Huge Western Caribbean low bringing heavy rains; Wisconsin levee failing

By: Dr. Jeff Masters , 12:26 PM GMT on September 27, 2010

Today, for the first day since August 20, the National Hurricane Center will not be issuing any advisories for an Atlantic named storm. Thus ends a remarkably active 36-day period that saw the formation of ten named storms, six hurricanes, and five intense hurricanes--an entire hurricane season's worth of activity, compressed into just five weeks of the six-month season. This season is not done yet, as we still have three more weeks of peak hurricane season left to go, and the Western Caribbean is looking poised to generate a tropical storm sometime in the next ten days.


Figure 1. Morning satellite image of the Western Caribbean and Central America, showing the remains of Matthew over Mexico, and a large area of disturbed weather beginning to develop over the Western Caribbean.

A wet week ahead for the Western Caribbean, Florida, and the Western Bahamas
Pressures are falling over the Western Caribbean today as a large area of low pressure develops over the region. This low is bringing heavy rains across a huge area, from the Pacific shores of El Salvador, Guatemala, and Mexico, to eastern Cuba and Haiti. All of Central America, eastern Mexico, the western 2/3 of the Caribbean, plus the Bahamas and Florida can expect sporadic periods of very heavy tropical rains over the coming week, with peak amounts of 3 - 6 inches per day possible. In the Western Caribbean, a few hundred miles east of Mexico's Yucatan Peninsula, a region of concentrated thunderstorms has built this morning, and has the potential to develop into a tropical depression by Wednesday. A large trough of low pressure over the Eastern U.S. is producing steering currents that will pull this area of disturbed weather to the north-northeast across western Cuba on Tuesday and Wednesday. The disturbance should move over Florida on Wednesday and Thursday, and over North Carolina by Thursday and Friday. All of these regions can expect very heavy rains from the disturbance, and NHC is giving a 30% chance that the disturbance will develop into a tropical depression by Wednesday. The Hurricane Hunters are on call to investigate the disturbance this afternoon, if necessary.

Once the disturbance moves out of the Caribbean, the GFS and NOGAPS models predict that the Western Caribbean will "reload" and produce another tropical disturbance capable of developing into a tropical depression late this week or early next week. The steering currents are not expected to change over the coming ten days, and Florida and western Cuba can expect to see this second disturbance potentially bring a second round of heavy rain late this week and early next week.

Levee failing in Wisconsin due to rains from Hurricane Karl's moisture
In Portage, Wisconsin, about 25 miles north of Madison, a sub-standard 120-year-old levee is failing, thanks to flood waters 3.5 feet above flood stage on the Wisconsin River. The river was swollen last week by heavy rains of up to seven inches that fell in its watershed to the northwest. The rains were generated by a plume of very moist air associated with what was Hurricane Karl. This moisture was lifted over a warm front draped over Minnesota and Wisconsin on Wednesday and Thursday. These types of rain events are called Predecessor Rain Events (PREs), because they typically precede the actual arrival of the rain shield of a tropical storm.


Figure 2. Rainfall over Minnesota and Wisconsin for the seven-day period ending 8pm EDT Sunday 9/26/10. Heavy rains to the northwest of Portage, Wisconsin led to flooding along the Wisconsin River in Portage. Image credit: NOAA.

Canadian Military responds for Hurricane Igor relief
At least twenty communities in Newfoundland, Canada are still cut off from civilization after Tuesday's rampage by Hurricane Igor. The Canadian military has sent three warships and a number of helicopters into the disaster zone to deliver food, fuel, and medical supplies to those communities still cut off. Igor killed one person and caused over $100 million in damage to the island.


Figure 3. Miniature golf anyone? A house in St. John's Newfoundland now has a very three-dimensional front yard, thanks to Hurricane Igor's winds and rain. Image credit: Zach Goudie.

I'll have an update Tuesday morning.

Jeff Masters

Wisconsin River Flooding in Wisconsin Rapids September 2010 (LadyWriter)
Jackson Street Bridge late Saturday afternoon at cresting.
Wisconsin River Flooding in Wisconsin Rapids September 2010
Wisconsin River Flooding in Wisconsin Rapids September 2010 (LadyWriter)
Taken from First Avenue while looking eastward toward Grand Avenue Bridge/Elks Club when the flooding was at its worst
Wisconsin River Flooding in Wisconsin Rapids September 2010

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Quoting hydrus:
Whats happening Keep? What are your thoughts on 96L for track and intensity?

I would like to know your take on this also Keep.
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Quoting Twinkster:
I'm not saying we should totally discount the 12z BAMs but we should put up on the back burner reason being that the HPC, TPC, and all the dynamical guidnace are in very good agreement with track and they are nowhere near the track shown by BAMs.

I believe south florida should keep a very close eye on this storm despite what the BAMs show


I think this time of the year Florida should keep a close eye all of the time.
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does anyone have the link to the radar out of cancun mexico or belieze
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Quoting TropicalAnalystwx13:


In Eastern North Carolina (Where I used to live), they've picked up up to 8 inches of rain.


Just west of here they are sitting at 5". It's soggy!
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1561. ackee
THE tropical near windwird ISland is something to watch as well might be suprise TD TO affect the Lesser Antilles
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Quoting pilotguy1:
I don't want to down play anyone's opinion, however I have very little faith in anything out more than three or four days and for sure when it hasn't even developed yet.


Extra points for tact and diplomacy.
Member Since: August 21, 2007 Posts: 0 Comments: 856
Quoting Twinkster:
I'm not saying we should totally discount the 12z BAMs but we should put up on the back burner reason being that the HPC, TPC, and all the dynamical guidnace are in very good agreement with track and they are nowhere near the track shown by BAMs.

I believe south florida should keep a very close eye on this storm despite what the BAMs show


Your very right, we're 48hrs out now, time to toss the models and pay attention to the forecast and local NWS.
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1558. FLdewey
From MLB nws...

TUES NIGHT-WED NIGHT...WHILE MODELS CONTINUE TO WOBBLE WITH EACH
RUN...THE TREND HAS BEEN TOWARD A MORE EASTWARD SOLUTION THAT THE
ECMWF HAS BEEN SHOWING FOR THE PAST FEW DAYS. A SURFACE LOW IS
EXPECTED TO LIFT OUT OF THE NW CARIBBEAN AHEAD OF THE STALLED
FRONTAL BOUNDARY AND MOVE ACROSS SRN AND CTRL FL AND THEN INTO THE
ATLANTIC. ORIENTATION OF SLP/VORT AND PRECIP FIELDS INDICATE
INCREASING BAROCLINIC INTERACTION BETWEEN THE TROPICAL SYSTEM AND THE
SFC FRONT/MID LEVEL TROUGH...BECOMING SORT OF "RIGHT-SIDED" SYSTEM
AS IT MOVES NWD. WHETHER THE LOW IS TROPICAL IN NATURE OR NOT
...A
WET AND STORMY TWO DAYS ARE EXPECTED...ESPECIALLY FOR THE
SOUTHEASTERN CWA. ECMWF REMAINS THE SLOWEST MODEL...THE GFS THE
FASTEST...AND GIVEN THE LACK OF A CURRENT ORGANIZED SYSTEM IN THE
AREA SLOWER SEEMS THE WAY TO GO. HPC PROGS HAVE A COMPROMISE
BETWEEN THE TWO WITH AN EMPHASIS ON THE SLOW SIDE.

LATEST HPC QPF TOTALS SUGGEST AROUND 3.0 INCHES NW TO 6.0 INCHES
SOUTHEAST...WHICH ARE AREAL AVERAGES...AND LOCAL MAXIMA CAN
EASILY EXCEED THOSE AMOUNTS. THE MORE EASTERLY TRACK THE MODELS
ARE TRENDING TOWARDS WOULD KEEP THE EXTREMELY HEAVY/EXCESSIVE
RAINFALL TO OUR SOUTH AND EAST... ESPECIALLY AS THE SYSTEM PULLS
PARALLEL LATE WED NIGHT.

Starting to look like a nice rain event... and less like doom. Sorry Home Depot.
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1557. hydrus
Quoting KEEPEROFTHEGATE:
takes a little time for the weather to catch up to the pressure falls winds will increase soon in response as darkness falls and air temps fall below sst values to start the feeding off the water
Whats happening Keep? What are your thoughts on 96L for track and intensity?
Member Since: September 27, 2007 Posts: 1 Comments: 26896
I don't think it is a true tropical band but it has rotation,put long range loop in motion. The light blue moving to the west is high top blow off that is why system is slow to develop. All most forgot heads up Key West you have warning box just to your se.
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I don't want to down play anyone's opinion, however I have very little faith in anything out more than three or four days and for sure when it hasn't even developed yet.
Member Since: Posts: Comments:
I'm not saying we should totally discount the 12z BAMs but we should put up on the back burner reason being that the HPC, TPC, and all the dynamical guidnace are in very good agreement with track and they are nowhere near the track shown by BAMs.

I believe south florida should keep a very close eye on this storm despite what the BAMs show
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Quoting sailingallover:
The calm before the storm?
Nope..That is strange. Don't think in all my years of sailing around I have seen a Baro that low without some precipitation or wind. No squalls even?


Nope, no rain, nada. Conditions now 1005 mb and steady. Wind out of the SSE @ 6 mph !. Overcast
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Quoting kmanislander:


Exactly. My station now has 1004.4 and still falling. Not a good sign.
takes a little time for the weather to catch up to the pressure falls winds will increase soon in response as darkness falls and air temps fall below sst values to start the feeding off the water
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next TWO should be out within the next 30 Minutes
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1550. breald
Is this low still overland or is google earth wrong?
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Quoting pilotguy1:


A week from now?


Yes
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984 from the 18Z HWRF is a strong cat 1
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Quoting oceanblues32:
ok question what do the millibars usually have to drop to for a cat 3 storm


970-960
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Quoting Stormchaser2007:


Not really a big deal in the NE. More of a mid-Atlantic storm.




And for me, no power for 7 days, sewer spillage, ect.
Member Since: July 8, 2005 Posts: 259 Comments: 25342
Central Atlantic Disturbance is interesting.
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Quoting kmanislander:
Good evening

It's the strangest thing but the weather here is beautiful, the sun is just setting and the surface pressure is 1004.4 mbs and falling !

Something coming this way I guess.
The calm before the storm?
Nope..That is strange. Don't think in all my years of sailing around I have seen a Baro that low without some precipitation or wind. No squalls even?
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Quoting ackee:
what intresting with 96L is that, early models runs has it moveing near to caymans , and then central to Eastern cuba and not over western Cuba as previousy thought guess we see


Here's why

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ok question what do the millibars usually have to drop to for a cat 3 storm
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Quoting pilotguy1:


A week from now?


That would be correct, a week from now.

GFS has been dead on with this upcoming rain event.
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Quoting GTcooliebai:

Yes I noted that earlier on the 12z runs, so if it is showing it again, definately something to keep our eyes on.


They've been showing a second storm for a while now, surely not to let the guard down as this next one will take a similar track should it develop.
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Quoting gordydunnot:
First outer band closing in on key west radar.


No rotation that I can see. Some of it's going West and some going East.
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Quoting splash3392:
Well good luck tonight and tomorrow. I'll keep lurking.


Thanks
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Well good luck tonight and tomorrow. I'll keep lurking.
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1530. ackee
what intresting with 96L is that, early models runs has it moveing near to caymans , and then central to Eastern cuba and not over western Cuba as previousy thought guess we see
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Quoting pilotguy1:


A week from now?

Yes I noted that earlier on the 12z runs, so if it is showing it again, definately something to keep our eyes on.
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Quoting GTcooliebai:

Is the front lifting out on that run?


Yes, the front is forecast to stall/retrograde.
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Quoting pilotguy1:


A week from now?


Yes, that would be the 2nd storm. If it forms.
Member Since: July 29, 2006 Posts: 0 Comments: 3240
Quoting splash3392:
So kman and storm you guys ever feel like sitting ducks?


What's a duck ??. Just kidding.

No actually. From the fifties through to the late eighties when we had Gilbert there was very little tropical cyclone activity. Once this active period passes the pendulum will swing back to that in due course.
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First outer band closing in on key west radar.
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sooo not true. i was right about every storm including igor. do you all recall all the heading west none-sense with that storm? don't hate the truth embrace it.

as for cold fronts the earliest i ever saw one get to south florida was oct 9. as late as nov 17. on average i'd say betw oct 20 and nov 4. NEVER in september and not this year.
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Quoting IceSlater:
Looks like the GFS is putting a TS/Hurricane in SW Florida and stalling it near the coast...

That all happening on Monday. Quite interesting.


A week from now?
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Quoting CyclonicVoyage:
Latest thoughts from the TPC.



Is the front lifting out on that run?
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Quoting nrtiwlnvragn:
Hope the 18Z HWRF is not a blind squirrel and gets one right from the get-go.




Seems right in line with the TPC on track.
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Looks like the GFS is putting a TS/Hurricane in SW Florida and stalling it near the coast...

That all happening on Monday. Quite interesting.
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Quoting stormpetrol:

Not even raining at least on the SW side of the Island, got a feeling this slow mover could spell Trouble!!!
]

She's not forecast to move much over the next 24hrs or so.
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Also this frontal system parked over the SE is potentially a source of severe weather. We are going into fall storm/tornado season. Keep an eye on it.




MESOSCALE DISCUSSION 1900
NWS STORM PREDICTION CENTER NORMAN OK
0501 PM CDT MON SEP 27 2010

AREAS AFFECTED...PARTS OF NRN GA INTO UPSTATE S CAROLINA AND PARTS
OF WRN N CAROLINA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 272201Z - 280000Z

SUBSTANTIVE SEVERE POTENTIAL MAY BE CONFINED TO THE NEXT 2-3 HOURS
OR SO. SO THE NEED FOR A WW IS NOT CURRENTLY ANTICIPATED ...BUT
TRENDS WILL CONTINUE TO BE MONITORED.

RECENT RAPID INCREASE IN VIGOROUS LOW-TOPPED THUNDERSTORMS ACROSS
THE ATLANTA AREA IS LIKELY BEING AIDED BY STRONG DYNAMIC FORCING FOR
UPWARD VERTICAL MOTION NEAR A MID-LEVEL CLOSED LOW WHICH IS NOW
BEGINNING TO PIVOT OUT OF THE NORTH CENTRAL GULF STATES TOWARD THE
SOUTHERN APPALACHIANS. THE AIR MASS IS GENERALLY ONLY WEAKLY
UNSTABLE AS CHARACTERIZED BY MIXED LAYER CAPE ON THE ORDER OF 500
J/KG...BUT LOW-LEVEL LAPSE RATES HAVE BECOME RATHER STEEP WITH
DAYTIME HEATING...AS THE MID-LEVEL COLD POCKET ADVECTS ACROSS THE
REGION. IN THE PRESENCE OF STRONG VERTICAL SHEAR BENEATH 50-70 KT
SOUTHWESTERLY 500 MB FLOW...THIS ENVIRONMENT WILL PROBABLY REMAIN
CONDUCIVE TO MARGINALLY SEVERE HAIL AND GUSTY WINDS NEAR STRONGEST
STORMS THROUGH 00-01Z...AS THEY GRADUALLY DEVELOP
EASTWARD/NORTHEASTWARD ACROSS CENTRAL AND NORTHEAST GEORGIA TOWARD
THE WESTERN CAROLINAS. THEREAFTER...AS LARGE-SCALE FORCING
CONTRIBUTES TO EXPANDING/CONSOLIDATING CONVECTIVE DEVELOPMENT...AND
THE BOUNDARY LAYER BEGINS TO COOL...STABILIZING LAPSE RATES ARE
EXPECTED TO RESULT IN WEAKENING CONVECTIVE TRENDS.
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No real convective organization yet. Organization of this system into a tropical cyclone will be slow to occur.

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Quoting melwerle:


The marine layer is A BEAUTIFUL THING.


Well...it does a lot of good to keep things moderated, but it used to get very old to me after awhile. I grew up in Orange County, and also lived in Los Angeles, Santa Barbara, Ventura, and Ojai; it could be 100+ in Ojai, but 55 at the Ventura pier, a mere 15-minute car drive away. That was nice. But those all-day, everyday ML--aka "June Gloom"--events in Santa Barbara could be downright depressing.
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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