Bonnie barely alive

By: Dr. Jeff Masters , 12:58 PM GMT on July 24, 2010

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Tropical Depression Bonnie is barely clinging to life. Wind shear of 25 knots and dry air from an upper-level low pressure system over the Gulf of Mexico are taking their toll on Bonnie, which is now just a swirl of low clouds accompanied by a small clump of heavy thunderstorms on the north side of the center of circulation. These thunderstorms are now visible on New Orleans long range radar, and will arrive in coastal Louisiana early this afternoon, well ahead of the center. The Hurricane Hunters are in Bonnie, and have found a much weaker storm with top winds of just 30 mph.


Figure 1. Morning satellite image of Tropical Depression Bonnie. At the time, Bonnie had sustained winds of 30 mph.

Forecast for Bonnie
The current NHC forecast for Bonnie looks good, with the storm making landfall in Louisiana near 9pm CDT Saturday night. According to the latest tide information, this will be near the time of low tide. This will result in much less oil entering the Louisiana marshlands than occurred during Hurricane Alex in June. That storm brought a storm surge of 2 - 4 feet and sustained winds of 20 - 30 mph that lasted for several days, including several high tide cycles. Bonnie will be lucky to be a tropical depression at landfall, and should only create a storm surge of 1 - 2 feet that will come at low tide. This will result in a storm tide level that will inundate land to at most one foot above ground level.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

Elsewhere in the tropics
There are no other threat areas of concern today. The only model calling for possible tropical development in the next week is the NOGAPS model, which predicts a strong tropical disturbance could form off the coast of Nicaragua in the Southwest Caribbean about a week from now.

Next update
The next updates will be by wunderground meteorologists Rob Carver and Shaun Tanner. I'm taking advantage of a break in the tropical action to take a few days away. I'll be back blogging on Friday, at the latest.

Jeff Masters

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Quoting StormW:


B.


Thank you Chief. That is what I thought but someone was trying to convince me otherwise..
Member Since: July 1, 2005 Posts: 10 Comments: 1683
379. unf97
Quoting earthlydragonfly:
I have a question for a MET... When the local weather forecast is calling for 60% of rain... does that mean:

A. It will be raining on 60% of the local area?

OR

B. There is a greater 60% probability that your area will receive rain??

Which is it??


It means that there is a 60% probability in which rain will fall in that particular weather forecasting area. Probabilities are used in terms of how much of a particular region will see coverage in precipitation.
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378. SLU
Quoting StormW:
More food for thought. Just went through, and picked out years since the upswing in activity beginning in 1995, and compared the NAO as far as negative and positive in JUL and AUG. Looking at the NAO forecast, it appears to go positive until the first week of Aug. Out of the years that come close, 6 years had a positive NAO in either Jul or Aug. The average storm total worked out to be 14. This did not include 2005.


Good stuff. I'm sure they didn't have record warm SSTs like we do this year.
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There was a Bonnie?

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A Straight Dope Classic from Cecil's Storehouse of Human Knowledge
What does it mean when "X percent chance of rain" is predicted?
August 8, 1986

Dear Cecil:

When the weather service predicts some percentage chance of rain for the next day, what does this number mean? I always figured they compiled certain parameters about current conditions and compared them to analogous days in the past. The percentage of those days in which it rained is then used as the predicted chance of rain now. In other words, they base the percentages on historical data. However, a friend who is a pilot (and who presumably should know about these things) claims that the figure is determined by looking at the current conditions of a storm system which is expected to pass over us. The number represents the percentage of the area the storm is now passing over in which it is actually raining. This strikes me as complete bullshit.

Anyway, what's the straight dope on the predicted chance of rain? How can you ever have 100 percent chance of rain? How reliable are these figures?

— Ted F., Chicago

Cecil replies:

You are one shrewd hombre, Ted, no doubt as a result of having been exposed to this column regularly during your formative years. Your guess about what the percentages mean is pretty much on the money.

Here's what happens. The National Weather Service (and various other weather services around the world, under the guidance of the World Meteorological Organization, a UN agency) sends up measuring devices called radiosondes in helium balloons twice a day. These collect weather data continuously as they rise through the atmosphere--wind speed and direction, temperature, barometric pressure, and humidity. The information is radioed to the ground and eventually ends up at the National Meteorological Center near Washington, D.C., where it's fed into a computer. (There are other centers in other parts of the world that do the same thing.) Other data from satellites and ground reporting stations are also fed in, and what you end up with, metaphorically speaking, is a complete three-dimensional picture of atmospheric conditions around the world. The computer program then applies various laws of fluid mechanics to predict future conditions.

Unfortunately, there is only so far you can go with this. While it's possible to predict the temperature, say, with a reasonable degree of certainty, precipitation is much chancier. The best forecasters can do is to give the probabilities, which they do by having the computer compare present conditions with historical data. When you hear there's a 10 percent chance of rain, that means that out of the last 100 times the weather conditions were just like they are now, it rained 10 times. (More or less--I'm obliged to oversimplify a bit.)

The weather service has been calculating precipitation probabilities for as long as anybody can remember, but it's only been in the last decade or two that the nation's cadre of broadcast weather beings has deigned to convey this to the masses. Why the belated fascination with numbers I don't know; I suppose they feel it gives an aura of precision to a business that, let's face it, is still about one jump ahead of tea-leaf reading. But who can say?

As for your last couple of questions: a 100 percent chance of rain means that out of the last x number of times things were just like they are now, it rained every time. (It does not, incidentally, mean it's raining right this second.) On the question of how reliable the figures are, the amazing truth is that they are absolutely 100 percent reliable all the time--that is, presuming the raw data were fed in properly and the calculations done correctly. Remember, we're just talking about probabilities here. A probability isn't "wrong" if it tells you there's only a 10 percent chance of rain and it rains anyway; it's only wrong if a series of such predictions doesn't pan out over the long haul. Not much comfort if your dermis gets damp next time you're out on a picnic, but it'll have to do.

ANOTHER VIEW

In Washington, Oregon, and British Columbia, we have a different interpretation of precipitation forecasts. If the weatherman says there's a 20 percent chance of rain, that means it will rain 20 percent of the day. If there's a 50 percent chance, it will rain 50 percent of the time, etc., up to 100 percent, which means, of course, a typical January day. This interpretation seems to be quite accurate. --Joyce K., Seattle

— Cecil Adams
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373. IKE
Hey I'm an amateur at the tropics, but I had to put this on here....

1671. hurrkat05 1:21 AM CDT on July 24, 2010
PATRAP WE GOT A STORM ON OUR HANDS THE ULL IS MOVING INLAND IN TEXAS AND ITS NOT AFFECTING BONNIE NO MORE ...SHEAR IS NADA OVER BONNIE..


1686. hurrkat05 1:25 AM CDT on July 24, 2010
LEVI SIT BACK AND LEARN..


Nah...no shear bothering bumbling Bonnie....Bonnie is nada hurrkat05....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting sammywammybamy:



But i thought.

2am , 5am ,8 am , 11 am, 2 pm, 5 pm, 11pm?

At least hats how it was a day ago.

The Hurricane center only issues those advisories when when watches and warnings are in effect.
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Oil Spill Floater

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369. BA
Quoting Levi32:


Ya I am a high school graduate. He meant Met in a general way....I'm a weather forecaster with or without a degree, but no I have not had the formal training at a school yet.


passion to learn and access to learning material is the most important factor IMO...in my area (technical industry)...I would take someone with passion and knowledge (that can be proven) over someone with a degree any day
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I have a question for a MET... When the local weather forecast is calling for 60% of rain... does that mean:

A. It will be raining on 60% of the local area?

OR

B. There is a greater 60% probability that your area will receive rain??

Which is it??
Member Since: July 1, 2005 Posts: 10 Comments: 1683
Sammy, they issue it for the time zone it's located in, say 4 CST, it's 5 EST and that's why.
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Nothing Like Football on a Sunday Afternoon,,and rooting for a Front as well..

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362. SLU
Quoting StormW:


October should be decent.


You're right .. it shouldn't be the sort of season that will end abruptly like 2004 or 2006. It should linger on very late since La Nina should keep the wind shear at manageable levels. Windshear is pretty much what determines when the season ends.
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361. IKE
Quoting sammywammybamy:
2PM not out yet, they deciding to keep bonnie a td or issue last advisory.


No watches/warnings...next update at 4 pm CDST.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Levi32:


Ya I am a high school graduate. He meant Met in a general way....I'm a weather forecaster with or without a degree, but no I have not had the formal training at a school yet.

Oh gotya. My mind just got blown for a second there >.<. I liked Bonnie. It did what it was "supposed" to do meteorologically... I love when you use MET knowledge to make a forecast and it proves accurate. I was a little shaky on track as well (I was thinking Biloxi) But I did fairly well on intensity.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting SouthALWX:

wait, your a Met? I thought you were a highschool student?


Ya I am a high school graduate. He meant Met in a general way....I'm a weather forecaster with or without a degree, but no I have not had the formal training at a school yet.
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Quoting Levi32:


Well thanks but I was not perfect on the track, it was the intensity I did well on. Also never take one Met's word for it and believe everything....look at the stuff yourself and decide whether what I or anyone else says makes sense.

wait, your a Met? I thought you were a highschool student?
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Bonnie Squalls moving thru Plaqumines Parish ,Venice,,Belle Chase next.

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Quoting SLU:
July 24th, 2005....7-3-2.
July 24th, 2010....2-1-0.


It is at this very moment that 2005 slipped into a very quite period by 2005 standards in which only TS Harvey and H Irene formed. Things didn't pick up again until the last week of August.

This is where I believe 2010 might catch up with 2005 and the 2 seasons could be very similar in overall activity by say August 20th.

If the long range GFS is correct, 2 named storms within the next 2 weeks isn't that far fetched.


that is a very good point

Gert formed on July 23rd and then there were only 2 named storms from July 24th - August 23rd when Jose formed
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Quoting mcluvincane:


Levi, just wanted to tell you that doubted your forecast on Bonnie and I will never doubt you again. I love watching you tidbits. Props to you. Your one hell of a met and know your weather very well. Thanks for all your time and effort.


Well thanks but I was not perfect on the track, it was the intensity I did well on. Also never take one Met's word for it and believe everything....look at the stuff yourself and decide whether what I or anyone else says makes sense.
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98L was de invested..

If we get a new one it will be 99L
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351. SLU
July 24th, 2005....7-3-2.
July 24th, 2010....2-1-0.


It is at this very moment that 2005 slipped into a very quite period by 2005 standards in which only TS Harvey and H Irene formed. Things didn't pick up again until the last week of August.

This is where I believe 2010 might catch up with 2005 and the 2 seasons could be very similar in overall activity by say August 20th.

If the long range GFS is correct, 2 named storms within the next 2 weeks isn't that far fetched.
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Quoting leo305:


we already had an invest out of it


well we may get another one lol
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349. unf97
Quoting leo305:


we already had an invest out of it


Yep. It's formerly 98L.
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Quoting Hurricanes101:
that area in the BOC does not look to be moving ashore, I think it could move NNW or N and stay offshore

I could see us getting an invest out of it


we already had an invest out of it
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347. unf97
Quoting Hurricanes101:
that area in the BOC does not look to be moving ashore, I think it could move NNW or N and stay offshore

I could see us getting an invest out of it


I mean it is possible that it could hug the coast and move N/N-NW the next couple of days. It appears that the big ULL up near the Upper Texas Coast may be affecting the steering currents around the BOC/Mexican disturbance.
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Quoting StormW:


Exactly.

My belief, well not even my belief but scientific fact, since we have that setup, Mother Nature is going to "sense" that the Atlantic is much warmer than the spots that have cooled down...in other words, the dust and stronger A/B high we are seeing should somewhat be nullified by the fact conditions are much cooler in the PAC, bundling net heat energy in the Atlantic.


Mhm exactly, and even if the dust remains in the eastern Atlantic these waves are still coming off strong and will develop farther west. Remember Bonnie was a completely cloudless and naked wave before it hit the Caribbean islands and then she blew up. The relative humidity anomalies so far this month show the pattern with a dry east Atlantic but above-normal moisture in the SW Atlantic basin. That may not be the best pattern for hyperactive numbers like 2005, but it is a very bad pattern for potentially historic landfall impacts in the United States and Caribbean countries.

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This coming week will be a quite one.
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that area in the BOC does not look to be moving ashore, I think it could move NNW or N and stay offshore

I could see us getting an invest out of it
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Quoting Levi32:


Definitely.
Quoting Levi32:


Yeah, the cold PDO is the wildcard this year. Will be interesting to see what ultimate effect it has.


Levi, just wanted to tell you that doubted your forecast on Bonnie and I will never doubt you again. I love watching you tidbits. Props to you. Your one hell of a met and know your weather very well. Thanks for all your time and effort.
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342. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT JUL 24 2010

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON WEAKENING
TROPICAL DEPRESSION BONNIE LOCATED ABOUT 165 MILES EAST-SOUTHEAST
OF THE MOUTH OF THE MISSISSIPPI RIVER.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER ROBERTS/AVILA



From this mornings San Juan discussion.....

"MID-UPPER LEVEL RIDGE WILL BUILD OVER THE AREA SUN-MON WITH A
DRYING TREND EXPECTED. A SERIES OF TUTT LOWS ARE FCST TO DOMINATE
THE CARIBBEAN AND TROP ATLC NEXT WEEK MAKING TC FORMATION VERY
UNLIKELY. CAN EXPECT TYPICAL DIURNAL CONVECTION ESPECIALLY FROM
TUE ON THAT COULD BE ENHANCED BY PROXIMITY OF TUTTS OVER THE
AREA."

Member Since: June 9, 2005 Posts: 23 Comments: 37858
341. unf97
Quoting Patrap:
WUnder if we will get a invest out of the BOC..?




I mentioned that area a short time ago. That area was once 98L. It has stalled or meandered in that same vicinity of the Mexican coast the past 24-36 hours. I am thinking it will probably move a bit farther inland and eventually die out. But it is definitely an interesting feature to observe today on satellite for sure. Convection has really flared up today over the system.
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TD 2 was close to being Bonnie, which would have made Bonnie, well Colin lol

Invest 90L was borderline Sub-tropical and if it had a little more time, it gets a name

Invest 92L very well could have been a named storm, and probably should have been one

Invest 95L came close as well, although I think the NHC did the right thing by not classifying it

If Invest 98L stays over water as predicted, I think it gets classified. It moved ashore about 24 hours before it was forecasted to by the NHC.
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Enjoying reading the blog today! Riff raff being absent is sooo nice!! :)
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WUnder if we will get a invest out of the BOC..?

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Member Since: July 15, 2006 Posts: 170 Comments: 53503
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Quoting StormW:


However, look how much colder the EPAC/CPAC are


Yeah, the cold PDO is the wildcard this year. Will be interesting to see what ultimate effect it has.
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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.