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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1261. hydrus
Quoting wayfaringstranger:


Nice. Dont hold it against me if I am a Vol fan ok? That pretty much describes our season.
The Vols are cooldude...:) jmo
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Quoting Asta:
re:1138. BiloxiIsle
Here's one forecast that is easy-
Aug. Fri 27th-through Sun the 29th
The media will swarm like red fire ants again around New Orleans and the MS Gulf Coast

97L looks more organized IMHO

http://www.ssd.noaa.gov/goes/east/tatl/rb-l.jpg


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.
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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
Member Since: July 12, 2007 Posts: 0 Comments: 6069
1257. IKE
Quoting Hardcoreweather2010:


LOL! There is that chance.
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hey btw

it looks like its trying to bear hug florida
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1255. 10Speed
Quoting CosmicEvents:
The NHC says that it's not getting more organized right now. Nothing left to do but talk in circles, preferably yellow, orange, and red ones.


The NHC wears blinders on Wednesday. 97L is blowing up and we'll have Bonnie by morning.
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1254. xcool
ISEE 97L GET GOM IMO
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1252. leo305
Quoting SLU:
Surface observations - Turks & Caicos Islands

Providenciales, TI (Airport) - 3:00pm

Temp - 79 °F / 26 °C
Wind - ENE @ 32 mphPressure - 1012 hPa (Falling)



looks like the center is south east of the turks and caicos
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting Hardcoreweather2010:


Nice. Dont hold it against me if I am a Vol fan ok? That pretty much describes our season.
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1248. SLU
Surface observations - Turks & Caicos Islands

Providenciales, TI (Airport) - 3:00pm

Temp - 79 F / 26 C
Wind - ENE @ 32 mph
Pressure - 1012 hPa (Falling)

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1247. Levi32
Quoting StSimonsIslandGAGuy:
What is the shear forecast to be in the eastern Gulf 4-5-6 days out when this system is forecast to be there?

Yes, I know that's probably been answered multiple times, but just too lazy to wade back through hundreds of comments to find a post by someone knowledgeable.


Not perfect, but more favorable than 97L currently has, more aligned with the upper ridge over the gulf. This next system could be a sneaky problem if it materializes.

This is the GFS's interpretation of the thing in 6 days.

Surface pressure: (SE of NOLA)



Wind shear:



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Quoting fire635:


I finally put him on ignore... I think thats the best advice


Cmon guys - none of us really like the back n forth banter. Jason, cmon man ease it up a little. Its one thing to have fun but another to add provication. Your smart, probably a cool person, and Im sure you can reason.
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Quoting CosmicEvents:
The NHC says that it's not getting more organized right now. Nothing left to do but talk in circles, preferably yellow, orange, and red ones.

actully it is organising it looks ten times better than it looked yesterday it now has an llc
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Quoting hcubed:


I don't remember some of the 70's either...
What 70's......
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It's trying to moisten the atmosphere in front of it.
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1239. IKE
AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
325 PM EDT WED JUL 21 2010

.DISCUSSION...
SHOWERS IN THE SOUTHWESTERN MARINE PORTIONS OF OUR SERVICE AREA HAVE
DIMINISHED IN COVERAGE...WITH LINGERING PATCHES WELL SOUTH OF A DRY
TORTUGAS TO MARQUESAS KEYS LINE. MORE RECENT ECHOES HAVE DEVELOPED
OFF CUMULUS STREAMERS EXTENDING FROM ANDROS ISLAND...AND ARE ENTERING
THE STRAITS. WINDS ARE FRESH TO OCCASIONALLY STRONG FROM THE EAST ACROSS
THE EASTERN TWO THIRDS OF THE SERVICE AREA. SKIES ARE MOSTLY SUNNY
ALONG THE ISLAND CHAIN WITH TEMPERATURES CURRENTLY AROUND 90 DEGREES.

THE KEYS LIE BETWEEN A WAVE PUSHING QUICKLY WESTWARD IN THE WESTERN
GULF OF MEXICO AND A SOMEWHAT DISRUPTED WAVE CURRENTLY LYING ACROSS
HISPANIOLA FROM THE ATLANTIC INTO THE NORTHERN CARIBBEAN. SHORT TO
MEDIUM RANGE FORECAST REASONING HAS NOT CHANGED SIGNIFICANTLY FOR
THIS UPCOMING ISSUANCE. VISIBLE AND GOES SOUNDER IMAGERY ALONG WITH
MIMIC PRECIPITABLE WATER LOOPS SHOW A RELATIVELY DRY AIRMASS
EXTENDING FROM THE LOCAL AREA EAST/SOUTHEASTWARD TO THE WESTERN
FLANKS OF THE WAVE. MINIMAL POPS (10 PERCENT) WILL BE MENTIONED
TONIGHT TO ACCOUNT FOR A FEW SHALLOW SHOWERS THAT MAY MOVE QUICKLY
THROUGH THE SERVICE AREA. THIS WILL ONLY BE RAISED TO 20 PERCENT
THROUGH THURSDAY THANKS TO DRYNESS PERSISTING IN THE MID LEVELS OF
THE TROPOSPHERE.

AS THE WAVE APPROACHES FROM THE EAST THROUGH LATE THURSDAY...MOISTURE IS
EXPECTED TO GRADUALLY INCREASE. THE LATEST ROUND OF MODELS CONTINUE
TO SLIDE THE UPPER LEVEL LOW WEST/SOUTHWESTWARD AHEAD OF THE
WAVE...BUT AT A GREATER PACE THAN SOLUTIONS 24 HOURS AGO. AND...IN A
GENERAL SENSE ARE FURTHER SOUTH WITH A WEAKER SURFACE WAVE (AS
OPPOSED TO SOME MAKING A DISTINCT CIRCULATION EARLIER) PULLING ACROSS THE
AREA THROUGH THE DAY THURSDAY. AS FAR AS SENSIBLE WEATHER...NO LARGE
ADJUSTMENTS ARE EXPECTED FROM OUR PREVIOUS ISSUANCE AS THIS FEATURE
PROGRESSES. WILL STEADILY BRING OUR RAIN CHANCES THROUGH LATE
THURSDAY TO BE AT A HIGH CHANCE BY EARLY FRIDAY. THIS HIGH CHANCE
WILL BE MAINTAINED THROUGH SATURDAY...EVEN THOUGH BOTH THE GFS AND
ECMWF ARE SLIDING A POCKET OF DRIER AIR ON THE BACK SIDE OF THE WAVE
INTO THE MID LAYERS. WE WILL HAVE TO SEE HOW THE FEATURE ACTUALLY
EVOLVES BEFORE MAKING CHANGES BEYOND SATURDAY. A RETURN TO NEAR CLIMO
NUMBERS WILL BE KEPT THROUGH EARLY NEXT WEEK AS AN ATLANTIC HIGH
PRESSURE AXIS REMAINS ALIGNED ACROSS NORTH FLORIDA AND THE SOUTHEAST
STATES.

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What a waste of time this 97L, radar in TX is more intersting than this pitiful thing
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Quoting Floodman:


Well, to be honest there are some similarities between 97L and the other, more famous system...the ridge building into the SE for one...


Yup. I suppose each storm is an entity to itself...sort of. But historcal trends cannot be discounted.
Member Since: June 26, 2006 Posts: 0 Comments: 1115
hey storm or drak if you are out there seems like 97L is trying to get its act together your thoughts to help clear the minds of some on here so we dont have the same questions over and over again ???
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1235. hcubed
Quoting StormW:


I don't remember 3rd grade.


I don't remember some of the 70's either...
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1234. unf97
Quoting Seflhurricane:
do you also see on the visible its starting to pull moisture from hispaniola and the carribean from the SW


Yes, it is trying to that Seflhurricane. But, it is fighting the dry air from the SW as well, and this hindrance has been the culprit all along.
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Quoting 7544:
bottom line is 97l getting better organized at this hour or not everyone seems to be talking in circles here
The NHC says that it's not getting more organized right now. Nothing left to do but talk in circles, preferably yellow, orange, and red ones.
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1231. fire635
Quoting AlexEmmett:
jason, log off now we along with you family all dislike you


I finally put him on ignore... I think thats the best advice
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1230. Asta
re:1211. Chicklit
I agree- I guess time will tell.
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1229. Patrap

NOAA 49 on the Big Orbit around 97L this afternoon

Scheduled Actual/Estimated
Departure 01:44PM EDT 01:24PM EDT
Arrival 09:59PM EDT 04:40PM EDT
Speed Mach .77 394 kts
Altitude 41000 feet 45000 feet (track log & graph)
Member Since: July 3, 2005 Posts: 428 Comments: 129902
Amazing, looks like this 97 L is regaining strength? I am noticing more flow and perhaps a better circulation now?



StormW -Your thoughts?
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1226. 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)
Member Since: July 3, 2005 Posts: 428 Comments: 129902
Ahh, but those are used primarily to forecast the possible activity level for a season... not track or intensity. I think we can all agree that there are certain factors that increase activity...
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Quoting NCHurricane2009:
UNFAVORABLE UPPER-LEVEL WINDS AND THE EFFECTS OF THE HIGH TERRAIN OF
HISPANIOLA HAVE DISRUPTED THE STRUCTURE OF THE TROPICAL WAVE THIS
MORNING
. THE AXIS OF THE WAVE IS APPROACHING THE SOUTHEASTERN
BAHAMAS WITH MOST OF THE CLOUDINESS...SHOWERS AND GUSTY WINDS
EXTENDING EASTWARD FOR SEVERAL HUNDRED MILES. THIS ACTIVITY WILL
LIKELY SPREAD OVER THE BAHAMAS DURING THE NEXT DAY OR TWO AS THE
WAVE MOVES GENERALLY WESTWARD AT 10 TO 15 MPH. ALTHOUGH THE WAVE IS
CURRENTLY DISORGANIZED AND DEVELOPMENT IS NOT ANTICIPATED
TODAY...UPPER-LEVEL WINDS COULD BECOME A LITTLE MORE FAVORABLE ON
THURSDAY. THERE IS A MEDIUM CHANCE...50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Yes, I nailed my forecasts of 97L yesterday! Woohooo! I issued two forecats yesterday on my blog. 24 hours ago, I was predicting land interaction, shear from the upper low, and possibly dry air issues could cause 97L to not develop. Then early this morning, I was saying that 97L had re-focused NEward toward the Dominican Repbulic underneath a small upper ridge cell. I said in the last paragraph of that blog entry it could go one of two ways, (1) move westward and get sheared by the upper low and suffer from land interaction with northern Hispaniola, or (2) move more WNW, stay north of the island, and develop underneath the small upper ridge cell. Looks like choice (1) this afternoon. I didn't like my forecast this morning because I left two possibilities, I like just to suggest one possibility.

It feels good to be able to understand what's going on.

you were right about today but its organising it has a llc and all it needs is a good d-max remember it doesnt have to be picture perfect to be classifyed a td also with all the models in agreement that it will effect florida the nhc will be more hesitant not to screw up
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1223. 7544
oh oh look what that line of storms that is starting to feed 97l hmmmm from the gom didnt see that before or coming 97l is going to gain weight soon feeding right into it stay tuned
Member Since: May 6, 2007 Posts: 0 Comments: 6874
Quoting unf97:


Looking at the visible imagery loop, your estimated center position seems about right. You can see that swirl pretty good on visible, with the convection building N-Ne of the swirl, and voiding convection on the S and SW side.
do you also see on the visible its starting to pull moisture from hispaniola and the carribean from the SW
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Quoting CybrTeddy:
17:30 UTC.. its 17:52 UTC right now. Anyone got any data yet?


If you are talking about the NOAA jet, you're a day early.
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Maybe "poof" ball ElConado.
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Quoting NCHurricane2009:
UNFAVORABLE UPPER-LEVEL WINDS AND THE EFFECTS OF THE HIGH TERRAIN OF
HISPANIOLA HAVE DISRUPTED THE STRUCTURE OF THE TROPICAL WAVE THIS
MORNING
. THE AXIS OF THE WAVE IS APPROACHING THE SOUTHEASTERN
BAHAMAS WITH MOST OF THE CLOUDINESS...SHOWERS AND GUSTY WINDS
EXTENDING EASTWARD FOR SEVERAL HUNDRED MILES. THIS ACTIVITY WILL
LIKELY SPREAD OVER THE BAHAMAS DURING THE NEXT DAY OR TWO AS THE
WAVE MOVES GENERALLY WESTWARD AT 10 TO 15 MPH. ALTHOUGH THE WAVE IS
CURRENTLY DISORGANIZED AND DEVELOPMENT IS NOT ANTICIPATED
TODAY...UPPER-LEVEL WINDS COULD BECOME A LITTLE MORE FAVORABLE ON
THURSDAY. THERE IS A MEDIUM CHANCE...50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Yes, I nailed my forecasts of 97L yesterday! Woohooo! I issued two forecats yesterday on my blog. 24 hours ago, I was predicting land interaction, shear from the upper low, and possibly dry air issues could cause 97L to not develop. Then early this morning, I was saying that 97L had re-focused NEward toward the Dominican Repbulic underneath a small upper ridge cell. I said in the last paragraph of that blog entry it could go one of two ways, (1) move westward and get sheared by the upper low and suffer from land interaction with northern Hispaniola, or (2) move more WNW, stay north of the island, and develop underneath the small upper ridge cell. Looks like choice (1) this afternoon. I didn't like my forecast this morning because I left two possibilities, I like just to suggest one possibility.

It feels good to be able to understand what's going on.


Congrats... would you like a cookie?
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Quoting hydrus:
I have read that a lot of people like the ECMWF model....Why is this particular model so well liked?


I don;t pay much attention to models until a system reaches TS or CAT1, but the ECMWF has a opertty good track record...LOL
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the main thing for 97L to get its act together is that UUL to move quickly west then we should see 97L begin to get cranked
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Quoting leo305:


is that a good thing or a bad thing for 97L


If they are moving in tandem off to the WNW, status quo in the shear department however, the ULL appears to be outpacing the LLC which COULD reduce the effects of shear in time.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
1214. unf97
Quoting Seflhurricane:
center of 97L looks to be at 21.3N and 71.5 W in my opinion and with the last few frames the indications are that its starting to establish a southwest inflow into the center


Looking at the visible imagery loop, your estimated center position seems about right. You can see that swirl pretty good on visible, with the convection building N-NE of the swirl, and voiding convection on the S and SW side.
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Quoting Patrap:
Womp, wahhhhhhhhhhhh...










The puff ball of doom I say!
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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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