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 StormW:
Hey Drak, looks like the developing LLC is almost hugging the coast.

Thoughts?


Given some lovin.

Guess the shear forecast did not hold, for now.
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Quoting Thundercloud01221991:


I would say tomorrow because tonight I expect a TD and tomorrow it would be close enough for watches


depends on when landfall is predicted, watches and warnings would definitely go up for the Turks and Caicos; as well as the bahamas

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storm you are saying it should go left and thats points at what the central gulf states?
Quoting StormW:
Models should come left on the 18Z run


hmmmm, you sure about that?
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Quoting reedzone:
GFDL turns 97L towards my direction here in Central Florida.. ouch, not liking this, this was not expected a day ago... wow.


until 97L develops into atleast a depression,model tracks will
be highly questionable.
but i feel your excitement Reed.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting HellaGoose:
If this trend continues, when do you think a tropical storm watch will go up for Florida?

hell yah but i hope hell no
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Quoting HellaGoose:
If this trend continues, when do you think a tropical storm watch will go up for Florida?


I would say tomorrow because tonight I expect a TD and tomorrow it would be close enough for watches
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Developing Tropical Depression, spiral banding to the north, sustained convection. TD3 within the next 12 hours is likely.

Member Since: July 8, 2005 Posts: 259 Comments: 23494
post 928 lol hopefully pureto rico can become the 57th state!
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If this trend continues, when do you think a tropical storm watch will go up for Florida?
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Has anyone heard what the DWH spill incident command's evac plan is since the cap is on?...still the same?
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Jean on Central Florida approach [CAT3] 2004 ...
Member Since: July 3, 2007 Posts: 0 Comments: 524
Great call Drak. It looks like a circulation developing north of eastern tip of DR. If so, my analysis needs no changing. The spin north of Puerto Rico is probably the old circulation which has now reformed north of the DR, which will become the more dominant circulation given the structure currently of the convection and overall system. A strong trough of low pressure looks to affect the eastern US sometime Saturday or Sunday this upcoming weekend. So right now thoughts are that if the highs can stay strong enough the african wave will move westward more then northward, while if the highs weaken due to the trough then the African wave will move too far northward to affect the US. With a long track westward across the Atlantic awaiting this wave and its current latitude, thoughts are that the next two troughs will likely end this wave, or not be strong enough to lift it north and it becomes a threat to the eastern US coastline.
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Something that made me laugh yesterday, someone said this blog would explode when we got something to track and even moreso when we have multiple storms to track

In my experience here, this blog is much more tolerable when we have something to track because it seems people put aside their differences to make sure the right info gets out.

It is when it is slow that the arguments occur more often.
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Quoting btwntx08:
expect gfdl and hwrf to change to the left on their next run


you mean way right.......
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Quoting StormW:
Hey Drak, looks like the developing LLC is almost hugging the coast.

Thoughts?


...as you can guess, I am happy for it to stay South.
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Quoting StormW:
Alrighty den!


haha

I just had this thought....Sarah Palin as a Met predicting or describing this storm. Easy on the eyes but not the ears....LOL!!
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Good point Alex, it's gonna be burnin oil
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Quoting FLdewey:
At 2pm they will announce it's just ground clutter. Keep your Home Depot re ceipts.



Is it time to buy generators and water?
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Quoting Jeff9641:


Yeah, I looked at the wind patterns later this week and next weekend and I'm seeing a trough over the mid Atlantic which in turn causes a weakness in the ridge and sends 97L further north.


I live in Palm Coast, near Daytona, a bit north.. GFDL has me in TS sustained winds.
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957. JRRP
see you at night
Member Since: August 16, 2007 Posts: 0 Comments: 5236
Quoting MiamiHurricanes09:
ASCAT suggests that there is an area of low pressure, could close off as early as tonight.


crap i work tonight and this is going to be an interesting night
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GFDL turns 97L towards my direction here in Central Florida.. ouch, not liking this, this was not expected a day ago... wow.
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ncstorm --

I was? I don't want a storm....I'm a CHICKEN....I moved to s.fl from orlando....and I went through Charlie....I was hiding in a closet with my oldest son crying....lol...I'm too chicken for a storm!!! ....but I do like to watch them on tv!
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Oh, and somebody wake up Hicks!
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948. xcool
HA
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Quoting Jeff9641:
It is looking like the entire Orlando metro area could have 50 to 75mph winds as this moves thru if these models are correct.
How bout the Ft. Myers area? Thank you
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I am still staying with my prediction of a T.D.
later this evening , probably 8:00 PM update from NHC. It's trying to get a closed circulation going,notice the southern part of the storm isn't closed , once it establishes good
outflow from the north and south i think we should see T.D. at 8:00 P.M. EDT.
Member Since: July 20, 2010 Posts: 0 Comments: 225
ASCAT suggests that there is an area of low pressure, could close off as early as tonight.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting StormSurgeon:
My goodness.....

Link


one storm at a time place we dont want the blog going into cardiac arrest now do we lol
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How about the water is like jet fuel? Lol, it's making the shower curtains fog up :p
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942. JRRP
Quoting Drakoen:

Member Since: August 16, 2007 Posts: 0 Comments: 5236
Quoting hydrus:
The water temps this thing will be moving over is high octane for tropical cyclones. I know you know this, but I wanted to say high octane..pfffft


LOL...such a phrase dropper...

By the way, with the TWO and the NHC increase to 60% the panic has begun...all regular bloggers/commenters, man your battle stations!


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Quoting connie1976:
...sometimes this blog cracks me up!! You will have people post how an invest is going to be a super storm and hit in there area, but later on say how storms are bad and how they don't want one....but secretly you know they are wishing for the storm to come....the problem is....when once actually does come and they don't have a house or don't have power for a week they will never want a storm again...well, at least until the next year...lol.. ;)


umm .you were doing the same thing earlier..wishing for a storm..cracking up over yourself
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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.