New disturbance 94L a threat to the Lesser Antilles

By: Dr. Jeff Masters , 3:51 PM GMT on July 13, 2008

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A tropical wave midway between Africa and the Lesser Antilles Islands has become organized enough this morning to be classified as a threat area (Invest 94L) by NHC. This morning's QuikSCAT pass missed the disturbance, but last night's pass revealed 94L's large, elongated circulation near 9N 35W. Visible satellite loops show this circulation getting better defined this morning, although there is not yet much organized heavy thunderstorm activity. The disturbance is embedded in a large area of tropical moisture, and 94L should be unaffected by dry air or Saharan dust over the next few days. Water temperatures are favorable for development--27.5°C. Wind shear is favorable for development--10 knots.


Figure 1. NHC's graphical tropical weather outlook for Sunday Jul 13 2008 at 8 am EDT. Area "1" is Invest 94L. Image credit: NHC.

The forecast for 94L
NHC is giving 94L a medium 20-50% chance of developing into a tropical depression by Tuesday morning. Wind shear is expected to remain low, less than 10 knots, for the next four days, and the water temperatures will be plenty warm enough to support development. Three of the four global models we trust predict 94L will develop into a tropical depression. The ECMWF develops it and puts 94L into the Lesser Antilles islands on Saturday. The UKMET model does not develop it, but also puts it into the Lesser Antilles islands on Saturday. The GFS develops it but foresees that Bertha will be close enough and strong enough to pull 94L north of the Lesser Antilles about, 6-8 days from now. The NOGAPS model is much slower, and does not foresee a threat to the Lesser Antilles this week. In summary, there is the potential for a tropical depression to form later this week from 94L, and residents of the Lesser Antilles should anticipate the possibility of tropical storm conditions affecting the islands by Saturday.

Bertha
Tropical Storm Bertha stayed too long in one spot, and has churned up so much cold water from the depths that it has weakened to a tropical storm. Visible satellite loops still show a large and well-developed circulation, and the storm does have the potential to re-intensify if it can move away from the cold water it upwelled. However, the steering currents are very weak and are expected to remain so for several more days, making it unlikely Bertha can find any warm water. The outer spiral bands of Bertha are very close to Bermuda (see links below), and the storm is now visible on Bermuda radar. Bertha spent six days as a hurricane, making it the fourth longest-lived July hurricane on record (Emily of 2005 holds the record, at seven days). Bertha has been a named storm for 10 days, and will easily break the record for longest-lived July named storm (12 days).

Links to follow:
Bermuda radar
Current weather at Bermuda
Bermuda WebCam

High surf of 12-18 feet is expected to affect Bermuda through Monday, according to the Bermuda Weather Service. There is about a 64% chance the island will experience sustained winds of tropical storm force (39 mph), according to the latest tropical storm wind probability forecast by NHC. Given the very weak steering currents predicted to affect Bertha through Tuesday, the storm could easily approach closer to the island than the current official forecast.

South Carolina disturbance
A small low pressure system has developed off the coast of South Carolina at the tail end of an old cold front. This morning's QuikSCAT pass shows the circulation quite clearly, as do visible satellite loops. The low is too small to develop quickly, and is under about 20 knots of wind shear, which should also keep any development slow. The low is expected to move northeast, parallel to the coast.

My last blog entry until Saturday
This will be my last blog entry for five days (until Saturday). I'm headed to Lake Michigan for some camping and vacation. If you happen to be in Mackinaw City Tuesday night, be sure to catch the Straits Area Concert Band in Concert at 8pm at the band shell by Lake Huron. My dad and I will be in the trombone section, puffing our way through the band's usual assortment of Sousa marches, Gershwin medleys, and patriotic fare.

In my absence, our guest tropical blogger, Bryan Woods, will be doing my blog this week. Bryan has done a great job over the past three years blogging on the tropics over at thestormtrack.com. Here's Bryan's bio:

Bryan received his BS in Meteorology from the University of Massachusetts in Lowell, MA in 2005, and his M.Phil. in Geology & Geophysics from Yale University in New Haven, CT in 2007. Bryan is currently a Ph.D. candidate at Yale where he is also the graduate and professional student body president.

Bryan has spent two summers working on a National Science Foundation (NSF) sponsored field micrometeorological research project in Atlanta, GA, studying evapotranspiration rates in urban forest canopies. Currently, Bryan's research is focused on combining wavelet techniques and aircraft data from the NSF/NCAR Gulfstream V to diagnose energy and momentum fluxes from atmospheric gravity waves. Bryan has spent the past three hurricane seasons writing blogs on the tropics for thestormtrack.com.

Jeff Masters

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1624. WeatherfanPR
7:12 PM GMT on July 14, 2008
14/1745 UTC 12.1N 43.1W T2.0/2.0 94L -- Atlantic Ocean
Member Since: August 23, 2006 Posts: 0 Comments: 1592
1623. wxpaladin
11:29 AM GMT on July 14, 2008
I'm not entirely new IKE....I'm atleast 2 weeks older than some LOL :P
Member Since: June 29, 2008 Posts: 0 Comments: 19
1622. stoormfury
11:19 AM GMT on July 14, 2008
94L continues on a westtrack
after reviewing early morning visible and rgb loops of the system it now appears thar llc is at 9.0 n 41.0w and moving at 15 mph. recentQS does not show a closed circulation but showed winds under TD status, recently there has been a burst of convection near the low centre. 94L is encloed in an envelope of moisture and will have no problem with dry air. wind shear is very low which willallow 94L to slowly organised and the system could be clssified as a TD late today or as early tomorrow.
now fot the track of system, 94l will move westward or slightly north of west for the next few days before getting to the centaral windward islands.as a strong ts or cat one hurricane. wed night into thursday. the islands from st vincent northwards to the leewards should monitor the movement of this developing system which when it develops will be christened CRISTOBAL
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1621. IKE
11:03 AM GMT on July 14, 2008
New blog folks......
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1620. heretolearninPR
11:02 AM GMT on July 14, 2008
1617. I think the information about 94L will be in the 8am TWO.
Member Since: August 19, 2006 Posts: 0 Comments: 229
1619. sporteguy03
11:02 AM GMT on July 14, 2008
1607 What are you talking about, climotology has nothing to do with 94L conditions.
Member Since: July 7, 2005 Posts: 0 Comments: 5417
1617. Bobbyweather
10:59 AM GMT on July 14, 2008
Hmm... I can't find a Tropical cyclone Guidance Message for 94L...possibly a special advisory upgrade??
Member Since: September 7, 2006 Posts: 91 Comments: 2679
1616. aubiesgirl
10:54 AM GMT on July 14, 2008
1615....Isn't there some dry air affectng it or did i misunderstand?
1615. HurricaneMaryJane
10:52 AM GMT on July 14, 2008
Quoting aubiesgirl:
1606,,so is that sign of weakening,strengthing ,or what?


Strengthening =/...but this is what always happens to an invest destined to become a TS. Conditions are favorable for this thing, and I have a feeling it's going to take advantage of it.
1614. aubiesgirl
10:52 AM GMT on July 14, 2008
1613..what are you "crowing" about?...lol
1612. gwadaman
10:44 AM GMT on July 14, 2008

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON JUL 14 2008

...SPECIAL FEATURE....


STRONG TROPICAL WAVE IS ALONG 40W S OF 16N MOVING W 15-20 KT. A
1008 MB LOW IS ANALYZED ALONG THE AXIS NEAR 9N. SATELLITE IMAGES
SHOWS A LARGE WELL DEFINED ENVELOPE OF CYCLONIC TURNING...
FOCUSED NEAR THE LOW CENTER. AN AREA OF SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS N OF THE LOW CENTER FROM 9N-13N
BETWEEN 36W-43W. FURTHER S...SCATTERED MODERATE TO STRONG
CONVECTION
IS FROM EQ-5N BETWEEN 33W-41W. THIS SYSTEM HAS THE POTENTIAL TO
BECOME A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 59W/60W S OF 17N MOVING W 15-20 KT.
SYNOPTIC OBSERVATIONS FROM TRINIDAD AND TOBAGO...BARBADOS...ST
LUCIA AND OTHER ISLANDS ALL SHOW 24-HR PRES FALLS OF ABOUT 3 MB
DUE TO THE APPROACH OF THE WAVE. THIS FEATURE HAS BEEN WELL
DEFINED FOR THE PAST COUPLE OF DAYS BASED ON THE MIMIC-TPW
ANIMATION. SCATTERED SHOWERS WITH EMBEDDED ISOLATED MODERATE
CONVECTION IS OVER THE WINDWARD ISLANDS FROM 11N-14N BETWEEN
61W-65W.
Member Since: July 8, 2007 Posts: 0 Comments: 147
1611. KYhomeboy
10:39 AM GMT on July 14, 2008
climatology should be used as a guideline as to where / where not to expect development at a given time. But as we know...that often means nada
1610. aubiesgirl
10:38 AM GMT on July 14, 2008
1606,,so is that sign of weakening,strengthing ,or what?
1609. nrtiwlnvragn
10:37 AM GMT on July 14, 2008
Looks like an elongated circulation, WSW to ENE. Link
Member Since: September 23, 2005 Posts: 15 Comments: 11465
1608. wxpaladin
10:35 AM GMT on July 14, 2008
Has anyone noticed that Bertha seems to be taking on some extra-tropical characteristics? ...Maybe this will be short-term as Bertha interacts with the High and the trough to it's N and E??
Member Since: June 29, 2008 Posts: 0 Comments: 19
1606. HurricaneMaryJane
10:33 AM GMT on July 14, 2008
Morning everyone!

It seems as if 94l has lost some convection but has become more organized in return. Throughout the day we should see more convection flare up. Depression by tonight is very likely...
1605. breald
10:31 AM GMT on July 14, 2008
I thought it was strange they did not mention it. They talked about Bertha though..
Member Since: May 28, 2008 Posts: 38 Comments: 5303
1604. stoormfury
10:29 AM GMT on July 14, 2008
Looking at the RGB and VISIBLE loops this morning there are two low cntres spinning in 94L. the one at 9N 41.5W is the stroger of the two. the other is at 11.0N 41.0W.
convection has increase with the one at 9.0n 41.0W while the low centre at 11.0n 41w is showing signs of weakening. my thoughts are that the stronger of the two will prevail
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1603. InTheCone
10:27 AM GMT on July 14, 2008
Local Mets. here in WPB Fl. have been mentioning it for the last couple of days, but just in terms of it being a system that might develop.

BBL
Member Since: September 1, 2007 Posts: 0 Comments: 1990
1602. InTheCone
10:23 AM GMT on July 14, 2008
1597.

Just click on the storm 94 tab on the top of the page - sorry about that!
Member Since: September 1, 2007 Posts: 0 Comments: 1990
1601. IKE
10:22 AM GMT on July 14, 2008
Quoting breald:
I just watched the local weather and they did not mention 94L at all. Is it losing its steam?


TWC mentioned it.

Looks like dry-air or SAL is affecting it.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1600. breald
10:19 AM GMT on July 14, 2008
I just watched the local weather and they did not mention 94L at all. Is it losing its steam?
Member Since: May 28, 2008 Posts: 38 Comments: 5303
1599. IKE
10:19 AM GMT on July 14, 2008
Quoting InTheCone:
SFWMD spaghetti models - looks like 94l could be heading for the islands. Looks a bit more southerly than last night??

Link


You're right...they have.

Curious why the GFS seems to have dropped 94L? Did someone spike my coffee this morning? Did I sleep too long and miss something? LOL!
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1598. sullivanweather
10:14 AM GMT on July 14, 2008
If anyone is interested...

Early morning tropical synopsis issued in my blog. Complete Bertha/94L forecast as of 3am
Member Since: March 8, 2007 Posts: 273 Comments: 12612
1597. stoormfury
10:13 AM GMT on July 14, 2008
1594
wrong link
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1596. stoormfury
10:12 AM GMT on July 14, 2008
456 correction 41W
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1595. IKE
10:11 AM GMT on July 14, 2008
Looks like the GFS has dropped 94L.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1594. InTheCone
10:10 AM GMT on July 14, 2008
SFWMD spaghetti models - looks like 94l could be heading for the islands. Looks a bit more southerly than last night??

Link
Member Since: September 1, 2007 Posts: 0 Comments: 1990
1593. Cavin Rawlins
10:08 AM GMT on July 14, 2008
and 94L circulation is rather broad, despite the impressive curvature of the convection.

be back later
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1592. Cavin Rawlins
10:07 AM GMT on July 14, 2008
1590. stoormfury 5:59 AM AST on July 14, 2008
456
THERE APPEARS TO BE TWO LOW CEnTRES IN 94l
one at 11.0N AND 49W THE OTHER AT 9.2N 41.5 W
HAVE YOU SEEN THAT?


I havnt seen that since I have few visible images to work with but I can determined a center near 11.1N/41W.


49W is well out of reach of 94L
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1591. apocalyps
10:04 AM GMT on July 14, 2008
94L is headed for the carribbean.
Luckely for the US shear is very high over there.
Member Since: May 10, 2007 Posts: 0 Comments: 960
1590. stoormfury
9:59 AM GMT on July 14, 2008
456
THERE APPEARS TO BE TWO LOW CEnTRES IN 94l
one at 11.0N AND 49W THE OTHER AT 9.2N 41.5 W
HAVE YOU SEEN THAT?
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1589. Cavin Rawlins
9:54 AM GMT on July 14, 2008
Impressive...a it organizes some more today...we should have a TD anytime...but a big change from 48 hours ago.


Member Since: July 24, 2005 Posts: 407 Comments: 19076
1588. stoormfury
9:50 AM GMT on July 14, 2008
navy has 94L at 11N 40.5W but it looks more like 9N 41.4W

Link
Member Since: August 22, 2006 Posts: 0 Comments: 2733
1587. KYhomeboy
9:43 AM GMT on July 14, 2008
Yes...cloud tops have warmed some but the circulation has clearly tightened and overall structure improved. If the NHC don't upgrade it this time around....they soon will once it can maintain deep convection long enough. Looked more impressive a few hours ago but it will continue to fluctuate as all systems like this do.
1586. SCwannabe
9:41 AM GMT on July 14, 2008
This is for the experts. which models are considered the most reliable? Thanks
Member Since: August 14, 2007 Posts: 0 Comments: 535
1585. HadesGodWyvern (Mod)
9:39 AM GMT on July 14, 2008


Hmm if 094 AL looks like that, I sort of see why the NHC didn't bother to designate it 03L..
Member Since: May 24, 2006 Posts: 54 Comments: 48528
1584. GetReal
9:38 AM GMT on July 14, 2008
94L has been tracking almost due west for the last 5 or 6 hours that I have been watching it, along 11N.
Member Since: July 4, 2005 Posts: 204 Comments: 8898
1583. KYhomeboy
9:36 AM GMT on July 14, 2008
Does anyone see a northerly component in 94L? Maybe I'm wrong...but looks due west to me....although a couple of frames from a visible loop would really help to confirm or reject that.
1582. GetReal
9:35 AM GMT on July 14, 2008
The first daylight satellite photographs indicate that 94L has become much better organized. Impressive banding... Clearly IMO 94L is now a TD and on the way to becoming a TS.
Member Since: July 4, 2005 Posts: 204 Comments: 8898
1581. HadesGodWyvern (Mod)
9:34 AM GMT on July 14, 2008
probably has to wait since the Dvorak Intensity was only 1.0 near 6:00 AM UTC. Then again Berth is analysed at 2.5 and the NHC gave it 55 knots.
Member Since: May 24, 2006 Posts: 54 Comments: 48528
1580. SCwannabe
9:32 AM GMT on July 14, 2008
Link

latest visible satellite image of 94L

Looks like it can't figure out where it wants the COC.
Member Since: August 14, 2007 Posts: 0 Comments: 535
1579. GetReal
9:30 AM GMT on July 14, 2008
Still no new advisory out from NHC... There has to be an upgrade to 94L involved.
Member Since: July 4, 2005 Posts: 204 Comments: 8898
1578. HadesGodWyvern (Mod)
9:26 AM GMT on July 14, 2008


JMA TROPICAL DEPRESSION






Tropical Depression (08W/HELEN/NONAME)
Member Since: May 24, 2006 Posts: 54 Comments: 48528
1577. GetReal
9:20 AM GMT on July 14, 2008
IMO the latest advisory is late probbly due to NHC upgrading 94L to a TD.... Getting the graphics together, etc...
Member Since: July 4, 2005 Posts: 204 Comments: 8898
1576. HadesGodWyvern (Mod)
9:18 AM GMT on July 14, 2008
The tropical cyclone discussion for TS Bertha has her near hurricane status again (60 knots)...
Member Since: May 24, 2006 Posts: 54 Comments: 48528
1575. HadesGodWyvern (Mod)
9:17 AM GMT on July 14, 2008
anyway.. The Japan Meteorological Agency has upgraded the sustained winds of 95W to 30 knots.

WWJP25 Tropical Weather Summary

TROPICAL DEPRESSION 1006 HPA
AT 23.8N 136.0E SEA SOUTH OF JAPAN MOVING NORTHNORTHWEST SLOWLY.
POSITION POOR.
MAX WINDS 30 KNOTS NEAR CENTER.
Member Since: May 24, 2006 Posts: 54 Comments: 48528
1574. SCwannabe
9:16 AM GMT on July 14, 2008
Quoting HadesGodWyvern:
1565. Bobbyweather 8:56 AM GMT on July 14, 2008
Why is NHC not issuing advisories on Bertha (or TD 3)? It's 5 min before 5.

---
they updated Elida first.. LOL

NHC are busy people with two or three system to write summaries for now.

I think they fell asleep!
Member Since: August 14, 2007 Posts: 0 Comments: 535

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