97L gets disrupted by Hispaniola

By: Dr. Jeff Masters , 12:53 PM GMT on July 21, 2010

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A tropical wave (Invest 97L) near the north coast of Hispaniola has been disrupted by interaction with the island, plus the effects of moderate wind shear of 10 - 20 knots. The storm is no longer a threat to develop into a tropical depression today, and the Hurricane Hunter flight that was scheduled for today has been postponed until Thursday. The disturbance has brought heavy rains of 8+ inches to Culebra, Vieques, the Virgin Islands, and some of the northern Lesser Antilles Islands. Wunderblogger Weather456 reported that the power was knocked out on the island of St. Kitts for about 24 hours, due to the intense lightning associated with 97L. All of Puerto Rico and the Virgin Islands are under flash flood watches today.

Satellite images of 97L show a relatively meager number of heavy thunderstorms that are not well-organized. The curved bands to the north and east of the center have disappeared, and there is no evidence of low-level spiral banding or of a surface circulation. Surface observations over the northern Dominican Republic show only light winds, with no westerly winds indicating that a surface circulation is forming. Long-range radar loops from San Juan show a much reduced amount of thunderstorm activity.


Figure 1. Total radar-estimate rainfall for 97L.

Track Forecast for 97L
The storm is in a fairly straightforward steering current environment, and 97L should progress steadily to the west-northwest through Saturday. The rains from 97L's thunderstorms will bring the threat of isolated flooding to the Dominican Republic today, and to Haiti on today and Thursday. Heavy rains from 97L will affect eastern Cuba, the Turks and Caicos Islands, and the eastern Bahamas Thursday, and South and Central Florida can expect heavy rains to arrive Thursday night or Friday morning. The latest suite of model runs from 2am EDT this morning (6Z) foresee 97L making landfall on the Florida coast somewhere between Miami and Cape Canaveral on Friday, then continuing into the Gulf of Mexico on Saturday. Only the Canadian model foresees a threat to Texas, and the other models predict a second landfall between eastern Louisiana and the Florida Panhandle.

Intensity Forecast for 97L
The primary detriment to development of 97L today will be its close proximity to the landmass of Hispaniola. Once the storm pulls away from the island tonight, 97L has a better chance of development. Also hindering development over the next two days will be the presence of dry, stable air in its path over the Bahamas, thanks to the upper-level low to the north of the Dominican Republic. The SHIPS model predicts shear will stay in the moderate range, 10 - 20 knots, over the next three days, which should allow for some steady development of 97L on Thursday and Friday before it reaches Florida. NHC is giving 97L a 60% chance of developing into a tropical depression by Friday, which is a reasonable forecast. I think there is a 70% chance 97L will eventually become Tropical Storm Bonnie, sometime in the next five days. Sudden rapid development before 97L reaches Florida is unlikely, due to the storm's current state of disorganization and the dry air over the Bahamas. It's very unlikely that 97L has time to organize into a hurricane before hitting Florida. I put the odds of 97L making it to hurricane strength before reaching Florida at 5%, and I give a 20% chance it will be a hurricane in the Gulf of Mexico. The probability of 97L being a hurricane in the Gulf of Mexico will depend heavily upon how long the storm spends over water in the Gulf, which is very uncertain. The environment in the Gulf of Mexico should be favorable for intensification, if passage over Florida does not disrupt the storm too much.

I'll have a new post Thursday morning, or earlier if there's a major change to 97L.

Famed climate scientist Steven Schneider dies
Steven Schneider, one of the most influential and talented climate scientists of our time, died on Monday. Ricky Rood has a tribute to Dr. Schneider in today's blog. Ricky comments, "He is known for feistiness. His last book was Science as a Contact Sport: Inside the Battle to Save Earth's Climate. He was a man who was, bluntly, harassed and threatened by those who did not like his message. He never shrank from the battle."

Jeff Masters

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662. IKE
SYNOPSIS FOR THE GULF OF MEXICO
1030 AM CDT WED JUL 21 2010

.SYNOPSIS...SURFACE TROUGH EXTENDING ALONG 28N93W 23N94W 18N93W
WILL MOVE ACROSS THE WESTERN GULF THROUGH THU AND INLAND THU
NIGHT. A RIDGE FROM NORTHERN FLORIDA TO LOUISIANA THROUGH FRI AS
A TROPICAL WAVE OR A LOW PRES POSSIBLY ENTERS THE EASTERN GULF
SAT AND SUN.



SYNOPSIS FOR CARIBBEAN SEA AND TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W
1130 AM EDT WED JUL 21 2010

.SYNOPSIS...TROPICAL WAVE ALONG 76W MOVING W 15 KT. THE WAVE
WILL MOVE THROUGH THE WESTERN CARIBBEAN THROUGH THU AND MOVE
INTO THE YUCATAN PENINSULA FRI. ANOTHER TROPICAL WAVE WELL E OF
THE AREA WILL MOVE INTO THE TROPICAL N ATLC WATERS THU NIGHT AND
INTO THE E CARIBBEAN SEA SAT AND SUN.


Member Since: June 9, 2005 Posts: 23 Comments: 37858
The High pressure ridge currently laying around 30N is suppressing things in FL... and, yes, the conditions are anomalous...

East central Florida forecast discussion
National Weather Service Melbourne Florida
950 am EDT Wednesday Jul 21 2010


Discussion...


Today-tonight...precipitable water on the xmr sounding this morning of 1.19 is running well below the climatology 25 percentile value which is around 1.65. The current low value might actually lie near only around 10 percent of normal at best visually estimating from the late July/early August curve.


Nassau Bahamas currently located closer to WV indicated moisture ribbon is at a precipitable water of 1.70 and this relatively higher upstream moisture will work toward the area later today. Full effects of high pressure near area will effectively shut down precipitation potential and we recently put the radar in clear air Mode. No forecast update is planned.
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ULL is moving quickly to the southwest, you can see it by looking at the CIMMS shear map, notice a direct eratic movement southwest of it's last postion. Also, the area that detatched from 97L last night has a nice curve and outerbanding convection. This area was in 20 knots of wind shear earlier this morning but new CIMMS shear map shows wind shear has decreased to 10 knots while shear has increased to 20 knots over 97L. The ULL should continue it's fast pase to the WSW and conditions should be favorable for development with 97L tomorrow.
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Quoting IKE:
I'm 52...my memory may not be the sharpest, but I don't remember seeing this much SAL over Florida and the Bahamas this often. I'm sure it happens, but I sure don't remember much of it.
I didn't remember this one either: African Dust Clouds Push Challenger Liftoff Back A Day Until Sunday
January 23, 1986

Edit: That delay was due to dust IN Africa, "Dust at the emergency landing strip in Dakar, Senegal, in western Africa is not expected to clear soon, so NASA found a new site in eastern Africa -- Casablanca, Morocco." Challenger did not launch until January 28, 1986, which was the the day of the explosion disaster.
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Traffic: Freedom Rider

like a hurricane around your heart

when earth and sky are torn apart...
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634. DestinJeff 11:35 AM CDT on July 21, 2010

from no pants to a dress...you're scarin me Jeff :)
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Good discussion at to the current position of the TUTT:

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
621 AM EDT WED JUL 21 2010

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. A TUTT LOW NORTH OF THE ISLANDS CONTINUES TO RETROGRESS TOWARDS THE BAHAMAS AS A MID/UPPER LEVEL RIDGE BUILDS OVER THE WESTERN ATLANTIC TO THE NORTHEAST CARIBBEAN ISLANDS. DOWNSTREAM FROM THIS AXIS THE ANALYSIS SHOWS ANOTHER TUTT...WITH AXIS EXTENDING BETWEEN 60W-40W TO NORTH OF THE GUIANAS. TWO CLOSED LOWS EMBED IN THIS AXIS...WITH ONE NEAR 20N 53W AND THE OTHER TO THE NORTH OF 30N. UNDER INFLUENCE OF THE BUILDING RIDGE...THE LOW/MID LEVEL FLOW WILL TAKE A SOUTH-SOUTHEASTERLY COMPONENT ACROSS THE EASTERN CARIBBEAN ISLANDS TO PUERTO RICO/USVI. THIS IS TO PREVAIL DURING THE NEXT
FOUR TO FIVE DAYS. CONVERGENCE ON THE WESTERN SIDE OF THE APPROACHING TUTT WILL LEAD TO EROSION OF AVAILABLE MOISTURE THROUGH FRIDAY MORNING...WITH A BRIEF SURGE ON SATURDAY AS THE
TUTT ENTERS THE ISLANDS.

THE MODELS ARE HAVING AN UNUSUALLY HARD TIME DEALING WITH THE APPROACHING TUTT...FAILING TO MAINTAIN CYCLE-TO-CYCLE CONTINUITY. ON THE SHORT RANGE THEY ONLY AGREE THROUGH 36-48 HRS...WHEN THE AXIS IS TO START ENTERING THE ISLAND CHAIN/EASTERN CARIBBEAN. AT THAT TIME...THE LOW TO THE NORTH WILL MOVE TO 28N 60W...WHILE THE ONE TO THE SOUTH WILL LIE JUST EAST OF THE LEEWARD ISLANDS. THE LATTER IS PUZZLING THE MODELS...WITH THE GFS GRADUALLY DISSIPATING THIS AXIS THROUGH 60-72 HRS...WHILE THE EUROPEAN SHOWS THE LOW/TROUGH STALLING OVER THE ISLAND CHAIN THROUGH 96-108 HRS. BUT
NOT EXPECTING THIS SYSTEM TO HAVE A MAJOR IMPACT ON THE LOCAL FORECAST...AS IT IS GOING TO LIMIT TO THE LESSER ANTILLES/NORTHEAST VENEZUELA. THEY...HOWEVER...ARE IN BETTER
AGREEMENT ON THE LOW TO THE NORTH...AS THEY SHOW THE CLOSED LOW REPOSITIONING JUST NORTH OF PUERTO RICO BY 72 HRS...TO THEN MAKE A
BEELINE TO THE TURKS BY 96 HRS.

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653. CJ5
As consolidation and vorticity goes, I think 97L looks much better now than it has in previous days.
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652. IKE
Quoting weathermanwannabe:
That upper level low East of Florida, while moving towards the West, is currently sucking the life out of 97L IMHO.....


The ULL looks more pronounced or at least more visible because it's getting it's appearance off some of 97L.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting 1900hurricane:

When is the first model run to incorporate that data? The next 00Z maybe?


Z = UTC. Bird will still be dropping sondes when the 00Z runs fire off. Might have data from the early part of the flight in for 00Z, but the full data won't make it until next after that
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Quoting wxvoyeur:
"Like a Hurricane"

Neil Young


U2 -Awesome band, "electrical storm"
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616. weathermanwannabe 11:26 AM CDT on July 21, 2010
That upper level low East of Florida, while moving towards the West, is currently sucking the life out of 97L IMHO.....




May be the simplest, most accurate post of the morning. Until the ULL moves away from 97L, or until it gets a sfc circ going and moves out/away from the TUTT, 97L is going to have a slow, tough go of it, especially considering its proximity to land. The ULL seems to be moving west, and unless its weak condition prevents it, 97L will be attracted towards the ULL, moving the track a bit more northerly, but bringing it closer to FL's east coast. And, that's where the test will come - over the warmer waters of the Gulf Stream, and see if it can get anything going at the surface.
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646. IKE
Quoting bappit:

I think that image shows dry air more than it shows SAL. It's just that the SAL is dry air.

Around 1972 or so I do remember seeing Saharan dust high in the air over Baton Rouge. Looked like someone drained some blue out of the sky. That was highly unusual.

Of course, the sky was a lot bluer back then. Didn't have as much pollution. Might not be able to see any difference if such an outbreak of dust occurred today.


You may be correct. How often is there not one shower in the entire peninsula on a summer afternoon?

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
I'm 52...my memory may not be the sharpest, but I don't remember seeing this much SAL over Florida and the Bahamas this often. I'm sure it happens, but I sure don't remember much of it.
Back in 2005: African Dust Cloud Heads For Florida
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Rock you like a Hurricane - Scorpions
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Quoting will45:


Pat is traveling i think


Will thanks for answering me. I just knew it was kinda unusual.
sheri
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As the ULL is pulling away, it looks on satellite as if it's tugging 97L Nward a bit in the CCwise flow around the back side of the ULL.
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640. IKE
Wednesday afternoon in peninsula Florida....





Quoting catastropheadjuster:


Morning Ike, that is a lot of SAL, i really can't remember it being like that either, I remember a yr or 2 ago the SAL was really bad, I wonder if this yr will be like that. I think it hurt a lot of storms, I am no weather expert but don't SAL make storms have a harder time getting the junk in there trunk together?
Sheri



Look at the radar above^^^
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting 1900hurricane:

When is the first model run to incorporate that data? The next 00Z maybe?


Yes, most will go into the 00Z cycle. The last few may not make it in time.
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Don't know how many times we've written off an invest and its come back to bite us. I think every one actually that developed.
Member Since: July 8, 2005 Posts: 259 Comments: 23923
Quoting IKE:
I'm 52...my memory may not be the sharpest, but I don't remember seeing this much SAL over Florida and the Bahamas this often. I'm sure it happens, but I sure don't remember much of it.


Morning Ike, that is a lot of SAL, i really can't remember it being like that either, I remember a yr or 2 ago the SAL was really bad, I wonder if this yr will be like that. I think it hurt a lot of storms, I am no weather expert but don't SAL make storms have a harder time getting the junk in there trunk together?
Sheri
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Quoting IKE:
I'm 52...my memory may not be the sharpest, but I don't remember seeing this much SAL over Florida and the Bahamas this often. I'm sure it happens, but I sure don't remember much of it.

I think that image shows dry air more than it shows SAL. It's just that the SAL is dry air.

Around 1972 or so I do remember seeing Saharan dust high in the air over Baton Rouge. Looked like someone drained some blue out of the sky. That was highly unusual.

Of course, the sky was a lot bluer back then. Didn't have as much pollution. Might not be able to see any difference if such an outbreak of dust occurred today.
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Ike it's been along time but once or twice I believe we even got a little dust to settle out. It's suppose to make for beautiful sunsets.So heads up at sunset.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
Quoting catastropheadjuster:
Wonder where Pat and Atmo is today, I haven't seen them at all. I hope Pat is ok after his fall, I think he fell he hurt his hand.

So 97L looks like a slow one to mature.
sheri


Pat is traveling i think
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Quoting nrtiwlnvragn:
Dropsonde plan for this afternoon's mission.






Mission Plan :

NOAA 49RF will fly an NHC-tasked Synoptic Surveillancd mission around Tropical Disturbance AL97. The G-IV will leave MacDill AFB, FL 1730 UTC and will recover back at MacDill by 0150 UTC next day.


When is the first model run to incorporate that data? The next 00Z maybe?
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"Like a Hurricane"

Neil Young
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Wonder where Pat and Atmo is today, I haven't seen them at all. I hope Pat is ok after his fall, I think he fell he hurt his hand.

So 97L looks like a slow one to mature.
sheri
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.
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624. IKE
Quoting 900MB:


(9) Blank- caster


LOL.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
622. 900MB
Quoting IKE:
Blog topics today....

(1)Rock groups.
(2)Singing tunes.
(3)Praises on the back.
(4)Bye-bye 97L.
(5)It's coming back.
(6)Give it time.
(7)Season is a bust.


(9) Blank- caster
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621. IKE
I'm 52...my memory may not be the sharpest, but I don't remember seeing this much SAL over Florida and the Bahamas this often. I'm sure it happens, but I sure don't remember much of it.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
620. IKE
Maybe SAL is one reason the GFS(both versions), keep it as a wave/weak low and then lose it....


Member Since: June 9, 2005 Posts: 23 Comments: 37858
In the spirit of the blog today...

97L is flirting with Oblivion.
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Quoting Jeff9641:


What does that mean? Sorry..

It means that dry air is having 97L for lunch.
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That upper level low East of Florida, while moving towards the West, is currently sucking the life out of 97L IMHO.....
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615. Skyepony (Mod)
Looking over the buoys.. Little gustier last hour...whoa those water temps. No big pressure fall offs. West winds are gone again..though it's moving farther from buoys & the ship.
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OK..so help me out here..aren't there times when an upper level high helps a storm? I think I remmeber reading how it can help improve outflow or something? Is that true and what is the difference here?
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Quoting patrikdude2:
no.


Hmm, then maybe a Parrot with Tourettes is on the loose. I could swear someone keeps repeating himself over and over, ad nauseum (not you btw).
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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.

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