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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1662. scott39
Quoting NCHurricane2009:


This is why I am still thinking this is not going to develop. This is a vigorous surface trough at the moment with wind shear preventing further development.
Im not sold on ULL keeping tandum with 97L in regards to the GOM yet.
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Quoting wayfaringstranger:
Currently in Mayaguana, BF as of 2010-07-21 20:00 UTC Wind: E 32 mp Pressure :29.89 in
Hey wayf, where u getting the reading from? TIA.
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Quoting scott39:
If 97L developes into a TD before FL, doesnt that mean that ULL is farther away by then and the gom is open for more developement?


It could mean that the ULL is further from 97L.
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Quoting StormW:
Broad LLC at 20.6N;72.1W?


Interesting way to look at it, makes sense.

Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting Drakoen:
Pine Cay airport is reporting winds around 35mph with gusts to 42mph and a pressure of 29.79in.


1008 mb. Interesting.
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IF this mess develops, it won't very strong. IMHO
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1655. guygee
Providenciales, Turks Islands
Scroll to the bottom for near-realtime updates.
Current lowest pressure:
Provo Golf Club, Grace Bay - 29.76 in
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when will the next ASCAT come out i am really curious to see
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Quoting alcomat:
well it is possible.Not all storms head for florida when they develop,as a lot of the bloggers on here tend to think.
Given the location of this storm, though, I'd be very surprised if it didn't. There's a certain logic to expecting FL impacts given current conditions, and a certain counterintuitivity to the converse.
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Quoting Jeff9641:


Strong winds yes but still no closed low. I tried to find w wind but had no luck at all. What do you think?


This is why I am still thinking this is not going to develop. This is a vigorous surface trough at the moment with wind shear preventing further development.
Member Since: September 15, 2009 Posts: 574 Comments: 3734
Quoting sailingallover:

it has also broken off from the trough to its east..possible from the sheared off outflow of 97L
Right now I think what shear there is helping 97L with outflow and allowing more moisture and energy to come from the east. Granted it makes it tougher to form a good core but if enough warm air rises long enough..
I would love to see atmospheric cross section from the Vi's to about 200 miles east of Nassau


You and me both. I think this develops slowly across the straights.
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Quoting Patrap:
The G-4 is On Station Above 97L flightaware.com/live/flight/NOAA49


On its way back to Tampa as we speak.
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Quoting Jeff9641:


Strong winds yes but still no closed low. I tried to find w wind but had no luck at all. What do you think?

We need an scatterometer floater..qickscat gone ASCAT and WINDSAT miss 3/4 of the globe sometimes..
Write your elected officials..
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Quoting leo305:


There's shear but it may be nowhere near 40 knots.. based on visible satellite

in fact, there are other issues hurting it more so than the shear, and that is DMIN combining with the dry air, it's probable that tonight even with the shear, the low may start to develop some convection.



ok
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Quoting ElConando:


Not 1008 yet it just under 1009mb.

Still, that's 2 millibars lower than the 1011mb we had found earlier.
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1646. Drakoen
Quoting Jeff9641:


Strong winds yes but still no closed low. I tried to find w wind but had no luck at all. What do you think?


NOAA G-IV plan will be dropping dropsondes south of the system and that will let us know whether or not it is closed.
Member Since: October 28, 2006 Posts: 57 Comments: 31637
High:Mid:Low level winds

Rainbow IR
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1644. scott39
If 97L developes into a TD before FL, doesnt that mean that ULL is farther away by then and the gom is open for more developement?
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Quoting smmcdavid:


Congrats... would you like a cookie?





LMAO
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Quoting Jeff9641:


Strong winds yes but still no closed low. I tried to find w wind but had no luck at all. What do you think?
i have been looking also and i see none but 97L is starting to consolidate
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1641. leo305
Quoting Jeff9641:


Here is the link below.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.html


that isn't 40 knots
Member Since: April 17, 2010 Posts: 0 Comments: 1753
1640. Patrap
The G-4 is On Station Above 97L flightaware.com/live/flight/NOAA49
Member Since: July 3, 2005 Posts: 433 Comments: 132806
Quoting CybrTeddy:
ULL looks to also becoming a little weaker on the 200 mb vort.

3 hours ago, look at the deep reds.


Now


Probably doesn't mean much, but I thought it was slightly interesting.

it has also broken off from the trough to its east..possible from the sheared off outflow of 97L
Right now I think what shear there is helping 97L with outflow and allowing more moisture and energy to come from the east. Granted it makes it tougher to form a good core but if enough warm air rises long enough..
I would love to see atmospheric cross section from the Vi's to about 200 miles east of Nassau
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1638. xcool
Pressure drop faster
Member Since: September 26, 2009 Posts: 2 Comments: 15705
1636. leo305
Quoting Tazmanian:
guys turst me if 97L if there was 40kt wind t-storm would be blown right off there is no 40kt shear overe 97L in fac if there was 40kt shear we would not be seeing mb drops and organized going on


There's shear but it may be nowhere near 40 knots.. based on visible satellite

in fact, there are other issues hurting it more so than the shear, and that is DMIN combining with the dry air, it's probable that tonight even with the shear, the low may start to develop some convection.
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting xcool:
Link

HERE.


Not 1008 yet it just under 1009mb.
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Quoting alcomat:
well it is possible.Not all storms head for florida when they develop,as a lot of the bloggers on here tend to think.


Not all - just 40%
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1633. Patrap
Advanced Microwave Sounding Unit (AMSU) - Based Intensity Estimates

The Advanced Microwave Sounding Unit or AMSU, which is an instrument on the NOAA operational polar-orbiting satellites, has the capability to make temperature soundings. Using a combination of AMSU-based soundings, the hydrostatic relationship, and statistics, a tropical cyclone intensity estimate can be made. The methodology used here is discussed in Demuth et al (2004) and updated in Demuth et al. (2006). Estimates are created by the National Centers for Environmental Prediction and the estimates as well as other products are available for the last two days at NCEP Central Operations. While overall statistics are comparable with the Dvorak technique, this method is most useful and accurate for tropical cyclones with intensities less than ~90 kt. Shown in this product are time series of the operational warning intensities versus the AMSU-based intensity estimates.

Member Since: July 3, 2005 Posts: 433 Comments: 132806
The longer this entity remains a disturbance/TD/weak TS, the more likely it becomes that it may go through the Florida straits.
Member Since: June 29, 2009 Posts: 13 Comments: 5318
Afternoon everybody. I see 97L has gone back to 50% at 2 pm. Does that mean the centre's still tracking more west than north?
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Currently in Mayaguana, BF as of 2010-07-21 20:00 UTC Wind: E 32 mp Pressure :29.89 in
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1629. Drakoen
Pine Cay airport is reporting winds around 35mph with gusts to 42mph and a pressure of 29.79in.
Member Since: October 28, 2006 Posts: 57 Comments: 31637
1628. xcool
Link

HERE.
Member Since: September 26, 2009 Posts: 2 Comments: 15705
just got home from work... what the heck is the CMC 12Z doing?... looks like 97L has an offspring; very strange
please advise :)
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1624. alcomat
Quoting Tazmanian:



are you a wishcaster ??? P
well it is possible.Not all storms head for florida when they develop,as a lot of the bloggers on here tend to think.
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guys turst me if 97L if there was 40kt wind t-storm would be blown right off there is no 40kt shear overe 97L in fac if there was 40kt shear we would not be seeing mb drops and organized going on
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The shear falling in front of it won't mean much unless the ULL moves out faster. That area of a ULL usually has lower shear values. Assuming the ULL doesn't slow down and 97L speeds up which doesn't seem at all likel.
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Quoting xcool:
Turks and Caicos Pressure 1008MB

O_O Are you sure that's official?
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Quoting CybrTeddy:
Looking at GOES-E the COC is ahead of the convection.. and appears to be getting tighter. While this is a sheared system it is getting better organized.


This is annoying, could this be pulling off another Henri 2009 or Fabian 1997? I am still believing this will not develop due to wind shear, but those two storms did. I am going with probability here because most (not all) systems that are under shear don't develop. I am still believing that this won't develop due to shear until I hear that there are surface obs that show west winds south of the "center."
Member Since: September 15, 2009 Posts: 574 Comments: 3734
Quoting xcool:
Turks and Caicos Pressure 1008MB


Link?
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1618. scott39
Quoting NCHurricane2009:


The ULL is south of dee-layered ridging spanning the southern United States into the western Atlantic for several hundered miles. Chances are, the ULL will continue westward while retrograding around the south side of the ridge, which would place the ULL eventually into the Gulf of Mexico. So, its possible that 97L will continue to be sheared by the ULL as it too moves into the Gulf of Mexico.
Thanks, I hope thats right!
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Quoting WxLogic:


I concur... but I do believe this broad load might be getting replaced by a new low attempting to consolidate near 21.5N 71.5W.


So I'm not the only one seeing a small spin just south of that popcorn convective cell..
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im out..... be back later.
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1614. xcool
TD MAYBE SOON ..
Member Since: September 26, 2009 Posts: 2 Comments: 15705
1613. scott39
Is it too early to know what the ULL is going to do in the GOM?
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1612. leo305
Quoting Jeff9641:


No, I just checked the Cimss site and there are no W winds right now. ULL has caused 30 to 40 knt winds over 97L. Convection is there yes but not organized as it looks is if the ULL wants to pull all of this NW or WNW toward the FL penisula. If they continue to move in tamdam then 97L will never develope but if the seperate and ULL moves away then 97L will have a chance. 97L and the ULL appear to moving WNW together which not good for potential developement.


The ULL is causing 40 knot shear over 97L?
Member Since: April 17, 2010 Posts: 0 Comments: 1753

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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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