97L a threat to become a tropical depression on Wednesday

By: Dr. Jeff Masters , 1:31 PM GMT on July 20, 2010

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1038 - 988

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27Blog Index

time is no longer a factor in how strong this system gets. it has PLENTY of time and bathtub (albeit a tad oily) water to carry on it's cyclogenesis.....

oil-a-geddon
Member Since: Posts: Comments:
1037. unf97
Quoting reedzone:
Keep in mind everyone, this will most likely NOT head for Mexico or southern Texas.. The pattern change is finally occurring, tracks more towards Upper Texas to Florida are now becoming likely, especially with 97L. The entire Gulf Coast should be watching this one. Also folks on the East Coast of Florida from Jax to Miami should watch it to, the weakness may be stronger, but we'll see.


Good observation Reed. Yeah, I am watching the models to see just how much the western periphery of the ridge will erode by this weekend. If there is a significant weakness, then a more poleward motion would be definitely probable. That would make things very interesting all along the East Coast of FL. I'm here in Jax, so the next set of model runs in the next 36 hours or so will hopefully provide us some clues for sure.
Member Since: Posts: Comments:
Quoting StonedCrab:


Aren't they only released at 2a, 8a, 2p, and 8p until it is named?


The TWO's are always done. When a TD is designated is when they issues updates on a specific storm at 5 and 11 (am and pm). And 2 and 8 (am and pm) when there are watches and warnings up.
Member Since: Posts: Comments:
Quoting ElConando:


and if it doesn't move unexpectedly south prior to landfall.


very true... I didn't want to bring up the "K" word, but Katrina jogged a lot to the SW which caused it to swing over and hit N.O.... All the Friday A.M. before model runs were consistent on bringing Katrina into the Panhandle... but then BAM she started going WSW
Member Since: Posts: Comments:
Quoting StormW:


Yep.


Glad you are, but that northerly dry air intrusion is making me take a second look.
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Im thinking circulation right around 20N 67.5W north between PR and DR

that is where the greatest 850mb vorticity is too
Member Since: Posts: Comments:
Quoting TheDawnAwakening2:
Radar and satellite imagery suggests that the MLC or circulation north of PR is now becoming subjected to the overall circulation center north of eastern DR coast. This is now the dominant and only circulation center associated with 97L. Intensification to a TD is expected by tomorrow morning. Wind shear is the only detriment and could be a fatal one if it does not subdue some over the next 24 hours. However given what is currently happening on visible satellite imagery, my best guess is that CIMSS is overdoing wind shear values at this time.


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.
Member Since: Posts: Comments:
Quoting AlexEmmett:

its pray for the best with your tail bettwen your legs lol they have no plan


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
Member Since: Posts: Comments:
Right now, Invest 97L continues to become better organized, but gradually, as a low level circulation center slowly becomes better defined near NE Dominican Republic this afternoon. In reviewing satellite imagery, I'm not too impressed with the system overall as outflow struggles to establish itself over the western half of the system and land interaction continues to choke the system to the south. It will take more time for this to develop, but in my opinion, is well on the way to becoming a tropical depression in the next 24 hours or so.
Member Since: Posts: Comments:
Quoting ElConando:


Has a shot at 11 but it is likely to occur after recon at this point. If it was in the middle of the atlantic it would have been designated tonight.


Aren't they only released at 2a, 8a, 2p, and 8p until it is named?
Member Since: Posts: Comments:
Vort at the 850 mb level continues to become better defined. This is currently in the process of working down the surface.

Member Since: July 8, 2005 Posts: 259 Comments: 24263
Quoting louisianaweatherguy:


I totally agree... it has stayed on a more westward track recently and I think this thing is headed more towards kay west/miami... and then a possible Destin/Panama City 2nd landfall... of course it depends on how strong it gets in the gulf...


and if it doesn't move unexpectedly south prior to landfall.
Member Since: Posts: Comments:
Keep in mind everyone, this will most likely NOT head for Mexico or southern Texas.. The pattern change is finally occurring, tracks more towards Upper Texas to Florida are now becoming likely, especially with 97L. The entire Gulf Coast should be watching this one. Also folks on the East Coast of Florida from Jax to Miami should watch it to, the weakness may be stronger, but we'll see.
Member Since: Posts: Comments:
Crap I only had one simple request yesterday, that was no use of the F-word as in Fl.. Now I have to shop one day in advance of weekly specials. Oh while sometimes the inconvenience of proper preparation can be daunting.
Member Since: Posts: Comments:
I made this image using paint.

Red shows the outflow trying to come in and the blue shows where outflow needs to get established soon to close off the circulation
when that happens, we should see a T.D.


Member Since: July 20, 2010 Posts: 0 Comments: 225
One thing that might be a detriment to making this a TD by tonight at least, besides the shear is the overall convective nature of the system. Still somewhat disorganized, but this will be corrected as the LLC becomes more organized and consolidated. It is a big circulation.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
TCFA should be issued soon. IMO, 97L may become a tropical depression tonight, with a higher chance tomorrow when Recon investigates.



Has a shot at 11 but it is likely to occur after recon at this point. If it was in the middle of the atlantic it would have been designated tonight.
Member Since: Posts: Comments:
1016. Grothar
Member Since: Posts: Comments:
Puerto Rico NWS Radar:



Nasa View:


Member Since: Posts: Comments:
Quoting wayfaringstranger:


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!!


lord i cant stand her whiney yankee voice! it runs me right slap up a wall.
Member Since: Posts: Comments:
Turning is definitely seen on satellite imagery. Also cirrus outflow is becoming better established on the southern side of the circulation all the way into central eastern Caribbean Sea. We could start to see the development of an upper level anticyclone if one is not already there.
Member Since: Posts: Comments:
TCFA should be issued soon. IMO, 97L may become a tropical depression tonight, with a higher chance tomorrow when Recon investigates.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting StormW:
Models should come left on the 18Z run


I totally agree... it has stayed on a more westward track recently and I think this thing is headed more towards kay west/miami... and then a possible Destin/Panama City 2nd landfall... of course it depends on how strong it gets in the gulf...
Member Since: Posts: Comments:
Quoting Jeff9641:


Yeah I got one 2. LOL!


Ignore em he is as Pat would say "un-sub"
Member Since: Posts: Comments:
Quoting AlexEmmett:

crap i work tonight and this is going to be an interesting night


Call in sick!
Quoting FLdewey:


It was time this morning... too late now it's mostly gone. Cars in parking lots overturned and burning... women going into labor early. It's a real disaster.


Did Sarah Palin come to town?
Member Since: Posts: Comments:
Admiral Thad Allen, National Incident Commander

Media briefing to provide update on ongoing Deepwater Horizon/BP oil spill response efforts

WHEN: Tuesday, July 20, 2010, 3:30 p.m. EDT.
Member Since: Posts: Comments:
TCFA should be issued soon. IMO, 97L may become a tropical depression tonight, with a higher chance tomorrow when Recon investigates.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Why do I have the biggest star in Orca's google map. If anything it should be Storm. LOL
Member Since: Posts: Comments:
Quoting NCHurricane2009:
Call Me a Downcaster! Invest 97L May not Develop, LOL, I might be eating my biggest crow ever on this one with the way the NHC upgraded the probability to 60%. I guess I am on my way to the grocery store to buy crow, but I am not eating it yet (it isn't a tropical depression yet).

At least in a blog post before that, I said TD 2 would not become TS Bonnie, I was right about that. Hey, you win some, you lose some, LOL.


Nothing but love 4 ya bro...no one is perfect.

I kinda wish you were right because the latest BP cameras showed "bubling" from the cap. Not an encouraging thought for a storm to rip through those rigs...
Member Since: Posts: Comments:
Dry Air might not be a problem either, 97L has a fairly large moisture field.
Member Since: July 8, 2005 Posts: 259 Comments: 24263
Quoting TropicalNonsense:


until 97L develops into atleast a depression,model tracks will
be highly questionable.
but i feel your excitement Reed.


Ehh, brings more customers to my job :).. I'll accept a TS, but more then a category 1 hurricane is not good. Problem is, if it goes through the straits, we may have a major in our hands do to those extremely hot sst and tchp. So this is a serious situation overall.
Member Since: Posts: Comments:
Quoting btwntx08:
expect the 18z coordinates to change


Unless it's stationary one would expect them to change from 12Z. The HWRF was correct on initialization however, @ 18Z (Current) was slow with the storm only reaching the western coast of PR and didn't reach it's current location until 12 hrs later. More than likely the reason it carries it so far N, 12hrs is a big difference. So yes, that was a bad run based on timing.

18Z FORECAST HWRF

Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting HellaGoose:
If this trend continues, when do you think a tropical storm watch will go up for Florida?


they now put watched up 48 hours in advance of tropical conditions beginning... i would imagine they may put up watches by wed. evening?? does that timing seem right? idk
Member Since: Posts: Comments:
Radar and satellite imagery suggests that the MLC or circulation north of PR is now becoming subjected to the overall circulation center north of eastern DR coast. This is now the dominant and only circulation center associated with 97L. Intensification to a TD is expected by tomorrow morning. Wind shear is the only detriment and could be a fatal one if it does not subdue some over the next 24 hours. However given what is currently happening on visible satellite imagery, my best guess is that CIMSS is overdoing wind shear values at this time.
Member Since: Posts: Comments:
Quoting StormW:
Hey Drak, looks like the developing LLC is almost hugging the coast.

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

Thoughts?


North of the tip of eastern Hispaniola
Member Since: Posts: Comments:
Quoting Hurricanes101:
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.


without a doubt.
Member Since: Posts: Comments:
Quoting tkeith:
Has anyone heard what the DWH spill incident command's evac plan is since the cap is on?...still the same?

its pray for the best with your tail bettwen your legs lol they have no plan
Member Since: Posts: Comments:
Call Me a Downcaster! Invest 97L May not Develop, LOL, I might be eating my biggest crow ever on this one with the way the NHC upgraded the probability to 60%. I guess I am on my way to the grocery store to buy crow, but I am not eating it yet (it isn't a tropical depression yet).

At least in a blog post before that, I said TD 2 would not become TS Bonnie, I was right about that. Hey, you win some, you lose some, LOL.
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:

Viewing: 1038 - 988

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.