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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238. IKE
Quoting twhcracker:


this story kills me Ike! I remember when it happened. it just hurts my heart! I hope you got another dog!


I've got another one...had him since he was a pup.

I'll check back later today.


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Storm...got a question...Our local mets in New Orleans are saying that a strong "HIGH" will be in place (around the La/Miss line)by Fri. Bringing very dry air and HOT temps...Wouldn't that "HIGH" force anything that might be headed for the gulfcoast west??
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Quoting hydrus:
I think hurricane 5 hit S.E.FL in 1933.


Cat 5 storms making landfall in the US

1935 - Labor Day storm (Mid keys)
1969 - Camille
1992 - Andrew
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Quoting BahaHurican:
They're more likely to pick it up as a depression.
I saw a "tropical update" in the news this morning when the NHC bumped up the chances. They started showing the models and all that propaganda.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
G'moring, StormW, all.


Seems the season "bust" yacking would wane with a developing system. LOL. It's still early - lots of season of left! Soon we could have more going on than we can shake a stick at - not looking forward to it either! Thanks to you folks who do the good, solid work - not just posting model and chart, one after another. Appreciate it. It's good to hear your thoughts, even be it maybe wrong sometimes - that's okay. If we wanted puters to tell us what we should do all the time, not sure I'd call that living or forecasting - that's just punching buttons, kind of like an ATM machine, looking for that instant result.
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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.
sorry for your loss. god bless
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Hope Everyone in South Flordia has got a Hurricane Kit Ready Likes Beacuse this looks like a nasty Storm
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Quoting StormW:


I believe they may have. We had a rep. from FLA. at the National Hurricane Conference who's office does the EVAC zones specifically for FL. She did say that some zones would be changed this season.


Storm - we saw major changes here in Pinellas... with the new recalculated SLOSH basin and better land elevation.

Here's the site for Monroe's evac policy:

http://www.monroecounty-fl.gov/pages/MonroeCoFL_Emergency/evacuation
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Quoting dolphingalrules:


still NOTHING from the media...dade..broward or both county....we havent had a storm since wilma...
They're more likely to pick it up as a depression.
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Quoting FLdewey:


That's not the dood with the trashcan on his head is it? :-0


No, we would be wearing black motorcycle helmets equipped with bluetooth interphones.
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226. beell
Still maybe a tough road ahead for 97L. The ULL is backing to the SW and strong northeasterly flow around the eastern edge of the upper ridge is progged to build in just to the NW-over Florida. Could be 30-40 knots at 200mb here.

GFS continues to hint at a large inverted upper trough over FL/Cuba with 97L trying to stack up under the upper level features. Would be an odd looking system.
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Hmmm...been living in Palm Beach County since Feb 2006, so I haven't had to break out the shutters yet. Hope I don't have to now...who knows what's back in that corner of the garage...spiders? Iguanas? herds of wild Alpaca?

Amazing that the time frame for a POTENTIAL impact in South Florida is only a few days away and we haven't had nonstop local news coverage.
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Quoting Floodman:


This one doesn't count; it hit Jax as a TS:



This one's closer, but still no cigar:



Nothing else since 1925...
I think hurricane 5 hit S.E.FL in 1933.
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Thanks for the analysis Dr. Masters - with my husband on a cargo ship doing a Caribbean run, this early information is very helpful for him and the ship to plan their route.
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Quoting hurricanejunky:
The Xtreme Team is ready for action! Trying to solidify timeline and forecasts would be most welcome! Hey Reedzone and MiamiHurricanes09, time for a blog forecast update?



Soon, I'd like to see some changes on the wind shear before I do an update on my thinking.
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As far as I know our evacs. are still the same, not that it matters much, we only had 6 to 7% for Wilma.
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This looks like a typical WPAC system, the COC will appear right in the middle of all that convection.
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Quoting hurricanejunky:
The Xtreme Team is ready for action! Trying to solidify timeline and forecasts would be most welcome! Hey Reedzone and MiamiHurricanes09, time for a blog forecast update?

I'll be posting an entry on my blog here at WU and over there on your website this evening.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting StormW:


Now dats one of the best statements I've heard in the past few days.



Agreed. The charts, the models get prettier and prettier while the solid observations and real forecasting gets thinner - well, of course, except for the good handful that keep up the good work. Kudos! ;)
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The Xtreme Team is ready for action! Trying to solidify timeline and forecasts would be most welcome! Hey Reedzone and MiamiHurricanes09, time for a blog forecast update?

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Quoting Drakoen:


AVN is the GFS, should not be used for intensity
Ok, changed it.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Did Monroe County change their evacuation policies? I know they were talking about it last year about "easing up" on them. CAT3 is MANDATORY evac for everyone in the keys.
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Quoting MiamiHurricanes09:
The majority of the 12z intensity models have 97L making landfall in 96 hours, thus the weakening noted. Then when 97L re-emerges into the GOMEX it begins to intensify. Thing to note, every model (except for the AVNI) takes 97L to a tropical storm, with the majority taking it to hurricane strength before landfall.



AVN is the GFS, should not be used for intensity
Member Since: October 28, 2006 Posts: 57 Comments: 29888
Morning all. [note I left out the "good" part of that greeting.]

Quoting sporteguy03:
I am sure Baha won't be too excited about 97L's potential.
You got THAT right...

Quoting Jeff9641:


Dare I say Frances and Jeanne tracks.
Nope. This is worse. More like 1926 - 1928 hurricane tracks... The implication of the northward swing is IMO stronger storm expected, which I do not at all like...

Quoting Drakoen:


The SHIPS text indicates shear should become much more conducive for development. The biggest problem will be dry air, the 700mb-500mb RH values decrease from the 60s to the 50s which is an indication of some mid level dry air. The other thing is, though, that the OHC will be increasing on the storms path into the Bahamas. It is not out of the question to see a minimal hurricane out of this before landfall.
The irony with the dryness is this is the driest it's been here in weeks.... lol

Well, here we have sunshine, partly cloudy with light winds and occasional gusts. At 9:00 this was the airport:

Nassau, BS (Airport)
Updated: 1 hr 41 min 44 sec ago
88 °F / 31 °C
Scattered Clouds
Humidity: 70%
Dew Point: 77 °F / 25 °C
Wind: 16 mph / 26 km/h / 7.2 m/s from the East

Anyway, I have stuff to do today, so if I'm not posting much, doesn't mean I'm not looking in from time to time. I just hope I don't come back here in a few hours and find some RI foolishness going on....
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Ike...
I'm sorry...poor guy!!
when I was a kid, we used to swim in lakes with gators....but I wouldn't do it now!! I don't blame ya for not going in...especially at night!
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.
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Quoting IKE:


New Years evening...I was helping my wife clean up after supper. He was a small poodle...about 7 pounds. I let him out to do his business. He always did and came right back scratching on my front door.

He didn't this time. He ran down to the lake I live on...must to have run up on the dock and fallen off. My wife and I heard him...ran down there..saw him paddling in the lake.

I should have gone in after him, but was scared with alligators in the lake, plus it was pitch black dark.

His mind apparently was going. My cousin is a vet and told me how older dogs can suffer senility.


this story kills me Ike! I remember when it happened. it just hurts my heart! I hope you got another dog!
Member Since: July 30, 2007 Posts: 6 Comments: 1448
The majority of the 12z intensity models have 97L making landfall in 96 hours, thus the weakening noted. Then when 97L re-emerges into the GOMEX it begins to intensify. Thing to note, every model takes 97L to a tropical storm, with the majority taking it to hurricane strength before landfall.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
97L still lacks organization at the surface: surface pressures are not falling and there continues to be little evidence of a surface circulation forming.
Member Since: October 28, 2006 Posts: 57 Comments: 29888
Quoting Waltanater:
That won't happen...SFLA will get some of this action!


still NOTHING from the media...dade..broward or both county....we havent had a storm since wilma...
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man! 97L does not want to move any!! is my imagination, or has 97L moved VERY LITTLE from where it was last night?!?! what's going on with this little monster? - It's already wanting to be a little surprising? lol
Member Since: July 9, 2007 Posts: 0 Comments: 692
Quoting IKE:


New Years evening...I was helping my wife clean up after supper. He was a small poodle...about 7 pounds. I let him out to do his business. He always did and came right back scratching on my front door.

He didn't this time. He ran down to the lake I live on...must to have run up on the dock and fallen off. My wife and I heard him...ran down there..saw him paddling in the lake.

I should have gone in after him, but was scared with alligators in the lake, plus it was pitch black dark.

His mind apparently was going. My cousin is a vet and told me how older dogs can suffer senility.

:,(
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200. Prgal
Quoting WeatherNerdPR:

I've had 3 dogs die at my house...One of them earlier this year. I have a Shih-Tzu that had her 3rd birthday on May 31.


Its so sad when pets die. I've had my share too on losing dogs. I love my dogs and see them as family members.
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Quoting catastropheadjuster:


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


I think it'll be what it'll be; it's very disorganized right now but 5 days from now we could all be watching a nasty
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.
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Quoting StormSurgeon:


One thing for sure, daddy is the one cleaning up the next couple of days.......


when i was a kid growing up in fla on a bayou, hurricanes were such fun. As a kid, had no worries, we got to stay up all night with hurricane lanterns, my dad would tell scarey stories, my mom would give us peanut butter sandwiches in the middle of the night, no school the next day, and we were too young and dumb to know there was something to fear. i remember walking out onto our porch during the eye of a storm and the yard was full of limbs and moss and debris, and we stood and it was so silent, then the eyewall started coming and we could hear a roar and rumble as a tornado went through town and cut all the trees off at the top, like a giant lawn mower. The only thing i hated was that the big roaches started flying when the gusts shook the house, an old wood frame florida house on piers. so i guess i came by my hurricane excitement honestly :)
Member Since: July 30, 2007 Posts: 6 Comments: 1448
195. unf97
Quoting StormW:


What are you confused on:

At the moment, I prefer the southern portion of the Dynamic Model guidance, maybe a little further south (at this moment), and will not rule out the CMC solution at the moment. Bear in mind, this will most likely change numerous times, until we see whether or not 97L develops or doesn't develop. Should decent development occur, I will not rule out a further northward solution. Again, I will be monitoring these parameters throughout the day.



StormW, thanks! I agree with you that a stronger tropical cyclone should it manifest will tend to shift a little more north in the long term. All depends on how 97L will ultimately track of course.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
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.....


Yeah! The next Theme Park Ride! Welcome to Jurassic Hurricane folks! LOL
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193. IKE
Quoting connie1976:
ik, how did your poodle drown in a lake? poor puppy...


New Years evening...I was helping my wife clean up after supper. He was a small poodle...about 7 pounds. I let him out to do his business. He always did and came right back scratching on my front door.

He didn't this time. He ran down to the lake I live on...must to have run up on the dock and fallen off. My wife and I heard him...ran down there..saw him paddling in the lake.

I should have gone in after him, but was scared with alligators in the lake, plus it was pitch black dark.

His mind apparently was going. My cousin is a vet and told me how older dogs can suffer senility.
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Quoting 7544:
but really a storm from the east in july has that ever happen hitting so fla in july


This one doesn't count; it hit Jax as a TS:



This one's closer, but still no cigar:



Nothing else since 1925...
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Quoting FLdewey:
My cat would have loved to have seen all this. :(
Poor Vorticity!
Member Since: August 16, 2007 Posts: 1 Comments: 2337
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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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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