Winter rains ease Southeast U.S. drought; Brazilian storm could go subtropical

By: Dr. Jeff Masters , 5:59 PM GMT on February 29, 2008

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The winter of 2007-2008 is in the books, as today marks the last day of meteorological winter (December, January, and February). Winter rains have eased the drought gripping the Southeast U.S., where the area covered by extreme to exceptional drought has shrunk by about 50% since the beginning of the year (Figure 1). Some regions of southern Georgia and southern Alabama, where winter rains have been more than six inches above average (Figure 2), are no longer suffering drought conditions at all.


Figure 1. Drought categories for the Southeast U.S. from December 25, 2007, and February 28, 2007. Image credit: U.S. Drought Monitor.

However, A large swath of the Southeast U.S., including Atlanta, Charlotte, and Huntsville, have received 1-4 inches of precipitation below usual for this time of year. The shortfall is particularly acute in northern Alabama, where Huntsville has received only 6.77" this year, compared to the normal 10.47". The below average rains during this winter rainy season bode ill for the summer, when drought conditions could easily return to last year's extreme levels. The Southeast badly needs one or two landfalling tropical storms or hurricanes in 2008 to help break the drought.

Central Florida surrounding Lake Okeechobee is also suffering from below average rains this winter. The lake, which reached its all-time low water mark of 8.82 feet on July 2, 2007, has risen to 10.02 feet, but this is still a record low for this time of year. The surface area of the lake has shrunk to about 2/3 of normal, and the water level is more than four feet below normal. Part of the reason for the record low lake levels is the fact that the lake was deliberately drawn down before the 2006 hurricane season, in anticipation of another very active hurricane season.


Figure 2. Departure of precipitation from average for January and February 2008. Image credit: NOAA Advanced Hydrologic Prediction Service.

The forecast
The short-range rainfall forecast is good for the Southeast, with significant rainstorms possible both Tuesday and Thursday. The longer range three-month forecast calls for a continuation of below average precipitation for the spring season, thanks to the continued presence of a strong La Niña event in the Equatorial East Pacific. La Niña events usually deflect the jet stream into a pattern that takes the Southeast U.S. out of the the usual storm track needed to bring typical spring rains. However, for the summer months of June, July, and August, NOAA's CFS Climate Forecast System Model is predicting a return to normal levels of rainfall over the Southeast U.S.

Severe weather outbreak coming on Monday
A strong low pressure system is forecast to develop over Texas on Sunday, bringing a slight chance of severe weather to eastern Texas Sunday afternoon. By Monday afternoon, the storm is expected to track northeastwards over the Ohio Valley, dragging a strong cold front across the south. A significant severe weather outbreak is possible Monday afternoon in advance of this cold front.

Interesting South Atlantic storm could become subtropical
An extratropical storm centered near 31S 30W, a few hundred miles east of the Brazil-Uruguay border, has begun to acquire subtropical characteristics and could become a subtropical storm this weekend. The storm is not expected to hit land. NASA/MSFC has a clickable satellite image of Southern Hemisphere one can use to zoom in on the storm. An ASCAT pass at 5:29am EST this morning showed winds of 50 mph near the center of the storm. Water temperatures are about 26°C, which is right at the boundary where tropical storm formation can occur. Subtropical and tropical storms are quite rare in the South Atlantic. I'll update this section of the blog through the weekend if the storm develops. There is no naming system in place to name any tropical or subtropical storm that may form in the South Atlantic. It would be up to the World Meteorological Organization (WMO) to institute such a scheme. The last time I checked into this, they had no plans to consider a naming system. Here's nice MODIS image of the storm from 15:30 GMT today.



Figure 3. Visible satellite image of extratropical low off the coast of Brazil that is beginning to acquire some subtropical characteristics. Image credit: NASA/MSFC.

Jeff Masters

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210. BahaHurican
6:08 PM EST on March 02, 2008
Also noticed this area in the S. Indian, which looks like it may be of interest in the ensuing week.

Member Since: October 25, 2005 Posts: 19 Comments: 20686
209. BahaHurican
6:05 PM EST on March 02, 2008


South Atlantic storm.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
208. Patrap
5:01 PM CST on March 02, 2008
Notice the inflow here..Wichita Live Cam..Link
Member Since: July 3, 2005 Posts: 414 Comments: 125515
207. weatherbro
10:59 PM GMT on March 02, 2008
Hows that South Atlantic storm doing?
Member Since: May 26, 2007 Posts: 47 Comments: 1213
206. weatherbro
10:25 PM GMT on March 02, 2008
Although with the first storm system, severe weather will remain more north of FL Peninsula. I doubt the associated front will stall out since:

1. storm #2 isn't close enough to #1

2. Atlantic ridge is weak.

Yet it may slow down a bit. Friday night Saturday morning will be the main thing to watch.

Like CCHSweatherman mentioned that computer models are divided.
Member Since: May 26, 2007 Posts: 47 Comments: 1213
205. NorthxCakalaky
10:47 PM GMT on March 02, 2008
Some places out west are under a tornado warning and a blowing snow advisory.

I hope we get some heavy rain here in
N.C.As always, the mountains will block the severe weather and some rain for the rest of the state.

Anyone have a good guess how much rain the southeast will get?
204. IKE
4:30 PM CST on March 02, 2008
18Z GFS shows some heavy rain into south Florida the end of next week....

Link
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203. FLWeatherFreak91
5:22 PM EST on March 02, 2008
weatherman, I've seen the models and I'm not sure what you're so excited about...most of the weather looks like it will happen right around Tampa Bay on Thursday into Friday....I don't see much around South Florida
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202. BahaHurican
5:08 PM EST on March 02, 2008
Another PDO link
http://www.srh.noaa.gov/bro/pdo.htm

I also found this interesting site showing Jet Stream location in the N and S hemispheres . . . It has current data, forecasts, AND a map archive going back to 2005.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
201. cchsweatherman
5:03 PM EST on March 02, 2008
Weather will get interesting here in South Florida this week as the front will stall out over us. Could be a focal point for some much needed rains over the area. Looking at the latest GFS model, I have become concerned about Saturday where there will be very strong surface vorticity riding the frontal boundary over us. This could cause some significant severe weather here late Friday into Saturday. Nonetheless, we will finally return to a wet pattern for longer than a couple days. Thoughts on Friday and Saturday here?
Member Since: April 14, 2007 Posts: 8 Comments: 5030
200. IKE
4:01 PM CST on March 02, 2008
Area forecast discussion
National Weather Service Amarillo Texas
339 PM CST sun Mar 2 2008


Discussion...
strong cold front is now blasting through the southeast Texas
Panhandle and should be out of the County Warning Area by the time this forecast GOES
into affect. Will go ahead and cancel the Severe Thunderstorm Watch
with this forecast as well. Since low level moisture will continue
to get scoured with the front.


Our eyes then turn to developing winter storm that is moving
southeast into northwest New Mexico. The upper low over
northwest New Mexico is expected to close off as it moves into
southeast New Mexico/West Texas on Monday morning. The dynamics
with this system will be quite strong when this system closes
off with plenty of divergence aloft with the coupling of the
upper jets. Low level moisture will get drawn northward into the
panhandles and this moisture will ride up and over the vigorous
frontal zone. A 700 mb low is expected to form as well and it should
move right across the Texas Panhandle. The north winds will continue
to be quite gusty and will be in the 20 to 30 mile an hour range
with gusts near 45. Snow will spread from northwest to southeast
across the panhandles overnight and will slowly exit the
southeast Texas Panhandle by Monday afternoon. Snowfall amounts
look to be in the 2 to 4 inch range...with locally higher
amounts. There is a possibility of greater than 4 inch amounts...
especially in the southern Texas Panhandle...closer to the upper
low track. Thought about issuing a Blizzard Warning due to
reduced visibilities in blowing and drifting snow...but
confidence is not high enough right now that enough snow will
fall to get considerable blowing snow considering the expected wet
nature of the snow. If it does look like some areas will get
greater than 4 inches in a more widespread area...then a Blizzard
Warning will be considered.
Member Since: Posts: Comments:
199. Patrap
3:41 PM CST on March 02, 2008

Area forecast discussion
National Weather Service New Orleans la
337 PM CST sun Mar 2 2008



Middle and upper air analysis showed the trough axis from North
Dakota to The Four Corners region. Moist southwest flow was
noted over southern and Central Plains...mainly from 850 to 700mb.
Visible satellite imagery showed a cloud shield at this same layer
over southern and Central Plains.


With the approach of the system Monday...low level south to
southwest winds will increase. Storm relative helicity values will
increase to 300 to 350 M/S by 12z Monday. At the same...southwest
flow will bring in the warm nose or slight cap. If canopy is in
place...surface will not heat sufficiently. High temperatures closer to
80 will overcome the lid and cells are likely to develop in the
warm sector Monday. Surface forcing with the front approach will
force development through this lid. The main trough axis will be
located from north Missouri to north central Texas Monday afternoon. At
the this time...the jet maximum of 120 knots should be located just
east of the base of the trough or from the Texas Hill country to
the arklatex region...placing the best divergence over Louisiana
and Mississippi. Moreover...model area forecast sounding at 00z
Tuesday displayed cape values from 700 to 1000 j/kg across the
forecast area. With all these features in place...strong cell storms
are possible over west zones Monday afternoon becoming more linear
and more speed shear during the evening and overnight. The main
threat will be isolated tornadoes...one or two strong north and
west of Lake Pontchartrain...wind damage and hail. Will issue a Special
Weather Statement to highlight these threats. Boundary winds and
low level winds ahead does not appear as strong in the models as
previous runs have indicated. In addition...cold air advection
does not appear to be as strong as previously thought. However...the
pressure gradients associated with a deep 1004mb passing east
across the deep south maintain bl winds to the sea surface near
100 percent...especially Monday evening.
Member Since: July 3, 2005 Posts: 414 Comments: 125515
198. hurricane23
4:38 PM EST on March 02, 2008
As always most of the energy will ride north of extreme southeast florida.

NWS-Miami Discussion.

TUESDAY THROUGH WEDNESDAY...THE WEATHER QUESTION FOR THIS PERIOD
IS, FROPA OR NO FROPA? LOOKS LIKE NOW THE OPERATIONAL GFS IS MORE
IN PHASE WITH THE ENSEMBLE MEAN. AND THIS IS DEFINITELY MORE
ENCOURAGING WHEN IT COMES TO BELIEVING THE MDL'S OUTPUT. THIS
LATEST RUN SHOWS A NOT SO DEEP S/W MOVING ACROSS SE U.S AND
LIFTING FURTHER NORTHWARD TO JUST SOUTH OF GREAT LAKES BY TUE
NIGHT. SRN PORTION OF CDFNT LOOSES ITS PUNCH AND SLOWS DOWN
CONSIDERABLY AS MOST OF THE ENERGY IS TRANSFERED NORTH, AN SO
IT CRAWLS THROUGH S. FL THROUGH WED MORNING BEFORE STALLING AND
STARTS MOVING BACK NORTH WED AFTERNOON/EVENING. WHILE WILL NOT
RULE OUT THE POSSIBILITY OF A STG TSTM OR TWO WITH THIS SYSTEM, IT
NOW LOOKS THAT ANY SVR WX ASSOCIATED WITH THIS SYSTEM WILL LIKELY
REMAIN WELL NORTH OF THE AREA WHERE BETTER DYNAMICS ARE FORECAST.


Sounds good.Overall a wettern pattern seems to be instored for the area.

www.AdriansWeather.com
Member Since: May 14, 2006 Posts: 8 Comments: 13597
197. Ivansrvivr
8:10 PM GMT on March 02, 2008
CCW, I would tell all interests in the southeast US including the FL peninsula to watch the 2nd storm closely. With the trailing front possibly stalling out over S.Fl from the 1st storm, there is flood potential for the Fl Peninsula, and Severe wx threat for Gulf Coast states from both storm systems, maybe big snow not far north of severe wx with the 2nd system. This could be an interesting week.
196. lindenii
7:43 PM GMT on March 02, 2008
181. BahaHurican 4:24 PM GMT on March 02, 2008
A totally unrelated question:

Should Wunderbloggers seriously consider their efforts and discussions part of the advancement of weather science, whether locally or globally, or should they view their activities as simply "personal events" that contribute mainly to their own enjoyment and interpretation of the world around them?


*************

The answer is...probably both.

You never know when a Wunderblogger will put an idea out there that will be the exact missing piece to another Wunderbloggers puzzle. By allowing all to participate regardless of their particular theoretical persuasion regarding the science of weather, we will all benefit.

It is only when we choose to become 'edict based' that damage is done to our pursuit of the truth.

Nature is Random...Get over it.
195. pottery
3:15 PM AST on March 02, 2008
Interesting stuff there, STL.
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193. pottery
2:58 PM AST on March 02, 2008
weather456, that was a good post at 8;23 this morning.
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191. Patrap
12:59 PM CST on March 02, 2008
120 Hour GOM Surface Current Forecast

Link
Member Since: July 3, 2005 Posts: 414 Comments: 125515
190. Patrap
12:57 PM CST on March 02, 2008
GOM 120 Hour Sea Surface Surface Temperature Forecast
Link
Member Since: July 3, 2005 Posts: 414 Comments: 125515
189. Weather456
1:36 PM AST on March 02, 2008
Baha, thank you for that comment there.

***************************************

....SYNOPSIS....

GULF OF MEXICO/NORTHWEST ATLANTIC OCEAN WEST OF 50W....

As a an extratropical storm system moves across the Eastern Rockies, a modest ridge extends from Florida to the Bay of Campeche providing moderate anticyclonic flow, 4-5 ft seas and fair weather across much of the Gulf of Mexico and Southeast United States. Meanwhile, the pressure gradient between the ridge and the aforementioned storm system is resulting in pronounce onshore flow and enhancing the Plains Low Level Jet resulting in widespread overcast low clouds cover much of Texas and surrounding states. The weather pattern across the Gulf should become more interesting in the upcoming days as a frontal system pushes into the region in 48 hrs time accompanied by gale force conditions over the Gulf west of 90W. Expect northwesterlies of 20-35 knots and swells of 14-17 ft. This will then spread southeastward across the remainder of the Gulf of Mexico but with less umph than that experienced further west.

A swath of cloudiness and showers extends from the Northwest Cuban Coast, across the Central-Northern Bahamas and along 25N/70W 30N/60W and beyond. This activity is associated with a stalled out fontal boundary. The Tropical Prediction Center has analyzed this feature as a surface trough but I cannot understand why, when there a frontal ropes, wind and temperature gradients present. Exceptionally fair skies and fine weather behind this feature due to dry offshore flow and surface ridging. Meanwhile, patches of subtropical low clouds...typical...are seen within the return flow ahead of the front/trough between 50W and 70W north of 15N.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

The aforementioned surface front/trough extends into the Northwest Caribbean between Western Cuba and the Gulf of Honduras. Here, motions of the scattered low clouds more clearly depict a weak surface trough. A fair amount mid-upper level dry air covers the entire Caribbean basin, thereby deep convection remains absent and only low scattered tradewind clouds are seen. Trades are blowing at 10-20 knots and building swells of 6-7 ft everywhere, with 11 ft seas along the Colombian Coast/SW Caribbean due to the pressure gradient between the subtropical ridge and the Colombian Low and Eastern Pacific Equatorial Trough.

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
188. stormdude77
12:37 PM AST on March 02, 2008
Good afternoon all

With all the talk about La Nina, check out my blog, with early La Nina predictions.
187. Patrap
10:36 AM CST on March 02, 2008
The Applied Meteorology Unit
A cooperative effort of NASA, the USAF and the NWS

Link
Member Since: July 3, 2005 Posts: 414 Comments: 125515
186. BahaHurican
11:33 AM EST on March 02, 2008
Say, I just looked at the TIME!!!

I gotta go! I'll check in later to see what people are thinking about lots of things.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
185. Patrap
10:35 AM CST on March 02, 2008
Da Thinka, LOL
Member Since: July 3, 2005 Posts: 414 Comments: 125515
184. BahaHurican
11:32 AM EST on March 02, 2008
Pat, LOL, and /swipe/

Saving that one for future use . . .
Member Since: October 25, 2005 Posts: 19 Comments: 20686
183. BahaHurican
11:24 AM EST on March 02, 2008
Here's a link to interesting information on The Pacific Decadal Oscillation (PDO)

Take a look at this chart.



Is it my imagination, or is there a correlation between volume of ATL hurricane formation and PDO orientation?
Member Since: October 25, 2005 Posts: 19 Comments: 20686
182. Patrap
10:24 AM CST on March 02, 2008
Hmmmmmmmmmmmmmmmmmmm?...

Member Since: July 3, 2005 Posts: 414 Comments: 125515
181. BahaHurican
11:21 AM EST on March 02, 2008
A totally unrelated question:

Should Wunderbloggers seriously consider their efforts and discussions part of the advancement of weather science, whether locally or globally, or should they view their activities as simply "personal events" that contribute mainly to their own enjoyment and interpretation of the world around them?
Member Since: October 25, 2005 Posts: 19 Comments: 20686
180. lindenii
4:21 PM GMT on March 02, 2008
175. ShenValleyFlyFish 3:25 PM GMT on March 02, 2008
169

If you are going to give that particular individual the time of day please do not post quotes. The season is fast approaching and unless he has recovered from his need to obsessively post on 1 topic ad-infinitum with nothing new from post to post I consider it a major waste of space.


***************

Thanks for providing a perfect example of the 'edict based' metality.

Somehow excising our words and ideas will result in a more perfect world where only your way of discussion is practiced. Sniff sniff...almost smells of censorship.

Fortunately, many of those who visit here and are lurkers do not engage in such censorship practices are still being reached. They are the ones I am most intent on reaching out to. Those of you in the 'edict based' world have your minds made up and it is senseless to attempt to convice you otherwise.

To you 'edict based' shunners I say ...Please...Please...Keep shunning me, I sleep better at night knowing I am making a difference.
179. BahaHurican
10:57 AM EST on March 02, 2008
After looking at 5 strong La Nina seasons and 8 moderate to strong El Nino seasons, I can say I am totally confused about patterns related to storm numbers and storm landfalls
LOL

The la nina seasons averaged about 13 storms, half of which did not affect any mainland area (for my convenience, I am leaving out the islands). A lot of the stronger hurricanes stayed out to sea.

The el nino seasons fluctuated wildly. There is one season, 1969, with 20 systems!!! However, the storm average per season is around 10 (5 of the 8 seasons had 8 or fewer storms). Also the percentage of landfalling storms was smaller, though the same wild fluctuations were seen (anywhere from 13 to 75 percent, in fact). About 40% of the storms affected the mainland. Some notable "record" hurricanes happened during these years, but the majority of systems were not especially powerful.

I guess what I am getting at is what 23 was stating last night; ENSO is not the sole determining factor, so perhaps it is wiser to stick to the 2-week formation prognosis. OTOH, I encourage the Dr. Grays of the world, so long as they don't suggest that people's lives should depend on their forecasts . . .
Member Since: October 25, 2005 Posts: 19 Comments: 20686
178. lindenii
4:08 PM GMT on March 02, 2008
169. BahaHurican 2:52 PM GMT on March 02, 2008

I don't see wanting to answer the question "WHY" as going against science or common-sense prediction. If my memory serves me (it does occasionally :o) it is that very question which has driven scientific discovery over the centuries. Observation is integral to the scientific method, but it all just produces a bunch of numbers and facts unless we look for patterns in what we see.

The trick is not to become dogmatic about the patterns, to recognise that our understanding is never complete, and even if it happened to become complete, the patterns change.


**************

Exactly. Asking 'Why' is the scientific thing to do. Unfortunately, what seems to continually happen is that 'theory' somehow becomes 'edict' and those who are not in step with that 'edict' ie global warming is man-made... are called 'coolies' or 'denialists'.

I intend to continue to 'shine the light of truth' on those 'edict based' individuals and their tactics until they go back to being true scientists who are willing to let both sides be discussed and debated without the name calling and shunning.

Those who want to jump to the ignore button when a serious challenge is made to their desire for a 'edict based' view of weather and mans being at the cause of it all are doing themselves and the rest of us a disservice by impeeding the forward progress of weather observation and prediction.

Nature is Random...get used to it.
177. surfmom
3:57 PM GMT on March 02, 2008
funny you should bring up the word Chaos. In my uneducated mind, I often wonder how much of weather can be successfully predicted with the "rules" of science. And how much does random chaos play a part - rendering humans limits in our predictions.
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176. BahaHurican
10:52 AM EST on March 02, 2008
175. ShenValleyFlyFish 10:25 AM EST on March 02, 2008
169

If you are going to give that particular individual the time of day please do not post quotes.


Advice taken. (Hopefully some other people will take advice also.) I will make use of wundermail in future.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
175. ShenValleyFlyFish
10:16 AM EST on March 02, 2008
169

If you are going to give that particular individual the time of day please do not post quotes. The season is fast approaching and unless he has recovered from his need to obsessively post on 1 topic ad-infinitum with nothing new from post to post I consider it a major waste of space.
Member Since: Posts: Comments:
174. cchsweatherman
9:56 AM EST on March 02, 2008
Since the computer models nor the NWS or SPC have a very good handle on this major storm forecasted for Friday and Saturday, I will have to put off my forecasts for those days until we can have some confidence in the forecast. Right now, I want to forecast widespread showers and strong storms for South Florida late Friday and Saturday, but cannot do that yet. Any advice on how I should forecast those days with such low confidence?
Member Since: April 14, 2007 Posts: 8 Comments: 5030
173. cchsweatherman
9:48 AM EST on March 02, 2008
Good morning all! It looks like one nasty storm is going to develop for Friday and Saturday all across the eastern half of the country. This could cause major chaos at the airports and on the roads.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
172. BahaHurican
9:54 AM EST on March 02, 2008
Member Since: October 25, 2005 Posts: 19 Comments: 20686
171. BahaHurican
9:53 AM EST on March 02, 2008


Latest on Ophelia.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
170. BahaHurican
9:52 AM EST on March 02, 2008
BTW, what's the latest on TC Ophelia?
Member Since: October 25, 2005 Posts: 19 Comments: 20686
169. BahaHurican
9:41 AM EST on March 02, 2008
165. lindenii 9:11 AM EST on March 02, 2008

It is very curious that Dr. M. has yet to comment on the fact that the sun is at a minimum of sunspot activity ....


Why don't you drop him an email about it? He may not have seen your comments in the bulk of the blog.

Observing El Nino and La Nina is appropriate...predicting when and where flies in the face of Chaos Thoery and, in the long run distracts from good old common sense weather prediction.

I don't see wanting to answer the question "WHY" as going against science or common-sense prediction. If my memory serves me (it does occasionally :o) it is that very question which has driven scientific discovery over the centuries. Observation is integral to the scientific method, but it all just produces a bunch of numbers and facts unless we look for patterns in what we see.

The trick is not to become dogmatic about the patterns, to recognise that our understanding is never complete, and even if it happened to become complete, the patterns change.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
168. BahaHurican
9:37 AM EST on March 02, 2008
160. Weather456 7:23 AM EST on March 02, 2008
Good Morning, for the hurricane seasons of 2004, 2005, 2006 and 2007. I used these indicators to help put together a hurricane season forecast


BEAUTIFUL! Thanks 456! I'm seriously considering trying my hand at a season forecast this year, and this information is very useful to me. I have a lot of respect for your interpretation of tropical weather events, so I am saving this post to a Word file for future reference.
Member Since: October 25, 2005 Posts: 19 Comments: 20686
167. BahaHurican
9:27 AM EST on March 02, 2008
Good morning.

156. MichaelSTL 11:26 PM EST on March 01, 2008

There are several theories to explain the cycles; the recharge oscillator one sounds good to me (El Nino events deplete heat in the upper ocean while it builds up again during La Ninas, as is currently happening):


I think I agree with you, STL, that the "recharge oscillator" sounds logical. We already understand the concept of the cycle. Our next task, following this theory, is to determine at what point the depletion or buildup is likely to trigger a new event. If this is the case, there is hope for reliable prediction to take place.

It also supports my thinking that since hurricanes are a part of this heat distribution system, understanding this larger system is likely to lead to improved tropical forecasting ability.

I'm also thinking I understand why some scientists expect increased / radical global warming to result in a severe cooling period. However, taking the same point to its logical conclusion, wouldn't a period of severe cooling (like that experienced in the 1800s)trigger a warming trend as seen in the 1900s?

Member Since: October 25, 2005 Posts: 19 Comments: 20686
166. TerraNova
2:16 PM GMT on March 02, 2008
Good morning everyone...

From what ive seen so far the GFS doesn't have much run-to-run consistency or support for the Friday-Saturday storm. It does show a potent frontal boundary affecting Florida with QPF ranging from 0.50 to 1.25.

The "big one" seems like the first system that will develop in the southcentral US and bring very heavy rainfall to the northeast on Wednesday and severe weather to the south on Monday.


Member Since: July 30, 2007 Posts: 76 Comments: 4062
165. lindenii
2:11 PM GMT on March 02, 2008
BahaHurican 4:23 AM GMT on March 02, 2008
Hey, 23. I'm not thinking so much about forecasting when it will happen as I am about WHY it happens. After looking at all the different years, I have been wondering what causes such a drastic, and seemingly arbitrary, shift. I find it hard to believe it "just happens"
.

Baha...It is called Chaos and more specifically, it is Chaos Theory that can be used to explain your disbelief that it "just happens"

A good explanation can be found in 'Jurasic Park', where Jeff Goldbloom explains how water arbritraily flows down the finger of the other character.

When it comes to attempting to forcast weather issues such as global warming we must always keep in mind that weather patterns occur over periods of hundreds and thousands of years...not in periods of single and groups of single digit years.

Another thing that is important to keep in mind is the fact that the sensitivity of our instrumentation has come into its own in the last twenty years and with that sensitivity comes the ability to see small perturbations in weather activity. If our observers were better trained, they would know not to attempt to dogmatically tie the information gathered with the new instrumentation with the old data gathered with much less sensitive instrumentation.

It is very curious that Dr. M. has yet to comment on the fact that the sun is at a minimum of sunspot activity and that means significantly less energy production which means that all bets are off when it comes to global warming. Doesn't it seem odd to you that we now have two significant issues that he has appeared to avoid discussing. The first is the report from NOAA and the second being the sunspot issue.

It all boils down to this...forcasting the weather and hurricanes is still best done by old style forcasting which accepts the randomness of the weather and still attempts to make common sense of it. Observing El Nino and La Nina is appropriate...predicting when and where flies in the face of Chaos Thoery and, in the long run distracts from good old common sense weather prediction.

Maybe there is a book called Statistics for Dummies out there. If there is maybe we could all read it and see why those who engage in the hysterical alarmist wailings are inappropriate and even dangerous. Read the article describing the report by NOAA scientists debunking the alarmist claims of 'worst damage in history'.

Good old weather science...yeah that's the ticket.
164. Ivansrvivr
1:30 PM GMT on March 02, 2008
Note: when I was comparing the 2nd storm to the 93 S.S it was in forecast track and available ingredients. I also stated that 93 was a 1 in 100yr event, and while the 2nd storm may have similarities, It would be doubtful that it would have the strength of 93. The 1-2 punch of these 2 storms could be a huge rainmaker for the whole state of FL. While the severe threat would likely be farther north, the frontal boundary will pass over us at least twice with ample moisture. It may even go stationary in between the two storm systems over S.Fl making next week very wet.
163. Weather456
9:10 AM AST on March 02, 2008
Anticyclonic Divergence Aloft displayed by Ioke in 2006



Low Level Convergence - Hurricane Florence in 2006

Member Since: July 24, 2005 Posts: 407 Comments: 19076
161. Weather456
8:24 AM AST on March 02, 2008
Just more info, All will me reposted later in the year.

Atlantic Tropical Cyclone Formation Sources
a. Persistent area of thunderstorms or convection (synoptic in size)
b. The monsoon trough, NECZ, or ITCZ
c. A tropical wave
d. A dissipating frontal boundary or frontal low
e. An extratropical cyclone/a subtropical cyclone
f. An upper level low
g. A surface trough of low pressure (other than NETs)
h. The interaction between remnant disturbances, tropical waves, upper–mid tropospheric troughs

NETs - Nearequatorial Troughs like the monsoon trough, ITCZ, etc.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
160. Weather456
8:17 AM AST on March 02, 2008
Good Morning, for the hurricane seasons of 2004, 2005, 2006 and 2007. I used these indicators to help put together a hurricane season forecast at the beginning of each month for June, July, August, September and October. I donot make one forecast in June for the whole season because some of these indicators are highly variable from June to September and September to December.

Tropical Forecasting

a. Surface Pressure and SST Anomalies

b. Upper Wind Anomalies (Westerly, Increasing)

c. Location and intensity of the monsoon trough, ITCZ, subtropical high-pressure ridge*, African Easterly Jet.

d. The Southern Oscillation

e. The Madden-Julian Oscillation (MJO)

f. Quasi-biennial Oscillation (QBO)

g. The North Atlantic Oscillation (NAO)

h. The Saharan Air Layer (SAL)

i. The Tropical Upper Tropospheric Trough/Lows (TUTT)


Medium-Long Range Forecasts 30-60 days

These are just brief descriptions, details will be posted as the hurricane season nears

During the QBO, Atlantic tropical cyclones are more frequent when 30 mb winds are westerly and increasing, rather than easterly and increasing.

During El Nino, high SST over the eastern Pacific causes more deep convection there. The resultant outflow aloft enhances upper tropospheric westerlies over the Caribbean and western equatorial Atlantic. Consequently, the 200 mb anticyclonic flow necessary for tropical cyclones to develop is reduced. During Neutrals and weak to moderate La Ninas, low SSTs over the eastern Pacific supresses deep convection there. The resultant subidence enhances lift and weak to moderate upper level easterlies over the Tropical Atlantic Summer, which favors tropical cyclone development.

During the hurricane season in the Caribbean basin, below normal monthly mean sea level pressure is associated with increased hurricane activity. Pressure anomalies tend to persist from spring through summer.

During times of wind surges into the Monsoon trough, NECZ or ITCZ during late July, August and September, expect increase tropical convection and activity.

During the MJO Active Phase, low level rising and upper level drivergence, thus enhanced convection is favored.

Increase velocities of the African Easterly Jet was found to increase in the intensity and frequency of African Tropical Waves. Examples include Ivan (2004), Florence and Helene (2006) and Dean (2007).

SAL can affect tropical cyclones is several ways but during the period from 2004-2007 I observed only two. Increase African Dust actually lowers SSTs not the entire tropical Atlantic but the area just west of the Cape Verde. Increase African Dust creates a dry enviroment within the mid-levels which enhances subsidence and downdraft and suppresses tropical convection.

The Positive NAO index phase shows a stronger than usual subtropical high pressure center and a deeper than normal Icelandic low. The negative NAO index phase shows a weak subtropical high and a weak Icelandic low. African easterly waves are impelled along the southern periphery of the Azores High away from coastal West Africa towards North America and the Caribbean, sometimes triggering tropical cyclogenesis. The position and intensity of high also affects upwelling along the African Coast, how arid West African gets during the summer months (SAL), surges into the ITCZ, Monsoon Trough, etc., the pressure gradient between a TC low pressure and the high pressure cell. All these factors are compiled and made into a forecast. A stronger High also increases SSTs in the Caribbean and Gulf of Mexico due to downwelling (the opposite of upwelling). A stronger high also indicates that tropical cyclones move faster and make it more westward than usually (like Frances, Ivan, Dean). It must be remembered that the Bermuda High is just a westward extentsion of the Azores High and only becomes seperated during the passage of frontal troughs and in rare cases, tropical cyclones (Maria 2005).

The Famous TUTT, my second most favorite tropical feature of the summer months (Tropical Cyclone 1st). The TUTT should not be confused with troughs in the mid-laltitude westerlies because unlike those troughs, the TUTT is tropical and mainatined by subidence. The TUTT extends from the North central or Northeastern Atlantic roughly 35-40N/40W all the way to Central America in some cases. The TUTT is more of a short term forecasting tools as it is so variable during the hurricane season. TUTTs can either increase wind shear over tropical system or enhanced outflow through outflow channels. Also TUTTS are respobsible for the sudden "blow-up" in convection of inverted V tropical waves in the Eastern Caribbean which can lead to genesis (Ernesto 2006).

Well most of this information came from those four hurricane seasons. But Climatology is an important tool and the Atlantic Ocean is the most well studied basin in the world. Another useful tool is by looking at past tropical cyclone season and see how each phenomena mentioned above affected that season. Like Neutral-Enso in 1995.

I hope this help those who want to try a hand at forecasting.


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About JeffMasters

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