97L a threat to become a tropical depression on Wednesday

By: Dr. Jeff Masters , 1:31 PM GMT on July 20, 2010

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A tropical wave (Invest 97L) near the east coast of Puerto Rico has become more organized overnight and is a threat to develop into a tropical depression as early as Wednesday. The disturbance has brought heavy rains of 8+ inches to Culebra and Vieques islands over the past day (Figure 1), and all of Puerto Rico and the Virgin Islands are under flash flood watches today. The storm could bring an additional 3 - 6 inches of rain to the islands over the next two days. The upper level low centered a few hundred miles north of the Dominican Republic is no longer bringing high levels of wind shear to 97L; wind shear has fallen to the moderate range, 10 - 20 knots, which may allow 97L to continue to develop today. Satellite images of 97L show a moderate area of disorganized thunderstorms, but no signs of a surface circulation, no low-level spiral banding, and no upper-level outflow. There is a large amount of dry air to the northwest of Puerto Rico that will interfere with development of 97L. Surface observations show only light winds over Puerto Rico, with no signs of a surface circulation. The Hurricane Hunters are on call to investigate 97L this afternoon, if necessary.


Figure 1. Total radar-estimated rainfall from Invest 97L.

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 flooding to the Dominican Republic today and Wednesday, and to Haiti on Wednesday and Thursday. Heavy rains from 97L will begin moving into eastern Cuba, the Turks and Caicos Islands, and the eastern Bahamas on Wednesday, and South Florida can expect heavy rains to arrive as early as Thursday night. We do have several models developing 97L into a tropical depression or tropical storm. The GFS and HWRF both take 97L to tropical storm status over the Bahamas by Thursday, with the storm then tracking over South Florida on Friday and entering the Gulf of Mexico on Saturday. The NOGAPS is similar, but portrays a weaker system. All of these models foresee a threat to the oil spill region by Saturday night or Sunday, with the storm making a second landfall somewhere between the Florida Panhandle and Louisiana. One factor potentially aiding the storm will be the Madden-Julian oscillation, which currently favors upward motion over the Gulf of Mexico and Caribbean. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. Also in favor of development are the warm ocean temperatures of 29°C. The SHIPS model predicts shear will remain moderate, 10 - 20 knots, over the next 4 - 5 days, and I believe the primary detriment to development of 97L 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. NHC is giving 97L a 40% chance of developing into a tropical depression by Thursday, which is a reasonable forecast. I think there is a 60% chance 97L will eventually become Tropical Storm Bonnie, sometime in the next five days. Sudden rapid development today or on Wednesday is unlikely, due to the dry air over the Bahamas, and I put the odds of 97L making it to hurricane strength before reaching Florida at 10%. There is a better chance that 97L could attain hurricane strength in the Gulf of Mexico, perhaps 20%. These probabilities will depend heavily upon how long 97L (or Bonnie) spends over land or interacting with land over the next four days, which is very uncertain.

Time to cut the forecast numbers for the coming hurricane season?
Here are the number of Atlantic named storms, hurricanes, and intense hurricanes predicted by the various forecast groups in their late May or early June forecasts:

23 named storms: PSU statistical model
20 named storms: UKMET GloSea dynamical model
18.5 named storms, 11 hurricanes, 5 major hurricanes: NOAA hybrid statistical/dynamical model technique
18 named storms, 10 hurricanes, 5 intense hurricanes: CSU statistical model (Phil Klotzbach/Bill Gray)
17.7 named storms, 9.5 hurricanes, 4.4 intense hurricanes: Tropical Storm Risk (TSR), hybrid statistical/dynamical model technique (Note: TSR increased their numbers to 19.1, 10.4, and 4.8 with their July 6 forecast)
17 named storms, 10 hurricanes: FSU dynamical model
10 named storms, 6 hurricanes, 2 intense hurricanes: climatology

The group forecasting the lowest activity was the Florida State University group led by Dr. Tim LaRow. They use a new dynamical forecast model called COAPS, which is funded by a 5-year, $6.2 million grant from NOAA. This year's June forecast by the COAPS model called for 17 named storms and 10 hurricanes. However, Dr. LaRow emailed me yesterday to say that the COAPS model is now calling for reduced activity. Using the state of the atmosphere and ocean as of July 15, a new run of the COAPS model was performed over the weekend. The new forecast is now calling for two fewer hurricanes--a total of 15 named storms and 8 hurricanes (including Alex.) The COAPS model generated an "ensemble" of five different forecasts, done by varying the initial sea surface temperatures by a few percent at the beginning of the model run. These five forecasts came up with a range of 12 - 16 named storms (including Alex), and 7 - 10 hurricanes. It will be interesting to see when CSU issues its August 4 forecast if they also cut their numbers. With only one named storm (Alex) thus far this year, it's getting pretty hard to have a season with 19 or 20 named storms. Only four hurricane seasons since 1851 have had as many as nineteen named storms. These four seasons--1887, 1933, 1995, and 2005--all had at least three named storms by July 20.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Invest 97
2) A look ahead at the coming two weeks

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

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The conversion to an upper level low may be due to interaction with the trough--which increases its height. The ridge then moves in and causes a cap at the mid-levels. However, I doubt this forecast is correct.
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Quoting Floodman:


Too late...the freaking out has begun...LOL



Morning Flood, I was wondering do u know what happened to 456? I haven't seen him lately.
So what do ya think a bout this 97L? It looks kinda messy right know. But I don't have a trained eye either.
sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3676
Quoting jasoniscoolman2010x:
last night i said that about 10,000 times There is a large amount of dry air to the northwest of Puerto Rico that will interfere with development of 97L. i am right to much dry air..i said that last night by looking at the map i win this time around.


Great observation Jason. The drier air will likely be caused by the subsidence associated with the deep-layered ridge that is expected to move in.

The GFS 06z showed that The deep-layered ridge will interact with 97L's outflow, and perhaps caused mid-level dry air intrusion.

Look closely at the GFS' forecast at 06z. You will notice that the organized outflow from 97L disappears shortly after the ridge moves in. The GFS then forecast 97L to become an upper level low LOL.

Cold Low



Upper Level Low

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This morning is the time to use real time data(Satellite, Radar, etc..) then to look at the shear maps. I have found some discrepancies over the years with the shear values that CIMMS puts out. Still a good tool overall, but sometimes not as accurate especially when the atmosphere is changing quickly.
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181. unf97
Quoting MiamiHurricanes09:
That's when 97L will begin to take off. Depression when Recon investigates tomorrow?


If the shear levels are low during the next 24 hours, indeed 97L will begin to spin up.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
Quoting gator23:

that didnt help, it said Extreme south FLorida and the straits. This is different from the model guidance so I am even MORE confused.
I'm sticking with the Official track, unfortunately that one takes it right over south Florida.

12z "Official" track takes 97L as a category 1 hurricane through south Florida in 96 hours.

AL, 97, 2010072012, 03, OFCI, 0, 190N, 658W, 30, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 12, 194N, 671W, 30, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 24, 199N, 687W, 30, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 36, 207N, 705W, 32, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 48, 216N, 724W, 38, 0, , 34, NEQ, 37, 28, 28, 37,
AL, 97, 2010072012, 03, OFCI, 60, 225N, 743W, 46, 0, , 34, NEQ, 39, 29, 29, 39,
AL, 97, 2010072012, 03, OFCI, 72, 235N, 763W, 55, 0, , 34, NEQ, 40, 30, 30, 40,
AL, 97, 2010072012, 03, OFCI, 72, 235N, 763W, 55, 0, , 50, NEQ, 29, 29, 19, 29,
AL, 97, 2010072012, 03, OFCI, 84, 245N, 782W, 64, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 96, 256N, 801W, 69, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 108, 266N, 819W, 69, 0, , 34, NEQ, 0, 0, 0, 0,
AL, 97, 2010072012, 03, OFCI, 120, 277N, 836W, 66, 0, , 34, NEQ, 0, 0, 0, 0,
Member Since: September 2, 2009 Posts: 130 Comments: 21193
179. IKE
Quoting Prgal:


Ohh..ok. I am sorry to hear about your dog! I have a poodle and they are wonderful dogs...very intelligent. So sorry!


I've still got a 14 year-old black poodle.

Thanks.
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Quoting Relix:


Hurricane Hortense, Marilyn, freaking Hurricane Georges, a few other close calls where I've experience strong weather that accompains these systems and T.Storm Jeanne back in 2004 and some others I can't remember. As I said, I get excited by them!

Though I was little, I LOVED the thrill of being in TS Jeanne. I was a month old baby when Georges hit us.
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ik, how did your poodle drown in a lake? poor puppy...
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Quoting Drakoen:
Wind shear is 17 knots and is forecasted by the SHIPS to reduce down to 6 knots by 18z
That's when 97L will begin to take off. Depression when Recon investigates tomorrow?
Member Since: September 2, 2009 Posts: 130 Comments: 21193
175. IKE
Quoting portcharlotte:
Bastardi


And also meaning business is what should be our 2cnd ts of the season by the time it reaches Florida Friday or Saturday. This could mess up my weekend plans as Joey cant travel if tropical cyclones are on the map. It also means that I was wise to choose not to go to the Bahamas this year with our friends, for it was later this week we were supposed to go. Believe me, if this things spins up, everyone in this house is going to know about it since it was one of the reasons I didnt want to go this year, me fear of the season starting to rev up about now. In any case the track by the GFS looks a little too far north, but we have to wait and see where the low level center pops out.

One cant help but notice how this does not rev up over the gulf. That makes sense, if it crosses Florida from the southeast then they dont increase again back to their original intensity. Its the ones coming from the east, or in the case of Katrina, east northeast, or passing south of the state, that are the big ones in the gulf. The eastern gulf is a dead zone for these things moving from the southeast..



He brings up a good point about the track across Florida(if it crosses Florida), being important.
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Sooo. If 97 goes over south fla.. it will likely re emerge in the GOM?
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Quoting ShesACaneiac:
Good morning. Working and lurking. Thinking that 97 will go too far south for me (Port St Lucie) to get a long weekend.


Track forecast is rather straight forward with this one. It will all depend on how quick it gets going and how strong it gets. A stronger system in this case will want to head more north and could bring it further up the coast. Too close for comfort, IMO. Eyes wide open with this one.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting cg2916:
I just realized something. It'll be hard to have a 20 or even an 18 storm season, when we'll be going to the downward cycle of the MJO for part of the active part.


The models are not in agreement on that. One of them shows a stronger downward motion while the other shows weak upward motion for August. I'd say the second one is more likely to happen.
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Quoting MiamiHurricanes09:
Read StormW's blog.

that didnt help, it said Extreme south FLorida and the straits. This is different from the model guidance so I am even MORE confused.
Member Since: August 26, 2008 Posts: 0 Comments: 2182
Quoting Drakoen:
Wind shear is 17 knots and is forecasted by the SHIPS to reduce down to 6 knots by 18z


Yea, the CIMSS is overdoing shear in that case like I suspected.
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168. Prgal
Quoting Relix:


Hurricane Hortense, Marilyn, freaking Hurricane Georges, a few other close calls where I've experience strong weather that accompains these systems and T.Storm Jeanne back in 2004 and some others I can't remember. As I said, I get excited by them!


Georges was TERRIBLE here in PR!
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Quoting Squid28:


Trust me they are not the only one on her getting excitd about the possibility of a strike.

Myself, I am on the other end of the spectrum, just waiting and watching.

There are those who have never been in a storm but want to be in one; and then there are those of us who would gladly go without ever experiencing another one again.

Just wish we could pitch in for a bus to give everyone a ride who wanted to experience one first hand.....


Yep, a bus, with a giant hot air balloon attached, then they could float up in the eye and take direct barometric readings as they rise and wait for the........oh cr$%p....
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Looks like the EURO lost this one, did good on Alex though.
Member Since: July 1, 2008 Posts: 13 Comments: 7387
164. Prgal
Quoting IKE:


I am. That's my wife and poodle that drowned in the lake I live on, in my avatar.


Ohh..ok. I am sorry to hear about your dog! I have a poodle and they are wonderful dogs...very intelligent. So sorry!
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Quoting IKE:


I am. That's my wife and poodle that drowned in the lake I live on, in my avatar.
I am sorry for your loss.:(
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Wind shear is 17 knots and is forecasted by the SHIPS to reduce down to 6 knots by 18z
Member Since: October 28, 2006 Posts: 57 Comments: 30489
Quoting reedzone:
Hmm while shear is over 20 knots with 97L, it seems to be organizing well..


The cloud pattern is not indicative of stronger shear. It is quite possible that the shear is being overdone by the CIMSS.
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160. Relix
Quoting divdog:
you nust have never been thru a bad one because you would not make thost type of comments


Hurricane Hortense, Marilyn, freaking Hurricane Georges, a few other close calls where I've experience strong weather that accompains these systems and T.Storm Jeanne back in 2004 and some others I can't remember. As I said, I get excited by them!
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Quoting Seflhurricane:
i am hoping and praying this stays away from south florida
That won't happen...SFLA will get some of this action!
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Quoting MiamiHurricanes09:
As Drakoen pointed out earlier, outflow is now apparent on satellite. Also look at the 925mb vorticity, we might have an area of low pressure in a couple of hours. 97L is pulling together, something I really don't want to see.


I knew a low was to develop today, they may up the chances at the next TWO, but they're the experts.
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I just realized something. It'll be hard to have a 20 or even an 18 storm season, when we'll be going to the downward cycle of the MJO for part of the active part.
Member Since: Posts: Comments:
Bastardi


And also meaning business is what should be our 2cnd ts of the season by the time it reaches Florida Friday or Saturday. This could mess up my weekend plans as Joey cant travel if tropical cyclones are on the map. It also means that I was wise to choose not to go to the Bahamas this year with our friends, for it was later this week we were supposed to go. Believe me, if this things spins up, everyone in this house is going to know about it since it was one of the reasons I didnt want to go this year, me fear of the season starting to rev up about now. In any case the track by the GFS looks a little too far north, but we have to wait and see where the low level center pops out.

One cant help but notice how this does not rev up over the gulf. That makes sense, if it crosses Florida from the southeast then they dont increase again back to their original intensity. Its the ones coming from the east, or in the case of Katrina, east northeast, or passing south of the state, that are the big ones in the gulf. The eastern gulf is a dead zone for these things moving from the southeast..

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155. IKE
Quoting Prgal:
IKE, I thought you were a guy...no disrespect.


I am. That's my wife and poodle that drowned in the lake I live on, in my avatar.
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153. unf97
Good morning to everyone!

97L is looking more and more interesting in the long term for sure. I just got done catching up on looking through the model runs, and it appears that the models keep trending to a shift to the right. This is a very interesting pattern evolving with the models which I started noticing last night. Everyone from the Central Gulf Coast region to the FL peninsula needs to closely monitor the evolution of 97L. This weekend could be a very interesting one indeed.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
12Z model runs from the NHC
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Anyone know for sure if the 12z HWRF and GFDL will be run?
Member Since: September 2, 2009 Posts: 130 Comments: 21193
150. Prgal
IKE, I thought you were a guy...no disrespect.
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Hmm while shear is over 20 knots with 97L, it seems to be organizing well..
Member Since: July 1, 2008 Posts: 13 Comments: 7387
Quoting Squid28:


Trust me they are not the only one on her getting excitd about the possibility of a strike.

Myself, I am on the other end of the spectrum, just waiting and watching.

There are those who have never been in a storm but want to be in one; and then there are those of us who would gladly go without ever experiencing another one again.

Just wish we could pitch in for a bus to give everyone a ride who wanted to experience one first hand.....
I've been thru too many to count and am not excited about anything that may come near what is left of the oil. For those getting excited remember we are trying to clean up a disaster of unknown proportions and don't need any weather making it worse than it has been.
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Quoting Floodman:


Too late...the freaking out has begun...LOL

Good morning Flood. Do you have a link to the HWRF model? If you do please post a link.
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Quoting Floodman:


Too late...the freaking out has begun...LOL



Time for some folks to start stress testing the f5 key for the next few days.... or months....
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145. IKE
Quoting MiamiHurricanes09:
As Drakoen pointed out earlier, outflow is now apparent on satellite. Also look at the 925mb vorticity, we might have an area of low pressure in a couple of hours.



That's where weatherguy03 says it's developing.


Quoting TampaSpin:


The TUTT is disapating it appears


Looks like it.
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Thanks for the support IKE!!:-)
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Quoting IKE:
ULL is losing out on 97L. Less of an influence.


The TUTT is disapating it appears
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Quoting extreme236:
97L definitely appears to be continuing to become better organized.
As Drakoen pointed out earlier, outflow is now apparent on satellite. Also look at the 925mb vorticity, we might have an area of low pressure in a couple of hours. 97L is pulling together, something I really don't want to see.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting divdog:
excited about getting a hurricane.. how old are you


Trust me they are not the only one on her getting excitd about the possibility of a strike.

Myself, I am on the other end of the spectrum, just waiting and watching.

There are those who have never been in a storm but want to be in one; and then there are those of us who would gladly go without ever experiencing another one again.

Just wish we could pitch in for a bus to give everyone a ride who wanted to experience one first hand.....
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http://moe.met.fsu.edu/~acevans/models/al972010_inten.png
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Quoting Relix:


I am 21 and I get excited when a Hurricane comes. AS I've said, if I could live in a island, solo, that receives at least 2 hurricanes per year I would be the happiest guy ever. =P
you nust have never been thru a bad one because you would not make thost type of comments
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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.