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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1311. xcool
Turks and Caicos


From ENE at 32mph
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1310. Levi32
Quoting StSimonsIslandGAGuy:
Thanks Levi!


I really hate to say it, but the comments here are really getting out of control. It's been happening a long time, but it is harder and harder to find useful information in the comments than ever before.


Yeah....that's what happens. Eventually the blog traffic will become so heavy that the admin will have to create conditions for who can post on here, which we all have discussed before with the suggestions of only paid members or stuff like that.
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1309. 7544
watch so fla get cought off gaurd once again and this get stronger right at thier doorstep watch it always happen never enough time till the last min
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Quoting IKE:
Lat/Lon: 21.8° N 72.3° W..Providenciales, TI (Airport)

That's right about where it is...appears to have sped up to the W to WNW.


I see it speeding up too. If you zoom out and look at this visible animation:

http://www.ssd.noaa.gov/goes/east/nwatl/flash-vis.html

And also click on the HDW-high wind vectors check box in the animation. The fact that its moving faster to the WNW is not good for development, its about to head into upper westerlies on the south side of the upper low, that could make shear even worse.
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1307. Patrap

#1300


Indeed..a good swim is always refreshing..Like a Cold FRESCA
Member Since: July 3, 2005 Posts: 424 Comments: 128269
Quoting Floodman:


The point is that it's ridiculous to say things like "it's going to track just like Francis in '04" because odds on it won't...analog years are fine, I guess, for guesstimation of the overall season, but really...for track and intensity? Every storm is different regardless of where it forms and while it may take a similar track, that's opretty much coincidental and the similarity ends there


Exactly. ;)
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Conditions at

2010.07.21 1900 UTC
Wind from the ENE (070 degrees) at 32 MPH (28 KT)
Visibility 5 mile(s)
Sky conditions partly cloudy
Temperature 78 F (26 C)
Dew Point 75 F (24 C)
Relative Humidity 88%
Pressure (altimeter) 29.89 in. Hg (1012 hPa)
ob MBPV 211900Z 07028KT 9000 SCT015 SCT050 26/24 A2989 

observation form the Turks and Caicos
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Quoting WatchingThisOne:


Where did that flight come from? It's not on today's flight plan. Good to see it up there though ... good upper level data would be quite handy about now. Will that make it into the 00z runs?


I saw the flight plan earlier today. It had it circling 97L and then returning Tampa.
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Quoting hurrkat05:
this low will not develop like is aid yesterday it has to many things against...shear is its #1 enemy..so all you people n he gulfcoast can rest easy the most you are going to get out of this is some much needed rain..i said bonnie will not form until at least august 10...this shear and dry air wil rule the tropics for the next 2 weeks..so people no need to get all ecited about something this weekend regardless of what the models say...the models have been out shopping on this one...


What is shear at the moment?
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1302. hydrus
Quoting connie1976:
is the thing weakening or strengthening? too many conflicting comments....I'm confused!! lol thanks all!
It is going to pulse and fluctuate in strength and size as long as it keeps interacting with the upper low.
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Quoting connie1976:
is the thing weakening or strengthening? too many conflicting comments....I'm confused!! lol thanks all!


Based on falling pressure, buoy winds, climatological conditions, and satellite presentation, it appears to be strengthening, at least for the moment. (Which doesn't mean it'll continue to do so; that's just where it's at now.)
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Quoting connie1976:
is the thing weakening or strengthening? too many conflicting comments....I'm confused!! lol thanks all!
Try to weed out the good from the not so good on here. It will help a lot.
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Quoting AlexEmmett:

pressures are falling which means it is strenthaning


Correct - however sometimes just because pressure's are falling it may not mean an increase in intensity.
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pressure at Pine Cay is now 29.81 inches or 1009.3mbs
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Quoting Baybuddy:


Yup. I suppose each storm is an entity to itself...sort of. But historcal trends cannot be discounted.


The point is that it's ridiculous to say things like "it's going to track just like Francis in '04" because odds on it won't...analog years are fine, I guess, for guesstimation of the overall season, but really...for track and intensity? Seriously? Every storm is different regardless of where it forms and while it may take a similar track, that's pretty much coincidental and the similarity ends there
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1295. Patrap
Dunno,...
Member Since: July 3, 2005 Posts: 424 Comments: 128269
Quoting Patrap:
Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 21st day of the month at 18:37Z
Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)
Mission Purpose: Investigate second suspect area (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 02

Part A...

Date: Near the closest hour of 18Z on the 21st day of the month
Highest Mandatory Level For Which Wind Was Reported: 250mb
Coordinates: 29.0N 77.0W
Location: 273 miles (439 km) to the N (4°) from Nassau, Bahamas.
Marsden Square: 080 (About)


Where did that flight come from? It's not on today's flight plan. Good to see it up there though ... good upper level data would be quite handy about now. Will that make it into the 00z runs?
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1291. hydrus
Quoting AlexEmmett:

make it 500 tons of nasty bloody old crow
It sounds like a song title..(500 tons of nasty bloody old crow).
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Quoting connie1976:
is the thing weakening or strengthening? too many conflicting comments....I'm confused!! lol thanks all!

pressures are falling which means it is strenthaning
1289. hydrus
Quoting CaicosRetiredSailor:
Here on Providenciales this afternoon the wind direction has definitely backed from East toward the Northeast. My highest gust recorded so far is 43 mph. Still no significant rain today.

This is reliable Wx station on a nearby island:

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IPINECAY2
C.R.S. When did you experience your last full blown hurricane and how many have you been through total? I ask this because you live in the Bahamas...I think..:)
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is the thing weakening or strengthening? too many conflicting comments....I'm confused!! lol thanks all!
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In Tampa we are Watching and wondering. Great site minus a few people
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Quoting est1986:
TD by tomorrow morning?

by 2pm tommarow not eariler
Quoting StSimonsIslandGAGuy:
Caicos, I am glad that you will be dealing with at most a weak tropical storm instead of something worse.


Thanks, I am also, it has been ODD to watch this "aiming" at us for 48 hours.
Member Since: July 12, 2007 Posts: 0 Comments: 6032
Quoting Levi32:


I was talking about the upper low, but 97L or what's left of it may end up in Texas as well right behind it. I wouldn't be concerned about it, as it is unlikely to be any significant threat to the gulf coast. It should be watched for a possible try at winding up in the western gulf, but I doubt it will be anything but a potential rain-maker for you guys.


ok, that is fine with me....I'd rather that then the hot humid sun...... :)
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Quoting leo305:


looks like the center is south east of the turks and caicos


It makes sense winds are changing from E to more NE over the eastern Bahamas & Turks & Caicos Islands right now. There's a sharp soutwhest-northeast elongated trough approachign the area from the east. What would be more interesting to see if there are any W winds being reported in NW Haiti. That could imply a higher chance of their being a closed circulation. Anyone have obs from Haiti?
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Quoting StSimonsIslandGAGuy:
Thanks Levi!


I really hate to say it, but the comments here are really getting out of control. It's been happening a long time, but it is harder and harder to find useful information in the comments than ever before.


There are just too many dang people on here honestly haha, many of which are loco, it has gotten out of hand for sure, I wish it was like the good old blog days.
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South Texas sends some rain North, pretty darn dry where i live. The rains are going to the flooded Rio Grande again.
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Quoting Seflhurricane:
i see the same thing but its elongated


Dvorak Infrared Loop shows pretty cold center.
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1275. est1986
TD by tomorrow morning?
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1274. 900MB
Quoting CaicosRetiredSailor:
Here on Providenciales this afternoon the wind direction has definitely backed from East to Northeast. My highest gust recorded so far is 43 mph. Still no significant rain today.

This is reliable Wx station on a nearby island:

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IPINECAY2


Pretty gusty down there in T&C. Gotta say, I'm jealous- love Provo!
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1273. Patrap
Quoting StSimonsIslandGAGuy:
Thanks Levi!


I really hate to say it, but the comments here are really getting out of control. It's been happening a long time, but it is harder and harder to find useful information in the comments than ever before.


Not if you use the controls and, well, not bite on every thing you dont agree with.


One has a choice here.

Always..

ignore..or tangle with idiocy

Member Since: July 3, 2005 Posts: 424 Comments: 128269
1272. hydrus
Quoting AlexEmmett:
hey btw

it looks like its trying to bear hug florida
It is my belief that if the upper low were out of the way, our invest would intensify pretty quick. even with the dry air in the vicinity.jmo
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Quoting CaicosRetiredSailor:
Here on Providenciales this afternoon the wind direction has definitely backed from East to Northeast. My highest gust recorded so far is 43 mph. Still no significant rain today.

This is reliable Wx station on a nearby island:

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IPINECAY2

wow look at the pressure
15:30 79.0 °F 76.0 °F 29.81in NE 30.0mph 42.0mph 89% - 0887 watts/m^2
1270. IKE
Lat/Lon: 21.8° N 72.3° W..Providenciales, TI (Airport)

That's right about where it is...appears to have sped up to the W to WNW.
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1268. 7544
yeap btw it now has energy to feed off on its going to get real fat reeal fast this just showed up this hour and what has been missing all along 97l is getting hungry now 8pm we should see a big red ball imo and now with the low well u know whats going to happen and maybe sooner
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Pine Cay Wx Station
right now sustained at 22mph
pressure down to 29.81 which is about 1010mb...
gusts up to 42mph with highest sustained winds about an hour ago at 34mph...
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1266. unf97
Quoting leo305:


looks like the center is south east of the turks and caicos


It is. You can depict the swirl on visible imagery, just SE of the lowestmost island in the Turks.
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In the space of 4 hours 97L has gone from random cloud in the ATL/Carribean to a remotely organised invest.
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Quoting 10Speed:


The NHC wears blinders on Wednesday. 97L is blowing up and we'll have Bonnie by morning.
I know that is just YHO
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Quoting NCHurricane2009:


I was at first glance going to say its getting better organized, but I look at this visible loop:

http://www.ssd.noaa.gov/goes/flt/t1/flash-vis.html

It looks like there is some sort of sharp vorticity in the low clouds just north of Haitia and south of the Turks/Caicos. I can see vorticity in the low clouds extending also well to the southwest too, looks to me like an elongated southwest-northeast surface trough with the thickest white clouds sheared to the north of the surface trough. Its almost tempting to say there's a closed circulation just south of the Turks and Caicos, but I don't think there is one right now.
i see the same thing but its elongated
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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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