90L in the Gulf disorganized; Leslie almost stationary; Michael hits Cat 3

By: Dr. Jeff Masters , 3:24 PM GMT on September 06, 2012

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A remnant of Hurricane Isaac pushed southwards through Alabama on Wednesday and emerged over the Gulf of Mexico, and this disturbance is now being tracked as Invest 90L. Long-range radar out of New Orleans shows only a small area of heavy rainfall associated with 90L. The echoes show a little spiral banding behavior, and there is some slight evidence of rotation to the echoes. Visible satellite loops and surface observations from buoys and oil rigs in the Gulf suggest that 90L has formed an ill-defined, elongated surface circulation. The area covered by heavy thunderstorms is relatively small, and is pushed to the south side of the circulation center by strong northerly winds that are creating a high 20 - 30 knots of wind shear. There is a large amount of dry air that surrounds 90L on all sides that is interfering with development. A hurricane hunter aircraft is scheduled to investigate 90L this afternoon, but this flight may be cancelled if 90L does not show more organization in the next few hours.


Figure 1. Invest 90L off the coast of the Florida Panhandle as seen by NASA's Aqua satellite at 4:30 pm EDT Wednesday September 5, 2012. Image credit: NASA.

Forecast for 90L
Wind shear is predicted to fall to the moderate range, 10 - 20 knots, by tonight. Ocean temperatures in the Gulf have been cooled down considerably by the passage of Hurricane Isaac last week, and are 28.5° - 29°C. This is plenty warm enough to support formation of a tropical storm, and I expect 90L will increase in organization today and Friday as it moves slowly south-southwest. A trough of low pressure and an associated surface cold front will move southeastwards over the northern Gulf of Mexico on Sunday, and this trough should be capable of pulling 90L to the northeast to a landfall along the Florida Panhandle or west coast of Florida on Sunday. In their 8 am Tropical Weather Outlook, NHC gave 90L a 40% chance of developing into a tropical depression by Saturday morning. I put these odds a bit higher, at 50%.

Leslie remains nearly stationary
Hurricane Leslie continues to remain nearly stationary south of the island of Bermuda. Moderately high wind shear of 10 - 20 knots due to strong upper-level winds out of the west drove dry air to Leslie's west into the core of the storm last night, eroding away Leslie's eye. However, satellite loops show that Leslie is pulling a curved band of heavy thunderstorms around the west side of the center, in an attempt to form a new eye. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification, and NOAA buoy 41049 recorded a 1°C (1.8°F) drop in water temperature over the past 24 hours. A uncrewed Global Hawk NASA research aircraft is scheduled to fly in the stratosphere above Leslie this evening to study the hurricane's upper-level outflow. An Air Force hurricane hunter aircraft is scheduled to do a regular mission on Friday afternoon.


Figure 2. Hurricane Leslie as seen by NASA's Aqua satellite at 1:15 pm EDT Wednesday September 5, 2012. At the time, Leslie was a Category 1 hurricane with 75 mph winds. Image credit: NASA.

Forecast for Leslie
Leslie will stay stuck in a weak steering current environment until a strong trough of low pressure approaches the U.S. East Coast on Saturday. The timing of this trough is such that Leslie will be pulled northwards and then north-northeastwards over the weekend. There is significantly less agreement among the models today in the timing and speed of Leslie's track, though. The models have shifted eastwards, which lessens the threat to Bermuda and puts the island on the weak (left) side of the hurricane. If the official NHC forecast verifies, tropical storm-force winds will not begin on Bermuda until late Saturday night or early Sunday morning. According to the latest SHIPS model forecast, the shear is expected to fall to the low category, 5 - 10 knots, by Friday night. Leslie is over warm ocean waters of 29 - 30°C, and the reduction in shear and warm waters should aid intensification, and potentially allow Leslie to be at Category 2 strength at its closest pass by Bermuda Sunday morning, as indicated by the official NHC forecast. The latest 11 am EDT NHC wind probability forecast calls for a 40% chance that Leslie will be a Category 2 or stronger hurricane Sunday morning at 8 am EDT. Leslie is a huge storm, and tropical storm-force winds are expected to extend outward from its center 230 miles by Sunday.

Most of the models still indicate Leslie is likely to make landfall in Canada, but have shifted eastwards towards Newfoundland and away from Nova Scotia. The GFS model predicts a Thursday landfall in Newfoundland, but the ECMWF model is much faster, predicting a Tuesday landfall in Newfoundland. Given the wide spread in model guidance, what Leslie might do as it approaches Canada is highly uncertain. Large swells from Leslie are pounding the entire Eastern Seaboard, and these waves will increase in size as Leslie grows in size and strength this week.


Figure 3. Morning satellite image of Hurricane Michael.

Hurricane Michael hits Category 3
The first major hurricane of the 2012 Atlantic hurricane season is Hurricane Michael, which put on a unanticipated round of rapid intensification last night to become a Category 3 storm with 115 mph winds. Michael is the 7th hurricane of the season, putting 2012 in 3rd place behind 1893 and 1886 for earliest formation date of the season's 7th hurricane. We made it through 12 named storms before getting our first major hurricane, which is a rare occurrence. The only times the Atlantic has had as many as 12 named storms before getting a major hurricane was in 1936 and 1934. In both years, Hurricane 13 was the first major hurricane (note, though, that the 5th storm of 1936 is listed as a Category 3 landfall in Florida, but had maximum winds of 90 mph--definitely not Cat 3 winds--so there is a problem with the hurricane database for this storm.) Satellite loops show that Michael is an impressive storm with a well-developed eye, excellent spiral banding, and solid upper-level outflow. Michael is far out over the open Atlantic, and none of the models show that Michael will threaten any land areas during the coming seven days. Michael has likely peaked in intensity, and will not reach Category 4.

Elsewhere in the Atlantic
Most of the reliable computer models are predicting that a new tropical wave due to move off the coast of Africa on Friday will develop into a tropical depression by the middle of next week. This wave is predicted to exit Africa too far north to threaten the Lesser Antilles Islands, but it is too early to be confident of this.

I'll have a new post this afternoon.

Jeff Masters

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Quoting RitaEvac:


They must read the blog because there's no way that term is used anywhere.


LOL that must be it :) of course it has been said since the 1500's, too just ask Gro.
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Quoting ILwthrfan:
lol, its good to see this from your local NWS. I love it when they come out state they blew the forecast! Can't get them all, but they do well. This guy made me laugh

000
FXUS63 KLSX 061800
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
100 PM CDT THU SEP 6 2012

.SHORT TERM...
ISSUED AT 332 AM CDT THU SEP 6 2012
(TODAY THROUGH FRIDAY NIGHT)

STILL EATING CROW AFTER YESTERDAY`S BUSTED FORECAST...AND IT`S A
BITTER BIRD.
THE COLD FRONT HAS MADE IT THROUGH KIRKSVILLE BUT IS
TAKING ITS TIME DRIFTING THROUGH THE NORTHWEST PORTION OF THE CWFA.
CURRENT THINKING IS THAT THE FRONT WILL CONTINUE DRIFTING SOUTHEAST
BUT WILL PROBABLY NOT CLEAR THE SOUTHERN PORTION OF THE CWFA BEFORE
AFTERNOON. RAP AND HRRR DEVELOP DECENT INSTABILITY IN EXCESS OF
2000 J/KG WITH LITTLE OR NO CAP. HAVE ADDED POPS SOUTH OF THE STL
METRO AREA ACROSS THE EASTERN OZARKS. ALSO...SINCE THE COLD AIR
ADVECTION IS SOMEWHAT LACKING FROM PREVIOUS FORECASTS...HAVE BUMPED
UP TEMPS A COUPLE OF DEGREES TODAY.

LOL. Our mets in Birmingham never admit to an error in forecasting. They go right on with the next discussion and treat whatever happened as a forecasted event. Maybe that's why the Birmingham office has one of the highest rates of false positive tornado warnings in the country. They get real hostile when you even question them about blown forecasts.
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Quoting K8eCane:


yes i guess you are saying i would be surprised at how many people know there will be destruction but wish it anyway? Ok yes maybe i would be surprised, but then again, maybe you would


This blog basically has three types:

The Hand Wringers
The Cheerleaders
The Weather Junkies

It is pretty easy to ascertain who belongs to which group.

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Quoting CaicosRetiredSailor:



islander101010.is.spaced.out.today: )

Maybe he got the new keyboard for his birthday, as he claimed that was the reason for all the dots.
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NOAA - August 9, 2012
12-17 storms
5-8 hurricanes
2-3 major hurricanes


At 13-7-1, that hurricane number will probably need adjusting up.
The storm number and Major hurricane numbers are in jeopardy too, but not as badly as is the hurricanes forecast.
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Good afternoon everyone. Leslie's struggling to get her act together... I'm thinking the NHC intensity forecast is probably too aggressive. Bermuda has dodged a bullet it appears.



Michael's still a good looking storm, it's likely he's peaked but I wouldn't be shocked if he tried for one more burst of intensification.

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252. VR46L
Michael was a cutie




and this little guy still is

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12z Euro isn't much help. It initialized Leslie 20mbs and 30 knots stronger than she is in reality. Meanwhile, Michael is intialized 40mbs and 60 knots too weak. So I wouldn't pay too much attention to the tracks shown on the 12z ECMWF. One thing we can take away is that Leslie has about the next 2, maybe 2.5, days to strengthen before the upper level winds become too unfavorable for strengthening (though it will have to deal with issues with its core, dry air and upwelling if it wishes to intensify over these days).

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.
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If this trough and strong front wasn't coming down the plains into TX and the gulf coast, 90L would've came to TX especially with the ridging we've had all year. Another missed opportunity for rain over TX. And this passage will probably end the season for TX as significant fronts tend to do.
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ATL
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Quoting NOLALawyer:


Why, do you think he is alone? I think you would be shocked if you realized how many people here were just like him.


yes i guess you are saying i would be surprised at how many people know there will be destruction but wish it anyway? Ok yes maybe i would be surprised, but then again, maybe you would
Member Since: April 26, 2006 Posts: 5 Comments: 3120
Quoting Gearsts:
Do you think our next wave that the models show developing will recurve? Because and earlier model run had it all the way in the gulf, now it recurves east of the islands.
With the system forecasted to exit Africa with about 15 degrees of latitude, climatology favors a recurve out before the US. At the moment, the models are in strong agreement that the storm will curve out into the massive weakness left behind by Leslie. Still, a lot can change as this is long a ways out.
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Major Michael made a minor:

AL, 13, 2012090618, , BEST, 0, 304N, 411W, 95, 964, HU, 64, NEQ, 15, 15, 10, 10, 1015, 150, 15, 0, 0, L, 0, , 0, 0, MICHAEL, D,
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Phew so Leslie will miss Atlantic Canada pretty much altogether, that's great news.Had some people a bit worried there but we knew it would become a fish storm.
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Quoting TomTaylor:
Because the Intertropical Front (ITCZ/Monsoon Trough) is further north over Africa. This front is drawn further north when the pressure gradient between the Saharan heat low and relatively higher pressures over the Gulf of Guinea is strengthened. Since the stronger gradient leads to greater instability in the African Easterly Jet, we can also expect stronger African Easterly Waves which form within the jet. Thus, when ITCZ/monsoon trough over Africa is further north, it is a sign that waves will be coming off Africa stronger.

Position of the African Intertropical Front (ITCZ/Monsoon Trough) Relative to Climatology




Unfortunately for the waves, however, when they exit Africa further north they usually enter cooler SSTs and a more stable environment over the Atlantic ocean. They are also more likely to round the periphery of the ridge earlier and therefore recurve sooner as we saw with Gordon, Kirk, and now Michael.
Do you think our next wave that the models show developing will recurve? Because and earlier model run had it all the way in the gulf, now it recurves east of the islands.
Member Since: August 2, 2010 Posts: 0 Comments: 1741
Quoting LargoFl:
I lived not far from there when Fay came through..got a few gusts, a few drops of rain, but overall nothing spectacular. Tallahassee, on the other hand, got a lot of feeder band action.
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It seems that all of the male names (except Alberto which was a pre-season storm) have been able to achieve hurricane status, but the females seem to wanna keep it simple. Leslie is actually the 1st female hurricane. You go guys!
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Quoting TomTaylor:
Because the Intertropical Front (ITCZ/Monsoon Trough) is further north over Africa. This front is drawn further north when the pressure gradient between the Saharan heat low and relatively higher pressures over the Gulf of Guinea is strengthened. Since the stronger gradient leads to greater instability in the African Easterly Jet, we can also expect stronger African Easterly Waves which form within the jet. Thus, when ITCZ/monsoon trough over Africa is further north, it is a sign that waves will be coming off Africa stronger.

Unfortunately for the waves, however, when they exit Africa further north they usually enter cooler SSTs and a more stable environment over the Atlantic ocean. They are also more likely to round the periphery of the ridge earlier and therefore recurve sooner as we saw with Gordon, Kirk, and now Michael.


So you are back.
I supppose your appeal went well then :)
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Quoting K8eCane:


find your own blog then


Why, do you think he is alone? I think you would be shocked if you realized how many people here were just like him.
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Quoting islander101010:
it will be there tomorrow good day all


you got spaces?
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Leslie's winds and pressure are unchanged, says the ATCF:

AL, 12, 2012090618, , BEST, 0, 265N, 622W, 65, 985, HU, 64, NEQ, 20, 20, 15, 15,
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Quoting K8eCane:
I wonder EXACTLY who is responsible for inputting current data into model runs? I mean, who actually stands there and punches the numbers? or how is that done?


Some Supercomputers.
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Quoting CaribBoy:
Why do the waves exit this far north this year.
Because the Intertropical Front (ITCZ/Monsoon Trough) is further north over Africa. This front is drawn further north when the pressure gradient between the Saharan heat low and relatively higher pressures over the Gulf of Guinea is strengthened. Since the stronger gradient leads to greater instability in the African Easterly Jet, we can also expect stronger African Easterly Waves which form within the jet. Thus, when ITCZ/monsoon trough over Africa is further north, it is a sign that waves will be coming off Africa stronger.

Position of the African Intertropical Front (ITCZ/Monsoon Trough) Relative to Climatology




Unfortunately for the waves, however, when they exit Africa further north they usually enter cooler SSTs and a more stable environment over the Atlantic ocean. They are also more likely to round the periphery of the ridge earlier and therefore recurve sooner as we saw with Gordon, Kirk, and now Michael.
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Quoting ProgressivePulse:
Seesh, yall are slow today. Recon postponed till tomorrow.

Not worth the fuel.
Member Since: May 18, 2006 Posts: 10 Comments: 6020
Quoting islander101010:
it will be there tomorrow good day all



islander101010.is.spaced.out.today: )
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..................GFS at 384 hours..whew
Member Since: August 6, 2011 Posts: 4 Comments: 38410
Michael sure is impressive. However, I'm doubtful Michael will be able to intensify more as he seems to be pretty near the maximum intensity his environment will currently support. The fact that Michael's cloud tops have not gotten below -70C leads me to believe the environment is not unstable enough to support much more strengthening. With the lightening shear, we may see better structure tonight and tomorrow, so long as outflow from Leslie doesn't become an issue. However, as far as intensity, I wouldn't expect much more strengthening. Beyond tomorrow it looks like the upper flow from Leslie will begin to eat away at Michael, causing weakening.

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230. viman
Recon flight cancelled...
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Quoting K8eCane:
I wonder EXACTLY who is responsible for inputting current data into model runs? I mean, who actually stands there and punches the numbers? or how is that done?


you're joking, right?


Almost all of that is automated.

Our different sensors, radars, satellites, etc, send data to the various groups' computers in a formatted manner, and the computer receives it as input and initializes it's run based on all the data it has received.


There is no way humans could manually input all the data for the entire planet, or even just for a small region.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
new GFS at 72 hours.............
Member Since: August 6, 2011 Posts: 4 Comments: 38410
it will be there tomorrow good day all
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new Nam at 72 hours.............
Member Since: August 6, 2011 Posts: 4 Comments: 38410
I wonder EXACTLY who is responsible for inputting current data into model runs? I mean, who actually stands there and punches the numbers? or how is that done?
Member Since: April 26, 2006 Posts: 5 Comments: 3120
Member Since: August 6, 2011 Posts: 4 Comments: 38410
Seesh, yall are slow today. Recon postponed till tomorrow.

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU SEP 6 2012

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
LESLIE...LOCATED ABOUT 430 MILES SOUTH-SOUTHEAST OF BERMUDA...AND
ON HURRICANE MICHAEL...LOCATED ABOUT 980 MILES WEST-SOUTHWEST
OF THE AZORES.

1. AN ELONGATED AREA OF LOW PRESSURE CENTERED ABOUT 75 MILES SOUTHEAST
OF THE MOUTH OF THE MISSISSIPPI RIVER HAS BEEN DRIFTING SOUTHWARD
DURING THE PAST FEW HOURS. SINCE THE SHOWER ACTIVITY ASSOCIATED
WITH THE LOW REMAINS POORLY ORGANIZED...THE AIR FORCE
RECONNAISSANCE MISSION SCHEDULED FOR TODAY HAS BEEN POSTPONED TO
TOMORROW. THERE IS STILL POTENTIAL FOR SOME DEVELOPMENT DURING THE
NEXT DAY OR SO BEFORE ENVIRONMENTAL CONDITIONS BECOME UNFAVORABLE.
THIS WEATHER SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER AVILA
NNNN
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Quoting GeorgiaStormz:


for who?
Nobody in particular--too early to know where. Just heading towards US at this point.
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Quoting RTSplayer:
What is the deal with so many mal-functioning or otherwise useless buoys in the Gulf?

Half of them aren't working at all, and about another half of them only record data that doesn't much matter, or record one data point every 8 or 24 hours.

It's ridiculous that there are so many buoys in the area, and only ONE of them is giving any relevant data regarding 90L...

Wind but no pressure

Station KIPN
Federal Aviation Administration
Location: 28.085N 87.986W
Date: Thu, 06 Sep 2012 17:15:00 UTC
Winds: SW (230°) at 28.0 kt
Air Temperature: 78.8 F
Dew Point: 75.2 F
Visibility: 7.8 nmi


Here are some others that are semi-useful...


Wind and pressure, but very far away.

Station PILL1
NOS
Location: 29.178N 89.258W
Date: Thu, 06 Sep 2012 17:06:00 UTC
Winds: NNE (30°) at 12.0 kt gusting to 15.0 kt
Atmospheric Pressure: 29.88 in
Air Temperature: 83.1 F
Water Temperature: 84.6 F


Wind, but no pressure

Station KMIS
Federal Aviation Administration
Location: 29.296N 88.842W
Date: Thu, 06 Sep 2012 17:15:00 UTC
Winds: ESE (120°) at 8.9 kt
Air Temperature: 82.4 F
Dew Point: 75.2 F
Visibility: 7.8 nmi


Pressure, but no wind.

Station 42012
NDBC
Location: 30.065N 87.555W
Date: Thu, 06 Sep 2012 16:50:00 UTC
Significant Wave Height: 2.3 ft
Dominant Wave Period: 5 sec
Mean Wave Direction: S (191°)
Atmospheric Pressure: 29.95 in and rising
Air Temperature: 81.0 F
Dew Point: 74.5 F
Water Temperature: 82.6 F




Was NWS defunded this badly?

Most of this is useless.

Those buoys are funded by the FAA, not NOAA or the NWS. They are primarily used for reporting surface level information used in flight planning. It's an old system, and I suspect Isaac may have torn up some of them. The FAA is moving away from bouys to a combination of oil platform mounted sensors and satellite/GPS coverage for the Gulf. See the link for more information.
Link
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Member Since: August 6, 2011 Posts: 4 Comments: 38410
May have pulled them back, lol.

Decoded recon data in the last 30 minutes:

No decoded data could be found.
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Member Since: August 6, 2011 Posts: 4 Comments: 38410
Quoting SLU:


Why are they wasting fuel flying into a system with no apparent circulation on visible imagery?


Go here:

Gulf RGB


Turn on LL coordinates and look about where the official center fix is (NE of the convection).


If you still can't see it, turn on the "Fronts" overlay.

It is currently analyzed at 1012mb.

Though it must be lower than that by now, since the station in Plaquemines parish is also 1012mb.


It's pathetic that none of the buoys close to the convection or suspected LLC have barometers.

the storm is centered on a patch of about 25 buoys and other stations, and only one of them has both wind and pressure, and it's too far away to matter..


Based on what little useful data there is, any LLC would need to be about 50 to 70 miles SE of the mouth of the Mississippi to make sense...which is about where they analyzed it.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
This is Bad for those still without power huh......
Member Since: August 6, 2011 Posts: 4 Comments: 38410
........models are useless right now
Member Since: August 6, 2011 Posts: 4 Comments: 38410
Quoting CaicosRetiredSailor:


90L ...pick-a-swirl


How 'bout 28N 88W?
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Quoting Hurricanes101:


Because the only have to fly like 5 feet to get there lol
LOL good point
Member Since: August 6, 2011 Posts: 4 Comments: 38410
Quoting SLU:


Why are they wasting fuel flying into a system with no apparent circulation on visible imagery?

I think that's the point. It continues to move SW at 8 mph. There are no real steering currents to make it move east. The trough that should be in or near the Gulf by Saturday may not get far enough out if 90L manages to get too far SW, so the models that show the trough is what will move it east may be flawed. The assumption is that dry air and shear will keep it in check but, the further SW it moves, the total land area potentially under threat increases. A HH flight will give them a better look at any circulation that may be developing, as well as what the real winds are within the storm. Given the history of Isaac, I think it's prudent to take a closer look now, before things start to change too fast. I'm hoping they just find a blob, but I don't trust anything having to do with Isaac.
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90L ...pick-a-swirl
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Quoting unknowncomic:
This does not look good.



for who?
Member Since: February 11, 2012 Posts: 0 Comments: 9727

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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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