91L no concern; more postcards from the AMS hurricane conference

By: Dr. Jeff Masters , 1:12 PM GMT on April 18, 2012

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I'm in Ponte Vedra Beach, Florida this week, where the world's hurricane experts are gathered to attend the 30th Conference on Hurricanes and Tropical Meteorology of the American Meteorological Society. Most of the Hurricane Specialists from the National Hurricane Center are here, and they are keeping an eye on the waters a few hundred miles east of Bermuda, where an extratropical storm has cut off from the jet stream and is slowly acquiring tropical characteristics. This system was designated Invest 91L last night by NHC. Ocean temperatures are around 20°C (68°F) in the region, which is well below the 26°C usually needed for a tropical storm to form. Wind shear is a high 20 - 30 knots. Nevertheless, 91L has managed to develop a small amount of heavy thunderstorm activity near its center, and may continue to show more organization as it moves slowly southeastward over the next day or two. I give 91L a close to 0% chance of becoming a named storm in the next two days, and NHC seems to have stopped issuing new products for the system. By the end of the week, 91L should get picked up by a trough of low pressure and move off to the northeast. The storm is not a threat to any land areas.


Figure 1. Morning satellite image of Invest 91L. The island of Bermuda is seen at the left side of the image.

Global tropical cyclones and climate: current signal
Now, I'll summarize a few of the excellent talks given at this week's AMS hurricane conference. Dr. Greg Holland of the National Center for Atmospheric Research talked about the impact of global warming on hurricane intensities. Using data beginning in 1975, the beginning of the satellite era, he showed that while the total number of hurricanes globally has decreased in recent years, the proportion of hurricanes that are of Category 4 - 5 intensity has increased by 40%. He showed that this change could be related to a 0.8°C increase in global temperature during the period. He concluded that when hurricanes form, they are finding that it is easier for them to reach higher intensities.

Sensitivity of the strongest hurricanes to ocean surface warmth
Dr. Jim Elsner of Florida State University showed that observations indicate a sensitivity of hurricane winds of 8.2 m/s +/- 1.19 per degree Centigrade of ocean warmth, using data in the Atlantic from 1981 - 2010 (for oceans areas warmer than 25°C.) Using a high resolution model (HiRAM) with 50 km resolution, a sensitivity of only 1.5 +/- .6 m/s was found, calling into question the usefulness of current models for assessing future hurricane activity.

How will climate change affect hurricane tracks?
Angela Colbert of the University of Miami used 17 global climate models, the BAM hurricane tracking model, and the Atlantic historical HURDAT data base to see how hurricane tracks might change in the future. She classified storms as either straight moving (which tend to hit the Caribbean or U.S. Gulf Coast), recurving landfalling (U.S. East Coast impacts), or recurving ocean storms that miss landfall. She projected a 6% increase in recurving ocean storms and an 8% decrease in straight-moving storms by the end of the century, due to climate change. A decrease of 1- 2 storms per decade is predicted for the Caribbean and Gulf of Mexico, and an increase of 1 - 2 storms per decade in the waters of the mid-Atlantic, and along the East Coast of Florida. This occurs primarily because of an increase in westerly winds over the Central Atlantic, and to a lesser degree, an eastward change in genesis location closer to the coast of Africa. Both of these factors would tend to increase the number of recurving storms.

Jeff Masters

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Dr. Greg Forbes Torcon Index-added Friday

Wednesday April 18
All areas - less than 2

Thursday April 19
KS east - 2 to 3
MO west, north - 2 to 3
OK southwest - 2 to 3
OK north-central - 2 to 3

Friday April 21
AR southwest - 2 to 3
LA northwest - 2 to 3
TX east (east and north of San Antonio) - 2 to 3
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Quoting MAweatherboy1:

Models have absolutely no handle on the NAO right now beyond a few days... Looks like maybe a dip negative and then it's anyone's guess as to whether it stays negative or goes back positive.

yeah, that's quite a spread
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The SPC has added a slight risk area for tomorrow

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Quoting nigel20:

Models have absolutely no handle on the NAO right now beyond a few days... Looks like maybe a dip negative and then it's anyone's guess as to whether it stays negative or goes back positive.
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Member Since: November 6, 2010 Posts: 11 Comments: 7974
This anticipated Gulf of Mexico low pressure system is complex, as the features it will form upon are not yet in place. Adding to the complexity is the fact that the most reliable computer models are not in agreement as to the strength, timing and direction of the low. Here’s what we know: A low pressure center in Colorado today moves to the Great Lakes by Thursday. Trailing off the low, a cold front that will push off the Texas Coast late tomorrow. That cold front languishes in the Gulf on Thursday — putting into place the ingredients for the formation of the infamous West Gulf Low. What happens after that is where things get a bit murky. First, will the low form? If so, where? If it forms, how strong will it get and where will it go?
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Gonna be a BeaUtiful sunny weekend in SE TX, except Saturday with strong winds
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CMC mirrors the GFS in taking this low into the Gulf then up the eastern US.
Member Since: October 26, 2011 Posts: 0 Comments: 2651
"How will climate change affect hurricane tracks?
Angela Colbert of Florida State University used 17 global climate models..... A decrease of 1- 2 storms per decade is predicted for the Caribbean and Gulf of Mexico, and an increase of 1 - 2 storms per decade in the waters of the mid-Atlantic, and along the East Coast of Florida. This occurs primarily because of an increase in westerly winds over the Central Atlantic, and to a lesser degree, an eastward change in genesis location closer to the coast of Africa. Both of these factors would tend to increase the number of recurving storms.
"

What is the cause of the eastward change?
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the 12Z CMC is slower with the low and creates another low off the SE coast









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HAZARDOUS WEATHER OUTLOOK FOR EASTERN NORTH CAROLINA
NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC
1016 AM EDT WED APR 18 2012

NCZ029-044>047-079>081-090>095-098-103-104-191430 -
MARTIN-PITT-WASHINGTON-TYRRELL-MAINLAND DARE-GREENE-BEAUFORT-
MAINLAND HYDE-DUPLIN-LENOIR-JONES-CRAVEN-PAMLICO-CARTERET-O NSLOW-
OUTER BANKS DARE-OUTER BANKS HYDE-
1016 AM EDT WED APR 18 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THE POTENTIAL EXISTS FOR A STORM SYSTEM TO BRING HAZARDOUS
WEATHER CONDITIONS TO EASTERN CAROLINA THIS COMING WEEKEND
INCLUDING LOCALLY HEAVY RAINS WITH AMOUNTS IN EXCESS OF AN INCH
POSSIBLE. RESIDENTS ARE URGED TO MONITOR THE LATEST FORECASTS
THIS WEEK FOR TIMING AND LOCATION DETAILS OF POTENTIAL WEATHER
THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

$$
Member Since: Posts: Comments:
Quoting MississippiWx:
Hazardous weather outlook for my area in Mississippi. Basically the impacts of a tropical depression/weak tropical storm:

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...NORTHEAST
LOUISIANA AND EXTREME SOUTHEAST ARKANSAS.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A SLOWING STORM SYSTEM FRIDAY NIGHT THROUGH SATURDAY NIGHT WILL HAVE
THE POTENTIAL TO PRODUCE STRONG SURFACE WINDS AND VERY HEAVY RAINFALL
ONCE AGAIN. BY SATURDAY EVENING...NORTHERLY WINDS OF 25 TO 35 MPH
AND WIDESPREAD RAIN AMOUNTS OF 2 TO 3 INCHES APPEAR LIKELY WITH
LOCALLY HIGHER TOTALS POSSIBLE GENERALLY EAST OF THE INTERSTATE 55
CORRIDOR
. FLOODING COULD BECOME A CONCERN AND RESIDENTS SHOULD STAY
IN TOUCH WITH LATER FORECASTS FOR FUTURE UPDATES.


Yeah GFS has strong winds and heavy rains battering New Orleans on Saturday as they will be close to where the low is expected to take off.

Member Since: October 26, 2011 Posts: 0 Comments: 2651
Anybody see this on the GFS and this right when the MJO is forecast to spike again. Look at the Bahamas. We could be going into hurricane season with a bang if this keeps up and the MJO continues to stay here.


Member Since: October 26, 2011 Posts: 0 Comments: 2651
Quoting Minnemike:
Hydrus.. that was an Awesome entry about the gravity waves formed by those storms!! usually i'm checking those out in environments storms are approaching, to factor their involvement with supercell rotation and bearings.. but i've never really paid much attention to the impact of those overshooting tops and the atmosphere behind the firing lines being impacted so heavily.. that was a hell of an explosive dryline!!!
If a storm is strong enough to punch a hole through the tropopause into the stratosphere, it is worth the extra attention. One Met described the gravity waves like dropping a rock into a pond or shooting one out of it, either way you get the rippling effect. They are a weird weather phenomenon indeed.
Member Since: September 27, 2007 Posts: 1 Comments: 20951
Quoting nigel20:
April 17, 2011

April 17, 2012




No surprise that the MDR has stopped warming with the re-emergence of a +NAO. If the Euro is right, a -NAO should be back around day 8 or 9.
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Hazardous weather outlook for my area in Mississippi. Basically the impacts of a tropical depression/weak tropical storm:

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...NORTHEAST
LOUISIANA AND EXTREME SOUTHEAST ARKANSAS.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A SLOWING STORM SYSTEM FRIDAY NIGHT THROUGH SATURDAY NIGHT WILL HAVE
THE POTENTIAL TO PRODUCE STRONG SURFACE WINDS AND VERY HEAVY RAINFALL
ONCE AGAIN. BY SATURDAY EVENING...NORTHERLY WINDS OF 25 TO 35 MPH
AND WIDESPREAD RAIN AMOUNTS OF 2 TO 3 INCHES APPEAR LIKELY WITH
LOCALLY HIGHER TOTALS POSSIBLE GENERALLY EAST OF THE INTERSTATE 55
CORRIDOR
. FLOODING COULD BECOME A CONCERN AND RESIDENTS SHOULD STAY
IN TOUCH WITH LATER FORECASTS FOR FUTURE UPDATES.
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April 17, 2011

April 17, 2012


Member Since: November 6, 2010 Posts: 11 Comments: 7974
Looks like i will be camping in 3 days of rain w no severe weather in N GA.
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HAZARDOUS WEATHER OUTLOOK FOR EASTERN NORTH CAROLINA
NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC
1016 AM EDT WED APR 18 2012

NCZ029-044>047-079>081-090>095-098-103-104-191430 -
MARTIN-PITT-WASHINGTON-TYRRELL-MAINLAND DARE-GREENE-BEAUFORT-
MAINLAND HYDE-DUPLIN-LENOIR-JONES-CRAVEN-PAMLICO-CARTERET-O NSLOW-
OUTER BANKS DARE-OUTER BANKS HYDE-
1016 AM EDT WED APR 18 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THE POTENTIAL EXISTS FOR A STORM SYSTEM TO BRING HAZARDOUS
WEATHER CONDITIONS TO EASTERN CAROLINA THIS COMING WEEKEND
INCLUDING LOCALLY HEAVY RAINS WITH AMOUNTS IN EXCESS OF AN INCH
POSSIBLE. RESIDENTS ARE URGED TO MONITOR THE LATEST FORECASTS
THIS WEEK FOR TIMING AND LOCATION DETAILS OF POTENTIAL WEATHER
THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

$$
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Good Afternoon all
Member Since: November 6, 2010 Posts: 11 Comments: 7974
Quoting MississippiWx:
A -NAO should help the low pressure system this weekend to race up the East Coast and strengthen. Could be quite the storm before it's all said and done with gale or storm force winds up and down the coastline from New Orleans to Maine.

Edit: My image was old and not refreshed. It showed a predominantly negative NAO. Now I see it's positive. LOL. Move along....



Regardless, the models still show it racing up the East Coast with most likely the same impacts that I discussed.


On another matter,is forecast to be negative by the end of April,and that should help warm the MDR a little bit.
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Quoting jeffs713:

I think what RitaEvac meant is that the long-range forecasts were maintaining the drought, with a high probability for below-normal rain. What ended up happening was well-above normal rainfall.

Many of us understand forecasts in general are probabilistic in nature. But in long-range forecasts, any time there is a 50% chance of one trend maintaining (below normal rainfall), and the opposite happens (above normal rainfall), it is safe to say that the exact opposite of the forecast happened. In other words... reality bucked the forecast probabilities. (I'd start busting out math with standard deviations and such... but I'm lazy)


Pretty much right on
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America's most trusted weather forecaster (even though he is from Canada) has a warning for the northeastern USA and Canada starting Saturday.

img src="">
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A -NAO should help the low pressure system this weekend to race up the East Coast and strengthen. Could be quite the storm before it's all said and done with gale or storm force winds up and down the coastline from New Orleans to Maine.

Edit: My image was old and not refreshed. It showed a predominantly negative NAO. Now I see it's positive. LOL. Move along....



Regardless, the models still show it racing up the East Coast with most likely the same impacts that I discussed.
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Hydrus.. that was an Awesome entry about the gravity waves formed by those storms!! usually i'm checking those out in environments storms are approaching, to factor their involvement with supercell rotation and bearings.. but i've never really paid much attention to the impact of those overshooting tops and the atmosphere behind the firing lines being impacted so heavily.. that was a hell of an explosive dryline!!!
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Quoting nrtiwlnvragn:
Manuscript
Impacts of Climate Change on Tropical Cyclone Tracks

Excerpt:

The changes in the large-scale steering flow are the primary contributor to the shifts in TC track frequency. However, the significant decrease in SM TCs is not observed when the large-scale steering flow is isolated suggesting that the eastward shift in genesis in the MDR is an important factor to changes in TC tracks.


In the last two seasons, it seems to me that there has been an increased frequency of recurving Atlantic systems, and that this has been caused by troughs induced by the jet stream in the western Atlantic region.

Jet stream activity is the joker in the pack of climate change. Although there should be an overall movement northwards, the highly erratic nature of its 'loops' means that many future regional trends will be completely unexpected.

Who could have predicted the unprecedented Pakistani floods, Ukrainian/Russian heatwave or the surreal record breaking March temperatures in th US this year?

All were caused by unusual jet stream activity and it's been hypothesised that the recently discovered Arctic dipole effect believed to be caused by record low summer sea ice extent in the Arctic ocean is resposible for the recent erratic movement of the jet stream.

Just goes to show how tough it is to predict the future effects of global warming. As far as I know, no one predicted any of this.
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Quoting GTcooliebai:
I've seen some of you post the CAPE Values, I'm guessing this is to determine the amount of energy available in the atmosphere to produce severe thunderstorms?


VALUE PARAMETER UNITS
190 Storm-relative Helicity m**2/s**2
191 U-component Storm Motion m/s
192 V-component Storm Motion m/s


At the National Centers the data will appear in a GEMPAK a "gdinfo" listing of the Meso Eta model output as:

PARM VCORD LEVL1 LEVL2

HLCY HGHT 3000 0
USTM HGHT 6000 0
VSTM PRES 6000 0


References:

Bunkers, M. J., and co-authors, 2000: Predicting supercell motion using a new hodograph technique. Wea. Forecasting, 15, 61-79.

Davies, J. M., and R. H. Johns, 1993: Some wind and instability parameters associated with strong and violent tornadoes. Part I: Wind shear and helicity. The tornado: Its Structure, Dynamics, Prediction, and Hazards, Geophys. Monogr., No. 79, Amer. Geophys. Union, 573-582.

What about the high values of helicity?

The units of helicity are m^2/s^2. The value of 150 is generally considered to be the low threshold for tornado formation. Helicity is basically a measure of the low-level shear, so in high shear situations, such as behind strong cold fronts or ahead of warm fronts, the values will be very large maybe as high as 1500. High negative values are also possible in reverse shear situations. img
CAPE
Convective Available Potential Energy. A measure of the amount of energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft; thus, higher values indicate greater potential for severe weather. Observed values in thunderstorm environments often may exceed 1000 joules per kilogram (J/kg), and in extreme cases may exceed 5000 J/kg.

However, as with other indices or indicators, there are no threshold values above which severe weather becomes imminent. CAPE is represented on an upper air sounding by the area enclosed between the environmental temperature profile and the path of a rising air parcel, over the layer within which the latter is warmer than the former. (This area often is called positive area.) See also CIN.
Member Since: September 27, 2007 Posts: 1 Comments: 20951
"One disaster after another": poll finds most people tie extreme weather to global warming.
69% of those polled agree that "global warming is affecting the weather in the United States"...
...and believe that the weather is getting worse by a 2to1 margin.
Taken as a whole, the polls suggest that direct experience of erratic weather may be convincing some people that the problem is no longer just a vague and distant threat.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
What's troubling to me with this system that is coming to Florida this weekend perhaps..is that if the current timetable is correct, it will begin to cross our state late Saturday Night into Sunday morning, if it is strong and we get severe weather with it..we will all be sleeping and not aware of the perhaps danger...hopefully we Floridians are listening to the warnings like the people in Oklahoma etc did when their dangerous weather was approaching
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Quoting ncstorm:
if this had been last year's winter..we would be looking at a good noreaster
:)
Member Since: September 27, 2007 Posts: 1 Comments: 20951
Almost looks like a Nor,Easter set up..
Member Since: September 27, 2007 Posts: 1 Comments: 20951
if this had been 2010 winter..we would be looking at a good noreaster
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Manuscript
Impacts of Climate Change on Tropical Cyclone Tracks

Excerpt:

The changes in the large-scale steering flow are the primary contributor to the shifts in TC track frequency. However, the significant decrease in SM TCs is not observed when the large-scale steering flow is isolated suggesting that the eastward shift in genesis in the MDR is an important factor to changes in TC tracks.
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HPC's thinking of the tracking of the Potential Low
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Quoting aerojad:
Related to climate change & increasing SSTs - is there a threshold that could be crossed this century where sub/tropical activity becomes more common in the Mediterranean Sea?

They won't have tropical waves to jump start development, but if storm tracks & strong westerlies retreat northward, could that increase the chances?

I guess it could... I mean we saw a storm there last year... The problem is the Mediterranean Sea is very small at least compared to areas of normal tropical activity and it is also situated near a desert on one side so we will probably never see significant activity there just due to land interaction and dry air.
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Quoting LargoFl:
Finally I got it..i think
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Quoting jeffs713:

Where do you see it going north of Tampa? I see the northern extent as well south of Tampa.

WAVCIS forecasts


Tampa is nearly due east of the Loop current basd on that. Either way I feel were splitting hairs here. On that last run it's close enough. I agree with you not becoming an STS all I'm saying is that the models have it vertically stacked basically the same as our invest 91L. So you really never now sometimes.
Member Since: October 26, 2011 Posts: 0 Comments: 2651
I've seen some of you post the CAPE Values, I'm guessing this is to determine the amount of energy available in the atmosphere to produce severe thunderstorms?

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Related to climate change & increasing SSTs - is there a threshold that could be crossed this century where sub/tropical activity becomes more common in the Mediterranean Sea?

They won't have tropical waves to jump start development, but if storm tracks & strong westerlies retreat northward, could that increase the chances?
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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MELBOURNE FL
1138 AM EDT WED APR 18 2012

AMZ550-552-555-570-572-575-FLZ041-044>047-053-054 -058-059-064-141-
144-147-182200-
COASTAL WATERS FROM FLAGLER BEACH TO VOLUSIA BREVARD COUNTY LINE
OUT 20 NM-
COASTAL WATERS FROM VOLUSIA BREVARD COUNTY LINE TO SEBASTIAN
INLET OUT 20 NM-
COASTAL WATERS FROM SEBASTIAN INLET TO JUPITER INLET OUT 20 NM-
WATERS FROM FLAGLER BEACH TO VOLUSIA BREVARD COUNTY LINE 20 TO
60 NM OFFSHORE-
WATERS FROM VOLUSIA BREVARD COUNTY LINE TO SEBASTIAN INLET 20 TO
60 NM OFFSHORE-
WATERS FROM SEBASTIAN INLET TO JUPITER INLET 20 TO 60 NM OFFSHORE-
INLAND VOLUSIA-NORTHERN LAKE-ORANGE-SEMINOLE-SOUTHERN BREVARD-
OSCEOLA-INDIAN RIVER-OKEECHOBEE-ST. LUCIE-MARTIN-COASTAL VOLUSIA-
SOUTHERN LAKE-NORTHERN BREVARD-
1138 AM EDT WED APR 18 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

.THUNDERSTORM IMPACT...
STORMS ARE NOT EXPECTED UNTIL SUNSET APPROACHES AND THE EAST AND
WEST COAST SEA BREEZES COLLIDE OVER THE INTERIOR OF THE STATE.
STORM COVERAGE MAY BE LIMITED...BUT ANY STORMS THAT FORM WILL
PRODUCE DANGEROUS CLOUD TO GROUND LIGHTNING AND HEAVY DOWNPOURS.
ALSO...STORMS WILL BE CAPABLE OF PRODUCING STRONG WIND GUSTS AND
HAIL UP TO THE SIZE OF COINS DUE TO COOL AND DRY MID LEVELS OF
THE ATMOSPHERE. STORMS WILL MOVE TOWARD THE EAST COAST AT 15 MPH
THROUGH THE LATE EVENING HOURS.

.RIP CURRENT IMPACT...
A SMALL LONG PERIOD SWELL COMBINED WITH A 10 TO 15 MPH SOUTHEAST
WIND WILL BRING AN ELEVATED RIP CURRENT RISK TO AREA BEACHES TODAY.
THE GREATEST RISK WILL BE THIS AFTERNOON DUE TO TIDAL EFFECTS. BEACH
VISITORS SHOULD CHECK CONDITIONS WITH BEACH PATROLS BEFORE ENTERING
THE WATER. NEVER SWIM ALONE...ESPECIALLY AT UNGUARDED BEACHES.

.MARINE THUNDERSTORM GUST IMPACT...
EVENING LIGHTNING STORMS WILL HAVE THE POTENTIAL TO PRODUCE WIND
GUSTS TO 35 MPH...HAIL AND CLOUD TO WATER LIGHTNING. STORMS WILL
MOVE FROM THE INTERIOR SECTIONS TO THE INTRACOASTAL WATERS AND
ATLANTIC COASTAL WATERS THROUGH THE LATE EVENING HOURS.

.FIRE WEATHER IMPACT...
ONGOING DRY CONDITIONS WILL CREATE A HIGH TO VERY HIGH FIRE DANGER
ACROSS PARTS OF EAST CENTRAL FLORIDA TODAY. ANY NEW FIRES WILL BE
CAPABLE OF SPREADING QUICKLY MAKING CONTAINMENT DIFFICULT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
ISOLATED TO SCATTERED LATE AFTERNOON AND EARLY EVENING LIGHTNING
STORMS CAN BE EXPECTED THURSDAY AND FRIDAY.

A GREATER THREAT FOR STORMS ARRIVES THIS WEEKEND...AS A LOW PRESSURE
SYSTEM APPROACHES FROM THE NORTHERN GULF OF MEXICO. WHILE THE SYSTEM
IS STILL A FEW DAYS AWAY...COMPUTER MODELS ARE IN AGREEMENT THAT IT
HAS THE POTENTIAL TO PUSH AN ORGANIZED SQUALL LINE OF THUNDERSTORMS
ACROSS THE FLORIDA PENINSULA. THE LATEST TIMING FROM THE MODELS
INDICATE THE LINE OF STORMS WILL SWEEP THROUGH EAST CENTRAL FLORIDA
SATURDAY NIGHT INTO EARLY SUNDAY.

ALL PERSONS IN EAST CENTRAL FLORIDA SHOULD CLOSELY MONITOR THE
WEATHER INTO THIS WEEKEND...AS THE EXPECTED TIMING AND IMPACTS
FROM THIS SYSTEM WILL BE REFINED AS THE WEEKEND APPROACHES.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY. SPOTTERS SHOULD REPORT
ANY EVENING STORMS THAT PRODUCE COIN SIZE HAIL OR WIND DAMAGE TO THE
NATIONAL WEATHER SERVICE OFFICE IN MELBOURNE.

$$

WIMMER/GLITTO
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Quoting StormTracker2K:
Loop Current goes to just north of Tampa right now (in the C Gulf).


Where do you see it going north of Tampa? I see the northern extent as well south of Tampa.

WAVCIS forecasts
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Quoting nrtiwlnvragn:
Senate Panel Would Shake Up Satellite Program

Excerpt:

The Commerce, Justice, Science and Related Agencies Subcommittee of the Senate Appropriations Committee today approved a fiscal year 2013 appropriations bill that would shift responsibility for building four major satellite systems from the National Oceanic and Atmospheric Administration (NOAA) to NASA.


That is completely idiotic.

Everything NASA does lately is 5 years late and 500% over budget.

I thought the government was looking for ways to CUT spending?!?

NASA should be decommissioned.

It would be cheaper to hire space flights from the up-and-coming private organizations than it is to continue funding NASA.
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Quoting StormTracker2K:


No it isn't. I think the Loop Current is further north right now. I'll check that. Thanks man!





As a note, I used the rough line of Naples/KW as "going over" the loop current to mean the center of circulation is going solidly over the current. Just cutting over one edge doesn't really count, as the system wouldn't get the full effect. Also, as Chucktown mentioned, the system is cold-core in nature, and won't have anything close to enough time to even get subtropical characteristics to fully tap the loop current. At best, the system will just get some extra moisture which it would get anyway from the GOM as a whole. Doesn't matter if it tracks 10 miles off the coast, or directly over the loop current. The end result will likely be the same.
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Nice looking low, just hope my house don't blow away.

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Quoting RTSplayer:
[q]This occurs primarily because of an increase in westerly winds over the Central Atlantic, and to a lesser degree,[/q]

What exactly is the explanation of why global warming should increase westerlies?

This is the way I see this situation.

If the greenhouse effect works the way it has been described, by trapping heat globally, and of course bringing the planet closer and closer to equilibrium by distributing much of the excess heat to the polar regions, then why would westerly winds in the steering layers or the surface increase?

If the difference in temperature between different latitudes and longitudes decreases due to a thermal blanket effect, then that should decrease the maximum thermodynamic potential between any two points at the same elevation, which should in turn decrease maximum potential non-tropical winds.

This is not to be confused with potential tropical cyclone winds, because tropical cyclones are powered by differences in temperature vertically, while westerlies are powered by horizontal differences in temperature.

If the temperature of the poles will be increasing faster than the temperature at the equator and mid-latitudes; for example, the pole increases by 6C and the equator increases by like 1C, then the difference between the two is reduced by 5C, but average global temperature might be just 2C or 3C warmer than today by then. That means a lower thermodynamic potential between the equator and the poles. This should translate into weaker troughs, which will fail to pick up hurricanes, and therefore fail to pull them northwards.


Combining both of these effects, then this should translate to stronger, slower moving, persistent hurricanes which track more west.



Now that's my highly intuitive understanding based on thermodynamics 101.


If anyone cares to explain why I'm wrong, I'm willing to be "educated".

I agree with most of your logic but I think the simplest reason that more recurving storms are predicted in the future is that with warmer ocean temperatures we would expect more Cape Verde storms to form sooner coming off of Africa and have more oppotunity to recurve since they would have a longer distance to travel
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Loop Current goes to just north of Tampa right now (in the C Gulf).

Member Since: October 26, 2011 Posts: 0 Comments: 2651
Quoting ScottLincoln:


The long range CPC forecasts are not binary, and as such, you cannot have "the complete opposite of what was forecasted." The forecasts are probabilistic in nature, and generally show the probability of three choices... above normal, below normal, equal chances. An area indicated as "above normal" with a 50% contour does not mean a forecast of above normal; it means there is a 50% chance of above normal with a 50% chance of normal or below normal.

A 60% contour must be forecasted before you really even reach a true forecast for either below/above to be the most likely scenario.

I think what RitaEvac meant is that the long-range forecasts were maintaining the drought, with a high probability for below-normal rain. What ended up happening was well-above normal rainfall.

Many of us understand forecasts in general are probabilistic in nature. But in long-range forecasts, any time there is a 50% chance of one trend maintaining (below normal rainfall), and the opposite happens (above normal rainfall), it is safe to say that the exact opposite of the forecast happened. In other words... reality bucked the forecast probabilities. (I'd start busting out math with standard deviations and such... but I'm lazy)
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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.

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