Danny weakens further; 94L worth watching

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

Share this Blog
2
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 24 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 — Blog Index

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.
Member Since: Posts: Comments:
Quoting rmbjoe1954:
94L is too far away for any reasonableness from the models.
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.
Member Since: Posts: Comments:
Quoting mikatnight:
Quoting Dr. Masters:

"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."

So, maybe it'll miss ol' Herbert and his box of tricks...



Hopefully..
Member Since: Posts: Comments:
19. IKE
Quoting Chiggy007:
can anyone verify that center I am seeing with 94L is at 10N - 36.5W...

anyone agree?


It's close to that area. System appears to be moving faster than 15 mph(as the NHC states), to me.
Member Since: Posts: Comments:
Quoting Dr. Masters:

"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."

So, maybe it'll miss ol' Herbert and his box of tricks...
Member Since: Posts: Comments:
Would you like it hot or cold?

Member Since: Posts: Comments:
Quoting Chiggy007:
can anyone verify that center I am seeing with 94L is at 10N - 36.5W...

anyone agree?
Per RAMMB (Colo.State) - Would be a bit (oops - meant east) of 36.5 as of 2 hours ago.

Member Since: Posts: Comments:
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.



it still is a long way out, but hopefully a US hit wont happpen, if 94L develops
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:
THanks for the update Dr. M. I did notice that Dr. M did NOT say anything about a possible US hit from 94L.

Member Since: Posts: Comments:
Thanks Dr. Most of the forecasts you make come true so I am going to have hope that 94L will go north of the islands.
Member Since: Posts: Comments:
Quoting Bordonaro:
Good morning everyone! I get to eat a lil' crow, I was way off on TS Danny! I had thought it would " get it together", BOY, was I ever WRONG!!


im in the same boat as you
Member Since: Posts: Comments:
12z NAM 24hours
Member Since: Posts: Comments:
Good morning everyone! I get to eat a lil' crow, I was way off on TS Danny! I had thought it would " get it together", BOY, was I ever WRONG!!
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Good mornng all... sure is a quiet season...

12C and rain here on Sunday... burr....
Member Since: Posts: Comments:
Thx Dr. M
Member Since: Posts: Comments:
Good Morning Everyone! Thanks Dr. Masters for the update...
can anyone verify that center I am seeing with 94L is at 10N - 36.5W...

anyone agree?
Member Since: Posts: Comments:
94L is too far away for any reasonableness from the models.
Member Since: Posts: Comments:
Thanks, Dr. Masters
Member Since: Posts: Comments:

Viewing: 24 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 — Blog Index

Top of Page

About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.