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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638. JRRP
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I believe we will have a T.D. later tonight.
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New Orleanen.......I have to leave on that note.
Member Since: September 1, 2007 Posts: 0 Comments: 1793
All NOAA Floater Imagery

Da Funktop of 97L

Member Since: July 3, 2005 Posts: 428 Comments: 129904
Should see a TCFA soon for 97L.
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Quoting DestinJeff:
Is there precedent for issuing TS or Hurricane watches/warnings while the system is still an invest?

If 97L has all signs pointing to development and 72 hrs until threatening S FL, then it make sense that watches may be warranted over the next 12 - 24 hrs right?
LOL, watches are warranted when conditions will be felt in 48 hours or less. So if it becomes a tropical depression tomorrow, watches should be warranted for the Florida coast either tomorrow or Thursday depending on speed (looks like it will be affecting Florida in 96 hours).
Member Since: September 2, 2009 Posts: 130 Comments: 21194
630. 7544
if its a td they will destin jeffbut imo i wront post till maybe thurs night that will be 36hrs before
Member Since: May 6, 2007 Posts: 0 Comments: 6874
Quoting southernbell72:
pat , since u are a new orleanen , do u think that we have anything to worry about , im from the westbank


Watch the guidance and Cone when one is issued...is my advice always.

Now is a good time heading into the meat of the season to ready oneself for anything that may come our way.
Member Since: July 3, 2005 Posts: 428 Comments: 129904
NMFC Norfolk Tropical Feed
No Active Tropical Warnings in the Atlantic, Caribbean, or Gulf of Mexico
By Maritime.CDO@navy.mil (NMFC CDO) from Naval Maritime Forecast Center Norfolk Virginia. Published on .

As of Tue 20 Jul 2010 16:15:02Z



2010 Storms
All Active Year


Atlantic
97L.INVEST(POSS T.C.F.A.)
East Pacific
NONE
Central Pacific
NONE
West Pacific
97W.INVEST(T.C.F.A.Cancelled)
04W.CHANTHU
Indian Ocean
NONE
Southern Hemisphere
NONE


203

NOUS42 KNHC 201445

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

1045 AM EDT TUE 20 JULY 2010

SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)

VALID 21/1100Z TO 22/1100Z JULY 2010

TCPOD NUMBER.....10-050



I. ATLANTIC REQUIREMENTS

1. SUSPECT AREA (NORTH OF HISPANIOLA)

FLIGHT ONE -- TEAL 70

A. 21/1800Z

B. AFXXX 01BBA INVEST

C. 21/1400Z

D. 21.0N 70.0W

E. 21/1700Z TO 21/2100Z

F. SFC TO 10,000 FT



FLIGHT TWO -- NOAA 49

A. 22/0000Z

B. NOAA9 02BBA SURV

C. 21/1730Z

D. NA

E. NA

F. 41,000 TO 45,000 FT



FLIGHT THREE -- TEAL 71

A. 22/0600Z, 1200Z

B. AFXXX 0303A CYCLONE

C. 22/0400Z

D. 22.0N 72.0W

E. 22/0500Z TO 22/1200Z

F. SFC TO 15,000 FT



2. SUCCEEDING DAY OUTLOOK: CONTINUE 6-HRLY FIXES IF

SYSTEM REMAINS A THREAT. A POSSIBLE G-IV

MISSION FOR 23/0000Z.



II. PACIFIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

JWP


Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting Patrap:
A whole page again with no Floater Images..?


Man..were slipping


I found a floater but everytime I look at it is moves out of view.

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Ok Right on. Will keep my eye on it. Just built a chicken coop in my back yard this could be a good test. LOL.
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Quoting extreme236:
97L should be upped to "red"

Don't you mean "CODE RED".
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623. xcool
come soon code red ")))) i hope
Member Since: September 26, 2009 Posts: 2 Comments: 15684
pat , since u are a new orleanen , do u think that we have anything to worry about , im from the westbank
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Quoting Patrap:
If 97L develops and rides the current Ensemble Pkg Guidance,,down the Middle and Into the GOM via the Straits or S. Florida.

Were going to have to watch the Nose of the High as to when we get a turn N to Nw downstream.


The Nose of the High is going to be someones best friend,,and not so much for others.
That is exactly right. Follow the nose!
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A whole page again with no Floater Images..?


Man..were slipping
Member Since: July 3, 2005 Posts: 428 Comments: 129904
By the way IKE, did I mention this?

Hoopdy Loop
Member Since: September 1, 2007 Posts: 0 Comments: 1793
Quoting extreme236:
97L should be upped to "red"
From everything I'm seeing I completely agree.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
97L should be upped to "red"
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Quoting Patrap:
If 97L develops and rides the current Ensemble Pkg Guidance,,down the Middle and Into the GOM via the Straits or S. Florida.

Were going to have to watch the Nose of the High as to when we get a turn N to Nw downstream.


The Nose of the High is going to be someones best friend,,and not so much for others.


well said Pat. I was thinkin something similar.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Gracias, by the way loved the paint by numbers graphic showing the weakness earlier.
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Quoting StormW:
Model guidance should shift slightly left next run.


Hi Strom....Do you think this will be a Florida storm or S. Florida and then another state?
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609. 7544
if it makes td it will interesting to see the cone fropm the nhc
Member Since: May 6, 2007 Posts: 0 Comments: 6874
GOM 120 Hour Surface Current Forecast Model
Member Since: July 3, 2005 Posts: 428 Comments: 129904
Quoting CybrTeddy:
imo NHC will play conservative and give it 50% at 2 pm.



Most of the time I would agree however, with the oil spill in the cross hairs, I'm sure they will be quick to act.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
right, that westward developing llc would have an effect. I think the models could have quite a bit of difference to the end of the runs after an llc develops (perhaps that northward turn at the end.....ever so slight troughing...I'll see if I can find a good link.

Quoting StormW:


Based on the current steering layer mean, visible and RGB satellite loop imagery, forecast steering layers, and the fact we could have a LLC developing further to the west (as in where it may be forming right now).

This is why I believe a slight shift in model guidance.
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O lordy..

Das poof
Member Since: July 3, 2005 Posts: 428 Comments: 129904
Quoting SavannahStorm:
Impressive wave, but I hope it likes...


RIPs and SALsa.

what sal ??????????????????????????
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Quoting Patrap:
12z Early Cycle NHC model tracks
Invest97
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)



the models mostly show landfall around s florida but look at how straight those lines are, light beams towards s florida , we know that storms dont travel in straight lines
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We might be getting a clean ASCAT pass of 97L's circulation.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
System on the GFS looks more potent than previous runs as it impacts south Florida, perhaps dry air becomming less of a factor.

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imo NHC will play conservative and give it 50% at 2 pm.
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xx/xx/97L
MARK
19.3N/65.9W

Member Since: July 15, 2006 Posts: 178 Comments: 56141
Quoting StormW:


Aye...'cept I don't like using the terms north or south when it comes to model guidance...gives folks the tendency to think a system is now actually heading in those compass directions.


Gotcha.
Member Since: July 3, 2007 Posts: 0 Comments: 524
Quoting StormW:


Aye...'cept I don't like using the terms north or south when it comes to model guidance...gives folks the tendency to think a system is now actually heading in those compass directions.


I know what you mean. Polar or equatorial shift in movement would blow some minds....
Member Since: September 1, 2007 Posts: 0 Comments: 1793
If 97L develops and rides the current Ensemble Pkg Guidance,,down the Middle and Into the GOM via the Straits or S. Florida.

Were going to have to watch the Nose of the High as to when we get a turn N to Nw downstream.


The Nose of the High is going to be someones best friend,,and not so much for others.
Member Since: July 3, 2005 Posts: 428 Comments: 129904
You can see the new wave coming off of Africa in this pic it is so big.

Meteostar EarthView ...
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I made this...
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Quoting Goldenblack:
StormW, Would that be because of the impending strength of the High Pressure expected to build in behind the exiting TUTT?

That would certainly make good sense.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
589. xcool
I SEE red CODE AT 2PM IMO IMO
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Angle and conditions are not right IMO. I think this time we have a strengthening high, not a high that is maintaining or shifting east with time.

Quoting ClearH2Ostormchaser:
Hey StormW. Real quick question if the models shift left a little could land break up the system and if not will it be strong enough to take the infamous "Charley right Hook".
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