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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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?
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1611. WxLogic
Quoting StormW:
Broad LLC at 20.6N;72.1W?


I concur... but I do believe this broad low might be getting replaced by a new low attempting to consolidate near 21.5N 71.5W.
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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.
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is the dynamic model usually right more than the statistical?
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1608. Patrap
Quoting 69Viking:
Gotta run, nothing happening with 97L fast that's for sure, guess I'll check on it later this evening!


3 Hours between views is best for looking at Synoptic Changes..

Frame to frame will allow one to drive right off the Page into the Drink..
Member Since: July 3, 2005 Posts: 421 Comments: 127566
Quoting scott39:
Do you think the ULL will effect 97L in the GOM?


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.
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Quoting xcool:
Turks and Caicos Pressure 1008MB



we have had a good drop in mb today and still going
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Quoting 7544:
Tazmanian 4:44 PM EDT on July 21, 2010
21/1745 UTC 21.2N 71.3W T1.0/1.0 97L -- Atlantic


td coming taz



yup
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1604. xcool
Turks and Caicos Pressure 1008MB
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1603. 7544
Tazmanian 4:44 PM EDT on July 21, 2010
21/1745 UTC 21.2N 71.3W T1.0/1.0 97L -- Atlantic


td coming taz
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Seems like the ULL is starting to speed up.
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Gotta run, nothing happening with 97L fast that's for sure, guess I'll check on it later this evening!
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Recent Conditions -- NE Bahamas

Air temperature: 28.5 °C (84.0 °F)
Dewpoint temperature: 23.5 °C (74.8 °F)
Sea level pressure: 1021.3 hPa (34585.2 in)
Significant wave height: 1.8 m (5.9 ft)
Water temperature: 28.7 °C (84.3 °F)
Wind gust speed: 9.0 m/s (17.5 kts)
Wind speed: 7.0 m/s (13.6 kts)
Last reported: 5:49 PM GMT 07/21/2010
12:49 PM EST 07/21/2010
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1599. unf97
Quoting Patrap:



One can always use the wu-mail system for Questions,as they tend to bring unwarranted comments and ridicule from some here always.
I answer tons of stuff by mail daily.

Its easier than Broadcasting the question Globally here.


Thanks patrap. Wu-mail is another method for sure that I should utilize more often.
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Quoting CybrTeddy:


Would like to see an ASCAT pass.


Hopefully it will not miss it this time.
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1596. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127566
Quoting Tropicaddict:


StormW, do you think 97L is caput?


I'm not Storm, of course, but the answer to your question is "yes"...if, that is, you consider strengthening a sure sign of kaput-ness... :-)
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StormW, can this system, which doesn't look TOO great at this point, become a TD before affecting Fl?
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Quoting Floodman:


Latest Shear tendency...CIMSS


I see a line of increasing shear tendency along 50*W.
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Quoting hurricanejunky:


and besides, we NEED the rain. At least here in N. Ft. Myers, we've had yet another dry rainy season thus far. Seems when I was a kid and up until recently, every day between 3 and 5 pm the thunderboomers and heavy rains would come.
Not anymore...weirdness...


yes it has been dry this year...we are in north cape coral and work in NFM off bayshore road usually get storms in afternoon everyday not this year lots of sunshine
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Quoting Tazmanian:
21/1745 UTC 21.2N 71.3W T1.0/1.0 97L -- Atlantic




nop its at 21N 71W where we have a 1.0 T #
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Quoting wayfaringstranger:
Jason?


If you're asking if that's my name, then no. :P
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Quoting jlp09550:
Struggling?



Yes. The low-level white clouds in that image are exposed underneath the south side of the upper low while all colorized deep convective clodus are sheared off to the northeast.
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1587. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127566
1586. scott39
Quoting Patrap:


Indeed..the ULL Clockwise Flow is creating a 20-30 Knt S westerly Shear and thats impeding any Progress with 97L's attempt to organize.
Do you think the ULL will effect 97L in the GOM?
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1585. 7544
uul moving out preety fast now this might get 97l going some more as it starts to incerase in size
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Quoting StormW:
Broad LLC at 20.6N;72.1W?


Yes, I think I see that, StormW.
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Quoting Patrap:


Thats a false assumption always.

A Algorithm runs that tracks the Overall envelope embedded in the Easterlies..

The CoC is always known at the beginning of a Given run to best estimate.

One can figure the Center easily.

And with Human Eyes and the algorithm a best est is made.

Thats not a GIGO scenario as thats a analog term..


And we aint Flying Apollo with these Puters


So you're saying that the models ALWAYS initialize in the right spot? Is that troll bomb getting to you?
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Quoting jlp09550:
Struggling?



definitely stuggling... you can see it battling the shear... however.. its doing so surprisingly well.. because its not really gaining organization... nor losing it.
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Quoting StormW:
Broad LLC at 20.6N;72.1W?


Would like to see an ASCAT pass.
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1580. xcool


BY Ivanhater


storm2k.org/
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting StormW:
Broad LLC at 20.6N;72.1W?


Could be but I rather let someone else with better sat watching skills to affirm your sighting.
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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.

If the ULL is ever so slightly weaker, so is the wind shear. The small ball of pink shrunk slightly, which is a sign of SLIGHT weakening.
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21/1745 UTC 21.2N 71.3W T1.0/1.0 97L -- Atlantic
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1574. Patrap
Quoting jlp09550:
Struggling?



Indeed..the ULL Clockwise Flow is creating a 20-30 Knt S westerly Shear and thats impeding any Progress with 97L's attempt to organize.
Member Since: July 3, 2005 Posts: 421 Comments: 127566
Quoting redUK:
Does anyone have a link to the 18z GFS 200-850 shear 200-850 forecast?


Latest Shear tendency...CIMSS

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I see lots of comments about obs near and north of the alleged "center." Low pressures around 1011 to 1009 mb, NE winds NW of the "center," etc. However, a "center" is not a center until there are W winds south of the center.

I am really really curious :) to know if there are any west winds south of the center. Anyone know?
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Quoting jlp09550:
Struggling?

Jason?
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Quoting Patrap:


Thats a false assumption always.

A Algorithm runs that tracks the Overall envelope embedded in the Easterlies..

The CoC is always known at the beginning of a Given run to best estimate.

One can figure the Center easily.

And with Human Eyes and the algorithm a best est is made.

Thats not a GIGO scenario as thats a analog term..


And we aint Flying Apollo with these Puters


I wish we where flying Apollo still.. /back on topic.
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thunderstorms continue to build on the east side and trying to build near center.
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1567. xcool
Tazmanian LMAO :0
Member Since: September 26, 2009 Posts: 2 Comments: 15620
All I can say is, the whole thing is a house of cards,
the deck is stacked,
and there's too many jokers in here.
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1565. Patrap
Quoting unf97:


I read Storm's blog often since I became a member of WU a couple of years ago. I just have become so accustomed of asking him questions here on Dr. Masters' blog. I forget that when it is busy on this blog here like right now with systems to follow like with 97L out there to ask questions on Storm's blog.

Thanks for reminding me of that. When it is busy, I definitely will make more attempts to get Storm questions on his blog.



One can always use the wu-mail system for Questions,as they tend to bring unwarranted comments and ridicule from some here always.
I answer tons of stuff by mail daily.

Its easier than Broadcasting the question Globally here.
Member Since: July 3, 2005 Posts: 421 Comments: 127566
Quoting CybrTeddy:


Right here.
Link


ty
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Quoting StormW:
Taking a quick look at satellite loop imagery (RGB) those interested in the area SE of Puerto Rico...no worry at the moment. If you look closely, you can see the tops of the convection streaming south, being affected by the outflow pattern for 97L.

RGB LOOP


StormW, do you think 97L is caput?
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Struggling?

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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.