Danny weakens further; 94L worth watching

By: Dr. Jeff Masters , 1:54 PM GMT on August 28, 2009

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Tropical Storm Danny continues to weaken, and may merely be a tropical depression. Data from the Hurricane Hunters early this morning showed top winds of just 40 mph at the surface, and satellite intensity estimates of Danny's strength are now rating the storm a tropical depression. Danny looks very disorganized on satellite imagery (Figure 1), with the low-level circulation center exposed to view. There is no heavy thunderstorm activity near Danny's center, and only a small area of heavy thunderstorms lying several hundred miles east of the center.


Figure 1. Morning satellite image of Danny, showing the exposed swirl of clouds where Danny's center is, well displaced from the heaviest thunderstorm activity to the east.

The forecast for Danny
With wind shear at 15 knots this morning, and forecast to increase to 20 knots tonight and 30 knots Saturday morning, is is unlikely Danny will be able to strengthen to more than a 50 mph tropical storm. Dry air from the upper-level low that has been keeping Danny disorganized continues to be a problem for the storm, as well. The GFDL and HWRF models continue to insist Danny will strengthen to a strong tropical storm or weak Category 1 hurricane, but this seems very unrealistic given Danny's current struggles. With Danny's heavy thunderstorms all on the east side of the storm, it is unlikely that New England will feel tropical storm force winds from Danny when it scoots past on Saturday. Large swells from Danny creating high surf along the beaches of New England will be the primary hazard from the storm.

Massachusetts hurricane history
Two tropical storms have affected Massachusetts in the past decade, though neither of these storms brought sustained winds of tropical storm force (39 mph) to the state. Tropical Storm Beryl of 2006 just missed Cape Cod as a weak tropical storm with 45 mph winds. Beryl brought wind gusts to tropical storm force to Nantucket Island, and a 1 foot storm surge. Tropical Storm Hermine hit southeast Massachusetts on August 31, 2004, as a minimum-strength tropical storm with 40 mph winds. No land stations in Massachusetts reported tropical storm force winds during Beryl. The last time Massachusetts measured tropical storm force winds was in 1991 during Hurricane Bob, which hit Rhode Island as a Category 2 hurricane. Provincetown, Massachusetts measured sustained winds of 98 mph, gusting to 115 mph, and Buzzard's Bay received a 15 foot storm surge.


Figure 2. Tropical wave 94L, a few hundred miles west of the Cape Verdes Islands.

Invest 94L
A well-organized tropical wave (94L) lies a few hundred miles west-southwest of the Cape Verdes Islands. This disturbance has shown little change this morning. This morning's QuikSCAT pass shows a complete circulation, elongated in the east-west direction, with top winds of 30 mph. Satellite imagery shows only a small amount of heavy thunderstorm activity near the circulation center, but considerable thunderstorm activity south of the center. Shear is low, about 10 knots, and is expected to remain low to moderate, 5 - 15 knots, over the next five days. The waters are warm enough to support development, 28°C, and are expected to remain in the 27 - 28°C range over the next five days. The dry Saharan Air Layer (SAL) lies about 200 miles to the north and west of 94L, and it appears from water vapor satellite imagery that a modest amount of dry air from the SAL is now being ingested into the storm, slowing development. Dry air will continue to slow development until 94L's heavy thunderstorm activity can moisten the atmosphere enough to shield the storm from the Saharan Air Layer. NHC is giving 94L a medium (30 - 50% chance) of developing into a tropical depression by Sunday. The GFDL and SHIPS models both predict 94L will be a Category 1 hurricane five days from now. However, the HWRF model does not develop 94L. Most of the models predict 94L will take a significant northward jog 3 - 5 days from now, in response to a strong trough of low pressure passing to the north (this is the same trough of low pressure that will be recurving Danny out to sea). It is then probable that 94L will be forced to the west again as the high pressure ridge steering the storm builds back in, and 94L will likely be a few hundred miles northeast of the Northern Lesser Antilles Islands seven days from now.

I'll have an update this afternoon.

Jeff Masters

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Quoting IKE:
LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO.
...

from a 40 mph tropical storm?


ha my grandma generates bigger swells than that when she gets in the bath tub....
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Good morning, fellow Wunderbloggers.

Interesting.
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Quoting IKE:
DANNY REMAINS DISORGANIZED...
11:00 AM EDT Fri Aug 28
Location: 30.1°N 75.5°W
Max sustained: 40 mph
Moving: NW at 10 mph
Min pressure: 1008 mb

So the CHIPS model had a decent handle on it with that 06 Z forecast. GFDL, HWRF, and the official forecast called for strengthening, CHIPS called for ~34 knots about now (39 mph).

We'll see if it continues to do well.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting atmoaggie:
Thanks Dr M.

"However, the HWRF model does not develop 94L."
Wow. So HWRF is a special discrete model that says that systems are either off or all the way on.
I hope that new forecast program yields some quality improvements to our model capabilities.


There is currently an upgrade to HWRF waiting in the que that includes a modification to the initialization that testing has shown to improve intensity forecasts. Its been waiting for the switchover to the new computers, now changes to SREF and GEFS are ahead of it in the que.
Member Since: September 23, 2005 Posts: 14 Comments: 11274
70. IKE
LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO.
...

from a 40 mph tropical storm?
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I think 94L may stay weak enough and S enough to miss that trough.
Member Since: August 10, 2007 Posts: 0 Comments: 3292
the way Danny looks, if the coc was in the gulf just west of Tampa, all the rain would be in the atlantic ocean.

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It is then probable that 94L will be forced to the west again as the high pressure ridge steering the storm builds back in

cmon guys read the whole thing....
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66. IKE
TROPICAL STORM DANNY ADVISORY NUMBER 9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052009
1100 AM EDT FRI AUG 28 2009

...DANNY REMAINS DISORGANIZED...

A TROPICAL STORM WATCH IS IN EFFECT FOR THE NORTH CAROLINA COAST
FROM CAPE LOOKOUT NORTHWARD TO DUCK...INCLUDING THE PAMLICO AND
ALBEMARLE SOUNDS. A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM
CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE...
WITHIN 24 HOURS. A TROPICAL STORM WARNING MAY BE REQUIRED FOR
PORTIONS OF THIS AREA LATER TODAY.

INTERESTS ELSEWHERE FROM THE CAROLINAS NORTHWARD TO NEW ENGLAND AND
THE CANADIAN MARITIMES SHOULD MONITOR THE PROGRESS OF DANNY.
ADDITIONAL WATCHES AND WARNINGS MAY BE REQUIRED FOR PORTIONS OF THIS
AREA LATER TODAY.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA
OUTSIDE OF THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR NATIONAL METEOROLOGICAL SERVICE.

AT 1100 AM EDT...1500 UTC...THE CENTER OF TROPICAL STORM DANNY WAS
LOCATED NEAR LATITUDE 30.1 NORTH...LONGITUDE 75.5 WEST OR ABOUT 350
MILES...565 KM...SOUTH OF CAPE HATTERAS NORTH CAROLINA AND ABOUT 830
MILES...1335 KM...SOUTH-SOUTHWEST OF NANTUCKET MASSACHUSETTS.

WHILE DANNY HAS BEEN MOVING TOWARD THE WEST OVER THE PAST COUPLE OF
HOURS...A MOTION TOWARD THE NORTHWEST NEAR 10 MPH...17 KM/HR...IS
EXPECTED TO RESUME SOON. A TURN TOWARD THE NORTH AND THE NORTH-
NORTHEAST WITH AN INCREASE IN FORWARD SPEED IS EXPECTED LATER
TODAY AND TONIGHT. ON THE FORECAST TRACK...THE CENTER OF DANNY IS
EXPECTED TO PASS NEAR THE OUTER BANKS OF NORTH CAROLINA OVERNIGHT...
APPROACH THE COAST OF SOUTHEASTERN NEW ENGLAND LATE SATURDAY
NIGHT...AND MOVE NEAR THE CANADIAN MARITIMES EARLY SUNDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER
GUSTS. SOME SLIGHT STRENGTHENING IS POSSIBLE TODAY...WITH LITTLE
CHANGE IN INTENSITY FORECAST AFTER THAT TIME.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 175 MILES...280 KM
...MAINLY TO THE EAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.

LARGE SWELLS FROM DANNY ARE EXPECTED TO PRODUCE DANGEROUS SURF
CONDITIONS AND LIFE-THREATENING RIP CURRENTS ALONG THE U.S. EAST
COAST DURING THE NEXT DAY OR TWO. PLEASE CONSULT STATEMENTS ISSUED
BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE FOR MORE
DETAILS.

...SUMMARY OF 1100 AM EDT INFORMATION...
LOCATION...30.1N 75.5W
MAXIMUM SUSTAINED WINDS...40 MPH
PRESENT MOVEMENT...NORTHWEST OR 325 DEGREES AT 10 MPH
MINIMUM CENTRAL PRESSURE...1008 MB

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 200 PM EDT FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 500
PM EDT.

$$
FORECASTER BRENNAN
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65. IKE
DANNY REMAINS DISORGANIZED...
11:00 AM EDT Fri Aug 28
Location: 30.1°N 75.5°W
Max sustained: 40 mph
Moving: NW at 10 mph
Min pressure: 1008 mb
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94L still moving slightly south of due west. it is begining to look like serious trouble for the islands. although still not very organised, the longer it takes more west it moves
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Quoting Dakster:


The only thing that would wreck the game is if FSU wins...

you got that right.

don't think 94L will be a factor in Tally.
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Quoting mikatnight:


How long do you think it'll be before they're able to shoot 30 fps from the satellites? Now that would be revealing...

I don't know that 30 fps would tell us anything that the 1 per minute SRSOs cannot. TCs don't move/evolve that fast.
Clearly, though, better obs are needed. I know that a guy at NASA/Marshall wants to launch a satellite-based SFMR. Don't get too terribly excited, though, the only way a satellite SFMR has any swath width is if the spatial resolution is degraded a bit from that on the HHs.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting NEwxguy:
As Dr. Masters indicated the trough moving through the east this weekend and early next week will be out in the Atlantic when 94L is moving by and that will probably pull 94L north at some point


Something will need to pull it north, or else it will slam into SA.

Of course, I personally wouldn't mind that. I don't wish bad on anyone, but after 2004, better somewhere else than here! :-)
Member Since: May 27, 2008 Posts: 0 Comments: 467
Quoting 900MB:


You think it can somehow be East enough to keep me dry at Giants Stadium tomorrow?


lol,well unfortunately Danny isn't the only rainmaker,the front pushing east is going to a lot of water on us and you.
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59. IKE
Quoting sfla82:


Because it wont. It will recurve like the rest of them.


So Claudette didn't hit anyone? Or Bill?
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Quoting Vortex95:


He is joking I wouldn't worry about that.


alright, wasnt trying to sound mad or anything, sorry!
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I see now how 94L will turn north. The through should grab it unless it still is an invest in the next 72 hours which is unlikely. It will get pulled north
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Quoting Dakster:
THanks for the update Dr. M. I did notice that Dr. M did NOT say anything about a possible US hit from 94L.



Because it wont. It will recurve like the rest of them.
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Quoting KEHCharleston:
If (as been noted on this blog) the convection is a couple of hundred miles to the east of the center, then Danny would have to go more than a couple of hundred miles west to have an effect.
However, I may have misunderstood the discussion.


Ah...yes, I see your point. But mostly, I was making an observation on the Danny's movement (or lack thereof). Faye got "stuck over florida and dumped a bunch of rain.

I wonder what the total rainfall under that Danny's area of thunderstorms is. You could probably measure it in feet!
Member Since: May 27, 2008 Posts: 0 Comments: 467
Quoting NEwxguy:
Danny,could never get its act together,thankfully,but it will join forces with a deepening low in the great lakes to give us a lot of rain here in southern new england tomorrow.


You think it can somehow be East enough to keep me dry at Giants Stadium tomorrow?
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This ought to be a good test for CHIPS. It diverges substantially from the other dynamical models on a system about which it could be correct.

So a 33 knot Danny or a 45 knot Danny in the wee early hours tomorrow morning? We'll see, but I am inclined to side with CHIPS prognostication at the moment.



Also looking for a 50 knot or 35 knot Danny at 1pm CDT tomorrow.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
As Dr. Masters indicated the trough moving through the east this weekend and early next week will be out in the Atlantic when 94L is moving by and that will probably pull 94L north at some point
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Quoting tornadodude:


while that might be a concern, shouldnt someone be concerned about more than that? not saying you arent a concerned citizen, just wondering if you have your priorities straight,you know?


The only thing that would wreck the game is if FSU wins...
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Quoting fmbill:
Wow! Danny is stuck.

If he was a couple hundred miles to the west, it would be a repeat of Faye last year.

Piles of rain!
If (as been noted on this blog) the convection is a couple of hundred miles to the east of the center, then Danny would have to go more than a couple of hundred miles west to have an effect.
However, I may have misunderstood the discussion.
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Quoting CaribBoy:
I still can't understand how 94L can make that northward turn.


i agree..IMO i see 94L passing between Antigua and Barbados
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Quoting noleweatherman:
im gonna be so mad if erika ruins the fsu/miami game


while that might be a concern, shouldnt someone be concerned about more than that? not saying you arent a concerned citizen, just wondering if you have your priorities straight,you know?
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@ Orcasystems. Regarding my comment before the blog eclipse (LOL). Certainly no snow, not this early. But a strong wind/rainstorm that follows a typical fall pattern? No doubt. Baroclinic dynamics are the same. Old-timers called them "line-storms" as they seem to occur near the equinoxes.
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Quoting atmoaggie:
Thanks Dr M.

"However, the HWRF model does not develop 94L."
Wow. So HWRF is a special discrete model that says that systems are either off or all the way on.
I hope that new forecast program yields some quality improvements to our model capabilities.


How long do you think it'll be before they're able to shoot 30 fps from the satellites? Now that would be revealing...
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im gonna be so mad if erika ruins the fsu/miami game
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I still can't understand how 94L can make that northward turn.
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39. IKE
Quoting atmoaggie:
Thanks Dr M.

"However, the HWRF model does not develop 94L."
Wow. So HWRF is a special discrete model that says that systems are either off or all the way on.
I hope that new forecast program yields some quality improvements to our model capabilities.


Models have been terrible w/Danny and I've just about quit looking at them as far as 94L is concerned.
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Wow! Danny is stuck.

If he was a couple hundred miles to the west, it would be a repeat of Faye last year.

Piles of rain!
Member Since: May 27, 2008 Posts: 0 Comments: 467
Quoting FLWeatherFreak91:
Not a problem.


I like our invisible Hurrcane shield.

As long as another football team doesn't figure out how to adapt it to them when the 'canes play.
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Thanks Dr M.

"However, the HWRF model does not develop 94L."
Wow. So HWRF is a special discrete model that says that systems are either off or all the way on.
I hope that new forecast program yields some quality improvements to our model capabilities.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
sounds like a florida wishcaster
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I think this precipitable water vapor loop agrees with the quikscat from earlier, and shows that the center of circulation with 94L is indeed at around 10/11N 31/32W.

It also shows Danny starting to lift north, and appears to show the overall circulation weakening...

wicked awesome update
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Quoting Dakster:


And this is a problem how?
Not a problem.
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It looks to me like 94L is moving quicker than yesterday (in the bottom RH corner):
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Quoting FLWeatherFreak91:
Yes, but the high will just not build back in. Each system that comes along will make that turn north off the east coast. We need a break in the storms for a week to allow the high to build in.


And this is a problem how?
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Danny is a lot like a 1914 storm during low sun spot activity. Click my blog for details. Also naked swirl has electrical meaning even to the clouds over a hundred miles away--click previous blog entry on Danny.

Mike
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Does anybody know what maintains a circulation in the absence of convection?

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Quoting klaatuborada:
Good morning. Klaat on Cape Cod. To tell you the truth, I won't feel good about this until it's gone over me. Anything can happen, as Danny has proven. Don't even plan to step out the door tomorrow. Perhaps the house will get clean.
whaaaatttttttttttttttt??????????????
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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.