 450-2979 (cell)


this was on nbc-2.com

It's about time LOL...
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school websites are generally the last to post. They're run by the local school board and this is Saturday... It will be posted, but generally notice is made, Superintendent starts the calls to admin, who begin the phone tree to teachers and staff. Someone from tech dept. eventually is notified to make the announcement on the webpage.
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1552. wpb
Quoting cchsweatherman:


Pretty much am maintaining that South Floridians and residents in the Keys should be prepared for hurricane conditions starting tomorrow evening and going into the early morning hours Monday.

Over the past 24 hours or so, this storm has had a tendency to go further north and east than the forecasters and computer models expected, so it would not surprise me to see Tropical Storm Isaac continue its current trend pulling away from Cuba and off in a general NW direction over the next 12 hours or so. Convection seems to be slowly, but surely rebuilding near and over the circulation center as Isaac recovers from its encounters with Haiti and Cuba.
do u have center over land
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Quoting Tazmanian:



its all ready back in too open water
Quoting Seflhurricane:
Isaac is leaving the coast now


You missed the point. I was stating that Isaac is hugging the coast, not deviating very far from Cuba. He is currently still at 21N moving parallel to the coast. For him to reach the next forecast point from the HWRF, he would have to move due north to 23N.



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For info. on school closures in the Tampa Bay area go here. Pinellas County Schools will make a decision tomorrow. Link
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1549. guygee
The MIMIC-TC pretty much tells the tale of landfall in Haiti, a more northerly jog in the Windward Passage, then a more westerly jog into the mountains of eastern Cuba. So far the NHC has done a very good job in forecasting the track of this difficult storm.

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Quoting dmh1026:
Lee District Schools closed Monday as well as FGCU, and Edison State College. Hodges University will remain open through any watches, but if officials declare a hurricane warning, operations will cease.


Hodges University
With the decision by the National Weather Service to place the Southwestern region of Florida under a hurricane warning in preparation for the arrival of Tropical Storm Isaac, Dr. Terry McMahan, President of Hodges University, has announced that the institution will be closed on Monday, August 27, and will reopen on Tuesday, August 28. This announcement is for both the Fort Myers and Naples campuses, as well as the Learning Site in Immokalee.

For any additiona lquestions, please contact Joe Turner, Publc Relations Coordinator.

Joe Turner
(239) 598-6169 (office)
(239) 450-2979 (cell)


this was on nbc-2.com
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Quoting Seflhurricane:
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


Pretty much am maintaining that South Floridians and residents in the Keys should be prepared for hurricane conditions starting tomorrow evening and going into the early morning hours Monday.

Over the past 24 hours or so, this storm has had a tendency to go further north and east than the forecasters and computer models expected, so it would not surprise me to see Tropical Storm Isaac continue its current trend pulling away from Cuba and off in a general NW direction over the next 12 hours or so. Convection seems to be slowly, but surely rebuilding near and over the circulation center as Isaac recovers from its encounters with Haiti and Cuba.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
Quoting scott39:
When does the updated track come out for Isaac?



5pm and 11pm 5am 11am is when the update the track
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
Quoting scott39:
When does the updated track come out for Isaac?

5PM
Member Since: August 1, 2012 Posts: 0 Comments: 269
Quoting tennisgirl08:
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.


Agreed. Wish they would hurry up to consensus.
Those of us out in the GOM need a better idea of track soon.
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Quoting Drakoen:
Looks like he is riding the coastline at the moment.
RAMSDIS zoomed loop
sure does but its over water
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Quoting chrisdscane:


what?

NW north and west at the same time so NW
Member Since: August 1, 2012 Posts: 0 Comments: 269
Quoting TampaFLUSA:

Convention underwater then???
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168




192


216


Triple threat.

I meant "fishy" in the sense of questionable, but near the run, "K" seems to get it's act together, and is coming around a persistent Bermuda High.

"L" hit Puerto Rico on this run, direct hit.

One more frame to go.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
testing...
Member Since: June 17, 2011 Posts: 11 Comments: 6539
1538. dmh1026
Lee District Schools closed Monday as well as FGCU, and Edison State College. Hodges University will remain open through any watches, but if officials declare a hurricane warning, operations will cease.
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1537. Drakoen
Looks like he is riding the coastline at the moment.
RAMSDIS zoomed loop
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1536. Michfan
Product: Air Force Tropical RECCO Message (URNT11 KNHC)
Transmitted: 25th day of the month at 18:46Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number: 09
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 16
Observation Number: 04

Mandatory Data...

Observation Time: Saturday, 18:46Z
Radar Capability: Yes
Aircraft Altitude: Below 10,000 meters
Coordinates: 20.9N 74.0W
Location: 133 miles (214 km) to the ENE (63°) from Santiago de Cuba, Cuba.
Turbulence: None
Conditions Along Flight Route: In the clear
Pressure Altitude: 1,530 meters
Flight Level Wind: From 160° at 41 knots (From the SSE at ~ 47.1 mph)
- The above is a spot wind.
- Winds were obtained using doppler radar or inertial systems.
Flight Level Temperature: 16°C
Flight Level Dew Point: 16°C
Weather (within 30 nautical miles): Thunderstorm(s)
850 mb Surface Altitude: 1,472 geopotential meters

Optional Data...

Estimated Surface Wind: From 120° at 45 knots (From the ESE at ~ 51.7 mph)

Remarks Section...

Surface Wind Speed (likely by SFMR): 43 knots (~ 49.5mph)

Good SFMR is back up.
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SFMR Back up but clearly giving bad readings... THey probably tried to reset it, but still bad when it came back.
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1534. robj144
Quoting MiamiHurricanes09:
Class is still scheduled for Monday.


Thank you.
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1533. scott39
When does the updated track come out for Isaac?
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1532. JasonRE
Oh my goodness. So now what is this thing doing? The GFS shifted West and the Euro shifted East? lol I'm losing it. Still waiting to see here in Louisiana.
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1531. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 174 Comments: 54353
Quoting RTSplayer:
Euro makes "K" and "L" within 6 days, though "K" looks fishy for now, and "L" looks like a redo of Isaac...

Are you saying we could have big bad Leslie down the road???
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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.




Local Channel 10 in Miami announced that Broward County Schools would be closed Monday. They didn't have a press conference a la Miami-Dade Cty. Just an announcement.
Watching 10 because of Mayfield.
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Quoting robj144:


Do you know anything about Palm Beach County schools?
Class is still scheduled for Monday.
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1526. Michfan
Anyone have a good link for the CIRA rapid scan?
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1525. pottery
Quoting RTSplayer:


I will as soon as it's finished updating.

It's only on 168 hours right now, and should go to 240.

Don't know why they bother with that.
The verification for 10 days out is pretty unlikely, in most cases.
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1524. robj144
Quoting MiamiHurricanes09:
Confirmed; press conference by the superintendent just finished right now.


Do you know anything about Palm Beach County schools?
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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.




as of 250pm broward county----NO SCHOOL on channel 10
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Quoting TomballTXPride:


The actual center (LLC) may be over water now, yes, but he is inferring that Cuba is still holding this system in check and not allowing any strengthening because of Isaac's close proximity to the landmass.




well see how far a way from landmass he is when recon gets in there
Member Since: May 21, 2006 Posts: 5091 Comments: 115235
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: 21194

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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.