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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LOL, yeah....I think there is a definite reason that Fay "intensified" over FL in 2008...

Quoting FLdewey:


Nah the high mountains of Florida will tear it apart. We've got landfills that reach tens of feet into the sky. ;)
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Quoting StormW:
INVEST 97L AND AREAS OF INTEREST SYNOPSIS ISSUED 9:40 A.M. JULY 20, 2010


Great analysis Stormw!
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12z GFS brings 97 into SFL
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Quoting germemiguel:
KABOUMMMMM




Those are some very strong winds of the coast of africa, do you think it will hold together?
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That cracked me up! I think I know what you mean

Quoting caneswatch:


Uh, what girl would that be?
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Quoting Sfloridacat5:
Don't forget many "Florida storms" end up going to LA, Texas, etc.

Surprisingly, Texas has actually only ever seen one storm make landfall that originally crossed florida.
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ASCAT showed that the vigorous tropical wave off the African coast is accompanied by an area of low pressure.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Sfloridacat5:
Don't forget many "Florida storms" end up going to LA, Texas, etc.


true. I guess there is some change or coming change that will make it take a recurve like that?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
477. unf97
Quoting Dropsonde:
I spoke too soon... at this point I honestly wouldn't rule out a recurve after the SFL hit, either into the peninsula or even away to sea... after all, it shifted from NOLA/Gulfport all the way to Panama City, Tallahassee, and even further east, depending on how much the ridge is eroded. It could shift again in either direction. But my instinct is that the ridge won't be eroded enough to keep it completely out of the Gulf.


This is why we can't speculate too far in the future of course. You know they are going to be more shifts in the track, the ol' "windshield wipers" with the models LOL..

But, yes, definitely there has been a pronounced shift to the right with the models during the past 24 hours. That's the beauty with weather overall and tropical forecasting.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
Quoting CybrTeddy:


Did you check out the OFCL intensity and track? Sheesh.. NHC thinks this will be a Category 1 landfall in South Florida. SHIPS thinks it will be nearing Category 2.


This is getting more and more interesting by the second. Good thing (for me) it will pass by in a few days. Going on vacation next Sunday.
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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
What would you do, solo, the rest of the year......
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Wants a K storm?

I haven't seen anyone want any storm, I think some are just comparing the two due to the region of development
Member Since: March 10, 2010 Posts: 1 Comments: 7831
Quoting msgambler:
Morning Pat, just got your mail this morning and figured you didn't want me calling you at 5am....lol


Well that wouldnt have went over well...

LOL
Member Since: July 3, 2005 Posts: 426 Comments: 128875
Quoting BFG308:


97L and possible tracking is reminding me of a girl I used to Know...


Uh, what girl would that be?
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Quoting Sfloridacat5:
Don't forget many "Florida storms" end up going to LA, Texas, etc.


Great Point!
Member Since: July 3, 2007 Posts: 0 Comments: 524
1998 Atlantic hurricane season similar to 2010
Season summary map
First storm formed: July 27, 1998 (1998-07-27)
Last storm dissipated: December 1, 1998
Strongest storm: Mitch – 905 mbar (hPa) (26.74 inHg), 180 mph (285 km/h)
Total storms: 14
Hurricanes: 10
Major hurricanes (Cat. 3+): 3
Total fatalities: Over 12,000
Total damage: $12.2 billion (1998 USD)
$16 billion (2010 USD)
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Quoting Floodman:


Get used to it...people here like to up the Category as well, as in "I don't believe it's a CAT1...the pressure indicates that it's a CAT 5, even though the sustained winds are only 80 knts"

These are typically known as "up-casters" though I have heard some far more derogatory comments...LOL


Most know I was joking about that.....
Member Since: September 1, 2007 Posts: 0 Comments: 1793




Member Since: July 3, 2005 Posts: 426 Comments: 128875
Quoting Patrap:
Everyone wants a K storm seems.

Watch what ya ask for..ya just might get it one day.

Morning Pat, just got your mail this morning and figured you didn't want me calling you at 5am....lol
Or you post from last night I mean.
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Quoting Drakoen:
Signs that a surface circulation may be trying to get going north of the northeastern DR
And you can see a blob of convection flaring up just north of northern D.R.
Member Since: July 20, 2010 Posts: 0 Comments: 225
Man they need to fix the Dominican Republic radar, it would have come in handy.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Everyone wants a K storm seems.

Watch what ya ask for..ya just might get it one day.

Member Since: July 3, 2005 Posts: 426 Comments: 128875
Don't forget many "Florida storms" end up going to LA, Texas, etc.
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KABOUMMMMM



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PUERTO RICO WEATHER UPDATE

I'M SURPRISED WITH THE LACK OF WIND, IT'S CALM RIGHT NOW, JUST A VERY LITE RAIN
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Quoting TropicalNonsense:



98L will soon exist! Look off the African Coast! LOL
looks better already than anything we have seen since ALEX.


Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting CybrTeddy:


Katrina formed in the Bahamas, this will likely form north of Hispaniola.


A brief stint over extreme south Fl would lead to a similar set-up of intensification and subsequent events for somewhere in the gulf coast if you ask me. People need to watch carefully. Only time will tell.
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TWC Quote;
"is that a developing low?"

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Quoting Drakoen:
Signs that a surface circulation may be trying to get going north of the northeastern DR
Yup, been analyzing it for a bit now.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Hurricanes101:


there is no 98L, it is getting kind of tiresome when people declare invests, TDs and Tropical Storms when they don't actually exist


Get used to it...people here like to up the Category as well, as in "I don't believe it's a CAT1...the pressure indicates that it's a CAT 5, even though the sustained winds are only 80 knts"

These are typically known as "up-casters" though I have heard some far more derogatory comments...LOL
Member Since: Posts: Comments:
I spoke too soon... at this point I honestly wouldn't rule out a recurve after the SFL hit, either into the peninsula or even away to sea... after all, it shifted from NOLA/Gulfport all the way to Panama City, Tallahassee, and even further east, depending on how much the ridge is eroded. It could shift again in either direction. But my instinct is that the ridge won't be eroded enough to keep it completely out of the Gulf.
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Good morning...I see 97L will be a Florida storm.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Signs that a surface circulation may be trying to get going north of the northeastern DR
Member Since: October 28, 2006 Posts: 57 Comments: 30578
Quoting Hurricanes101:


there is no 98L, it is getting kind of tiresome when people declare invests, TDs and Tropical Storms when they don't actually exist


98L will soon exist! Look off the African Coast! LOL
looks better already than anything we have seen since ALEX.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting AussieStorm:

No i am not feeling better but not letting it get me down/depressed.
Thanks for you concern <3

Oh sorry.Have you guys warmed up any?
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Quoting BFG308:


97L and possible tracking is reminding me of a girl I used to Know...


Katrina formed in the Bahamas, this will likely form north of Hispaniola.
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Quoting BFG308:


97L and possible tracking is reminding me of a girl I used to Know...
LOL 97L looks so tiny compared to the globe
Member Since: July 20, 2010 Posts: 0 Comments: 225
445. unf97
The outflow over 97L is definitely becoming more evident over the system. WV imagery showing improved outflow on the N and NE quadrant of the system. The ULL to its north may be showing signs of loosening its grip.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
Quoting AussieStorm:

when did crows come in low fat?

Ever since the bloggers ate all the fat ones.
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Good Morning All Is Quiet in Puerto Rico This Morning No Rain At All, Just Cloudy
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Quoting helove2trac:
What everybody fail to realize is that this thing has alot of time to organize it has about 5 days before it hits fla so dont be fooled because it not lookin good now 5 days can make a big difference
i think it looks pretty good right now. it looks to have 2 circulations. wonder if this will destroy it or make it bigger:)
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come on 97L everyone is pulling for you
Quoting hurricane23:
Watching 97 closely... Late morning hrs show what appears to be some banding developing north of were the greatest vorticity is.


Did you check out the OFCL intensity and track? Sheesh.. NHC thinks this will be a Category 1 landfall in South Florida. SHIPS thinks it will be nearing Category 2.
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I believe we will have 2 more named storms in July. 97L will become Bonny and one of the waves in the eastern Atlantic or coming off Africa will be our C storm (don't remember the name). Then get ready for a crazy August/September. Any thoughts?
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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.