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 extreme236:


I don't see this taking until Thursday night in my opinion. Probably tomorrow's recon if the organization continues.


I could very well be wrong. I just hope it doesn't become the 'Joker' part 2.
Member Since: July 8, 2005 Posts: 259 Comments: 23878
Quoting Chicklit:

Read Dr. Masters' forecast for 97L.
He usually takes all of the models into consideration and is right on with his forecasts.


Not always. I recall him forecasting a 20% chance of Alex becoming a hurricane in the Gulf, and well we see what happened. SHIPS does infact forecast 97L to become a hurricane.
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97L's developing low is forecast to be North of the Dominican Republic within 24Hrs. Cyclonic turning and Upper Level Outflow in the North and East quadrants noted. Did I miss anything new about 97L?
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help please how is it going north with the high pressure that is suppose to be stronger the end of the week?
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Quoting StormW:


Dat's where the buried treasure is located.


LOL! X marks the spot xd
Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting TropicalAnalystwx13:


OFCL has it hitting Cat 1 strength before landfall I think
Yup, category 1 hitting SFLA in 96 hours.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting CybrTeddy:


Convection starting to wrap around that area of 850 mb vort that is deep. This process is going to take a while, while it won't be as fragile and such a slow step at a time as we've seen with Alex and TD2, 97L most likely won't become a TD until Thursday night.


I dont think it will take that long, probably tomorrow when recon goes in.
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Quoting whs2012:
Okay, most of the models now are agreeing, that 97L is going straight to Florida, and up South Florida? Like, not even getting into the Gulf of Mexico? Lol, how tracks can change so suddenly.


I beg to differ.



Its going to Ike's house
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Check out this radar from P.R.
Link

It shows a spin just east of P.R. and convection flaring up around that area ..and i think it's slowly starting to move North-West,

Any thoughts on this?
Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting TropicalAnalystwx13:


OFCL has it hitting Cat 1 strength before landfall I think

Read Dr. Masters' forecast for 97L.
He usually takes all of the models into consideration and is right on with his forecasts.
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307. Orcasystems 11:15 AM EDT on July 20, 2010

You came at me pretty hard last night when I had not checked the models before I spoke; I will never do THAT again........... :)
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Quoting CybrTeddy:


Convection starting to wrap around that area of 850 mb vort that is deep. This process is going to take a while, while it won't be as fragile and such a slow step at a time as we've seen with Alex and TD2, 97L most likely won't become a TD until Thursday night.


I don't see this taking until Thursday night in my opinion. Probably tomorrow's recon if the organization continues.
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Quoting Chicklit:
Good news for Baha as it isn't forecast to get to named status until it gets into the Gulf.
By the way, been burned one to many times by impressive waves coming off Cape Verde this year. From now on am waiting until they get to 50W before I so much as look at them.


Actually, the OFCL intensity from the National Hurricane Center has it as a Category 1 over the Bahamas then a Category 1 landfall in Florida. SHIPS takes it to nearly a Category 2 landfall in Florida.


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: July 8, 2005 Posts: 259 Comments: 23878
Quoting CybrTeddy:


Convection starting to wrap around that area of 850 mb vort that is deep. This process is going to take a while, while it won't be as fragile and such a slow step at a time as we've seen with Alex and TD2, 97L most likely won't become a TD until Thursday night.
I can only hope. Just hope it keeps moving west the whole time, instead of stalling out and consolidating...
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Station 41043
NDBC
Location: 21.061N 64.966W
Conditions as of:
Tue, 20 Jul 2010 14:50:00 UTC
Winds: ESE (110°) at 19.4 kt gusting to 23.3 kt
Significant Wave Height: 10.2 ft
Dominant Wave Period: 8 sec
Atmospheric Pressure: 30.08 in and rising
Air Temperature: 77.5 F
Dew Point: 73.8 F
Water Temperature: 82.9 F

http://www.ndbc.noaa.gov/station_page.php?station=41043 North of PR
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HJ,Oz,Doug....I'll be on standby for a chase later this week!!!!
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Quoting CybrTeddy:


Convection starting to wrap around that area of 850 mb vort that is deep. This process is going to take a while, while it won't be as fragile and such a slow step at a time as we've seen with Alex and TD2, 97L most likely won't become a TD until Thursday night.
Looks like convection is trying to wrap around the vort max.



Member Since: September 2, 2009 Posts: 130 Comments: 21109
This'll be a good warm up for South Florida since it isn't forecast to be that strong if and when it does landfall there. The big story is going to be the oil spill area and what happens to that when this storm passes nearby or even over it.
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Quoting whs2012:
Okay, most of the models now are agreeing, that 97L is going straight to Florida, and up South Florida? Like, not even getting into the Gulf of Mexico? Lol, how tracks can change so suddenly.


...No
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Quoting MiamiHurricanes09:
Yep, but it's a start.


From it's current position, that's a rather steep WNW.
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Quoting StormW:


Too early to say. Depends on ACTUAL path and how much weakening would occur. Would look for a definite increase in POPS and rainfall as if and when it crosses FL.

StormW, Is the convection of 97L similar to a WPAC system?

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Quoting Chicklit:
Good news for Baha as it isn't forecast to get to hurricane status until it gets into the Gulf.


OFCL has it hitting Cat 1 strength before landfall I think
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Quoting Floodman:


Tom, we're talking about landfalling hurricanes in SFL from the east before August...any strength


A HA! Sorry... saw the Cat 5 mentioned and was wondering if I had my facts straight!
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Quoting MiamiHurricanes09:


Convection starting to wrap around that area of 850 mb vort that is deep. This process is going to take a while, while it won't be as fragile and such a slow step at a time as we've seen with Alex and TD2, 97L most likely won't become a TD until Thursday night.
Member Since: July 8, 2005 Posts: 259 Comments: 23878
Quoting extreme236:


Well nvm that actually, I forgot that it means it's forecasted to form and not actually there.
I got messed up too. Let me fix that.

An area of low pressure is forecasted to form within 24 hours in 97L.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting DestinJeff:


Man your Battle Curtains!


Stop that... I have my glasses on and the glare hurt.
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I hate staring down the business end of the TCVN.

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Quoting Jeff9641:


Where?


It's there if you look. It's a disjointed bilocation either north or south of Jamaica.....I think.....
Member Since: September 1, 2007 Posts: 0 Comments: 1793


As you see in the first image, a low pressure has formed near P.R.... interesting system we got here.I expect development to begin later on this evening.
Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting MiamiHurricanes09:
Yep, but it's a start.


Well nvm that actually, I forgot that it means it's forecasted to form and not actually there.
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Quoting Neapolitan:
Of course, there's also this:

98L?

The setup here is beautiful.

NEXT!


Now.. that is a beauty
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Good news for Baha as it isn't forecast to get to named status until it gets into the Gulf.
By the way, been burned one to many times by impressive waves coming off Cape Verde this year. From now on am waiting until they get to 50W before I so much as look at them.
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299. rlk
Recall that 2004 was an extremely active and destructive season -- "only" 15 named storms, but 6 majors including 3 cat 4's and a cat 5 (Ivan).
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Quoting Drakoen:


Oh yeah I forgot about that.
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Quoting extreme236:


Displaced from the majority of the convection still.
Yep, but it's a start.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting IKE:


LOL.


IKE Part Duex (with a 2)
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Quoting MiamiHurricanes09:
Apparently 97L has developed an area of low pressure (1011mb).



You mean will be developing an area of low pressure. X means an area of low pressure is forecasted to form there within 24 hours.
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Quoting Jeff9641:


Where?
North of the Dominican Republic. Note the "X". Means an area of low pressure is forecasted to form there.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
Quoting Floodman:


Tom, we're talking about landfalling hurricanes in SFL from the east before August...any strength


Do you mean moving east, or hitting the east coast of Florida? This storm reminds me a lot of Erin in 1995, which was just barely into August.
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Quoting MiamiHurricanes09:
Apparently 97L has developed an area of low pressure (1011mb).



Displaced from the majority of the convection still.
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289. IKE
Quoting Orcasystems:
IKE.. what did you do this time??



LOL.
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Quoting MiamiHurricanes09:


What is that wave right under the dominican rep.
doing? It's been there for a while now
Member Since: July 20, 2010 Posts: 0 Comments: 225

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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.