Karen struggling; Lorenzo sets a new intensification record

By: Dr. Jeff Masters , 2:42 PM GMT on September 29, 2007

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Tropical Depression Karen has weakened to a tropical depression, thanks to ferociously high wind shear levels exceeding 50 knots. Satellite loops show Karen's exposed low-level center of circulation, visible as a swirl of low clouds. Karen continues to generate new heavy thunderstorm activity, but these cells immediately get pushed several hundred miles east of the center by strong upper level winds from the west. This morning's QuikSCAT pass missed Karen.

Wind shear is expected to remain above 30 knots over Karen through Sunday, then decline to 15 knots by Sunday night. Although the storm has shown an unusual ability to maintain a strong wind pattern in the face of high wind shear, it is uncertain if Karen can survive past today. The GFS and ECMWF models predict the shear will destroy Karen. I put Karen's survival chances at about 25%.

If Karen survives, an upper level environment favorable for strengthening is expected to set up 3-5 days from now, and Karen would probably become a hurricane. Steering currents may become weak during that period, and Karen may move very slowly. By the middle of next week, I expect a ridge of high pressure will build over the eastern U.S. and western Atlantic, forcing Karen westward towards the U.S. The path Karen might take late next week is highly uncertain. Most of the models continue to predict the formation of a new tropical or subtropical cyclone somewhere between the coast of North Carolina and the Western Caribbean on Monday. Some of the models take this new storm northeastward out to sea, which would pull Karen northward in its wake. However, most of the models predict that the new storm will take a more westerly path into Georgia or Florida, or possibly the Gulf of Mexico. A storm-storm interaction between Karen and the new storm might ensue, an event the models are poor at handling.


Figure 1. This morning's visible satellite image with wind shear contours overlaid show a very unhealthy tropical depression. Wind shear of 50 knots is over the low-level circulation center of Karen, thanks to strong upper-level winds from the west (denoted by the big white arrow at the plot's bottom). These high winds have pushed all of Karen's heavy thunderstorm activity several hundred miles downwind of the center. Image credit: University of Wisconsin CIMSS.

Lorenzo sets another rapid intensification record for 2007
Hurricane Lorenzo hit Mexico's Veracruz coast near Tuxpan early Friday morning. The storm's heavy rains have triggered mudslides blamed for at least four deaths. Lorenzo has tied the Atlantic record for fastest intensification from a tropical depression to a Category 1 hurricane--twelve hours. Hurricane Blanche of 1969 was the only other storm on record that intensified from a tropical depression to a Category 1 hurricane in just 12 hours. Hurricane Ethel of 1960 may have done so faster, though. Ethel strengthened from a 45-mph tropical storm to a 85 mph Category 1 hurricane in just 6 hours. We don't know when Ethel started as a tropical depression, since this was before the satellite era.

Reliable record keeping of intensification rates of Atlantic hurricanes began in 1970, when regular satellite coverage became available. Since 1970, Hurricane Humberto of 2007 holds the record for fastest intensification from first advisory issued to hurricane strength--18 hours. (Actually, Humberto did the feat in 14 1/4 hours, but this will get rounded off to 18 hours in the final data base, which stores points every six hours). There have been six storms that accomplished the feat in 24 hours.

Since 1970, Hurricane Felix of 2007 holds the record for fastest intensification from the first advisory to a Category 5 hurricane. It took Felix just 54 hours to accomplish the feat. Hurricane Camille of 1969 also took 54 hours to do so, but the first advisory put Camille as a 60 mph tropical storm. It is likely that Camille would have been classified as a tropical depression earlier had reliable satellite imagery been available.

Is it a statistical fluke that we've had three record-speed intensifying hurricanes this year? It could be. Our reliable data records only go back to 1970, and there may have been periods in the past with similar events. No scientist has published a paper linking rapid hurricane intensification rates with global warming. However, three record-speed intensifying hurricanes in one season certainly raises questions, and is very odd.

Melissa
Tropical Storm Melissa formed this morning, far out in the eastern Atlantic. The storm is under about 10-20 knots of wind shear. Melissa will probably not affect land, since it is starting out too far north and will gain additional latitude in the coming days. The storm's expected track will take it northwest towards a region of high wind shear early next week, which should destroy the storm.

I'll have an update Sunday by noon.

Jeff Masters

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1877. CalvinSimonds
5:02 AM GMT on October 01, 2007
Beell wrote:

I'll try No. 2: Great Plains T-Storms/Tornadoes derive their spin from directional shear or a change in wind direction w/height. SE at the sfc, SW/Mid Level, and maybe NW higher up. Hurricanes die by speed shear or vertical shear-a change in wind speed-not necessarily direction above a semi-fixed point at the surface. In can be in the same direction as storm movement. If you sampled wind direction above any point in a mature hurricane, wind direction would be pretty much the same.

Now I am confused. Isnt it the case that over a mature hurricane we will find an anticyclone? Certainly if you look down on one the cirrus seems to be spiralling outward, even as the low clouds are spiralling inward.

Assuming for the moment I am right here, would not the winds in an upper air anti cyclone HAVE to be rotating in the opposite direction to a lower level cyclone beneath it????

Finally, assuming that the previous statements are correct, wouldn't this constitute a kind of sheer?


I may have reiterated what you already know-if so, please forgive.

On the contrary, I am learning gobs here. When we get this figured out we can both take the met test.

thanks,

Calvin

1875. beell
4:45 PM GMT on September 30, 2007
I'm a second liner Patrap
:-]
Member Since: September 11, 2007 Posts: 145 Comments: 16919
1874. stormybil
4:42 PM GMT on September 30, 2007
could the bahamma blob may be a td or ts before it aprocches fla ? where are the coorridiants for it is it around 22n 70 west anyone know thanks
1869. Drakoen
4:34 PM GMT on September 30, 2007
The cimss 15:00UTC shear map still shows strong vorticity maximum at 850mb with ex karen. Shear tendency map shows decreasing shear. There is still good lower level convergence and upper level divergence.
With the area of the Florida coast. The 500mb height shows a mid level rotation east of Miami. Still no signs of it working its way down to the surface. Wind shear in that area is 30-40kts.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1868. Cavin Rawlins
4:31 PM GMT on September 30, 2007
There are currently about 5 long-wave troughs in the N Hemisphere today

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1865. Drakoen
4:29 PM GMT on September 30, 2007
Posted By: Patrap at 4:27 PM GMT on September 30, 2007.
UTC is the ONLY base time...


I'm saying like regularyly in reference to everything else.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1861. Patrap
4:27 PM GMT on September 30, 2007
UTC is the ONLY base time...
Member Since: July 3, 2005 Posts: 427 Comments: 129435
1860. Drakoen
4:27 PM GMT on September 30, 2007
Looking at the GFS 12z run. It looks like it may want to spawn back up Karen as a weak system north of the lesser Antilles late this coming week.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1857. Drakoen
4:26 PM GMT on September 30, 2007
Posted By: msphar at 4:25 PM GMT on September 30, 2007.
The world doesn't live by EDT alone.


Its used as a base time.
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1856. FitzRoy
4:25 PM GMT on September 30, 2007
5 hours 25 minutes.
1855. msphar
4:25 PM GMT on September 30, 2007
The world doesn't live by EDT alone.
Member Since: August 20, 2006 Posts: 0 Comments: 289
1853. stormybil
4:22 PM GMT on September 30, 2007
hi all whats the coorrdinats we looking for a spin with the bahammas blob thanks
1851. hurricane23
4:20 PM GMT on September 30, 2007
000
NOUS42 KNHC 301400
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT SUN 30 SEPTEMBER 2007
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 01/1100Z TO 02/1100Z OCTOBER 2007
TCPOD NUMBER.....07-128

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW-LEVEL INVEST
NEAR 25.0N 84.0W AT 02/1800Z

Development seems possible as it moves westward.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
1850. BahaHurican
4:20 PM GMT on September 30, 2007
Who was it keeping track of blogger locations again?
Member Since: October 25, 2005 Posts: 19 Comments: 22682
1848. sngalla
4:18 PM GMT on September 30, 2007
Raining pretty good here now.
Member Since: February 18, 2003 Posts: 57 Comments: 5363
1842. zoomiami
4:12 PM GMT on September 30, 2007
It is beautiful, sunny, blue sky, and breezy here right now - must be coming my way :-}
Member Since: August 13, 2007 Posts: 10 Comments: 4158
1838. BahaHurican
4:10 PM GMT on September 30, 2007
Another way of watching non-floater "blobs" up close is via http://www.ghcc.msfc.nasa.gov/GOES/goeseastnheir.html , which is NASA's Interactive Viewers Page.
Member Since: October 25, 2005 Posts: 19 Comments: 22682
1837. IKE
4:09 PM GMT on September 30, 2007
Well, Doc didn't say which time zone. ;~D

LOL.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1836. Patrap
4:09 PM GMT on September 30, 2007
fxus62 kmfl 301259
afdmfl


Area forecast discussion
National Weather Service Miami Florida
859 am EDT sun Sep 30 2007


The frontal boundary will move little tonight through Monday. GFS/European model (ecmwf)
are both in agreement in cutting off a middle/upper low and moving it
SW across the Florida Straits tonight...with a weak surface low or
amplified trough developing along the frontal boundary. The models
both take the low/trough westward across the Keys or straits late
Monday into Tuesday with moisture making a rapid comeback across
the area then. Thus...after only isd/scattered activity expected tonight
and early Monday...trended probability of precipitation up to likely for the East Coast
Monday and Monday night...then likely across the entire area for
Tuesday. Winds will also subside in a hurry with the passage of
the low/trough late Mon/Tue. Behind this feature...high pressure
will build in from the north...but moisture will remain high...so
maintained chance probability of precipitation throughout the extended forecast.
Member Since: July 3, 2005 Posts: 427 Comments: 129435
1835. StAugustineWatcher
4:08 PM GMT on September 30, 2007
House
A HIGH SURF ADVISORY REMAINS IN EFFECT UNTIL 3 AM EDT WEDNESDAY.

SURF AND WAVE ACTION WILL INCREASE THROUGH THE PERIOD WITH BREAKERS
OF 5 TO 7 FEET SUNDAY AND 6 TO 8 FEET MONDAY. INEXPERIENCED SWIMMERS
SHOULD STAY OUT OF THE WATER.

I am thinking that experienced swimmers know better? Gonna go out shortly and see what red tide remains.
Member Since: September 6, 2005 Posts: 0 Comments: 53
1834. listenerVT
4:08 PM GMT on September 30, 2007
"I'll have an update Sunday by noon."




Well, Doc didn't say which time zone. ;~D
Member Since: July 11, 2007 Posts: 0 Comments: 5553
1833. BahaHurican
4:07 PM GMT on September 30, 2007
I notice NHC hasn't taken down the Karen paraphernalia just yet . . . guess they don't want double work if it does in fact manage to regenerate.

I'm thinking Karen's best chance for a comeback will occur tonight, when the shear levels are forecast to drop radically and when diurnal max can give the most assistance. If nothing happens, I think I'll be a lot more skeptical about regeneration. Right now I'm thinking she has a 60% chance of ending up like Ingrid.
Member Since: October 25, 2005 Posts: 19 Comments: 22682
1832. hurricane23
4:05 PM GMT on September 30, 2007
Thanks for posting that IKE....i read the discussion earlier before they updated it.This area has to be watched as sst's are plenty warm in the area and upper level winds could become more favorable for some development as it moves westward.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
1831. WXMongrel
4:05 PM GMT on September 30, 2007
Posted By: Weather456 at 4:02 PM GMT on September 30, 2007.

Great education shot...are the ropes formed by the dropping of air on the front that roll back under the leading edge or what?

I hope u understand what i'm about to say:


The ropes are caused by differential advection. Where cold air moves forwards and downwards undercutting warm air moving in the opposite direction but upwards. This opposite flow of streams rolls the cloud (i wish i could put into a better term)...like when you roll bread doe...one hand moves one way and the other hand moves the other.


Weather456...thanks, I did understand and it is much as I envisioned...thanks.
1830. Drakoen
4:04 PM GMT on September 30, 2007
little bit of a spin. Not well defined though.
Link
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1829. Patrap
4:04 PM GMT on September 30, 2007
fxus64 klix 301135 aaa
afdlix


Area forecast discussion...updated
National Weather Service New Orleans la
635 am CDT sun Sep 30 2007


Update...


Winds have increased above 20 knots across much of the Gulf
coastal waters. Therefore a Small Craft Advisory has been issued.

Long term...


Overall...have decided to go with a blend of the GFS/European model (ecmwf)
solution. A strong upper level ridge centered over the deep south
will continue to dominate the region on Wednesday. However...a
developing tropical upper tropospheric trough will slide beneath
the ridge into the southern Gulf of Mexico Tuesday night. At this
time...it appears that this area of low pressure will mainly be in
the upper levels of the atmosphere with an inverted trough axis
extending up into the northern of Gulf of Mexico Wednesday and
Thursday. The overall steering currents for this feature will be
east to west...so any surface features that develop will be
focused toward Mexico or south Texas.
However...increasing
moisture and pressure gradients can be expected from Thursday into
the weekend...as this tropical wave moves through the Gulf of
Mexico. Given this...have put in isolated probability of precipitation Wednesday into
Wednesday night over the coastal waters as deeper tropical
moisture and some upper level lift associated with the trough axis
moves into the region.
Member Since: July 3, 2005 Posts: 427 Comments: 129435
1828. Drakoen
4:02 PM GMT on September 30, 2007
Whatever kind of circulation is left of Karen appear to be covered per RAMSDIS "center" fix.
Karen
Member Since: October 28, 2006 Posts: 57 Comments: 30727
1827. Cavin Rawlins
4:02 PM GMT on September 30, 2007
Great education shot...are the ropes formed by the dropping of air on the front that roll back under the leading edge or what?

I hope u understand what i'm about to say:


The ropes are caused by differential advection. Where cold air moves forwards and downwards undercutting warm air moving in the opposite direction but upwards. This opposite flow of streams rolls the cloud (i wish i could put into a better term)...like when you roll bread doe...one hand moves one way and the other hand moves the other.
Member Since: July 24, 2005 Posts: 407 Comments: 19076

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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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