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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838. xcool



LOL AT MODELS
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Early afternoon,

Call Me a Downcaster! Invest 97L May Not Develop, is how I feel about the Atlantic tropics today, and is my latest blog entry. Its been a complex synopsis for 97L over the last 48 hours due to the complexity of the current upper atmosphere across the North Atlantic basin. See my entry for my reasoning (too long to explain here). You can weigh in on my blog to give views about what I have stated.
Member Since: Posts: Comments:
Quoting whs2012:


Lol, but where? Alabama, Mississippi, Louisiana, Texas?em>


yes...
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Quoting twhcracker:


are you going to take a xanax haha


Mmmm Xanex....
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Quoting MiamiHurricanes09:
That's fine, I'm just pointing out where it seems to me that the center is.


That's fine as well but, based on the official 12Z coordinates the HWRF was spot on.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting Drakoen:
Surface observations from the Dominican Republic indicate a closed low is forming with 97L.


where does one find these?

thanks.
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Quoting whs2012:
So where is 97L going after Florida?
who said it will hit florida.
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829. unf97
Quoting Hurricanes101:


depends on the track across florida

it could go into the Gulf or it could turn northward like Jeanne did and never get back over water

too early to tell, my guess is it will get over the Eastern Gulf for about 1 or 2 days


There is a possibility that it could make two FL landfalls (South FL, FL Panhandle).

No telling. We all just have to follow the old mantra "to keep watching it" LOL..
Member Since: September 25, 2007 Posts: 0 Comments: 1193
828. 7544
yepp
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NEXRAD Radar
San Juan, Base Reflectivity 0.50 Degree Elevation Range 248 NMI

Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting Drakoen:
Surface observations from the Dominican Republic indicate a closed low is forming with 97L.
And do you think that this low is north of the eastern tip of the Dominican Republic or not?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Drakoen:
Surface observations from the Dominican Republic indicate a closed low is forming with 97L.


Should the NHC make this a high risk area at 2 pm, in your opinion?
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823. xcool
oh boy here come big moomy
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting DestinJeff:
Fish


Oh, and by the way: schema, schema, schema, schema...

: P
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821. xcool
TropicalNonsense .lmao
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Surface observations from the Dominican Republic indicate a closed low is forming with 97L.
Member Since: October 28, 2006 Posts: 57 Comments: 30563
819. 7544
again i repeat a storm coming from the east in july to so fla wow this may get in the record books
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Quoting helove2trac:
will this thing hurry up and become a td then we can finally put our minds to rest this is driving me crazyyyyyyyyyyy


we already know....it is going to Florida....for now anyways. Who knows... :)
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Quoting xcool:
TropicalNonsense oh yeah.my brain is fried


a cold beer goes good with the tropics. stay cool x

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


Intensity is unknown. Remember Andrew?
The Gulf Stream and Herbert's Box is notorious.

although im not suggesting anything of the sort.


Exactly right: this feature isn't even a depression yet and the models are notoriously bad at intensity AND track with weaker systems...emphasis on weaker.

Now, tomorrow? This may all be different, but you have to remember that as far as tropical systems go, it's one in ten or so that really develop (with the odd year like 2005 thrown in for contrast)
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Quoting whs2012:
So where is 97L going after Florida?


The Gulf, lol.
Member Since: July 6, 2010 Posts: 113 Comments: 32275
will this thing hurry up and become a td then we can finally put our minds to rest this is driving me crazyyyyyyyyyyy
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Quoting sailingallover:
If 97L does not get in gear and move I'm going to have a beach front lot...

I have no doubts this will develop soon as it moves away from the islands a bit. There is basically a feeder band going straight over me right now and has been for the last 24 hours.
Pressure at
http://www.ndbc.noaa.gov/show_plot.php?station=41043&meas=wdpr&uom=E&time_diff=-3&t ime_label=ADT
Will start to drop soon....
Again as I said yesterday and especially since it has really slowed down T&C, Bahamas get ready and SFL as well...its to late when it is on you..


Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting StormW:
Back in a bit.


are you going to take a xanax haha
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809. xcool
TropicalNonsense oh yeah.my brain is fried
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting whs2012:
So where is 97L going after Florida?


depends on the track across florida

it could go into the Gulf or it could turn northward like Jeanne did and never get back over water

too early to tell, my guess is it will get over the Eastern Gulf for about 1 or 2 days
Member Since: March 10, 2010 Posts: 1 Comments: 7823
Quoting CyclonicVoyage:


all due respect but, I trust the NHC position is accurate.
That's fine, I'm just pointing out where it seems to me that the center is.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
12Z GFDL a lot further northward


HOUR: 72.0 LONG: -79.00 LAT: 27.49 MIN PRESS (hPa): 995.04 MAX SURF WIND (KNOTS): 58.78
HOUR: 78.0 LONG: -80.60 LAT: 28.23 MIN PRESS (hPa): 994.38 MAX SURF WIND (KNOTS): 54.03
HOUR: 84.0 LONG: -81.92 LAT: 28.87 MIN PRESS (hPa): 993.90 MAX SURF WIND (KNOTS): 31.31
Member Since: September 23, 2005 Posts: 14 Comments: 11215
804. JRRP
Quoting MiamiHurricanes09:
I understand that, but looking at vorticity and satellite imagery it looks like the center is just north of the eastern tip of the Dominican Republic.

yea
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Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
I understand that, but looking at vorticity and satellite imagery it looks like the center is just north of the eastern tip of the Dominican Republic.


all due respect but, I trust the NHC position is accurate.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting StormW:


Well, you do that! Be my guest! Ya know, if some of ya folks that have nothin' to do but come on and give us mets a hard time, would zip it up and actually read, think, and understand the synopses, ya might learn somethin'


Amen...I thought I knew a lot about the tropics until I came to this board. Wow, have I ever learned a lot from people like StormW and others. Keep up the good work.
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Quoting btwntx08:

exactly what i was pointing out


AL, 97, 2010072012, , BEST, 0, 190N, 658W, 30, 1013, DB,
Member Since: January 30, 2010 Posts: 0 Comments: 3259
san juan has a North wind at 5mph right now..
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Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting MiamiHurricanes09:
The HWRF initialization point looks to be too far east and south.



the 12Z coordinates are spot on actually

Member Since: March 10, 2010 Posts: 1 Comments: 7823
792. 7544
did everyone see the new moe gfs two so fla systems one follows the other
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Quoting CyclonicVoyage:



Looks right on the mark to me?

AL, 97, 2010072012, , BEST, 0, 190N, 658W, 30, 1013, DB,
I understand that, but looking at vorticity and satellite imagery it looks like the center is just north of the eastern tip of the Dominican Republic.



Member Since: September 2, 2009 Posts: 130 Comments: 21194
789. Prgal
Quoting sporteguy03:
I read that also I am wondering how the folks elsewhere in Turks and Caicos, Bahamas, DR, Cuba will fare.


Right! And a lot of people read this blog even if they are not posting comments every day (I am one of them).
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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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