97L growing more organized, will bring heavy rain to the Lesser Antilles
The tropical wave near 12N 52W, about 600 miles east of the Lesser Antilles Islands (97 L), has grown more organized this morning as it tracks west at about 20 mph. This wave is surrounded by an area of very dry air from the Sahara Desert, but 97L has been able to steadily moisten a large region of the atmosphere over the past day, insulating itself from the dry air. This moistening process has been aided by sea surface temperatures (SSTs) that have steadily increased from 26.5°C to 27.5°C, plus the presence of only 10 knots of wind shear. The system now has a small area of intense thunderstorms near its center, with some rotation of the cloud pattern evident at mid-levels of the atmosphere. An upper-level outflow channel has opened to the north, and there is evidence that surface spiral bands are beginning to form. This morning's QuikSCAT pass missed 97L, so we don't know what is happening at the surface.
Wind shear is a modest 10 knots over the disturbance, and is forecast to remain in the moderate 10 - 15 knot range through Monday morning. This should allow further development to occur today, and 97L could be approaching tropical depression strength on Monday as it moves through the central Lesser Antilles Islands. Monday night, shear is expected to rise to 20 - 30 knots, thanks to the presence of a trough of low pressure at upper levels of the atmosphere over the eastern Caribbean. Since 97L is a relatively small system, it is very vulnerable to wind shear. This shear may be able to drive some of the dry air west of 97L deep into its interior, significantly disrupting the disturbance. Shear will remain high along 97L's path through Thursday, when the storm should be in the western Caribbean near Cuba. If there is anything left of 97L by then, some development is possible. The National Hurricane Center gave 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours in their 8am Tropical Weather Outlook. However, I'd say the odds are now in the medium range (30 - 50%).
None of the computer models are forecasting tropical storm development over the next seven days.
Figure 1. Current satellite image of African wave 97L.
I'll have an update Monday morning. As 97L approaches the islands, you may want to follow local observations there using our wundermap for 97L.
Jeff Masters
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that map from WU has favorable shear in about 80% of the Atlantic about 95% of the time lol, I have found that it isnt very trustworthy
Will the GHCC site be the first imagery site that gets a view of 97 in rapid scan mode (update every 15min)?
um take a look at the two maps
The one from WU shows red, which on that map is favorable shear throughout the Caribbean for the entire forecast period
The one from CIMSS also shows red by the islands, but that red is unfavorable shear with white lines of inceasing shear of upwards of 20 knots in the last 24 hours.
Same colors on the two maps, two totally different meanings
The calm before the storm ?LOL
Updated: 58 min 33 sec ago
Clear
79 °F
Clear
Humidity: 56%
Dew Point: 62 °F
Wind: 5 mph from the North
Pressure: 30.06 in (Rising)
Visibility: 10.0 miles
Waiting to see if an ESE wind shows up here.
The cimss map shows the shear which is going to be there for a couple of days. The WU forecast map doesn't show shear. The WU forecast map really hasn't been correct since I can remember. It almost always shows good conditions when what actually could be occuring is 100kts of shear.
exactly, CIMSS is much more in depth in terms of shear and how it impacts tropical systems
and I want to thank you and SJ for backing me up on this one lol
we'll see what happens. If convection flares up tomorrow mornig and it continues to look organized like it has been then it will survive the shear. Again you are talking 15-30 kt shear so it could have a 50/50 chance of surviving the shear. When it does survive, it will head into very favorable area (GOM) with hot SST's and low wind shear and a very moist environment then this baby will fire up into a TS, perhaps a cat 1 at strongest at landfall.
Gfs 24 Hours:
Gfs 36 Hours:
Gfs 48 Hours:
First off none of the three of us said the shear would kill it
Second, anyting over 20 knots of shear can definitely kill a tropical system
Third, dont assume where this system is going and where it will find favorable conditions when we dont really know if it will survive the next 24 hours or how shear will be like the next few days.
Slowly but surely it shows that shear is becoming more and more favorable, right?
And yes the point Ike left out is that while we are just over a quarter of the way through The Season™; we still have about 85 percent of the worst portion of The Season™ to go.
That 85% is a guestimate...not sure exactly what it is, but we have a large portion of the worst of it to come was the point.
I'll reiterate a very important meteorological fact that almost no one seems to ever mention. If vertical shear is coming from the direction in which a tropical cyclone (or in this case, a tropical disturbance) is moving, then it will be more detrimental than normal, because it is blowing directly across the circulation center.
This is why Omar was able to intensify into a hurricane despite 20 knots of westerly shear; because it was moving in the direction opposite the shear.
I never said you said shear would kill it i said a 50/50 chance. Maybe i'm getting a little too ahead of myself. we'll just wait and see what happens...
THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHERN
CONNECTICUT...NORTHEAST NEW JERSEY AND SOUTHEAST NEW YORK.
.DAY ONE...TONIGHT.
HAZARDOUS WEATHER NOT EXPECTED AT THIS TIME.
.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY
AN APPROACHING WARM FRONT STALLING SOUTH OF LONG ISLAND COULD
SERVE AS THE FOCUS FOR HEAVY SHOWERS AND THUNDERSTORMS TUESDAY
INTO WEDNESDAY...AS TROPICAL MOISTURE SURGES NORTHWARD AND
OVERRIDES THE FRONT. LOCALIZED URBAN AND FLASH FLOODING
ARE POSSIBLE.
.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED TUESDAY INTO WEDNESDAY.
&&
arrrrrvvvvvvy - where in the world are you now??
Is that the 18z?
I never knew that could happen. Thanks for the educational info.
If a storm is going with the shear it lessens the effect the shear has on the storm. If a storm is going against the shear you have additional directional shear on the storm so the shear is worse.
No, 0z
and based on what I am seeing it is going head on into the shear
That means it's really old...Over 24hrs...
Good point. Thanks. So what is your thoughts for 97L?
That was bad...
http://www.sailwx.info
No buoys, but one ship report of SSW breeze.
That's correct.
If the hurricane (or storm) is going against shear, then it will get ripped apart. If it travels in the same direction as the shear then it won't have as much as an impact on the system.
No it's 0z valid Monday 20 July
Link
and 97L is going against the shear
What I said in different words. LOL
am now out the the watering hole
how is old 97L doing
Mid level shear
you need 200-850mb
Oops. Guess I was wrong. I will search for the correct one.
That's from early this morning. The latest model runs were the 18z. The new 00z is about to come out in a couple hours.
00z=late night/early morning
06z=morning
12z=afternoon
18z=late evening
And in case it sounds like I'm making this up... From the NHC's report on Omar:
One can speculate that the impact of the vertical shear during the second rapid intensification period was mitigated by Omar's motion being in the same direction as the shear vector.
no that is the 12Z from earlier today, it is even in the link
That is not what I heard, but I could have misinterpreted. Doubtful, though.
After all, why does westerly shear often destroy westward-moving tropical waves, and yet they can survive easterly shear?
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