A Gulf of Mexico and an Eastern Atlantic Disturbance Worth Watching

By: Dr. Jeff Masters , 1:53 PM GMT on July 06, 2013

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A tropical disturbance (designated 94L by NHC on Friday) is over the Western Gulf of Mexico, and is headed north towards the Texas/Louisiana coast at 5 - 10 mph. Satellite loops show a modest area of disorganized heavy thunderstorm activity that has been steadily growing this morning. Wind shear has fallen to the moderate range, 10 - 20 knots, since Friday, and the lower wind shear is likely responsible for the increase in thunderstorm activity. A trough of low pressure over the Western Gulf of Mexico is pumping dry air into the west side of 94L, interfering with development. The disturbance should move inland by Sunday morning, bringing heavy rains of 1 - 3" along the Upper Texas and Western Louisiana coasts through Monday morning. None of the reliable forecast models predict that the disturbance will develop, and the disturbance has only a day over water with marginal conditions for development. In their 8 am EDT July 6 Tropical Weather Outlook, NHC gave the disturbance a 20% chance of developing into a tropical depression or tropical storm by Monday.


Figure 1. The Saturday morning NHC Tropical Weather Outlook shows two "Invests" worth watching: 94L over the Gulf of Mexico (area 1), and 95L over the Eastern Atlantic (area 2.) Both were given 20% chances of developing by Monday. Image credit: NHC.

Cape Verdes tropical wave 95L
As we approach mid-July, it's time to begin turning our attention to tropical waves coming off the coast of Africa. We have our first such system worthy of attention today, a tropical wave designated 95L over the Eastern Atlantic near 8°N 33°W, about 800 miles southwest of the Cape Verde Islands. Satellite loops show a modest area of heavy thunderstorms that is showing a moderate amount of spin. Wind shear is moderate, 10 - 20 knots, and ocean temperatures are warm, 28°C. The 8 am EDT Saturday forecast from the SHIPS model predicted that 95L would encounter cooler waters of 27.5°C over the weekend as it headed west to west-northwest at 15 - 20 mph. Wind shear is expected to remain moderate though Monday, which may allow for some additional organization. However, 95L is embedded in a very large area of dry air associated with the Saharan Air Layer (SAL), and July African waves typically have considerable trouble getting organized in the very dry air of the SAL. The disturbance could arrive in the Lesser Antilles Islands as early as Tuesday. A band a strong upper-level winds associated with the subtropical jet stream is expected to be over the northern islands at that time, and if 95L has penetrated as far north as 15°N latitude by that time, it will have to face very high wind shear of 30+ knots. But if 95L stays farther to the south, wind shear should be lower, giving the storm a better chance of development. None of the reliable forecast models predict that 95L will develop. In their 8 am EDT July 6 Tropical Weather Outlook, NHC gave the disturbance a 20% chance of developing into a tropical depression or tropical storm by Monday.


Figure 2. MODIS image of 95L taken at approximately 11 am EDT Saturday, July 6, 2013. Image credit: NASA.

Elsewhere in the tropics
A large upper-level cold-cored low pressure system a few hundred miles north of Puerto Rico will move west over the next dew days, arriving in the Bahamas by Sunday and South Florida by Tuesday. The models do not show that this low will will acquire a surface circulation, and there is only minimal heavy thunderstorm activity associated with it.

In the Eastern Pacific, Tropical Storm Erick is brushing the southwestern coast of Mexico, and is expected to intensify into a Category 1 hurricane on Saturday afternoon. Erick will bring heavy rains of 3 - 5 inches to Southwest Mexico, but the core of the storm is currently expected to remain just offshore. Erick will likely weaken to a tropical storm on Monday, when it will pass just south of Baja.

Cool San Francisco time-lapse fog video
Videographer Simon Christen has created a spectacular 4-minute time-lapse video of fog rushing in past the Golden Gate Bridge into San Francisco. He writes: ""Adrift" is a love letter to the fog of the San Francisco Bay Area. I chased it for over two years to capture the magical interaction between the soft mist, the ridges of the California coast and the iconic Golden Gate Bridge. This is where “Adrift” was born. The weather conditions have to be just right for the fog to glide over the hills and under the bridge. I developed a system for trying to guess when to make the drive out to shoot, which involved checking the weather forecast, satellite images and webcams multiple times a day. For about 2 years, if the weather looked promising, I would set my alarm to 5am, recheck the webcams, and then set off on the 45-minute drive to the Marin Headlands. I spent many mornings hiking in the dark to only find that the fog was too high, too low, or already gone by the time I got there. Luckily, once in a while the conditions would be perfect and I was able to capture something really special. Adrift is a collection of my favorite shots from these excursions into the ridges of the Marin Headlands."


Video 1. Adrift from Simon Christen on Vimeo.

Jeff Masters

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this little guy may be in the next two at 2am or 8am


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1303. whitewabit (Mod)
We won't get a good feel for 95L until the Hurricane Hunters fly the storm and give us better info ..
Member Since: August 17, 2005 Posts: 365 Comments: 31767
Quoting 1297. eyewallblues:
We already have a "vigorous" wave BEHIND 95L. We may need to get a team on that one shortly. 94L is yesterday's news. Cape Verde time, baby!!!






yep this little guy that this came off will need too be watch
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Vorticity is not quite as elongated as earlier. Convergence is tighter now, and is obviously getting some surface lift shown by a comparative amount of divergence aloft. I think this confirms, despite its fast forward speed still, that its trying to cut its moisture umbilical to the Itcz. This may also mean that its gaining some strength and may well have or trying to close a surface circulation. As long as it can keep converging winds streaming in from all sides, create surface lift and divergence aloft, it can get the tropical engine going and build its moisture field protecting it from the dry air. Still needs to slow down though.



Convergence




Divergence
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting 1249. Patrap:
I wish I had a $ for every time I will see this during Hurricane season!!!
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1299. sar2401
Quoting flcanes:
Hello everybody, and I am back after a while of lurking.
Anyways, lets get down to it.
I am going to put in my 2 cents: 95l is going to develop eventually, but i dont know when. Also I want opinions. What do you think is the chance that this hits east florida (namely west palm) ?

I have two opinions.

1. Slim

2. None.

Seriously, let's see if gets above 15N before we start worrying about the east coast of Florida.
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Quoting 1288. sar2401:

Since models want to have it go everywhere from Grenada to North Carolina, I'd guess this system doesn't have a very well defined center of circulation and the models aren't intializing well. Once we have a well defined COC, you can then have a better idea of what's not good at all.


It does have a well define circulation but its not closed but it definately on its way. In anycase the models are in pretty decent agreement for being this early on so We will have to watch it carefully.

8pm Models:




Looks to me that the HWRF may have a general track that fits the potential setup as a trough will dig it out the Caribbean and put it in the Bahamas area. GFS looks to agree in the short term with it. Still too early though.
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We already have a "vigorous" wave BEHIND 95L. We may need to get a team on that one shortly. 94L is yesterday's news. Cape Verde time, baby!!!
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Quoting 1290. Patrap:
Nothing can tell at this time if 95L even survives the Atlantic trek, let alone any CONUS impacts.





Follow the track guidance as always.


Amen. Now for a Fresca...
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Quoting 1281. Hurricanes305:


Looks like a beginning stages of an ULAC is trying to form right over the LLC. Need to watch it closely as if it can become established it will just the thing 95L need once it lifts out the ITCZ to try to close off a low and develop without much shear disrupting it and ventilate to storm Northern and slow down the SAL (dry sinking air)to its N/W.



yep
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Quoting sar2401:Do you mean 94L and 95L? If so, 94L's long term foredast ends tomorrow bettwen 8:00 amd and 2:00 pm, when it will become an inland trough over LA and disappear from the NHC radar screen. 95L may have a chance to develop, but it's at least 48 hours before we know if it has a real chance or will just fade away




Thanks.. I'll be watching invest 95L because I know that until its upgraded to a depression or gets a name, the models are not always reliable..
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94 windin down a little, 95 cruisin' and the ULL headed for S. FL.....


Link
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1292. sar2401
Quoting Camille33:

Another east coast storm looks like as the trough comes in.

Wait a minute, didn't you just say a few days ago that something was going to intensify and flatten some place?
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Quoting 1277. hurricanes2018:
not good at all.


For the Greater Antillies. Landmasses on it's way to the East Coast might stop or hinder strengthening. It might turn out like Emily of 2011.. Or it might be strong when it gets here.
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1290. Patrap
Nothing can tell at this time if 95L even survives the Atlantic trek, let alone any CONUS impacts.





Follow the track guidance as always.
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting 1278. Grothar:
Wow, some of these models are putting Florida ...."In the Cone"



I dont know I think the Models are having gaining quite a bit of latitude I think it stay south of PR and DR and try to thread the needle or cross over Hait/Western Cuba into the Bahamas or Florida straits. where it can really spin up before reaching Florida or the Gulf. I see plenty of comparison to past storms but not much about Issac (2012) in terms of path. But this time track right over South Florida is in play. But that all speculation for now...
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1288. sar2401
Quoting hurricanes2018:
not good at all.

Since models want to have it go everywhere from Grenada to North Carolina, I'd guess this system doesn't have a very well defined center of circulation and the models aren't intializing well. Once we have a well defined COC, you can then have a better idea of what's not good at all.
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Despite its impressive appearance, 95L is lacking a closed surface circulation. Since it remains embedded within the ITCZ and moves at a relatively fast pace due to the strong trade wind flow, it would be extremely difficult for it to develop a closed circulation. In addition, dry air from the SAL would also slow the development. Regardless, 95L will continue to move westward, then gradually turn west-northwestward, and affect the Caribbean islands by the next several days.

Member Since: July 21, 2011 Posts: 83 Comments: 7167
1286. Patrap
PENN ST. E-WALL
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting 1277. hurricanes2018:
not good at all.

Another east coast storm looks like as the trough comes in.
Member Since: July 2, 2013 Posts: 0 Comments: 1523
1284. Grothar
This is is GFS ensemble model. 00Z



Member Since: July 17, 2009 Posts: 71 Comments: 26897
1283. flcanes
Hello everybody, and I am back after a while of lurking.
Anyways, lets get down to it.
I am going to put in my 2 cents: 95l is going to develop eventually, but i dont know when. Also I want opinions. What do you think is the chance that this hits east florida (namely west palm) ?
Member Since: Posts: Comments:
1282. Patrap


Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting 1258. Tazmanian:





Looks like a beginning stages of an ULAC is trying to form right over the LLC. Need to watch it closely as if it can become established it will just the thing 95L need once it lifts out the ITCZ to try to close off a low and develop without much shear disrupting it and ventilate to storm Northern and slow down the SAL (dry sinking air)to its N/W.
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Comment 1274, yes but it's the smaller storms who strenghten typically faster.
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1279. sar2401
Quoting lurkersince2008:
What is the long term forecast for the two disturbances ?

Do you mean 94L and 95L? If so, 94L's long term forecast ends tomorrow between 8:00 and 2:00 pm, when it will become an inland trough over LA and disappear from the NHC radar screen. 95L may have a chance to develop, but it's at least 48 hours before we know if it has a real chance or will just fade away.
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1278. Grothar
Wow, some of these models are putting Florida ...."In the Cone"

Member Since: July 17, 2009 Posts: 71 Comments: 26897
not good at all.
Member Since: March 12, 2013 Posts: 50 Comments: 82401
1276. Patrap
The Diurnal Cycle in the Tropics

Gui-Ying Yang and Julia Slingo
Centre for Global Atmospheric Modelling, Department of Meteorology, University of Reading, Reading, United Kingdom

Abstract
A global archive of high-resolution (3-hourly, 0.5° latitude–longitude grid) window (11–12 μm) brightness temperature (Tb) data from multiple satellites is being developed by the European Union Cloud Archive User Service (CLAUS) project. It has been used to construct a climatology of the diurnal cycle in convection, cloudiness, and surface temperature for all regions of the Tropics. An example of the application of the climatology to the evaluation of the climate version of the U.K. Met. Office Unified Model (UM), version HadAM3, is presented.

The characteristics of the diurnal cycle described by the CLAUS data agree with previous observational studies, demonstrating the universality of the characteristics of the diurnal cycle for land versus ocean, clear sky versus convective regimes. It is shown that oceanic deep convection tends to reach its maximum in the early morning. Continental convection generally peaks in the evening, although there are interesting regional variations, indicative of the effects of complex land–sea and mountain–valley breezes, as well as the life cycle of mesoscale convective systems. A striking result from the analysis of the CLAUS data has been the extent to which the strong diurnal signal over land is spread out over the adjacent oceans, probably through gravity waves of varying depths. These coherent signals can be seen for several hundred kilometers and in some instances, such as over the Bay of Bengal, can lead to substantial diurnal variations in convection and precipitation.

The example of the use of the CLAUS data in the evaluation of the Met. Office UM has demonstrated that the model has considerable difficulty in capturing the observed phase of the diurnal cycle in convection, which suggests some fundamental difficulties in the model’s physical parameterizations. Analysis of the diurnal cycle represents a powerful tool for identifying and correcting model deficiencies.

Received: March 6, 2000; Revised: August 22, 2000

Corresponding author address: Prof. Julia Slingo, CGAM, Department of Meteorology, University of Reading, Earley Gate, Whiteknights, Reading RG6 6BB, United Kingdom.

Email: j.m.slingo@reading.ac.uk
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting 1269. lurkersince2008:
What is the long term forecast for the two disturbances ?
Member Since: March 12, 2013 Posts: 50 Comments: 82401
1274. L1990
am i the only one noticing how tiny the 95l is lol... storms csn always grow... but right now since its so small it better prey for perfect conditions... it wouldnt take much to fizzle it out like a drop of water on the tip of s lite cigarette
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Looks like the DMAX is getting started.
Member Since: June 11, 2013 Posts: 20 Comments: 3351
Quoting 1229. stormpetrol:
Storms that low in Latitude rarely make it to the East Coast or recurve, they usually go through the Caribbean and end up in Central America or the Gulf Coast or Florida Panhandle , just sayin...


Hurricane Hazel 1954 just came to mind...as well as Tomas, 2010.
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1271. Patrap
Reading the above entry a good place to start
Member Since: July 3, 2005 Posts: 426 Comments: 129093
1270. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
What is the long term forecast for the two disturbances ?
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Appears the GFS likes the wave behind 95L more....


Member Since: September 23, 2005 Posts: 14 Comments: 11274
1267. Patrap
AL 95 Dvorak Image

Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting 1260. Jwd41190:


Yeah it was a pretty ugly storm.
I had Hurricane Hugo as my avatar from time I joined until few weeks ago because my mom survived it.
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According to this 95L hits South America.

Member Since: August 2, 2011 Posts: 0 Comments: 2108
1264. Patrap
94L still on the FNMOC page


FNMOC Satellite Data Tropical Cyclone Page

2013 Storms
All Active Year

Atlantic
green ball95L.INVEST
green ball94L.INVEST

East Pacific
green ball05E.ERICK
green ball04E.DALILA

Central Pacific

West Pacific
green ball92W.INVEST

Indian Ocean

Southern Hemisphere
Member Since: July 3, 2005 Posts: 426 Comments: 129093
A good chart to keep handy now that we are breaking out the Dvorak T-Numbers. For those not familiar with how the numbers translate in terms of structure:

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Confused me because the Navy site had 94L missing.
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Quoting 1257. Patrap:
Negative, 94L still a active invest



the atcf has not updated 94L since 12:39pm so there for i think its on it way of being deactivated
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Quoting 1245. Patrap:
Hugo hit in Sept

Total fatalities: 61

Highest winds: 162 mph (260 km/h)

Lowest pressure: 918 mb

Date: September 9, 1989 – September 25, 1989
Category: Category 5 Hurricane (SSHS)


Yeah it was a pretty ugly storm.
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20130706 2345 7.8 36.2 T1.0/1.0 95L 95L
20130706 1745 8.4 34.7 T1.0/1.0 95L 95L
Member Since: March 12, 2013 Posts: 50 Comments: 82401



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1257. Patrap
Negative, 94L still a active invest

All active Floaters

Member Since: July 3, 2005 Posts: 426 Comments: 129093
20130706 2345 7.8 36.2 T1.0/1.0 95L 95L
20130706 1745 8.4 34.7 T1.0/1.0 95L 95L the invest 95L MOVE TO THE SOUTH,
Member Since: March 12, 2013 Posts: 50 Comments: 82401
Was 94L deactivated?
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Quoting 1210. washingtonian115:
Now I asked my daughter where did she find the character in my avatar.She gave me this link since people have been e-mailing me about it.Don't laugh at something because it is different or else I'll put the evil clowns on you.

Link
I prefer DBZ and DBGT
Quoting 1231. washingtonian115:
Good.
Quoting 1231. washingtonian115:
Good.
Fof you not for me.Even though I am sure it will not affect CA.
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About

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