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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Quoting CyclonicVoyage:


It's going to be a matter of where the center develops how quickly it can organize.
Right.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting msgambler:
Sounds like Pat spent too much time yesterday downtown at Hour Happy


More of a stumble on the dogs chew toy paper thingee.

Never leave dog toys on the Stairs I tell the Dog all the time, But she listens Like tropical Bloggers..


Sparsely

..LOL

Member Since: July 3, 2005 Posts: 423 Comments: 127804
Quoting btwntx08:
12z candaian has it moving into nola


Canadian :)
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting MiamiHurricanes09:
Lol...probably not although I would certainly like it to be that way. StormW thinking that we will see a small shift to the left.


ALL of SOUTH/CENTRAL Florida should be keeping an eye out.

Don't get alarmed but stay informed and ahead of the game.
could be a track similar to Jean/Frances maybe slightly south.
Member Since: July 3, 2007 Posts: 0 Comments: 524
ANMIN.VIS.SW ATLANTIC


Member Since: July 15, 2006 Posts: 170 Comments: 53518
I cant wait until the cone of uncertainty comes out people will go completely nuts lol
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Quoting serialteg:
i was talking about 97l when it passed thru puerto rico and no one paid attention.


I saw, you had 8 to 10"? that's a lot!
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Quoting catastropheadjuster:


Pat r u ok? I sure hope so. You didn't fall down the stairs did u? Be careful
sheri
Sounds like Pat spent too much time yesterday downtown at Hour Happy
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Quoting connie1976:
i noticed the models seem to be taking it more north of broward now...is this going to be a trend?? I'm hoping... :)


Who knows what will actually happen but in terms of a Dade vs. Broward scenario, you can never be sure because a wobble or two on approach to landfall can mean a difference of a few hundred miles give or take..You would need to be prepared if you end up in the cone of uncertainly...
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725. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Quoting Patrap:
Dont let him watch FOX news


Post of the Day!!! haha
Member Since: July 3, 2007 Posts: 0 Comments: 524
Hey Flood & all,

Just don't want that thing in the GOMEX... we have enough to deal with! : )
Quoting Floodman:


Yeah, the sterring schema is pretty uncomplicated...the point i9s, be ready and if the current schema pans out, you'll be prepared. I will say that it's rather calm in here given that this feature could very well end up dumping on SEFL...wonder what the afternoon will bring
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Quoting MiamiHurricanes09:
We'll see. Steering has been pretty straightforward for the past couple days.


It's going to be a matter of where the center develops how quickly it can organize.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting Floodman:


Yeah, the sterring schema is pretty uncomplicated...the point i9s, be ready and if the current schema pans out, you'll be prepared. I will say that it's rather calm in here given that this feature could very well end up dumping on SEFL...wonder what the afternoon will bring
Yup.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting StormW:


Not too far left. I'm thinking right now, more in line with the OFCI forecast:



Well being u were more interested in the Jamaica wave yesterday and now is not much I will take your forecast with a grain of salt. Not even these so called experts can forecast mother nature its just a guessing game.
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IKE is a Guy..
Member Since: July 3, 2005 Posts: 423 Comments: 127804
I'm currently working on some analysis for Invest 97L and will have an update both on my website and in my blog sometime this afternoon. This will come with some graphics to better explain the situation and the potential future for the system.
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Quoting Patrap:



My Left hand is sprained from a Lil incident with my Stairs this am.

Ice and meds.


Pat r u ok? I sure hope so. You didn't fall down the stairs did u? Be careful
sheri
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Quoting MiamiHurricanes09:
We'll see. Steering has been pretty straightforward for the past couple days.


Yeah, the sterring schema is pretty uncomplicated...the point is, be ready and if the current schema pans out, you'll be prepared. I will say that it's rather calm in here given that this feature could very well end up dumping on SEFL...wonder what the afternoon will bring
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Quoting 69Viking:


Not a track I'm liking at all, I'm South of IKE along the coast in Fort Walton Beach right about where that Hoopdy Loop of yours makes it's second landfall! Good thing it's early and it will most likely change!


Hey Viking, just messing with IKE. She knows I'm in Mobile and I never want to see any N. Gulf Coast hurricane landfall scenario. Sure you don't either.
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Quoting extreme236:


The vorticity is not focused east of PR. Probably just a mid-level circulation of some kind, if there is one there at all.


NWS Radar shows 97L very clearly trying to wind up.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting Patrap:
Dont let him watch FOX news

roflmao
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Quoting connie1976:
i noticed the models seem to be taking it more north of broward now...is this going to be a trend?? I'm hoping... :)
Lol...probably not although I would certainly like it to be that way. StormW thinking that we will see a small shift to the left.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
708. xcool
Patrap why .lol
Member Since: September 26, 2009 Posts: 2 Comments: 15648
Dont let him watch FOX news
Member Since: July 3, 2005 Posts: 423 Comments: 127804
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting Floodman:


You're all wrong...CAT5 in Des Moines...LOL

By this time tomorrow the odds are that the models will be considerably different and may be looking at passage through the straits
We'll see. Steering has been pretty straightforward for the past couple days.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
My eleven year old son just asks me what happens if the oil gets picked up by a hurricane and then lightning strikes it...."do we get a fire cane mom?" Great. Where did I go wrong?
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703. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15648
i noticed the models seem to be taking it more north of broward now...is this going to be a trend?? I'm hoping... :)
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Quoting gator23:

hey Miami, Miami-Dade doesnt look like it will take a direct hit, looks more Palm Beach maybe Melbourne?


You're all wrong...CAT5 in Des Moines...LOL

By this time tomorrow the odds are that the models will be considerably different and may be looking at passage through the straits
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Member Since: July 3, 2005 Posts: 423 Comments: 127804
Quoting CosmicEvents:
Don't get me started, but it should have been RED last night. Certainly today. As the models continue to verify, just with the passage of time, we'll have RED this evening. Then it's in the "official" 48 hour window.
.
.
The thing is, we have a system where there's near 100% agreement amongst the models of at least a small TS hitting somewhere from Cuba up to south central Florida in 4 days. Shouldn't the people get that RED alert right now. The sooner the better. RED does not mean Cat5. It simply signifies that there's a good probability of a TD. If somebody needs to trim their trees, or pick up supplies, what's wrong with giving them an extra day instead of going by the official COLOR book?


How about we skip Code Red and go straight to TD!?
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Member Since: July 15, 2006 Posts: 170 Comments: 53518
Quoting TropicalNonsense:


It's called the "Gulf Stream"
Yep, and the shallow waters of the Bahamas allow for SSTs to get very hot very quickly. Also OHC by the Bahamas is very good.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
695. A4Guy
Hi. Can anyone please tell me why some of the model plots that have been posted have an "offical" forecast track (OFCL), when NHC hasn't issued an official forecast?
Thanks!
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Quoting P451:
Why hell, I'll throw it out there. lol.









Goodness gracious great balls of convection
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Quoting KEEPEROFTHEGATE:
its heading into high octane it will purrr like a kitty


[Laughs] 97L=Meow!
Member Since: July 3, 2007 Posts: 0 Comments: 524
692. JRRP
Quoting P451:
Why hell, I'll throw it out there. lol.







now i see ....
Member Since: August 16, 2007 Posts: 0 Comments: 5697
690. 7544
convection needs to build to the south and we may have something
Member Since: May 6, 2007 Posts: 0 Comments: 6750
i was talking about 97l when it passed thru puerto rico and no one paid attention.
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Dookie, lovin the squirell. Can you send that pic?
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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.