Tropical Depression Four arrives

By: Dr. Jeff Masters , 7:23 PM GMT on August 02, 2010

Share this Blog
2
+

Tropical Depression Four has made its debut over the mid-Atlantic Ocean, about 1300 miles east of the Lesser Antilles Islands. TD 4 is a small storm with very limited heavy thunderstorm activity, and is not very impressive at present. Wind shear is a low 5 - 10 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of TD 4 to allow further development, though. The main negative for development appears to be the storm's small size, which makes it vulnerable to modest increases in wind shear or dry air entrainment. Satellite imagery shows that TD 4 is gradually developing low-level spiral bands, but the intensity and areal extent of heavy thunderstorms has not increased over the past few hours. Upper-level outflow is not apparent yet.


Figure 1. Afternoon satellite image of TD 4.

Forecast for TD 4
The latest 12Z (8am EDT) models are fairly unified taking TD 4 to the west-northwest at 15 - 20 mph for the next three days. This would bring squalls from the storm's outer rainbands to the northern Lesser Antilles Islands, such as Antigua and Barbuda, by Wednesday afternoon. The center of TD 4 should pass to the northeast of the islands. A more southerly track through Puerto Rico, as predicted by the Canadian model, cannot be ruled out, though. As TD 4 makes its closest approach to the Lesser Antilles on Wednesday night, the storm will begin to encounter strong upper-level westerly winds associated with the counter-clockwise flow of air around an upper-level low pressure system centered between Bermuda and Puerto Rico. The latest SHIPS model forecast predicts that these winds will cause wind shear to rise to the moderate level, 10 - 20 knots, by Tuesday night, and to the high level, 20 - 30 knots, by Wednesday. There is a great deal of dry air associated with the upper level low that should cause problems for TD 4, as well. The high wind shear and dry air should greatly weaken and may destroy TD 4 late this week. NHC is giving TD 4 a 20% chance of attaining hurricane status by 8am EDT on Thursday. I think the storm will probably become Tropical Storm Colin tonight, and peak in strength on Wednesday as a 55 - 65 mph tropical storm. I agree that a 20% chance of it reaching hurricane strength is a reasonable forecast.

A trough of low pressure is expected to move off the U.S. East Coast on Friday, and this trough may be strong enough to recurve TD 4 far enough to the northwest that the storm will threaten Bermuda. The GFDL model predicts TD 4 could pass very near to Bermuda on Saturday. It is uncertain at this time if the trough will be strong enough to recurve TD 4 all the way out to sea early next week, or leave the storm behind to potentially move westward again into the U.S. East Coast. The amount of wind shear that might be present early next week is also highly uncertain.

Next update
I'll have an update Tuesday morning by 8:30 EDT.

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: 854 - 804

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45Blog Index

Quoting Drakoen:


Oh I am talking about the one in the subtropical atlantic.


But which one in the Subtropical Atlantic? LOL. The dry one looks to be interacting with the TUTT. Could Colin slide under the low like pre-Alex slid under dry air back in June? Or will the ULL erode the upper-level anticyclone that Colin might develop?
Member Since: Posts: Comments:
852. xcool
Link

go here.
Member Since: Posts: Comments:
Quoting sammywammybamy:


What did he do?



posted some in he sound not be posting on the main blog when we have a storm
Member Since: Posts: Comments:
Quoting thelmores:


I tend to agree with you Drak..... I don't see a solution from start to finish of any of the model runs that is totally believable....

At this point, I would not discount any possibilities of track or intensity! I also agree with Storms thinking that the official track will be moving left some......

If I had to guess at this point, 04 "could" make landfall on the east coast somewhere (Florida, Georgia, SC, NC)......

I don't at the moment see a Gulf Solution...... but not buying Fish storm/Bermuda yet either!


Just a question. What would keep this, if it does form into anything, from hitting more Northern regions like VA, Cape Cod..etc?
Member Since: May 28, 2008 Posts: 38 Comments: 5303
849. xcool
Member Since: Posts: Comments:
Quoting Hardcoreweather2010:
So we will have

at 11pm ?



plz dont post that here
Member Since: Posts: Comments:
Quoting Hardcoreweather2010:
So we will have

at 11pm ?



re ported
Member Since: Posts: Comments:
Quoting AstroHurricane001:


Reminds me of those 970 mb lows off the east coast of the US last winter followed by cold fronts and strong high pressure...

You mean a Nor' Easter? =P
Member Since: Posts: Comments:
Quoting SeaMule:


Andrew was a runt...a buzz saw.

this storm may outrace itself....it's moving so fast, perhaps it will lose it's vertical stacking. we'll see. shore looks like a dip westerly to almost wwsw to me.....
Yea, Im the runt in my family of 5 other brothers, and I had to learn how to pack a punch. Being a runt doesnt= weakness
Member Since: Posts: Comments:
Quoting AussieStorm:

a very deep east coast low is the culprit.


Reminds me of those 970 mb lows off the east coast of the US last winter followed by cold fronts and strong high pressure...
Member Since: Posts: Comments:
hahaha coops...now I'm cravin pork chops
Member Since: August 13, 2005 Posts: 163 Comments: 25481
837. xcool
lolol
Member Since: Posts: Comments:
Quoting scott39:
have to keep watching for more model runs to stay the same.


Agree but unlike the CMC at times, GFS doesn't usually conjure systems out of thin air. Quite odd in that never a hint prior to this run.
Member Since: Posts: Comments:
Quoting Drakoen:
Big shift to the right on the HWRF 18z. These models don't have a clue what's going to happen.


I tend to agree with you Drak..... I don't see a solution from start to finish of any of the model runs that is totally believable....

At this point, I would not discount any possibilities of track or intensity! I also agree with Storms thinking that the official track will be moving left some......

If I had to guess at this point, 04 "could" make landfall on the east coast somewhere (Florida, Georgia, SC, NC)......

I don't at the moment see a Gulf Solution...... but not buying Fish storm/Bermuda yet either!

Also would not dismiss that 04 croaks before landfall..... thus a real threat to nobody!
Member Since: September 8, 2005 Posts: 0 Comments: 3788
Quoting Thundercloud01221991:


do you mean TS


Yup. just corrected it. ;)
Member Since: Posts: Comments:
Quoting AstroHurricane001:


I thought that was about the northern low? I mean the one near 25N, 62W.


Oh I am talking about the one in the subtropical atlantic.
Member Since: Posts: Comments:
Quoting AstroHurricane001:


Wow, 68kt!! That's hurricane winds. Cold front coming your way?

a very deep east coast low is the culprit.
Member Since: Posts: Comments:
828. xcool
may be


COLIN
Member Since: Posts: Comments:
Quoting Snowlover123:


Nice spiral bandings! It's almost a TD!


do you mean TS
Member Since: Posts: Comments:
Quoting Tazmanian:



am playing a round lol and sure i will lol


:-)
Member Since: Posts: Comments:
Quoting swlaaggie:
Anyone notice the 18Z GFS? System just off NOLA in 168 hours?

Thoughts?
have to keep watching for more model runs to stay the same.
Member Since: Posts: Comments:
Quoting xcool:




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 02 AUG 2010 Time : 221500 UTC
Lat : 13:05:38 N Lon : 42:49:15 W


CI# /Pressure/ Vmax
2.4 /1005.8mb/ 34.0kt


Final T# Adj T# Raw T#
2.4 2.6 2.8


Nice spiral bandings! It's almost a TS!
Member Since: Posts: Comments:
Quoting scott39:
Bonnie was a runt too!


Andrew was a runt...a buzz saw.

this storm may outrace itself....it's moving so fast, perhaps it will lose it's vertical stacking. we'll see. shore looks like a dip westerly to almost wwsw to me.....
Member Since: Posts: Comments:
Quoting Drakoen:


Post 755


I thought that was about the northern low? I mean the one near 25N, 62W.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting fatlady99:


Umm... will you take a check?



am playing a round lol and sure i will lol
Member Since: Posts: Comments:
Anyone notice the 18Z GFS? System just off NOLA in 168 hours?

Thoughts?
Member Since: Posts: Comments:
Good evening everyone.I see we have TD4 now.And the models are still not sure where it will go as of now.
Member Since: Posts: Comments:
Quoting aquak9:
Corndogs it is, then. Needed an idea myself.

No thanks on the crow, Taz. But the raw fish sounds tasty.

anyone here named Cory?


ROFL - I keep telling you to scrounge through my fridge, Aqua. Still a couple of porkchops, and half a TBone... no more ham though - they killed that one, LOL.
Member Since: Posts: Comments:
814. xcool




UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 02 AUG 2010 Time : 221500 UTC
Lat : 13:05:38 N Lon : 42:49:15 W


CI# /Pressure/ Vmax
2.4 /1005.8mb/ 34.0kt


Final T# Adj T# Raw T#
2.4 2.6 2.8
Member Since: Posts: Comments:
Quoting Tazmanian:



that would be $500 thank you sire for comeing too taz restant plzs come back soon


Umm... will you take a check?
Member Since: Posts: Comments:
TD4 doesn't want to move WNW
Member Since: Posts: Comments:
Quoting DestinJeff:
Are we all doom?

TD4 still so incredibly small out there in the Atl (ocean, not airport). Threat is not obvious as of yet, but perhaps the overnight will bring surprises.
Bonnie was a runt too!
Member Since: Posts: Comments:
Quoting palmbaywhoo:

so if there is a trough pulling td4 out, it would be pulling this sytem across the state?


Not likely, that potential system is too far south/west to feel the trof.
Member Since: Posts: Comments:
Quoting Chicklit:
Hey Aussie,
Great shear maps. Do you have a link for those?


Chicklit,

http://cimss.ssec.wisc.edu/tropic2/real-time/windgridmain.php?&basin=europe&sat=wm7
Member Since: Posts: Comments:
806. CJ5
Quoting weatherman12345:
Im just wondering, is florida out of the question for a landfall by this system as of now


No
Member Since: Posts: Comments:
You got me laughing, Taz!! :)
Member Since: August 13, 2005 Posts: 163 Comments: 25481
Quoting Tazmanian:



raw fish and raw crow would you like some


Sashimi!!! Hand it over!
Member Since: Posts: Comments:

Viewing: 854 - 804

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45Blog 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.