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 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
you nust have never been thru a bad one because you would not make thost type of comments
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Quoting Jeff9641:



TampaSpin, it looks as if we are in for some weather this weekend.


Not much doubt if you believe in Models. They seem to have a good handle on this one but, let's see if this develops first...then things will change possibly!
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136. IKE
ULL is losing out on 97L. Less of an influence.
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97L definitely appears to be continuing to become better organized.
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Quoting jasoniscoolman2010x:
last night i said that about 10,000 times There is a large amount of dry air to the northwest of Puerto Rico that will interfere with development of 97L. i am right to much dry air..i said that last night by looking at the map i win this time around.
Actually you said it only 9,345 times.
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I'm more concerned with what will happen if and when it gets into the GOM.
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Good morning. Working and lurking. Thinking that 97 will go too far south for me (Port St Lucie) to get a long weekend.
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Quoting FLdewey:


I have to say I've been missing tropical weather too. I don't miss the Walmart freakouts, the cold showers or the lack of traffic lights (Floridians don't seem to remember what to do at an intersection with no lights) but I do miss the weather.


LOL, you'd be surprised how SC reacts when there's one inch of snow. People stock up like there's gonna be a two-week blizzard.
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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.
Very interesting. I'll be monitoring it closely since I live in Miami.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting divdog:
excited about getting a hurricane.. how old are you
Age isn't the only factor in a case such as this. Also age dosen't always matter.
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128. Relix
Quoting divdog:
excited about getting a hurricane.. how old are you


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
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I am not sure why people try to predict intensity this early but this one could be major.


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125. srada
Im interested to see how the 12z models pan out..will it be more northern or more westerly..only time will tell
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The Intensity Forecast Models are usually Conservative. Lets hope they are slighty the opposite this time.
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last frame of 97L sat loop looks interesting.

http://www.ssd.noaa.gov/goes/flt/t1/flash-wv.html
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Quoting MiamiHurricanes09:
Conservatively? Oh man, how about without conservativeness, lol?


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.
Member Since: October 28, 2006 Posts: 57 Comments: 30830
Quoting Floodman:


Too late...the freaking out has begun...LOL



Hey Flood, I know, it started around mid May....LOL
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Quoting FLdewey:


I have to say I've been missing tropical weather too. I don't miss the Walmart freakouts, the cold showers or the lack of traffic lights (Floridians don't seem to remember what to do at an intersection with no lights) but I do miss the weather.
Tempting fate this morning, I see....risky business!
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Quoting gator23:
Is South Florida likely, some of the models take it up past West Palm wahy is that?
Read StormW's blog.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
117. 7544
what more u need right tampa o it looks like a sofla strom from this end and in only 3 days coming from the east and not recurving like all the others do ?the rush will be on soon
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Quoting extreme236:


The SHIPS model has shear remaining below 20kts for the next 5 days.
Yep, and it plows 97L as a near category 2 through southern Florida. If dry air is minimal and the upper level environment is favorable we might be dealing with a stronger system, somewhat like what the 12z "official" track is showing.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting divdog:
excited about getting a hurricane.. how old are you


One thing for sure, daddy is the one cleaning up the next couple of days.......
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Quoting mara0921:
Good morning everyone. I live in Broward County, FL. Needless to say the last thing I want is storm making a surprise apprearance this weekend. I decided to look at todays developments and was a little shocked by whats happpening. The computer models and intensity forecast at first glance are worrisone. Could some please fill me in on this wave/depression and if it has a chance to make it to hurricane strength ? thanks I'll check back when I get to work.


Easy, mate. It has a small to medium chance of becoming a hurricane and even if it does, it won't be more than a small category 1 with, say, 85 MPH winds tops. I predict a strong tropical storm something like the same strength of between Fay and Ernesto.
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i am excited too :) I love hurricanes if they dont kill people or destroy homes. trouble is even a little one is bad for people right on the GOM but I guess they knew the risk when they bought property there... just hope everyone tries to be safe when storms come! I feel bad for the people in Pike County Kentucky!
Member Since: July 30, 2007 Posts: 6 Comments: 1448
110. IKE
Quoting weatherguy03:
Latest Update on 97L w/ Video


Nice update.

StormW...yours was too.

Thanks to both!
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Is South Florida likely, some of the models take it up past West Palm wahy is that?
Member Since: August 26, 2008 Posts: 0 Comments: 2182
Quoting StormSurgeon:
Let's not freak out. Remember, 97L is just an invest.


Too late...the freaking out has begun...LOL

Member Since: August 2, 2006 Posts: 10 Comments: 9922

CMC


GFS


NGP


HWRF

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Quoting hurricaneben:
YAY! I'm so excited. I never got a hurricane since 2005's Wilma and this invest MIGHT be the one. Not likely, but still a small possibility.
excited about getting a hurricane.. how old are you
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Quoting 7544:
but really a storm from the east in july has that ever happen hitting so fla in july



Not that I am aware of, could be one of 2010's unique features.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting hurricaneben:
YAY! I'm so excited. I never got a hurricane since 2005's Wilma and this invest MIGHT be the one. Not likely, but still a small possibility.


I wouldn't be excited. I've had a couple of remnant hurricanes come through (Charley, Frances, Ida), and they're not fun.
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Quoting reedzone:
There's too much wind shear right now, I just don't see anything but a sheared TS or TD hitting South Florida at this point. Maybe the shear will lessen greatly and I could be wrong. Conditions have gotten worse in the area, I really have a hard time believing what you guys are predicting.


The SHIPS model has shear remaining below 20kts for the next 5 days.
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102. 7544
but really a storm from the east in july has that ever happen hitting so fla in july
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AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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Latest Update on 97L w/ Video
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Quoting hurricaneben:
YAY! I'm so excited. I never got a hurricane since 2005's Wilma and this invest MIGHT be the one. Not likely, but still a small possibility.

GP
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looks like this could break tampas record of no storms in a while?
Member Since: July 30, 2007 Posts: 6 Comments: 1448
Quoting reedzone:
There's too much wind shear right now, I just don't see anything but a sheared TS or TD hitting South Florida at this point. Maybe the shear will lessen greatly and I could be wrong. Conditions have gotten worse in the area, I really have a hard time believing what you guys are predicting.
I believe that a ridge will be building in pushing the ULL away.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
YAY! I'm so excited. I never got a hurricane since 2005's Wilma and this invest MIGHT be the one. Not likely, but still a small possibility.
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Quoting MiamiHurricanes09:
12z sounding from San Juan suggests a circulation in the mid levels (600-700mb).



University of Wyoming? Where's the tornado?...LOL
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Dang dudes we got a code orange. Our local met in South Louisiana said don't worry about 97L until Sunday. So many landfallers that cross the peninsula in Fla hit LA a second time......the track angle may be in play!!
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Well, with 97L on top of deciding what to do, we here in the "Island of the enchantment" are been soak with rain, and it continues, specially to the east. Hope it start moving soon, don't see that 5 to 10mph movement, it's been in the same place more or less about 30 miles from the east coast of Puerto Rico. On the general area of our smaller islands Vieques and Culebra.
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There's too much wind shear right now, I just don't see anything but a sheared TS or TD hitting South Florida at this point. Maybe the shear will lessen greatly and I could be wrong. Conditions have gotten worse in the area, I really have a hard time believing what you guys are predicting.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting reedzone:
Wind shear has increased over 97L and also in it's path (30-40 knots). I have a hard time believing that conditions will become favorable so quick.


From Masters Blog:
" wind shear has fallen to the moderate range, 10 - 20 knots, which may allow 97L to continue to develop today."
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Quoting Drakoen:


Conservatively yes
Conservatively? Oh man, how about without conservativeness, lol?
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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