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:


Sorry, Friday morning.
Quoting nrtiwlnvragn:
HPC Day 3




Day 5




Oil for everyone, man that's a bad track.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting AlexEmmett:

craptastic



Crapcaster!
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Quoting Beachfoxx:
Geez, ya'll keep pointing to Destin/PCB - makes me wanna run for the hills.
Really do not want a tropical twirl dancing across that oil spill and bringing us more troubles. : (


Foxx a storm coming at us from the East would actually push the oil away from us and more back towards LA and TX. Just think about the counter clockwise rotation as it approaches, we'll get strong East and then SE winds to push it away from us. Not that I wish it on anyone else mind you!
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AL, 97, 2010072018, , BEST, 0, 195N, 682W, 30, 1012, DB,
Member Since: September 2, 2009 Posts: 130 Comments: 21032
HPC Day 3




Day 5


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ELCanado you are jumping the gun a little in MHO.
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Quoting patrikdude2:
Do you expect to see T.D.3 at 8:00 PM?

YES

or

NO



probably not, but wouldn't be completely surprised
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Quoting StormW:


Pretty good...has a half decent outflow channel to the NE and east, as evident by the "banding" features. If it can get an established upper level anticyclone, then organization would be easier.
Thanks StormW!
Member Since: July 20, 2010 Posts: 0 Comments: 225
Oh by the way, point number 2 I made in post 1058 (the convection and mid-level spin displaced NE of the wave axis) I feel is because of the southwesterly shear. I thought this would inhibit development, but the convection might be maturing the warm core mid-level spin to the surface. Thus, development won't occur on the axis itself, but perhpas NE of the wave axis. Lets see what happens.
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Quoting patrikdude2:
Do you expect to see T.D.3 at 8:00 PM?

YES

or

NO



If it were to be called it would be at 11pm.
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Looks like the models have shifted again!!! I love it! The suspense!!!
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Quoting futuremet:


Two days ago, many of us (including me) were thinking July was going to be a bust.


I held on to Bonnie forming before the month ends, guess it may turn out to be accurate.
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The 12z Official track brought it to a hurricane.

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,
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For those on the East coast of Florida by around this time tomorrow it would be wise to check if you are in an evac zone that calls for voluntary evacuations in an event of a Cat 1 if you were not aware already. Local news in your area would likely show you if you are in an evac zone as well.

Question: Anyone know of any areas that are evac zones even in TS's?

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Stormchaser2007 Thats the best place to be right in the middle 5 days out that means your safe.
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Had to leave for a second.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Do you expect to see T.D.3 at 8:00 PM?

YES

or

NO

Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting unf97:


Sorry about that Reed LOL. I did go back and edited that post, but it was too late, you replyed already. I thought you were Jeff9641 on that last post.


It's alright.
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Quoting CyclonicVoyage:
That's Friday afternoon folks from the NHC.


Sorry, Friday morning.

8am to be specific.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting bohonkweatherman:
A few days models were showing nothing thru July, bloggers were saying July is dead, how things can change. With the tropics you almost have to take one day at a time.


Two days ago, many of us (including me) were thinking July was going to be a bust.
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Quoting gator23:

the GFS upgrade predicted a senario were 97 L would go up to near JAX and go west 3 days ago.



odds are much better that this will effect the southern half of fl and possibly the west coast and/or panhandle,I doubt she'll go north of jupiter area...
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That's Friday afternoon folks from the NHC.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Member Since: January 30, 2010 Posts: 0 Comments: 3259
That very well organized circulation seen on the PR radar imagery yesterday, is no more now as the main low circulation is developing rapidly over or NE of the eastern tip of Hispaniola. Very interesting indeed. System has a greater than 50% chance of development into a tropical cyclone by tomorrow evening. Chances are it will be called a TC when the HH investigate tomorrow late morning/early afternoon. Right now outflow is tremendous on all but the western side, likely due to the continued strong wind shear coming out of the west, chances are it is not as strong as CIMSS is analyzing.
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Healthy wave for now, that's all....
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Given current observations and satellite imagery all indicating a developing closed low level circulation near NE Dominican Republic, I would expect the next computer model runs to shift some further west and south. For those living in both Central and Southern Florida (like myself), I would keep an eye on the system as things develop further. It would seem that a Friday to Saturday rain event is definitely in store at the least for the area.
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Quoting StormSurgeon:


Glad you are, but that northerly dry air intrusion is making me take a second look.


I also felt that way about the dry air on my latest blog post too. I am getting mixed messages from 97L.

1. Great banding features and mid-level rotation is displaced to the NE of the wave axis. Yeah it looks organized, but the surface wave axis isn't aligned with the mid-level rotation. Perhaps convection will touch off a surface low NE of the wave axis (instead of on the wave axis) as it matures the warm core mid-level spin. The wave axis itself will then continue uneventfully westward.

2. Dry air and some southwesterly shear from the ULL to its north may be a problem for 97L

3. And I thought land interaction with Hispaniola would also be a problem for 97L because the wave axis is already over Hispaniola. But I guess if the convection is developing a surface low NE of Hispaniola to the NE of the wave axis, then maybe that's whats happening.

97L is complex indeed, lets see what happens.
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Didnt expect the models to be pointing this at me when I got back...


Also didnt expect to see it at 60%
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1056. unf97
Quoting reedzone:


This is Allan, not Jeff lol... Think you have me confused with the wrong person. Also the upper level low should keep 97L away from the BOC and possibly Texas.


Sorry about that Reed LOL. I did go back and edited that post, but it was too late, you replyed already. I thought you were Jeff9641 on that last post.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
1055. xcool
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Miamihurricanes, are you 13 years old?
Member Since: July 20, 2010 Posts: 0 Comments: 225
1053. gator23
Quoting stillwaiting:



actually about 3 or 4 days ago I just about was guaranteeing that we'd be watching 1 maybe 2 disturbances near the GOM this weekend....

the GFS upgrade predicted a senario were 97 L would go up to near JAX and go west 3 days ago.
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Quoting MiamiHurricanes09:
TCFA should be issued soon. IMO, 97L may become a tropical depression tonight, with a higher chance tomorrow when Recon investigates.

what do you think of my image explanation?
Member Since: July 20, 2010 Posts: 0 Comments: 225
OK... I AM NOT saying this storm will be a Katrina... I hate people who suggest things like that, but I had no idea Katrina started as a spin north of Puerto Rico... Here is a segment of the beginnings of Katrina, found in a NHC report:

A tropical wave, which departed the west coast of Africa on 11 August, moved through the Leeward Islands and merged with the middle tropospheric remnants of Tropical Depression Ten on 19 August and produced a large area of showers and thunderstorms north of Puerto Rico. This activity continued to move slowly northwestward, passing north of Hispaniola and then consolidating just east of the Turks and Caicos during the afternoon of 22 August.
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1049. gator23
Quoting unf97:


Good observation Jeff. Yeah, I am watching the models to see just how much the western periphery of the ridge will erode by this weekend. If there is a significant weakness, then a more poleward motion would be definitely probable. That would make things very interesting all along the East Coast of FL. I'm here in Jax, so the nextset of model runs will hopefully provide us some clues for sure.

thats what I am waiting for too. We will find out what will happen when a LLC is established. I think everyone from the keys to Jax should be watching.
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A few days models were showing nothing thru July, bloggers were saying July is dead, how things can change. With the tropics you almost have to take one day at a time.
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Quoting StormW:


Hey! Where ya been? Good to see ya.


Been busy trying to find work, which I did as a certified tutor both online and in person, as well as spending some time with the family. Good to be back and working with some very knowledgeable people once again here. I'm trying to get back into the swing of things forecasting.
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Quoting NCHurricane2009:
Call Me a Downcaster! Invest 97L May not Develop, LOL, I might be eating my biggest crow ever on this one with the way the NHC upgraded the probability to 60%. I guess I am on my way to the grocery store to buy crow, but I am not eating it yet (it isn't a tropical depression yet).

At least in a blog post before that, I said TD 2 would not become TS Bonnie, I was right about that. Hey, you win some, you lose some, LOL.

I have to agree with you , i don't think this system is all that well organized, maybe I'm wrong, but now it looks like a new circulation is forming north of the eastern tip of the dominican republic
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Quoting unf97:


Good observation Jeff. Yeah, I am watching the models to see just how much the western periphery of the ridge will erode by this weekend. If there is a significant weakness, then a more poleward motion would be definitely probable. That would make things very interesting all along the East Coast of FL. I'm here in Jax, so the nextset of model runs will hopefully provide us some clues for sure.


This is Allan, not Jeff lol... Think you have me confused with the wrong person. Also the upper level low should keep 97L away from the BOC and possibly Texas.
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Quoting reedzone:
GFDL turns 97L towards my direction here in Central Florida.. ouch, not liking this, this was not expected a day ago... wow.



actually about 3 or 4 days ago I just about was guaranteeing that we'd be watching 1 maybe 2 disturbances near the GOM this weekend....
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Geez, ya'll keep pointing to Destin/PCB - makes me wanna run for the hills.
Really do not want a tropical twirl dancing across that oil spill and bringing us more troubles. : (
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Quoting StormW:


Hey! Where ya been? Good to see ya.
How is my image explanation i made with paint? I like to hear advice from a pro like you.
Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting Floodman:


Wrong..they have an evac plan in the event of weather systems...it takes 5 days to implement, but with the well capped they should be alright

i dont consider that a plan it tokk them a day to think that up
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1039. divdog
Quoting whs2012:
Okay, I'm confused. I thought we couldn't really have a reliable track on an invest. We had to wait for it to become a depression, but it seems like everyone is saying (seems like with little doubt) that it's going to Florida?
dont believe the hype. just watch and wait and believe what the nhc is saying. they are watching and formulating their theory. NOONE knows where the storm is going to hit.
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time is no longer a factor in how strong this system gets. it has PLENTY of time and bathtub (albeit a tad oily) water to carry on it's cyclogenesis.....

oil-a-geddon
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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.