Invest 91L Bringing Heavy Rains to Florida, Cuba, and Mexico

By: Dr. Jeff Masters , 3:44 PM GMT on June 03, 2013

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The Atlantic hurricane season began on June 1, and we already have a threat to discuss. A trough of low pressure has developed over the Western Caribbean, Mexico's Yucatan Peninsula, and Southeast Gulf of Mexico, and is dumping heavy rains over the area. Hurricane Barbara, which died on Thursday as it attempted to cross Mexico's Isthmus of Tehuantepec into the southernmost Gulf of Mexico, has contributed moisture to this disturbance, which has been designated 91L by NHC. Satellite loops show a large area of heavy thunderstorms with poor organization, and there is no evidence of an organized surface circulation trying to form. Wind shear is a high 30 knots, and is forecast to remain high, 20 - 30 knots, over the next five days, so any development should be slow to occur. NHC is giving the disturbance a 20% chance of developing into a tropical cyclone by Wednesday. The Hurricane Hunters are on call to fly into 91L on Tuesday afternoon, if necessary. Regardless of whether or not 91L develops into a tropical depression, heavy rains will be the storm's main threat. Mexico's Yucatan Peninsula, Western Cuba, and South Florida can expect 5 - 8" of rain from the disturbance over the next four days. Heavy rains from 91L may spread up the U.S. East Cost late this week. The computer models predict that 91L should stay large and poorly organized, and if it does develop, it will be difficult for it to get any stronger than a 45 mph tropical storm in the Gulf of Mexico.


Figure 1. Latest satellite image of Invest 91L.

Jeff Masters

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Quoting sar2401:

Hi Nigel. How are things in paradise?

The weather is pretty good, but the economy is not doing too well.
Member Since: November 6, 2010 Posts: 11 Comments: 7849
Quoting sar2401:

There will likely be many more views than we have available today since phased array radar is able to look at very small areas and stay focused on them for as long as needed. If you take a look at the picture of the Arleigh Burke class destoyer, you'll notice those white polygons on either side of the foreward superstructure. Those are phased array panels, and there are two more on the aft superstructure. If you know anything about naval vessels, the striking thing is how few other radar antennas are on this vessel. That's because the phased array radar is able to do almost every task that took multiple radars before. They can do everything from normal collision avoidance to targeting multiple incoming tagets, all at the same time, since the beams are controlled by computers and are able to assess threats almost instantly. A very simplified form of this MPAR is what was being used at OKC. If the NWS had the money it took to build one Arleigh Burke class destroyer, we could have these radars all over the country...but don't hold your breath.
Dang, that's pretty impressive that a single radar can do almost everything. You're right, NWS don't have that big of budget and they probably won't install these MPARs for awhile (until at least 2020 according to couple sources). The funny thing is after the tornadoes in 2011 and Hurricane Sandy fiasco, the general public were upset that the meteorologists were not well prepared and that we need more researching done to improve the forecasts, warnings, and stuff. The truth is that NWS, NOAA, or NHC had all kind of research being done but they can't go much forward due to budget tightness. Pretty much lose-lose for NOAA in the press. Also explain why it took so long before meteorologists were able to have dual-pol like you said even though they researched it and developed it decades ago. Pretty frustrating, but I guess scientists learn to deal with it.
Member Since: August 1, 2011 Posts: 28 Comments: 7902
Quoting moonlightcowboy:


There are some really smart cookies on this blog, and several can give you some great meteorological answers. I'm old school, can share what I know, but it won't be sophisticated, mind you. :)

Use this chart. Good one to work with.



Click on the vorticity layers. You'll see 800mb and 700mb levels - these are generally considered the low-levels, and 800mb is used most to help discern if there is a rotating surface low. The 500mb level is consider the mid-level, and is generally the layer that Sarahan dust reside especially out in the MDR (main development region) of the Atlantic. 200mb would then be the upper levels.

Generally, winds are always a bit slower at the surface than the upper levels. This is mostly due to simple friction with the earth's surface, although they can be still fairly strong and non-conducive to development.

Convection? Hhhmm, best straight-away answer is simple evaporation. The hotter it gets the more evaporation you have - the mid and upper level environments become more moist. Cyclogenesis basically has to have three things: 1. Warm water fuel, 2. Building convection overhead in the layers, 3. Colliding cool and warm air (rising and falling) that helps to create the rotation which ultimately gets the tropical engine going.

Now, these other folks, good smart folks, can give you a more detailed answer, but that's basically it. :)
I like old school. I still use the Beaufort scale quite a bit.B eaufort wind force scale
Specifications and equivalent speeds Beaufort wind scale Mean Wind Speed Limits of wind speed Wind descriptive terms Probable wave height in metres* Probable maximum wave height in metres* Seastate Sea descriptive terms
Knots ms-1 Knots ms-1
0 0 0 <1 <1 Calm - - 0 Calm (glassy)
1 2 1 1%u20133 1-2 Light air 0.1 0.1 1 Calm (rippled)
2 5 3 4%u20136 2-3 Light breeze 0.2 0.3 2 Smooth (wavelets)
3 9 5 7%u201310 4-5 Gentle breeze 0.6 1.0 3 Slight
4 13 7 11%u201316 6-8 Moderate breeze 1.0 1.5 3%u20134 Slight%u2013Moderate
5 19 10 17%u201321 9-11 Fresh breeze 2.0 2.5 4 Moderate
6 24 12 22%u201327 11-14 Strong breeze 3.0 4.0 5 Rough
7 30 15 28%u201333 14-17 Near gale 4.0 5.5 5%u20136 Rough%u2013Very rough
8 37 19 34%u201340 17-21 Gale 5.5 7.5 6%u20137 Very rough%u2013High
9 44 23 41%u201347 21-24 Severe gale 7.0 10.0 7 High
10 52 27 48%u201355 25-28 Storm 9.0 12.5 8 Very High
11 60 31 56%u201363 29-32 Violent storm 11.5 16.0 8 Very High
12 - - 64 33 Hurricane 14 - 9 Phenomenal

*

These values refer to well-developed wind waves of the open sea.
The lag effect between the wind getting up and the sea increasing should be borne in mind.
To convert knots to mph multiply by 1.15, for m/s multiply by 0.514.


T his is a photograph of a 19th century portrait painting. It was copied from the website of the UK National Maritime Museum ...WIKI..The scale was devised in 1805 by Francis Beaufort (later Rear Admiral Sir Francis Beaufort), an Irish Royal Navy officer, while serving on HMS Woolwich. The scale that carries Beaufort's name had a long and complex evolution from the previous work of others (including Daniel Defoe the century before) to when Beaufort was a top administrator in the Royal Navy in the 1830s when it was adopted officially and first used during the voyage of HMS Beagle under Captain Robert FitzRoy, later to set up the first Meteorological Office (Met Office) in Britain giving regular weather forecasts. In the early 19th century, naval officers made regular weather observations, but there was no standard scale and so they could be very subjective %u2013 one man's "stiff breeze" might be another's "soft breeze". Beaufort succeeded in standardizing the scale.
Sir Francis Beaufort

The initial scale of thirteen classes (zero to twelve) did not reference wind speed numbers but related qualitative wind conditions to effects on the sails of a frigate, then the main ship of the Royal Navy, from "just sufficient to give steerage" to "that which no canvas sails could withstand".
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Quoting zampaz:

Thanks for your help! I try not to be a distraction with dumb questions, like why levels are given by pressure (mb) instead of feet or meters above sea level. There is so much to learn just to follow along with the discussions, I try to spend a lot of time on wikimedia and google, but sometimes I get lazy and ask real people.
-z

Everyone on here is a lot smarter than me, but


Old School Rule: No such thing as a bad question! Just dumb answers! Don't be afraid to ask, and someone here will be helpful, promise. I've learned very much here! And, still learning too! Jump in - the water's fine! :)
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Well- another day, another heavy rain storm - gotta go check on the roof - sigh - heavy rains possible till Saturday -
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Shows same as ASCAT in #433

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441. Mikla
Quoting Patrap:
91L Multiplatform Satellite Surface Wind Analysis

You can see something similar on ASCAT and OSCAT
Member Since: October 13, 2006 Posts: 0 Comments: 286
Quoting anotherwrongyear:
by tommorow there might not even be a invest at all just some sheared rain showers hitting panhandle
its changed 6 times already since yesterday so why not

Indeed. There's also a chance I could be struck by a meteorite. I was mulling over that possibility earlier today but decided to go outside anyway.
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Quoting Luisport:
My friend do you have more updates on German Floods? Thank's!

Yes, I'm following multiple threads on a german weatherblog, but the situation in those widespread areas is too complicated to be posted on WU in detail. Situation in the Czech Republic seems to be serious. Some pics and a recent overview are here (coverage in English media is a bit slow, but this one is already from tomorrow :-)

Ten dead, thousands evacuated as floods sweep Europe
AFP, June 04, 2013 5:35AM

In Germany they are very concerned about the River Elbe and it's towns tomorrow (f.e. Magdeburg). A lot of emergency alerts, several villages are already abandoned.

New thunderstorms are right now moving in at the eastern border of our country to boot.

Tomorrow morning I'll go to our Rhine River when the waters will reach the maximum (but without danger for my town). They've already flooded some polder areas nearby in order to achieve some relief for the towns down the river.


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Quoting JNTenne:
Too Funny! (the article Comments) I did not realize Caymanians where as conspiratorial as the rest of us...

Yep, we have our fair share of 'challenged' people here too :-)
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Quoting moonlightcowboy:


There are some really smart cookies on this blog, and several can give you some great meteorological answers. I'm old school, can share what I know, but it won't be sophisticated, mind you. :)

Use this chart. Good one to work with. Click on the vorticity layers. You'll see 800mb and 700mb levels - these are generally considered the low-levels, and 800mb is used most to help discern if there is a rotating surface low. The 500mb level is consider the mid-level, and is generally the layer that Sarahan dust reside especially out in the MDR (main development region) of the Atlantic. 200mb would then be the upper levels.

Generally, winds are always a bit slower at the surface than the upper levels. This is mostly due to simple friction with the earth's surface, although they can be still fairly strong and non-conducive to development.

Convection? Hhhmm, best straight-away answer is simple evaporation. The hotter it gets the more evaporation you have - the mid and upper level environments become more moist. Cyclogenesis basically has to have three things: 1. Warm water fuel, 2. Building convection overhead in the layers, 3. Colliding cool and warm air (rising and falling) that helps to create the rotation which ultimately gets the tropical engine going.

Now, these other folks, good smart folks, can give you a more detailed answer, but that's basically it. :)

Thanks for your help! I try not to be a distraction with dumb questions, like why levels are given by pressure (mb) instead of feet or meters above sea level. There is so much to learn just to follow along with the discussions, I try to spend a lot of time on wikimedia and google, but sometimes I get lazy and ask real people.
-z

Everyone on here is a lot smarter than me, but
Member Since: Posts: Comments:
436. xcool


12 UKMET
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Quoting Bluestorm5:
Make sense. Is it only for base reflectivity or will there be multiple products like regular rotating radar?

There will likely be many more views than we have available today since phased array radar is able to look at very small areas and stay focused on them for as long as needed. If you take a look at the picture of the Arleigh Burke class destoyer, you'll notice those white polygons on either side of the foreward superstructure. Those are phased array panels, and there are two more on the aft superstructure. If you know anything about naval vessels, the striking thing is how few other radar antennas are on this vessel. That's because the phased array radar is able to do almost every task that took multiple radars before. They can do everything from normal collision avoidance to targeting multiple incoming targets, all at the same time, since the beams are controlled by computers and are able to assess threats almost instantly. A very simplified form of this MPAR is what was being used at OKC. If the NWS had the money it took to build one Arleigh Burke class destroyer, we could have these radars all over the country...but don't hold your breath.
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433. Skyepony (Mod)
Recent ASCAT of 91L.

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Quoting intampa:
it seems to me that whenever these models start that hype about noah ark type flooding for florida, tampa bay area .... its a bust.
it happened last year with debby. Water was in my house, so stop being a complacent tampan lol
Member Since: December 1, 2006 Posts: 2 Comments: 3619
Quoting Cayman2010:


There are ignorant people in all countries who don't understand the importance of how technology such as this can help so I wouldn't pay much attention to the few comments made in relation to the article.

To the best of my knowledge imagery from the radar is not yet publically available, but hopefully will be before the peak of the season.


Thanks. I really think this radar fills in a big gap in our coverage and look forward to it. - take care
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Quoting docrod:
Don't know if kman is around. Found this on the new Cayman weather radar operational June 1. As he said, a web page should go online sometime.

Judging from the comments - they don't seem to like it?

Link
Too Funny! (the article Comments) I did not realize Caymanians where as conspiratorial as the rest of us...
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Quoting docrod:
Don't know if kman is around. Found this on the new Cayman weather radar operational June 1. As he said, a web page should go online sometime.

Judging from the comments - they don't seem to like it?

Link


There are ignorant people in all countries who don't understand the importance of how technology such as this can help so I wouldn't pay much attention to the few comments made in relation to the article.

To the best of my knowledge imagery from the radar is not yet publically available, but hopefully will be before the peak of the season.
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Quoting Patrap:
91L Multiplatform Satellite Surface Wind Analysis

Thank you for the link!
=z
I lurk the wunderground
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it seems to me that whenever these models start that hype about noah ark type flooding for florida, tampa bay area .... its a bust.
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Quoting zampaz:

Thank you Moonlightcowboy. What altitudes are low level, mid-level and high-level shear and how are they measured. I find shear and convection interesting would like to learn more about these topics related to the tropics. thx
-zampaz
I lurk the wunderground


There are some really smart cookies on this blog, and several can give you some great meteorological answers. I'm old school, can share what I know, but it won't be sophisticated, mind you. :)



USE THIS CHART. Good one to work with.

LINK



Click on the vorticity layers. You'll see 800mb and 700mb levels - these are generally considered the low-levels, and 800mb is used most to help discern if there is a rotating surface low. The 500mb level is considered the mid-level, and is generally the layer that Sarahan dust resides especially out in the MDR (main development region) of the Atlantic. 200mb would then be the upper levels where there is more shear, and too, is the level we watch for verticalness and tropical maturity.

Generally, winds are always a bit slower at the surface than the upper levels. This is mostly due to simple friction with the earth's surface, although they can be still fairly strong and non-conducive to development.

Convection? Hhhmm, best straight-away answer is simple evaporation. The hotter it gets the more evaporation you have - the mid and upper level environments become more moist. Cyclogenesis basically has to have three things: 1. Warm water fuel, 2. Building convection overhead in the layers, 3. Colliding cool and warm air (rising and falling) that helps to create the rotation which ultimately gets the tropical engine going.

Now, these other folks, good smart folks, can give you a more detailed answer, but that's basically it. :)
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Quoting barbamz:
Time lapse of the Cancun cam with 91L from this morning ("Amanecer") is impressive (I hope the links works):
Link
Nice!
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I was just out for groceries and the roads are flooding pretty much everywhere from couple of hours of heavy rainfall. Not looking forward to 91L.
Member Since: August 1, 2011 Posts: 28 Comments: 7902
Quoting Patrap:
91L Multiplatform Satellite Surface Wind Analysis
wow. Impressive circulation... Now just waiting on shear to decrease
Member Since: December 1, 2006 Posts: 2 Comments: 3619
The models are not doing good with all the shear the rain will be in S FL and C FL not N FL
Quoting anotherwrongyear:
i don't believe daytona beach wil get to much of anything from all this hype on 91l most of the models now pull it more north might get a shower or 2 throught this week which is normal for here everyday
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419. 7544
Quoting K8eCane:


It aint that far from coast to coast except in the panhandle, is it?


thanks no but i still think they have to far north i think its going to come in further south looking aat the high rain totals for for south fl than the models show waiting for the next run we might see them go further south imo
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Quoting HondosGirl:
Measurable Rain in NWFL - Finally! Thank goodness!


Finally! Today was the 1st time it has rained at my house in over 3 weeks. I was begining to wonder if it would ever rain again. Ha! Hopefully we will get some more sometime this week.
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416. Mikla
91L is still a bit of a mess as a broad low, but has some things going for it:
- Decent SSTs
- Convergence is decent
- Divergence is decent with some anti-cyclonic winds aloft
- Low level Voricity is good but is all over the place as you go up, probably due to shear
- Moisture seems pretty good at all layers (from Cancun, MX - indicated by the red [temp] and blue [Dew Pt] being next to each other giving a high relative humidity)
- Shear Tendency shows some reduction in shear

But,
- Shear is still high and models don't really show it falling off
- There is Dry air to the NW that will impede development
- It also does not have much model support to develop

Steering is weak at 5 to 10 kts N to NNE so I am thinking that this will move slowly around the GOM and create a lot of rain and some wind for a few days in FL but not getting much over a tropical depression (maybe... maybe a tropical storm).
Member Since: October 13, 2006 Posts: 0 Comments: 286
Quoting barbamz:
Time lapse of the Cancun cam with 91L from this morning ("Amanecer") is impressive (I hope the links works):
Link
My friend do you have more updates on German Floods? Thank's!
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Don't know if kman is around. Found this on the new Cayman weather radar operational June 1. As he said, a web page should go online sometime.

Judging from the comments - they don't seem to like it?

Link
Member Since: Posts: Comments:
Time lapse of the Cancun cam with 91L from this morning ("Amanecer") is impressive (I hope the link works):
Link
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Storms are starting to build over Orlando.

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Quoting TomTaylor:
If I understand it correctly, MPAR has 4 facades, each facing a different region such that they are oriented 90 degrees to each other. Each side/face of the radar looks out over a 90 degree area, composing one fourth of the radar's full field of view. It appears that in this radar loop they were only using one side of the radar (likely because the other views were unnecessary). It is my understanding that each side operates independently from the others so I don't think them focusing on one quadrant made for faster scan times (i.e. it would have been just as quick with all the other quadrants up).

Here's an image of MPAR in action. Note the four different sides I described above. The radar can also rotate, changing the orientation of the faces of the radar.

Very neat! This will make it easier for meteorologists. This radar must be what Levi and UNCA students (the ones that went on chasing field trip) were talking about.
Member Since: August 1, 2011 Posts: 28 Comments: 7902
91L
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Quoting moonlightcowboy:
Mid-level shear is conducive at 5-10 kts, but there's still too much upper level shear although some relaxing seems to be forecast. Clearly 91L has some surface rotation although still quite unorganized, and marginal convection is still managing to be swept from over the coc. No readily visible closed low-level center that I can see, but my eyes are not what they used to be either. The real killer, however, for development now is dry air to its north and west;)

I see the NHC has upped its chances to 20%. Personally, that seems a bit optimistic given current conditions and observations. However, "IF" it can maintain some low to mid-level rotation, create some lift with convection, get some winds cycling, and gradually build some structure with relaxing shear, it might, just might spin up. That's a big IF though, I think. :)


Thank you Moonlightcowboy. What altitudes are low level, mid-level and high-level shear and how are they measured. I find shear and convection interesting would like to learn more about these topics related to the tropics. thx
-zampaz
I lurk the wunderground
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Quoting StormTrackerScott:
WOW!!



Model QPF and official number are actually increasing for Central Florida. For us this will be more beneficial than a flooding threat being that we were so dry and being near the coast flooding is a lower threat from rain. However, some areas around here did get absolutely soaked recently, I got 4 inches just on Saturday and most of Hillsborough and Pasco county received 4 to 5 inches with pockets up to 8 inches.

You guys already have very wet grounds after a wet April and May, a widespread 5 to 10 inch rain event could produce some flooding issues over there.
Member Since: August 21, 2008 Posts: 0 Comments: 7280
Quoting sar2401:

They can aim the phased array radar like a gun and follow any suspect areas and not have to wait for a scan by normal rotating radar. The phased array radar would only be used to look at particular areas during severe weather. The normal rotating radar is what we'll usually see.
Make sense. Is it only for base reflectivity or will there be multiple products like regular rotating radar?
Member Since: August 1, 2011 Posts: 28 Comments: 7902
Quoting Bluestorm5:
Very impressive! So we might have to have couple of those to get the whole area or they're trying to get quicker scan time for regular radar that scans the area?
If I understand it correctly, MPAR has 4 facades, each facing a different region such that they are oriented 90 degrees to each other. Each side/face of the radar looks out over a 90 degree area, composing one fourth of the radar's full field of view. It appears that in the radar loop they were only using one side of the radar (likely because the other views were unnecessary). It is my understanding that each side operates independently from the others so I don't think them focusing on one quadrant made for faster scan times (i.e. it would have been just as quick with all the other quadrants up).

Here's an image of MPAR in action. Note the four different sides I described above. The radar can also rotate, changing the orientation of the faces of the radar.

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Satellite of TS Debby look like 91L
Link
Link
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Quoting 7544:
do you guys think so fl east coast will get all that rain with the models taking this way north of there tia


It aint that far from coast to coast except in the panhandle, is it?
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Quoting MAweatherboy1:
Weird, the satellite images on the 91L floater just blacked out.


might need goes 15 :)
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Quoting moonlightcowboy:
And, what happened to that ghost storm that was supposed to perk up from the perennial Columbian Low again this year? ;)

It's too early still to get excited. Models are still transitioning seasonal data, conditions still not where they need to be for cycolgenesis proper. But, don't fret, I'm thinking the season's going to have several surprises in store for us. :(


the GFS' phantom storm?

the one that shows up every year?

the one that never happens??

ya I remember
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400. 7544
do you guys think so fl east coast will get all that rain with the models taking this way north of there tia
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Weird, the satellite images on the 91L floater just blacked out.
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I think this may possibly become Andrea very briefly if it stays over water long enuf to get to the panhandle there, rapidly dissipate ,leaving copious amounts of rain. But even depression status may be pushing it
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And, what happened to that ghost storm that was supposed to perk up from the perennial Columbian Low again this year? ;)

It's too early still to get excited. Models are still transitioning seasonal data, conditions still not where they need to be for cycolgenesis proper. But, don't fret, I'm thinking the season's going to have several surprises in store for us. :(
Member Since: July 9, 2006 Posts: 184 Comments: 29594

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