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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That is so true connie
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...And we have a red one @ 60%. ;-)
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...60 PERCENT...
Member Since: September 2, 2009 Posts: 130 Comments: 21091
000
ABNT20 KNHC 201740
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE JUL 20 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A VIGOROUS TROPICAL WAVE
EXTEND FROM THE NORTHERN LEEWARD ISLANDS WESTWARD TO HISPANIOLA.
ALTHOUGH THE SYSTEM DOES NOT YET HAVE A CLOSED CIRCULATION...
SATELLITE IMAGERY SUGGESTS THAT A SURFACE LOW PRESSURE AREA IS
BECOMING BETTER DEFINED JUST NORTH OF THE EASTERN TIP OF
HISPANIOLA. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE
FOR ADDITIONAL DEVELOPMENT AS THE SYSTEM MOVES WEST-NORTHWESTWARD
AT ABOUT 10 MPH DURING THE NEXT DAY OR SO. THERE IS A HIGH
CHANCE...60 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL DEPRESSION
OR STORM DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...
LOCALLY HEAVY RAINFALL AND GUSTY WINDS WILL LIKELY AFFECT THE
VIRGIN ISLANDS...PUERTO RICO...THE DOMINICAN REPUBLIC...HAITI...
EASTERN CUBA...THE TURKS AND CAICOS ISLANDS...AND THE SOUTHEASTERN
BAHAMAS DURING THE NEXT COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Member Since: Posts: Comments:
Quoting btwntx08:
miami will post the two
Sure!
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Drakoen:
97L is north of the eastern DR


I was going to think the same thing, but I think that is actually a mid-level spin that was generated yesterday N of Puerto Rico. The mid-level spin is to the NE of the surface wave axis, so this is still disorganized IMO.
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Quoting earthlydragonfly:


I nominate IKE


2nd that
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879. 7544
97 l is gonna look like a dounut a big dounut soon
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...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.. ;)
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Quoting KEEPEROFTHEGATE:
can we all pick someone anyone to post TWO just once that would be nice


I nominate IKE
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Quoting Drakoen:
97L is north of the eastern DR
correct drake i see it too
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872. Prgal
Quoting sailingallover:

Right now it would develop except PR is stopping it from getting a good circulation. Im on the west end of STT and gettign dumped on and my friends in Culebra at docity have been getting sustained 30knot winds with 45knot gusts..
A TD/TS or not 97L is dumping on us. SFL may get a hurricane..that cannot be ruled out..


Yeah, its been quite a system. Here we just have light rain and a great temperature. Be safe!
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Quoting KEEPEROFTHEGATE:
can we all pick someone anyone to post TWO just once that would be nice
I've tried...Never worked.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Drakoen:
97L is north of the eastern DR
Exactly what I'm thinking.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Member Since: September 1, 2007 Posts: 0 Comments: 1793
97L is north of the eastern DR
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Quoting extreme236:


The vorticity is not focused east of PR. Probably just a mid-level circulation of some kind, if there is one there at all.

You mention it crossing over Hispanola, which isn't going to happen...


The area of lowest surface pressure is usually the tropical wave axis itself, and I have noted the wave axis is the NHC surface analysis is over Hispaniola right now. That also puts the wave axis toward the western edge of the convection too. It looks like the bands to the northeast of Hispaniola are around a mid-level spin that developed yesterday N of Puerto Rico. I don't think that this mid-level spin is at the surface.
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Quoting jasoniscoolman2010x:
ITS GOING UP TO 50% AT 2PM
maybe up to 60 becuase as drak stated a closed low is forming
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Quoting KEEPEROFTHEGATE:
can we all pick someone anyone to post TWO just once that would be nice


Good Luck wit dat...
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864. unf97
Quoting Floodman:


That is potentially disastrous...


That is the worst case scenario should 97L reach the Eastern GOM, especially with the oil spill.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
862. xcool
ROB POSTING TWO
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Quoting Floodman:


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)


Right Flood. The only problem with the 1 in 10 deal
is ya never know when that exception# 1 is. [Laughs]

wait and see for now.
Member Since: July 3, 2007 Posts: 0 Comments: 524
can we all pick someone anyone to post TWO just once that would be nice
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key for 97L is that it did indeed slow down, this has several days to organized further
Member Since: March 10, 2010 Posts: 1 Comments: 7368
Quoting Prgal:


I even mentioned earlier about the circulation south of Vieques and I was mostly ignored. Ada Monzon said that there was a huge drop in pressure in the Fajardo area with the wind comming from the west. What does that tells us? We all know...

Right now it would develop except PR is stopping it from getting a good circulation. Im on the west end of STT and gettign dumped on and my friends in Culebra at docity have been getting sustained 30knot winds with 45knot gusts..
A TD/TS or not 97L is dumping on us. SFL may get a hurricane..that cannot be ruled out..
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Latest TAFB 48 hour forecast


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I see the CLOSED LOW on the radar site
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854. xcool
Hurricanes101 /Everything is up in the air right now..
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In this Image you can see the wind shear intensification potential map.

NOTE' if u right click then view image, u get bigger image

Member Since: July 20, 2010 Posts: 0 Comments: 225
Quoting KEEPEROFTHEGATE:
ACTIVATE F5 KEY NOW
Activation complete.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting xcool:



LOL AT MODELS


yeah.. pretty soon they may have it going straight north.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
maybe it will hit all of them states ROFLMAO
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Quoting btwntx08:
TWO will be in 30min or less
ACTIVATE F5 KEY NOW
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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


That is potentially disastrous...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting xcool:



LOL AT MODELS


why is that worth an LOL?
Member Since: March 10, 2010 Posts: 1 Comments: 7368
Quoting CaribbeanIslandStorm:
I think that invest 97 has some serious organization issues, there seems to be several centers forming, one right off the east coast of puerto rico and another about 175 miles north of the island. Will it be a depression soon? Maybe some time thursday or friday, i think SE florida needs to keep an eye on it.


The vorticity is not focused east of PR. Probably just a mid-level circulation of some kind, if there is one there at all.
Quoting NCHurricane2009:
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.


You mention it crossing over Hispanola, which isn't going to happen...
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Quoting DestinJeff:
Fish


It's a possibility....
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Quoting CyclonicVoyage:


That's fine as well but, based on the official 12Z coordinates the HWRF was spot on.
Yes that's right.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
climatology would suggest the stronger the storm the more likely to ride up the SE coast toward the Carolinas, I'm not suggusting thats going to happen but you never know, I do know the Gulf Stream is pretty much lava off of SC currently...
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Quoting btwntx08:
btw hwrf is wrong already look at post 781 and that is in 6 hrs lol


initial problems.
Member Since: July 3, 2007 Posts: 0 Comments: 524
838. xcool



LOL AT MODELS
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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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