Leslie near hurricane strength; Son of Isaac (90L) emerges in the Gulf

By: Dr. Jeff Masters , 3:05 PM GMT on September 05, 2012

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Tropical Storm Leslie is growing more organized and is approaching hurricane strength on its slow voyage northwards at 2 mph towards the island of Bermuda. Moderately high wind shear of 15 - 20 knots due to strong upper-level winds out of the northwest continues to keep most of Leslie's heavy thunderstorms pushed to the east side of the storm, but satellite loops show that Leslie now has an impressive blow-up of heavy thunderstorms with cold cloud tops near its center. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification, but the waters underneath Leslie are warm to great depth, making this less of a factor than usual. According to the latest SHIPS model forecast, the shear is expected to fall steadily today, reaching the low category, 5 - 10 knots, by Thursday afternoon. 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 Saturday night and early Sunday morning, as indicated by the official NHC forecast. The latest 11 am EDT NHC wind probability forecast calls for a 48% 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 250 miles by Friday. Bermuda is likely to see a 42-hour period of tropical storm-force winds beginning Saturday morning near 2 am AST, and lasting until 8 pm AST Sunday night. The official NHC forecast shows Leslie nearly making a direct hit on Bermuda, and Leslie will be capable of bringing an extended period of hurricane-force winds lasting six or more hours to Bermuda Saturday night through Sunday morning, should a direct hit materialize. NHC is predicting that hurricane-force winds will extend outwards from the center of Leslie by 35 miles on Thursday night, and I expect this will increase to at least 60 miles by early Sunday morning, when Leslie will be making its closest pass by Bermuda.


Figure 1. Morning satellite image of Tropical Storm Leslie. Heavy thunderstorms have built near the center of the storm, and Leslie is near hurricane strength.

Leslie's impact on Canada
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 are still significant differences among the models in the timing and speed of Leslie's track over the weekend, but we can now dismiss the threat of Leslie making a direct hit on New England. The storm is likely to make landfall in Nova Scotia or Newfoundland, though there are significant differences in the models' predictions of the timing of Leslie's arrival in Canada. The GFS model predicts an early Tuesday landfall in Newfoundland, but the ECMWF model is much faster and farther west, predicting a Monday afternoon landfall in Nova Scotia. Large swells from Leslie are pounding the entire Eastern Seaboard, and these waves will increase in size as Leslie grows in strength this week. The Hurricane Hunters are scheduled to make their first flight into Leslie on Thursday afternoon.


Figure 2. Morning radar image of Invest 90L off the coast of the Florida Panhandle.

Son of Isaac: Invest 90L emerges in the Gulf of Mexico
During Tropical Depression Isaac's trek across the center of the U.S. during the Labor Day weekend, the storm was ripped in half. One portion of the storm moved over the Northeast U.S., bringing heavy rains there, and another portion sank southwards over Alabama. You can see this split by studying an animation of the vorticity at 850 mb (the amount of spin at low levels of the atmosphere, near 5,000 feet above sea level) from the University of Wisconsin. This remnant of Isaac, which still maintained some of Isaac's spin, brought heavy rains of 5 - 10 inches that caused flooding problems over portions of Alabama on Tuesday. The storm has now emerged over the Gulf of Mexico near the Florida Panhandle, and was designated Invest 90L this morning by NHC. In their 8 am Tropical Weather Outlook, NHC gave 90L a 20% chance of developing into a tropical depression by Friday morning. According to NHC naming rules, "if the remnant of a tropical cyclone redevelops into a tropical cyclone, it is assigned its original number or name". Since "the remnant" refers to the primary remnant, and 90L does not fit the definition of a "primary remnant", the storm will be given a new name should it develop into a tropical storm, according to information posted on the NHC Facebook page. Esau or Jacob--the names of the sons of the biblical Isaac--would be fitting names for 90L, but the next storm on the list of Atlantic storms is Nadine.

Long-range radar out of Mobile, Alabama shows a large area of heavy rainfall along the coast due to 90L. The echoes do show some spiral banding behavior, but there is only a slight evidence of rotation to the storm. Infrared satellite loops show that the thunderstorms associated with 90L are not that vigorous and do not have particularly cold cloud tops, and the area covered by the thunderstorms is relatively small. Wind shear is a high 20 - 30 knots over the northern Gulf of Mexico, but is predicted to fall to the moderate range, 10 - 20 knots, by Thursday afternoon. Ocean temperatures in the Gulf have been cooled down considerably by the passage of Hurricane Isaac last week, and are 28 - 28.5°C. This is still plenty warm enough to support formation of a tropical storm, and I expect 90L will increase in organization on Thursday and Friday as it moves slowly south or south-southwest. 90L could become a tropical depression as early as Thursday, though Friday is more likely. A hurricane hunter aircraft is scheduled to investigate 90L on Thursday afternoon. 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.


Figure 3. Morning satellite image of Tropical Storm Michael.

Tropical Storm Michael in the Central Atlantic
Tropical Storm Michael has strengthened to 50 mph winds, and appears to have a favorable enough environment to become a hurricane later this week. Satellite loops show that this is a small tropical cyclone, far out over the open Atlantic, and none of the models show that Michael will threaten any land areas.

Elsewhere in the Atlantic
The GFS and ECMWF 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. It's too early to tell if this system might threaten the Lesser Antilles Islands.

Jeff Masters

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1074. sar2401
Quoting popartpete:
Is 90L anyhow somehow from the remnants of Karen? LOL...couldn't resist. This is the oldest humor on the blog, but it gets old gracefully.

These are my real questions:

Now, the thought is that 90L will be Nadine if named, not Issac, correct?

Who thinks Leslie could go west? The models are spread. I go by the NHC line, but it could go west just as much as it could east. I heard that if a closed low formed off of Florida, Leslie would be pushed more northwest. Has that happened? It seemed like it has, with 90L. How I looked at climatology and half of the hurricanes went west and scraped the East Coast as strong systems.

Please let me know.


A hurricane went west and scraped the East Coast? Your understanding of geography is a little deficient. 90L does not have a single model that shows it going west of LA before turning back east towards FL. 90L is drifting SW now because the steering currents are weak. A strong trough should be out in the Gulf by Saturday, thus the abrupt turn to the east, as the trough pushes it in that directon. The chances that 90L could continue on westerly path are as close to zero as you can get.

Edit: Never mind, I was totally confused with your mention of 90L and didn't read carefully enough. I think the chances of Leslie bumping along the east coast are also very low but not zero.
Member Since: October 2, 2004 Posts: 0 Comments: 15322
Michael really putting on a show tonight ...

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1071. bappit
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Is 90L anyhow somehow from the remnants of Karen? LOL...couldn't resist. This is the oldest humor on the blog, but it gets old gracefully.

These are my real questions:

Now, the thought is that 90L will be Nadine if named, not Issac, correct?

Who thinks Leslie could go west? The models are spread. I go by the NHC line, but it could go west just as much as it could east. I heard that if a closed low formed off of Florida, Leslie would be pushed more northwest. Has that happened? It seemed like it has, with 90L. How I looked at climatology and half of the hurricanes went west and scraped the East Coast as strong systems.

Please let me know.
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1069. bappit
Quoting SherwoodSpirit:


We went from being dry as a bone here in the St. Louis area, to having dewpoints so high you practically need scuba gear to breathe outside after Isaac. I can believe wherever the rest of that storm went, it's gonna POUR.

30% humidity in Houston. Weenie cumulus overhead.

FIRE...
WELL ABOVE NORMAL TEMPERATURES CONTINUE...HOT FEW DAYS BEFORE THE FRONT GETS HERE AND EXPECT THE DEWPOINT TO MIX OUT QUICKLY IN THE LATE MORNING HOURS WITH RH VALUES DIPPING TO THE UPPER 20S TO AROUND 35 PERCENT BUT WITH LIGHT WESTERLY WINDS BECOMING MORE SOUTHERLY WITH TIME.
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1068. LargoFl
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM 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 445 MILES SOUTH-SOUTHEAST OF BERMUDA...AND
ON HURRICANE MICHAEL...LOCATED ABOUT 1045 MILES WEST-SOUTHWEST
OF THE AZORES.

1. A LOW PRESSURE SYSTEM LOCATED OVER THE NORTH-CENTRAL GULF OF MEXICO
EAST OF THE MOUTH OF THE MISSISSIPPI RIVER IS PRODUCING
DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY...MAINLY TO THE SOUTH
AND SOUTHWEST OF THE CENTER OF CIRCULATION. UPPER-LEVEL WINDS ARE
EXPECTED TO BE MARGINALLY CONDUCIVE FOR DEVELOPMENT OF THIS
DISTURBANCE AS IT MOVES SLOWLY SOUTH-SOUTHWESTWARD DURING THE NEXT
COUPLE OF DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...50 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. AN AIR FORCE
RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE THE
SYSTEM THIS AFTERNOON...IF NECESSARY.

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

$$
FORECASTER BRENNAN
Member Since: August 6, 2011 Posts: 4 Comments: 38532
I see Isaac is back in the saddle again ...



Post 106. OracleDeAtlantis 7:23 PM GMT on April 05, 2012

No offense to the science of meteorology, but a butterfly in China can be observed to fly circles around Dr. Gray and his team; and I hear the butterflies in China are choking on U.S.

For upon her wings are the eyes of the earth, seeing the unfolding of every birth.

From above the trees and beyond sky, to the state of confusion what it denies.

Never before found such a plight that befell them that are without sight.

Now see before you the industry of sin, and return by fury the fallacy of men.

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90-L has a very small window of opportunity to
develop due to the approaching LW but we are
looking forward to cooler weather with the passage of
the Associated Cold front this weekend..Its not
often as a mariner we get Northerly winds and
drier air in Sept. Currently at 27.6 N and 91.9 W
we have WSW winds at 10 kts and 2 ft seas.
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Quoting Skyepony:
Check out the hot tower that was on 90L.. click pic, there is a lot of moisture there.


We went from being dry as a bone here in the St. Louis area, to having dewpoints so high you practically need scuba gear to breathe outside after Isaac. I can believe wherever the rest of that storm went, it's gonna POUR.
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Quoting sar2401:


Thankfully, I was never dumb enough to get tangled up in a really large storm, but I've been through some pretty good gales. If a bouy was in the wind field of one storm, so it produced wind driven waves, and the storm further away was only producing swells, the waves win every time. I don't think you'd even notice opposing swell until you were well out of the wind field.
Yeah you're right. The opposing swell would still be there though. It'd show up on the other side of the storm.
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1063. tj175
Wow Michael went from Ragged looking last night around this time all the way to a Cat 2. Wow talk about rapid intensification. Satellite presentation looks awesome
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1062. sar2401
Quoting Skyepony:
Check out the hot tower that was on 90L.. click pic, there is a lot of moisture there.


For some reason, QT is not working for me. At any rate, being in the middle of what has become 90L, I don't need convincing of how much moisture it carried with it. :) I still don't understand the forcing mechanisms that caused that storm to be so intense over land, and I really don't understand what it's doing over water. Wherever this thing lands up, it going to be mighty wet, that I can say with certainty.
Member Since: October 2, 2004 Posts: 0 Comments: 15322
Wait... what?

Michael not only became a hurricane this evening, he's well on his way to being our first major?!!
Well that's a fine howdy do!

When Dr. Masters wrote, "Tropical Storm Michael has strengthened to 50 mph winds, and appears to have a favorable enough environment to become a hurricane later this week." he probably didn't think it'd be later this DAY. haha
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Michael may very well be our 1 major of the season.
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1059. sar2401
Quoting TomTaylor:
Yeah makes sense. About the waves, I was assuming he was referring to what a buoy would feel if it were within the storm's circulation. Within the circulation, with the strong winds, you'd likely see large waves, though they wouldn't ever break, just sort of rise and fall.


Thankfully, I was never dumb enough to get tangled up in a really large storm, but I've been through some pretty good gales. If a bouy was in the wind field of one storm, so it produced wind driven waves, and the storm further away was only producing swells, the waves win every time. I don't think you'd even notice opposing swell until you were well out of the wind field.
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Quoting ededed:
HURRICANE MICHAEL SPECIAL FORECAST/ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132012
0500 UTC THU SEP 06 2012

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

HURRICANE CENTER LOCATED NEAR 29.4N 42.0W AT 06/0500Z
POSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE NORTHEAST OR 50 DEGREES AT 6 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 974 MB
EYE DIAMETER 10 NM
MAX SUSTAINED WINDS 90 KT WITH GUSTS TO 110 KT.
64 KT....... 15NE 10SE 10SW 10NW.
50 KT....... 30NE 20SE 15SW 20NW.
34 KT....... 60NE 40SE 20SW 40NW.
12 FT SEAS..120NE 90SE 30SW 60NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

That escalated quickly...
Wow. NHC not on the conservative side this time.

Eye has cleared out a bit more, and now the temperature contrast between the eyewall and eye is more significant, allowing dvorak estimates to jump.
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1057. sar2401
I see everyone was right on top of that special advisory. If we only have one major this season, it will hopefully be Michael. He can spin around in the open ocen, not hurt anything, and it will satisfy the salivating masses here. :)
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Quoting sar2401:


From my sailing days, they would be swells in the open ocean, rather than waves. As you said, they basically pass through each other. The larger swell just passed over the smaller swell with no real change in height. The only time I noticed two opposing swells is when they were actually hitting my hull. In that case, the larger and smaller swells kind of fought it out. Other than hitting something solid, like a hull or a shoreline, it was just what's called a "confused sea". Different swells coming from different directions. I was never able to pick out exactly what direction the swells were coming from if there were two different storms far away from each other.
Yeah makes sense. About the waves, I was assuming he was referring to what a buoy would feel if it were within the storm's circulation. Within the circulation, with the strong winds, you'd likely see large waves, though they wouldn't ever break, just sort of rise and fall.
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1055. Skyepony (Mod)
Check out the hot tower that was on 90L.. click pic, there is a lot of moisture there.
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1054. sar2401
Quoting TomTaylor:
Looking at intensity here are a few of the issues Leslie has at the moment...

After struggling for several days, Leslie has finally managed to get convection over its center and expand outflow in all quadrants. Shear is still present, however, and the NHC has noted the storm is not perfectly stacked. Some dry air has also been ingested into the circulation as evident by the areas void of convection around the circulation. Slow forward motion had cooled sea surface temperatures as a result of mixing and upwelling. TPW and WV imagery also shows pretty dry air to the west of Leslie.

Check that water vapor loop and you can see the upper level outflow clouds evaporating to the west of Leslie (a result of convergent flow aloft, drying the atmosphere) as well as pockets void of convection over the circulation (a sign of less instability, likely a result of some dry air and upwelling)



Good analysis. Leslie has never been able to fight off that shear and dry air to the west, and convection in the left quadrants has always been weak. Her huge size is what's managed to keep her alive long enough to get to a better environment. I'm sure glad she hasn't had the apparently perfect conditions that Michael has. Otherwise, she would be about a category 10 by now. :)
Member Since: October 2, 2004 Posts: 0 Comments: 15322
BULLETIN
HURRICANE MICHAEL SPECIAL ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132012
100 AM AST THU SEP 06 2012

...MICHAEL RAPIDLY INTENSIFIES INTO A CATEGORY 2 HURRICANE...


SUMMARY OF 100 AM AST...0500 UTC...INFORMATION
----------------------------------------------
LOCATION...29.4N 42.0W
ABOUT 1045 MI...1680 KM WSW OF THE AZORES
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...NE OR 50 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...974 MB...28.76 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM AST...0500 UTC...THE CENTER OF HURRICANE MICHAEL WAS
LOCATED NEAR LATITUDE 29.4 NORTH...LONGITUDE 42.0 WEST. MICHAEL IS
MOVING TOWARD THE NORTHEAST NEAR 7 MPH...11 KM/H...AND A TURN TO THE
NORTH AND NORTH-NORTHWEST WITH A DECREASE IN FORWARD SPEED IS
EXPECTED DURING THE NEXT 48 HOURS.

SATELLITE IMAGERY INDICATES THAT MAXIMUM SUSTAINED WINDS HAVE
INCREASED TO NEAR 105 MPH...165 KM/H...WITH HIGHER GUSTS. MICHAEL
IS A CATEGORY TWO HURRICANE ON THE SAFFIR-SIMPSON HURRICANE WIND
SCALE. SOME ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT
COUPLE OF DAYS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 15 MILES...30 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 70
MILES...110 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 974 MB...28.76 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BLAKE/BRENNAN
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting KoritheMan:


Nah, I'd say Category 2, about 85 kt. If you look closely, the eye is still a bit ragged and partially cloud filled.

According to the NHC, at least, Michael is a Cat 2. Looks like some dynamite in that small package.
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1051. Skyepony (Mod)
& WOW TRMM caught the eye of MICHAEL. Click pic for Very Large quicktime movie..

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DATE/TIME: 06/0415 UTC
LAT: 29.3N LON 42.1W
CLASSIFICATION: T5.0/5.0
STORM: MICHAEL -- Atlantic
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting KoritheMan:


Nah, I'd say Category 2, about 85 kt. If you look closely, the eye is still a bit ragged and partially cloud filled.


I was close. :P
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Quoting snowboy:
Michael has to be at least Cat. 2 if not Cat. 3..


Nah, I'd say Category 2, about 85 kt. If you look closely, the eye is still a bit ragged and partially cloud filled.
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1047. Skyepony (Mod)
TRMM of outer bands of Leslie. Click pic for quicktime movie.
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Ooooooh, special advisory! Go Michael! I want his autograph. He's Bad, and a Thriller to watch.

Leslie looks to be getting better organized again, she's moving ever so slightly more, which certainly helps.
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1045. sar2401
Quoting ededed:
HURRICANE MICHAEL SPECIAL FORECAST/ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132012
0500 UTC THU SEP 06 2012

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

HURRICANE CENTER LOCATED NEAR 29.4N 42.0W AT 06/0500Z
POSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE NORTHEAST OR 50 DEGREES AT 6 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 974 MB
EYE DIAMETER 10 NM
MAX SUSTAINED WINDS 90 KT WITH GUSTS TO 110 KT.
64 KT....... 15NE 10SE 10SW 10NW.
50 KT....... 30NE 20SE 15SW 20NW.
34 KT....... 60NE 40SE 20SW 40NW.
12 FT SEAS..120NE 90SE 30SW 60NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

That escalated quickly...


Wowsers! I withdraw my question, Snowboy. I guess a pretty face does mean something. :)
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1044. sar2401
Quoting TomTaylor:
Oh, yeah, if two waves met they would slosh together to produce a bigger wave. I'm not sure how well buoys account for this. I know wave models account for significant wave height for the dominant swell, but they don't account for waves coming from different directions and peaking. And I think buoys work similarly, accounting for the highest wave heights from a specific swell.

The thing in this case, however, is that Michael is so far away from Leslie that his waves will not meet Leslie's for a while.


From my sailing days, they would be swells in the open ocean, rather than waves. As you said, they basically pass through each other. The larger swell just passed over the smaller swell with no real change in height. The only time I noticed two opposing swells is when they were actually hitting my hull. In that case, the larger and smaller swells kind of fought it out. Other than hitting something solid, like a hull or a shoreline, it was just what's called a "confused sea". Different swells coming from different directions. I was never able to pick out exactly what direction the swells were coming from if there were two different storms far away from each other.
Member Since: October 2, 2004 Posts: 0 Comments: 15322
1043. ededed
HURRICANE MICHAEL SPECIAL FORECAST/ADVISORY NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132012
0500 UTC THU SEP 06 2012

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

HURRICANE CENTER LOCATED NEAR 29.4N 42.0W AT 06/0500Z
POSITION ACCURATE WITHIN 20 NM

PRESENT MOVEMENT TOWARD THE NORTHEAST OR 50 DEGREES AT 6 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 974 MB
EYE DIAMETER 10 NM
MAX SUSTAINED WINDS 90 KT WITH GUSTS TO 110 KT.
64 KT....... 15NE 10SE 10SW 10NW.
50 KT....... 30NE 20SE 15SW 20NW.
34 KT....... 60NE 40SE 20SW 40NW.
12 FT SEAS..120NE 90SE 30SW 60NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

That escalated quickly...
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HWRF 250mb Wind Streamline Intialization shows the incredibly convergent flow aloft to the west of Leslie. This is occurring as a result of SWerly flow between the ULL over the Bahamas and the ULAC over Haiti pushing air toward Leslie on the west side which creates convergence with Leslie's outflow. Furthermore, the ridge to the north of Leslie is bending the westerlies around the periphery of this feature causing it to converge with the SWerly flow produced by the ULL and ULAC as well as outflow from Leslie. The ULL over the Bahamas, ULAC over Haiti, and ridge to the north of Leslie have formed a trifecta to create strong upper convergence to the west and northwest of Leslie.

18z GFDL 250mb Wind Streamlines at 0hrs


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1041. sar2401
Quoting snowboy:
Michael has to be at least Cat. 2 if not Cat. 3..


Other than the fact he looks nice, what makes you think that?
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1040. snowboy
Michael has to be at least Cat. 2 if not Cat. 3..
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Quoting LBAR:


I was expecting a huge crescendo of waves when the 2 sets of propagating waves met.
Oh, yeah, if two waves met they would slosh together to produce a bigger wave. I'm not sure how well buoys account for this. I know wave models account for significant wave height for the dominant swell, but they don't account for waves coming from different directions and peaking. And I think buoys work similarly, accounting for the highest wave heights from a specific swell.

The thing in this case, however, is that Michael is so far away from Leslie that his waves will not meet Leslie's for a while.
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1037. Grothar
Quoting Jedkins01:


Probably the next torrential rain maker for Central Florida. Probably gonna get several inches of rain around Tampa Bay before all is said and done. The Bucs home opener is going to be this Sunday, the pirate ship may capsize, lol.


You lol at that? :)
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1036. LBAR
Quoting TomTaylor:
They pass each through each other...energy from one swell isn't significantly dissipated by the energy of another swell should their paths meet. At any given time a buoy is receiving swells from all different directions.


I was expecting a huge crescendo of waves when the 2 sets of propagating waves met.
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Quoting LBAR:
Are there any ship or buoy reports in the Atlantic between Leslie and Michael? I have wonder what happens when the waves moving east from Leslie meet the waves moving west from Michael.
They pass through each other...energy from one swell isn't significantly dissipated by the energy of another swell should their paths meet. At any given time a buoy is receiving swells from all different directions.
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1034. LBAR
Are there any ship or buoy reports in the Atlantic between Leslie and Michael? I have wonder what happens when the waves moving east from Leslie meet the waves moving west from Michael.
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Quoting LostTomorrows:
Every year someone expects a Fujiwara. I remember in 2005 when people were asking if one could happen wih Wilma and Alpha, but Wilma just ripped the kid apart and ate him. Now, Michael is much better defined than Alpha ever was, and can last longer if he gets tangled up in Leslie's circulation, but she will still chip away until he dies if he gets close enough. She has a large and powerful circulation.

That being said, I mused at the possibility that if he gets close enough and is strong enough, he might just latch onto her like a clingfish and let her spin take him for a ride, but she might just hurl him somewhere cold and far away or something.

I also think that his rapid intensification was aided by Leslie's sheer size; she's the buffer that's been shielding him from nearly every hostile thing thrown at him by the environment, she's just a monster that eats everything haha.
Fujiwaras and pinhole eyes...people love to point at the possibility of these events, though they rarely ever do occur.

And Leslie's massive outflow would destroy Michael if he got any closer. May even begin to shear the storm tomorrow.
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Looking at intensity here are a few of the issues Leslie has at the moment...

After struggling for several days, Leslie has finally managed to get convection over its center and expand outflow in all quadrants. Shear is still present, however, and the NHC has noted the storm is not perfectly stacked. Some dry air has also been ingested into the circulation as evident by the areas void of convection around the circulation. Slow forward motion had cooled sea surface temperatures as a result of mixing and upwelling. TPW and WV imagery also shows pretty dry air to the west of Leslie.

Check that water vapor loop and you can see the upper level outflow clouds evaporating to the west of Leslie (a result of convergent flow aloft, drying the atmosphere) as well as pockets void of convection over the circulation (a sign of less instability, likely a result of some dry air and upwelling)

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1031. SLU
NHC advisory aside .... Michael is probably closing in on cat 3 strength by now ...

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Quoting Grothar:


Undergoing rapid blobification.

Models a little more to Central Florida now



Probably the next torrential rain maker for Central Florida. Probably gonna get several inches of rain around Tampa Bay before all is said and done. The Bucs home opener is going to be this Sunday, the pirate ship may capsize, lol.
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Quoting KoritheMan:


I'd say like 2%, lol.

Rapid blobification happening with 90L, lol.
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1028. Grothar


Undergoing rapid blobification.

Models a little more to Central Florida now

Member Since: July 17, 2009 Posts: 71 Comments: 26152
1027. bappit
Alicia didn't do the RI thing. It hung out there for a while (60 hours after becoming a tropical storm) and intensified steadily.
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Quoting spathy:
This is a cruel joke!


I am directly under the y in Myers and not a drop.
And I am not kidding I pulled brown dry weeds today.




Brown Weeds? I haven't seen those since May. Although it hasn't rained since the rain from Isaac, we've had at 12 inches a month around here for June, July, and August each, because of that the ground is still wet and, the ponds and ditches are still full to the brim and everything is bright green.
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1025. bappit
Conditions were perfect for Humberto. The Gulf has cooled off some, has shear issues and there is lots of dry air over here towards Texas.
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Quoting lobdelse81:

Any possibility that 90L could undergo rapid intensification like Humberto or Alicia?


I'd say like 2%, lol.
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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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