GFS June 4 - 5 low crossing Cuba

[Weatherfreak000]

I don't understand. I'm looking at the current Water Vapor loop and i'm seeing no moderate wind shear impacting the system. However, wind shear to the North of the disturbance looks a little strong but wouldn't that help increase the outflow and fan the system out?

I don't really understand the argument against wind shear maps. I thought them to be highly accurate and consistent. After all, these maps are what the NHC uses to determine the future of system's right? Also, shear looks to be on the decrease in all areas around the system and assuming it moves north to northwest this can only help it right?

I've seen this from here and here, also where is this upper level low you see? I can't determine how shear will be on the increase in this area...

It's a fine line between enhancing outflow and producing unfavorable shear. I'm looking at a 48-hour loop and can see a sharp upper-level trof into the SW Caribbean that is very slowly lifting northward as another trof digs SE into the FL Panhandle (upper low over Midwest). So the digging trof into the NE Gulf is lifting out the trof over the SW Caribbean. This should have the effect of temporarily decrasing the shear but also decreasing the liifting to produce thunderstorms. It'll take a persistent concentration of squalls in one area to develop an LLC. That may be hard to come by.

As for the shear maps, they're only as good as the data that they're initialized with. I've looked at the GFS upper level wind maps many times then compared the flow to water vapor loops to find that the directions on the GFS output were 180 degrees off. There just isn't a lot of good data out over the oceans, so you have to be VERY careful trusting any upper-level wind forecasts (like shear maps) there. A good practice is to look at the 00hr upper wind map and compare it to the current WV loop to see how the model was initialized before even looking at the forecast.

Oh, and no, the NHC doesn't blindly use these shear maps. They know their weaknesses (as I've described above). The NHC forecasters would first make sure that the model being looked at appeard to initialize well.

Understood, I definitely see this system a little worse then I did before. However, I don't see the point your making with these troughs. With all due respect I don't see them. I looked at satelite imagery and I can't spot a trough in the area anywhere. Could you possibly describe the synoptic pattern your expecting a little better?


I mean realistically, how would you place this storm?

[SouthFloridawx]

wxman57, I have a question for you.

Ok looking at the upper level wind maps at 00 hour is good at see what how fast the wind is moving up there. I understand that so far... but, I have a question bout lower level winds. Since a Tropical system is steered by the winds at different levels depending on the height of the storm. For a developing storm wouldn't we want to look at the winds and shear in the lower to mid levels? I mean is a developing storm going to be in the upper atmosphere at 200MB or do we want to look at the 00 hour wind maps for 500mb since it would be closer to the surface?

Tropical Depression - lower levels 850-700mb
Tropical storm - 700-500mb
Hurricanes - 500-200mb

Would you say that the above is a pretty safe assumption or am I incorrect in my thinking?

Any Pro Met or Experience Amateur can chime in on this one.

[SouthFloridawx]

8:05PM TWD

CARIBBEAN SEA...
A MID/UPPER RIDGE DOMINATES THE EASTERN CARIBBEAN FROM A CLOSED
HIGH CENTERED E OF THE LESSER ANTILLES NEAR 14N54W. WESTERLY
UPPER FLOW DOMINATES THE REMAINDER OF THE BASIN. THIS RIDGE IS
LIMITING THE DEVELOPMENT OF CONVECTIVE ACTIVITY OVER PUERTO RICO
AND THE VIRGIN/LEEWARD ISLANDS. A SURFACE TROUGH EXTENDS FROM
20N75W TO A 1009 LOW PRESSURE CENTER LOCATED OVER THE SW
CARIBBEAN NEAR 11N75W. NUMEROUS SHOWERS AND TSTMS ARE ASSOCIATED
WITH THE LOW/TROUGH FROM 13N-17W BETWEEN 74W-80W. SCATTERED
MODERATE CONVECTION IS SEEN OVER JAMAICA...EASTERN CUBA AND
HISPANIOLA IN PART DUE TO LOCAL EFFECTS. THE GFS MODEL TRIES TO
DEVELOP THE LOW OVER THE SW CARIBBEAN INTO A TROPICAL CYCLONE
BUT...OTHER COMPUTER MODELS DO NOT SUPPORT THIS FORECAST.
SCATTERED SHOWERS AND TSTMS ARE OVER THE WINDWARD ISLANDS
TRIGGERED BY THE TROPICAL WAVE ALONG 61W/62W. THE REMAINDER OF
THE CARIBBEAN HAS BROKEN HIGH CLOUD AND ONLY ISOLATED SHOWERS.
15-20 KT TRADE WINDS DOMINATE THE BASIN MAINLY EAST OF 75W.
OF NOTE...MOST OF JUNE STORMS ORIGINATE IN THE GULF OF MEXICO
AND WESTERN CARIBBEAN SEA.

[gatorcane]

are you kidding me? The GFS is wanting to develop it!

Also we are in June - I wouldn't count on a ridge eroding so quickly thus keeping it more westerly than out into the Bahamas...this system bears watching..

[skysummit]

are you kidding me? The GFS is wanting to develop it!

Also we are in June - I wouldn't count on a ridge eroding so quickly thus keeping it more westerly than out into the Bahamas...this system bears watching..

Boca...the GFS has been developing it for the past 36 hours now. There's a front coming through tonight and tomorrow so it'll shunt that bad boy off in the Atlantic like nuttin!

[gatorcane]

yeah I was looking at the water vapor of the EC of the US and that is one heck of a trough digging down. Reminds me of 2004 in June

[bigmike]

yeah I was looking at the water vapor of the EC of the US and that is one heck of a trough digging down. Reminds me of 2004 in June

Hey boca since you and the other enthusiasts in here want a hurricane tell ya what. Next time a cat 4 threatens the us or the islands we'll charter s2k plane and take you there and drop it off so yaall can experience it firsthand and then you can get all of the storm enthusiasm out of your system.

[gatorcane]

Hey boca since you and the other enthusiasts in here want a hurricane tell ya what. Next time a cat 4 threatens the us or the islands we'll charter s2k plane and take you there and drop it off so yaall can experience it firsthand and then you can get all of the storm enthusiasm out of your system

How do you get that I want a hurricane out of what I said?

[MiamiensisWx]

Hey boca since you and the other enthusiasts in here want a hurricane tell ya what. Next time a cat 4 threatens the us or the islands we'll charter s2k plane and take you there and drop it off so yaall can experience it firsthand and then you can get all of the storm enthusiasm out of your system.

Dear Sir,

Sorry for the inconvenience, but this not the complaints office. Transfer your complaint over there in the proper thread. Thank you.

Sincerely,
The Thoughtful Police

Now, back to the topic of this thread... oh, wait, where is it?

[MiamiensisWx]

What I meant is that I think we should stick to the topic of this thread. If you have a problem, bigmike, you can PM one of the moderators or think before you post. It would save a whole lot of energy.



Thank you for putting your issue in the proper thread. You can release your energy there.

[SouthFloridawx]

Quote:
wxman57, I have a question for you.

Ok looking at the upper level wind maps at 00 hour is good at see what how fast the wind is moving up there. I understand that so far... but, I have a question bout lower level winds. Since a Tropical system is steered by the winds at different levels depending on the height of the storm. For a developing storm wouldn't we want to look at the winds and shear in the lower to mid levels? I mean is a developing storm going to be in the upper atmosphere at 200MB or do we want to look at the 00 hour wind maps for 500mb since it would be closer to the surface?

Tropical Depression - lower levels 850-700mb
Tropical storm - 700-500mb
Hurricanes - 500-200mb

Would you say that the above is a pretty safe assumption or am I incorrect in my thinking?


Any Pro Met or Experience Amateur can chime in on this one

[MiamiensisWx]

Back on the topic... even if no development materializes from the far southern Caribbean, I agree with the GFS on that the patterns definately will likely support development of some tropical activity in the Caribbean and, very likely, the BOC soon.

[MiamiensisWx]

Quote:
wxman57, I have a question for you.

Ok looking at the upper level wind maps at 00 hour is good at see what how fast the wind is moving up there. I understand that so far... but, I have a question bout lower level winds. Since a Tropical system is steered by the winds at different levels depending on the height of the storm. For a developing storm wouldn't we want to look at the winds and shear in the lower to mid levels? I mean is a developing storm going to be in the upper atmosphere at 200MB or do we want to look at the 00 hour wind maps for 500mb since it would be closer to the surface?

Tropical Depression - lower levels 850-700mb
Tropical storm - 700-500mb
Hurricanes - 500-200mb

Would you say that the above is a pretty safe assumption or am I incorrect in my thinking?


Any Pro Met or Experience Amateur can chime in on this one

A storm mostly depends on the upper levels in terms of steering. The reason why it is mainly the upper - not lower - levels that contribute to steering an Atlantic tropical cyclone is because many other factors come into play if the steering is lower levels, and that might cause the storm to head through the slightest weakness in the lower levels. Even in the upper levels, it is not entirely foolproof to a storm going through the slightest weakness, as that has happened many times on record. Still, the upper levels can sometimes contribute in steering a tropical cyclone on a more definite note than the lower levels; still, other variables need to be taken in that steer a cyclone and may have more influence than the upper or lower levels (other than troughs and the upper-level/lower-level ridges). Hope that helps.

[JonathanBelles]

Quote:
wxman57, I have a question for you.

Ok looking at the upper level wind maps at 00 hour is good at see what how fast the wind is moving up there. I understand that so far... but, I have a question bout lower level winds. Since a Tropical system is steered by the winds at different levels depending on the height of the storm. For a developing storm wouldn't we want to look at the winds and shear in the lower to mid levels? I mean is a developing storm going to be in the upper atmosphere at 200MB or do we want to look at the 00 hour wind maps for 500mb since it would be closer to the surface?

Tropical Depression - lower levels 850-700mb
Tropical storm - 700-500mb
Hurricanes - 500-200mb

Would you say that the above is a pretty safe assumption or am I incorrect in my thinking?


Any Pro Met or Experience Amateur can chime in on this one

A storm mostly depends on the upper levels in terms of steering. The reason why it is mainly the upper - not lower - levels that contribute to steering an Atlantic tropical cyclone is because many other factors come into play if the steering is lower levels, and that might cause the storm to head through the slightest weakness in the lower levels. Even in the upper levels, it is not entirely foolproof to a storm going through the slightest weakness, as that has happened many times on record. Still, the upper levels can sometimes contribute in steering a tropical cyclone on a more definite note than the lower levels; still, other variables need to be taken in that steer a cyclone and may have more influence than the upper or lower levels (other than troughs and the upper-level/lower-level ridges). Hope that helps.

as can tell by the following question i am an amature, Doesnt mb=millibars, and 200mb is like space pressure, how can that be?

[curtadams]

I expect no cyclone. The GFS is well-known to overestimate in the presence of substantial shear, and you don't even have to look at a shear map to see the shear around Cuba and northwards. The other models, which don't have the GFS's shear bias, are almost certainly right.

[CHRISTY]

Convection continues to flare up in the caribbean.....it will be interesting to see if it persists threw tonight.

[Taffy]

I need a satalite link to this convection, please. Thanks... I am very much an ameature, by the way.

[rockyman]

as can tell by the following question i am an amature, Doesnt mb=millibars, and 200mb is like space pressure, how can that be?

Hey, fact...here are a couple of webpages that explain the different pressures at different levels of the atmosphre:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/prs/prssfc.rxml

http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/pressure_height.rxml?hret=/guides/mtr/fw/prs/prssfc.rxml

You'll have to cut and paste the links...the bulletin board software does not like these urls with parentheses

[skysummit]

I need a satalite link to this convection, please. Thanks... I am very much an ameature, by the way.

Taffy...you can get some here. The "AVN" is probably the most used.
http://www.ssd.noaa.gov/goes/east/watl.html

[Hyperstorm]

I don't understand. I'm looking at the current Water Vapor loop and i'm seeing no moderate wind shear impacting the system. However, wind shear to the North of the disturbance looks a little strong but wouldn't that help increase the outflow and fan the system out?

I don't really understand the argument against wind shear maps. I thought them to be highly accurate and consistent. After all, these maps are what the NHC uses to determine the future of system's right? Also, shear looks to be on the decrease in all areas around the system and assuming it moves north to northwest this can only help it right?

I've seen this from here and here, also where is this upper level low you see? I can't determine how shear will be on the increase in this area...

It's a fine line between enhancing outflow and producing unfavorable shear. I'm looking at a 48-hour loop and can see a sharp upper-level trof into the SW Caribbean that is very slowly lifting northward as another trof digs SE into the FL Panhandle (upper low over Midwest). So the digging trof into the NE Gulf is lifting out the trof over the SW Caribbean. This should have the effect of temporarily decrasing the shear but also decreasing the liifting to produce thunderstorms. It'll take a persistent concentration of squalls in one area to develop an LLC. That may be hard to come by.

As for the shear maps, they're only as good as the data that they're initialized with. I've looked at the GFS upper level wind maps many times then compared the flow to water vapor loops to find that the directions on the GFS output were 180 degrees off. There just isn't a lot of good data out over the oceans, so you have to be VERY careful trusting any upper-level wind forecasts (like shear maps) there. A good practice is to look at the 00hr upper wind map and compare it to the current WV loop to see how the model was initialized before even looking at the forecast.

Oh, and no, the NHC doesn't blindly use these shear maps. They know their weaknesses (as I've described above). The NHC forecasters would first make sure that the model being looked at appeard to initialize well.

Understood, I definitely see this system a little worse then I did before. However, I don't see the point your making with these troughs. With all due respect I don't see them. I looked at satelite imagery and I can't spot a trough in the area anywhere. Could you possibly describe the synoptic pattern your expecting a little better?


I mean realistically, how would you place this storm?

I've never understood the fascination of "blobs" when conditions are outright unfavorable. You can see a trough moving in toward the east from the Yucatan Peninsula this morning. As I said it is moving EAST and that means it will go right through our Caribbean disturbance. One thing is to have strong upper-level winds and the system moving in tandem with those winds, than having winds coming in from another direction than the one the system is heading, just like what we're seeing.

Right now, that trough just east of the Yucatan is serving as an enhancer because it has slightly diminished the upper-level winds over the system. But, guess what? The system is decidedly moving northward and the flow over it will change dramatically soon. Depending on the speed of that trough moving east, means the amount of time of "not as unfavorable conditions" the system will be in. On top of that, the trough over the SE United States is moving east and southeast.

This morning, it is definitely trying to become a little better defined as you can see convection building up over a possible MLC. But, you can also see that the convection is fanning toward the east and southeast. This all means that the time for it to develop a LLC is running out. It will take another 24 hours of persistent convection for a LLC to develop. However, don't be surprised to see the NHC mention this system in their outlooks today due to the potential of heavy rain developing over Jamaica and Cuba.

If something develops (very weak if that happens), it will have to happen in the timeframe of 24-48 hours because once 50+ kts of wind shear start affecting the system, I can only say good luck...

EDIT: Area of visible turning is seen in the extreme SW Caribbean Sea. This means that the area of convection further NE is not the one that we should be looking at. See other Caribbean thread...