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 sailingallover:

When I talked to my friends in Culebra a couple hours ago they were asking why I was not there just in case...the harbor there is the best place to be in a boat in a storm.
I would have had to leave Saturday..but didn't for the last 36 hours it would have been crazy to try to go over there even though it's only 18 miles. Did anybody expect this wave to slow down and the convection to sit over us this long on Saturday?
So maybe a little early planning is best although I don't think anything happened this time..but it would have been very difficult for me to do anything yesterday or today..

Did you see the huge wave that just came off of africa? in the latest pass, there seems to be a circulation, and high winds.
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Quoting CyclonicVoyage:
Latest 18Z/12Z Models



For some reason, this track looks familiar.
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97L seems to have big potential...
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Quoting catastropheadjuster:
I had ask a ? earlier and I was just wondering if anyone answered it. I was wondering what happened to 456? Is he still here I haven't seen him lately and was just wondering. I don't mean to get of the topic.
Sheri

He is around I know he said he only comes on occasionally to the blog, although it would be nice to hear his input today.
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1184. leo305
wow the surface low really has developed since I last checked

moving WNW, tonight we may have a TD
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Afternoon, everyone.

It's amazing to look at the first frame of this visible loop and then the last one. It just shows how organized this system has become since daybreak. Pretty impressive.

Link
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1181. gator23
.
Member Since: August 26, 2008 Posts: 0 Comments: 2162
Quoting MiamiHurricanes09:
What? Lol, they obviously shifted a little left, but like you said, also came into a consensus.


Northward shift, thats what I call it, definitely not hooking towards the west as the 12Z.. More of a WNW track.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
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


They are now considering Top Kill Part Deux, which leads me to suspect that all is not well.

BP considering new version of failed ‘top kill’ operation

Considering BP's (and Thad Allen's, for that matter) recent record for "truthiness," I seriously wonder what is really behind this latest initiative. I guess we'll find out when we find out. Perhaps it is really as simple as is stated.

Meanwhile, the models are pointing a storm at the site. That has to affect the thinking about options and risks.

I'd say that news conference bears close watching.
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Dark purple looks scary.
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Is there a depression yet? If not, models are pfffffttt.
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Quoting reedzone:
18Z runs didn't shift left, they just came into a better agreement, north shift is a good way to call it. They shifted left some, and others shifted to the right, away from Southern Texas/Mexico and further away from Cuba.
What? Lol, they obviously shifted a little left, but like you said, also came into a consensus.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
STORMW called it he said it should shift left
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Quoting StormW:
Left shift?
Thinking the models ,might shift more to Northern Cuba and miss SFLA?
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18Z runs didn't shift left, they just came into a better agreement, north shift is a good way to call it. They shifted left some, and others shifted to the right, away from Southern Texas/Mexico and further away from Cuba.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Don't go crazy with that latest GFDL run. Note that it initializes the cyclone too strong and has it at over 50 knots in 6 hours. That's likely not happening. Could be a day before it's even a TD.
.
At least the NHC did the right thing and put up the RED alert. As I said last night and again today, this was close to guaranteed to become RED just with the passage of time, and it has. We've certainly seen some better structure today, but we have awhile until this gal gets her act together. This got upgraded to RED more on the TIMING than on on the structure.
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Puerto Rico Weather Update
pressures are falling in eastern Puerto Rico
Pressure: 1012.1 hPa (Falling)
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1166. Drakoen
12z dynamic models. TVCN looks like a good track in the middle of the computer forecast guidance.


Member Since: October 28, 2006 Posts: 57 Comments: 29905
1165. unf97
Quoting StormW:
Left shift?


Possibly. But you know the "windshield wiper" effect with the models will keep occuring.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
1163. xcool
LONG WEEK AHEAD
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Quoting StormW:
18Z DYNAMIC...



Good call on the slight shift south. Looks like a cone of doom is shaping up.

Till we see how quick this thing gets going, I'm thinking somewhere between Broward/Dade Line to Palm Beach / Martin line.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
just curious...I know models aren't suggesting this right now. But, should I be keeping an eye on 97L just in case it would go more west? I mean is there any chance this could come my direction (SE TX) or is that a long shot?
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Quoting NCHurricane2009:


What's funny is I was justifying 97L not developing partly due to the southwesterly shear on my latest blog post (its not intense shear, but still there). I was analyzing it due to the upper low to 97L's north reversing to a southwestward track overnight. I know upper lows that are cut-off fade with time, and this one might be fading faster than the CIMSS is saying. I was also thinking the wave axis was not aligned with the mid-level rotation N of Hispaniola, partly due to the shear.

I guess what's happening is that convection concentrated to the NE of the wave axis, and the surface rotation will develop beneath the convection & mid-level rotation, just off of the axis (makes sense because convection is developing a warm core surface low in the low pressure field NE of the wave axis I suppose). The axis itself will then continue westward uneventfully.


Dam Tony... Nice Job!
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Quoting ElConando:


Hispaniola has had a history of tricking people on this site with thinking they are seeing another circulation forming. It is probably nothing.
Is not only us is in the NHC 2:00pm update.
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Quoting StormW:
Left shift?


More like better agreement shift, north but also south with some... Talking bout the BAM runs here lol.
Member Since: July 1, 2008 Posts: 13 Comments: 7340
I had ask a ? earlier and I was just wondering if anyone answered it. I was wondering what happened to 456? Is he still here I haven't seen him lately and was just wondering. I don't mean to get of the topic.
Sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3653
Quoting AllStar17:


SATELLITE IMAGERY SUGGESTS THAT A SURFACE LOW PRESSURE AREA IS
BECOMING BETTER DEFINED JUST NORTH OF THE EASTERN TIP OF
HISPANIOLA.
Yea , your right look>>
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Quoting StormW:
Left shift?


you were right, that seems to happen a lot lol
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Quoting StormW:
Left shift?


Thats what I was wondering? But how far?
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1150. xcool
StormW good job .
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Look at those 18z dynamic models shift back towards the left. That's exactly why we just can't look at one run but rather look for a trend.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Baybuddy:
Well, lets hope for the best and prepare for the worst. Back to lurking...my dog just ate my nutty buddy while i was typing. Arrrgh!
rolf
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Quoting ElConando:


Understandable but I'm just recommending that people see if they are in an area that has been mandated for a voluntary evacuation in the event of category 1 Hurricane. Nothing more. Sorry if I was coming off in a alarming manner.

When I talked to my friends in Culebra a couple hours ago they were asking why I was not there just in case...the harbor there is the best place to be in a boat in a storm.
I would have had to leave Saturday..but didn't for the last 36 hours it would have been crazy to try to go over there even though it's only 18 miles. Did anybody expect this wave to slow down and the convection to sit over us this long on Saturday?
So maybe a little early planning is best although I don't think anything happened this time..but it would have been very difficult for me to do anything yesterday or today..
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Quoting louisianaweatherguy:
I'm just NOT seeing this thing forming at LLC... Like I said yesterday, Wednesday Evening, we may a TD (or maybe a TS) but not today...


SATELLITE IMAGERY SUGGESTS THAT A SURFACE LOW PRESSURE AREA IS
BECOMING BETTER DEFINED JUST NORTH OF THE EASTERN TIP OF
HISPANIOLA.
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1141. xcool


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Quoting ElConando:
I hope is not what Dan Gilbert meant as a curse for Miami getting LeBron.

"clevlands owner is a crazy person"
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Quoting Hurricanes101:


In 60 hours? Do you think that is a bit too fast?
Yeah a little too fast, I'm thinking more towards 72-84 hours as a strong tropical storm/minimal hurricane making landfall in southern Florida. Yes I know it sounds like I'm getting ahead of myself. Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Hurricanes101:


In 60 hours? Do you think that is a bit too fast?

the water its near is hotter then meghan fox
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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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