Isaac is strengthening

By: Dr. Jeff Masters , 2:58 PM GMT on August 24, 2012

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Tropical Storm Isaac is strengthening. An Air Force Reserve hurricane hunter aircraft measured surface winds of 60 mph on the east side of the center, about 170 miles south of Santo Domingo in the Dominican Republic, at 8:40 am EDT this morning. Winds at the aircraft's flight level of 5,000 feet were hurricane force, 76 mph. The surface pressure remained fairly high, at 1000 mb. Tropical cyclones have a warm core, and the Hurricane Hunters typically find that a storm's lowest pressure is also where the warmest temperature are. However, this morning's flight found that Isaac was still disorganized, with the storm showing almost no evidence of a warm core. Isaac's warmest temperatures were displaced 75 miles to the west of where the lowest pressure was. There were no signs of an eyewall beginning to build. Infrared and visible satellite loops show that Isaac is somewhat asymmetric, with a large band of intense thunderstorms to the east, separated from the core region. This is interfering with both the storm's low-level inflow and upper-level outflow, but the band appears to be dying out. An analysis of upper level winds from the University of Wisconsin CIMSS shows an upper-level outflow channel well-established to the north, and an intermittent outflow channel to the south.


Figure 1. Evening shot of Tropical Storm Isaac taken on August 23, 2012, by the NOAA Hurricane Hunters.

Isaac's rains
Radar imagery from Puerto Rico shows that Isaac is dumping some very heavy rains to the south and east of the center. Ponce, Puerto Rico had a wind gust of 37 mph this morning as a heavy band of rain moved through, and radar-estimated rainfall amounts are in excess of 7 inches for the region just north of Ponce. Power outages to 2,000 homes have been reported in Puerto Rico this morning. NOAA buoy 42085 offshore from Ponce reported a wind gust of 54 mph near 9 am EDT this morning. Rainfall estimates from microwave satellite instruments suggest that Isaac's heaviest rains are to the south of the center, and that the Dominican Republic and Eastern Haiti will escape the worst of Isaac's rains. Haiti's southwest peninsula and Eastern Cuba should suffer the heaviest rains.


Figure 2. Radar-estimated precipitation from the Puerto Rico radar shows the region near Ponce has received up to 7" of rain as of 10 am EDT August 24, 2012.

Latest model runs for Isaac
The latest set of 00Z and 06Z (8 pm and 2 am EDT) model runs have come into better agreement, thanks to the dropsonde mission by the NOAA jet yesterday afternoon and evening. Isaac should move over Haiti's southwest peninsula and then eastern Cuba, then track along the spine of Cuba before popping off into the Florida Straits on Sunday. A trough of low pressure will then pull Isaac to the northwest, and then north, towards the Central Gulf Coast. Landfall locations range from Mississippi (06Z HWRF model run) to the Florida Panhandle south of Tallahassee (06Z GFDL model run.) It is possible that the trough of low pressure pulling Isaac to the north may not be strong enough to pull Isaac all the way to the northeast and out to sea, and the ECMWF model indicates that Isaac could stall out after landfall over the Tennessee Valley for several days.


Figure 3. Predicted 5-day rainfall total ending at 2 am EDT Wednesday August 29, from Tropical Storm Isaac. Graphics were generated from the 6Z (2 am EDT) August 24, 2012 run of the HWRF model. Image credit: Morris Bender, NOAA/Geophysical Fluid Dynamics Laboratory.

Intensity forecast for Isaac
Isaac has not intensified as much as predicted, and I think that the storm's very large size is partially responsible for that. It's tough to spin up as much atmosphere as Isaac is attempting to do very quickly. Conditions remain favorable for intensification today, with wind shear low, 5 - 10 knots, ocean temperatures warm, 29°C, and dry air mostly mixed out of the storm's core. The large band of intense thunderstorms to the east, separated from the core region, appears to be dying out now, which will help the storm grow more organized. The storm's structure has improved considerably between 9 am - 10 am EDT, with a fairly tight center forming, exposed to view, on the north edge of Isaac's heaviest thunderstorms. A curved band of heavy thunderstorms is now trying to wrap around this center to the northeast, and this band will bring very heavy rains to Haiti and the Dominican Republic this afternoon. I expect that the Hurricane Hunters will observe a partial eyewall in their vortex reports between 2 - 4 pm EDT this afternoon. The storm's large size and disorganized structure suggests that Isaac will be able to intensify only slowly today, and will have top winds of 70 - 75 mph before encountering Southwest Haiti and Eastern Cuba tonight and Saturday. Isaac will likely be a 50 - 60 mph tropical storm on Saturday and Sunday as it moves over Cuba. Once Isaac pops off the coast of Cuba into the Florida Straits, it will be over very warm waters of 31 - 32°C (88 - 90°F), wind shear will be light to moderate. The upper-level wind pattern favorable may be quite favorable for intensification, with low wind shear due to an upper-level anticyclone over the storm--though the models disagree on whether or not this anticyclone will set up directly over Isaac or not. It will probably take at least 24 hours with the storm's center over water for it to become a hurricane. It is possible that Isaac could be approaching Category 3 strength by the time it makes landfall on Tuesday on the Gulf Coast, as suggested by the latest 06Z run of the HWRF model.

Impact on Tampa, Florida
The Republican National Convention begins on Monday in Tampa, Florida. The latest 11 am EDT wind probability forecast from NHC gives Tampa a 17% chance of receiving tropical storm-force winds and a 1% chance of receiving hurricane-force winds on Monday. Tampa is in the NHC cone of uncertainty, though near the edge of it. At a minimum, Tampa will receive very heavy rains and wind gusts in excess of 40 mph. Isaac is going to be hard-pressed to bring hurricane-force winds to the city, though, since any path that takes it close to Tampa would keep the storm too close to land for significant intensification to occur. I put the odds of a mass evacuation being ordered for Tampa during the convention at 1%. I have detailed information on Tampa's storm surge vulnerability in a post from last week.

Invest 97L off the coast of Africa
A tropical wave that moved off the coast of Africa on Thursday has been designated Invest 97L by NHC this morning. The storm has a modest amount of spin and heavy thunderstorms, and is under moderate wind shear of 10 - 20 knots. In their 8 am EDT Tropical Weather Outlook, NHC gave 97L a 30% chance of developing by Sunday morning. The 8 am EDT SHIPS model forecast predicts that 97L will track west-northwest over the next few days, and encounter a region of high wind shear associated with an upper-level low on Monday and Tuesday. This low may be capable of tearing the storm apart, as happened to Tropical Storm Joyce. None of the models currently foresee that 97L will affect the Lesser Antilles Islands, but 97L may pass near Bermuda 7 - 8 days from now.



20th anniversary of Hurricane Andrew
Today, August 24, is the 20th anniversary of Hurricane Andrew, which hit South Florida as a Category 5 hurricane with 175 mph winds--one of only three Category 5 hurricanes ever to hit the U.S. With Isaac churning through the Caribbean this week, I didn't have time to prepare a special post on Andrew, but our Hurricane Andrew archive page has links to satellite and radar images, newspaper headlines, and 49 YouTube videos. Here's an additional link for an Andrew damage video shot by wunderblogger/storm chaser Mike Theiss, when he was 14 years old.

Jeff Masters

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Quoting chum8888:


Weather newbie here. With Issac's close proximity to the South Coast of Haiti, would Adiabatic winds coming from the north off the mountains impact the left side of the storm thus inhibiting its ability to organize? Sorry if this is a dumb question.

Generally yes, this happens with a lot of storms that get near Hispaniola... The effects vary though, sometimes they are significant and sometimes barely noticeable.
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You've got to be kidding me right? Disregard the GFS and Canadian. Damm this sounds like Debby all over again. I will never foreget the NHC had the track of Debby hitting TX as Debby was near the FL west coast. Idiots!!

...ISAAC EXPECTED TO MOVE INTO THE MID-SOUTH BY NEXT FRIDAY...

THE WESTERLIES ACROSS THE NORTHERN PACIFIC ARE NORTH OF WHAT IS
NORMAL FOR LATE AUGUST. THIS FORCES ENERGY TO POOL DOWNSTREAM,
ACROSS THE PACIFIC NORTHWEST, WITH DOWNSTREAM TROUGHING EXPECTED
ACROSS THE NORTHEAST AND A WARM CORE RIDGE EXPECTED TO WAVER IN
POSITION AND STRENGTH BETWEEN THE CENTRAL ROCKIES AND CENTRAL
PLAINS. THE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE IS IN GOOD
AGREEMENT ON THESE GENERAL IDEAS. THE MODEL CHOICE THIS PERIOD
WAS PARTIALLY CONSTRAINED BY THE LATEST NATIONAL HURRICANE CENTER
(NHC) FORECAST FOR ISAAC, WHICH RESEMBLED THE 12Z UKMET THROUGH
THURSDAY MORNING. A 00Z GFS/00Z ECMWF COMPROMISE WAS USED
THEREAFTER, WITH INPUT RECEIVED FROM NHC REGARDING TROPICAL
SYSTEMS AT 17Z. THE 06Z/12Z GFS AND 12Z CANADIAN SOLUTIONS HAD TO
BE THROWN OUT BY DEFAULT.
THIS LED TO REASONABLE CONTINUITY WITH
THE MID-MORNING PRESSURES.

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1409. ncstorm
Quoting gustavcane:
THE 06Z/12Z GFS AND 12Z CANADIAN SOLUTIONS HAD TO
BE THROWN OUT BY DEFAULT.
 

there you have it folks.



they threw out the GFS with Debby too and we all know how that ended..
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It boggles my mind that people that are in the cone, or near the cone have to ask if they should get supplies in case it does come their way... WELL DUH!!

anyone that could POTENTIALLY be effected by this storm should prepare. If it hits, you are ready, if it does not hit, you are ready for the next one. For years I have kept what my daughter calls "DOOMSDAY BOXES".

Containers full of items in case of a hurricane. I have been through many storms and have never once been in need of anything. If you wait till the last minute, you will have long ;ines and everything picked over and gone... PREPARE EARLY AND BE AHEAD OF THE GAME.
Member Since: September 18, 2007 Posts: 0 Comments: 1073
Quoting ironbark:
why does everybody pick on this guy.he has a righy to his opinion

which guy? lots of guys on here that we pick on.
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1405. ncstorm
Quoting OBXNCWEATHER:


lol hey ncstorm... i would second that... there are quite a few times i remember sitting on Hatteras Island watching the GFS go right back to it's original forecast days out and come close to verifying...

i'm sure the entire pattern was different (i would be interested if anyone knows), but Floyd comes to mind....


Floyd..was supposed to hit florida..and where did it end up?
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THE 06Z/12Z GFS AND 12Z CANADIAN SOLUTIONS HAD TO
BE THROWN OUT BY DEFAULT.
 

there you have it folks.

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Quoting snow2fire:


Wow - bad timing for Haiti. One good thing is that Isaac took so long developing that it's not a hurricane - yet. Hopefully things will be less bad then they could have been.

Can't help worry about the people there in tents...


for many a tent would be a giant step up...for tens of thousands it's more like a filthy bedsheet strung up on some sticks...
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Quoting StormSurgeon:


I pop in and lurk occasionally just to get a giggle...
There are only a very small group of people and everybody who are serious about weather and visit this blog frequently know who this people are,very annoying!!! trying to guide the storm their way!!! when you are trying to get the best accurate information from this site,specially when there is a serious situation in the tropics right now.
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Quoting ncstorm:


LOL.."pick a model..any model"..

Makes sense, actually. It doesn't follow logic to use a model that shows a drastic change in short-to-medium term guidance, when looking at macroscale patterns, such as longwave troughs and ridges.
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Quoting caneswatch:
Interstatelover was right, at least Tropical Storm conditions for South Florida. This is an odd play out.
Yay! The first anybody said i was right!
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Just read Levi's forecast. I am so relieved everything will be okay. Just looks like Florida will have some pretty good rains. Thanks for the great news Levi!
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Quoting MAweatherboy1:

Not dry, but drier. Seeing a big strip of white inside these things indicates that they are struggling with dry air.



According to Master, what we are seeing is the eastern band weakening which indicates that the storm is organizing. I know it is hard to believe that with satellite but well they are the experts.
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why does everybody pick on this guy.he has a righy to his opinion
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1396. JasonRE
When is this thing supposed to break free of the islands and officially enter the GOM? Once it does enter the GOM, would warmer waters and less land have any effect on the path? Lastly, is there ANY chance of this thing still moving West and ending up where the EURO model places it?

Thank you
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ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT FRI AUG 24 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM ISAAC...LOCATED ABOUT 135 MILES SOUTH-SOUTHEAST OF PORT AU
PRINCE HAITI.

THE NATIONAL HURRICANE CENTER HAS ISSUED THE LAST ADVISORY ON
TROPICAL DEPRESSION JOYCE...LOCATED ABOUT 1030 MILES EAST OF THE
LEEWARD ISLANDS. UPPER-LEVEL WINDS DO NOT APPEAR CONDUCIVE FOR THE
REMNANT LOW TO REGENERATE INTO A TROPICAL CYCLONE DURING THE NEXT
COUPLE OF DAYS. THIS SYSTEM HAS A LOW CHANCE...10 PERCENT...OF
AGAIN BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT
MOVES WEST-NORTHWESTWARD TO NORTHWESTWARD AT ABOUT 20 MPH.

1. SHOWERS AND THUNDERSTORMS HAVE CHANGED LITTLE IN ORGANIZATION NEAR A
BROAD AREA OF LOW PRESSURE CENTERED ABOUT 150 MILES SOUTH OF THE
CAPE VERDE ISLANDS. UPPER-LEVEL WINDS ARE MARGINALLY CONDUCIVE FOR
DEVELOPMENT...AND THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
TOWARD THE WEST OR WEST-NORTHWEST AT 10 TO 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BERG
NNNN
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Quoting MAweatherboy1:

Not dry, but drier. Seeing a big strip of white inside these things indicates that they are struggling with dry air.



Weather newbie here. With Issac's close proximity to the South Coast of Haiti, would Adiabatic winds coming from the north off the mountains impact the left side of the storm thus inhibiting its ability to organize? Sorry if this is a dumb question.
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Pretty easy to see where the center is on RGB...

Member Since: September 3, 2011 Posts: 13 Comments: 3468
Quoting WxGeekVA:


For the first time in Isaac's life, the strongest convection is in the northeast quadrant of the storm.


Wow - bad timing for Haiti. One good thing is that Isaac took so long developing that it's not a hurricane - yet. Hopefully things will be less bad then they could have been.

Can't help worry about the people there in tents...
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Latest EURO

Member Since: September 18, 2007 Posts: 0 Comments: 1073
1390. hydrus
S
Member Since: September 27, 2007 Posts: 1 Comments: 20332
Quoting chevycanes:

lol.

you never give up, i give you that.

recon has already proven it's been moving NW. all you have to do is go back and see where they put the center early this morning while flying in the storm.


yes it is true that recon has proven it has moved NW however steering still says more W-WNW so I'm not saying its W-WNW movement the steering maps are and last I checked I am not the one who makes them
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Quoting presslord:
people on this blog bashing the NHC are an amusement to me....


I pop in and lurk occasionally just to get a giggle...
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1387. ncstorm
Quoting AtHomeInTX:
HPC

...TROPICAL STORM ISAAC...

THE TRACK OF ISAAC IN THE 12Z NAM NOW MORE CLOSELY RESEMBLES THE
MAJORITY OF GUIDANCE...WHEREAS EARLIER NAM RUNS HAD BEEN FAR TO
THE RIGHT. IN THIS RUN...HOWEVER...THE STRUCTURE IS MUCH
DIFFERENT. MOST OF THE MODELS INDICATE A BROAD AREA OF SURFACE LOW
PRESSURE...AND PERHAPS A SECOND LOCAL PRESSURE MINIMUM SOUTHWEST
OF THE TRACK CENTER-LINE. THE NAM NOW SHOWS THE MORE SOUTHWESTERN
MINIMUM BECOMING EQUAL TO THE ORIGINAL CENTER...AND THEN BECOMING
DOMINANT AS THE SYSTEM CROSSES CUBA. THIS NOTION IS NOT REFLECTED
IN THE OTHER MODELS...BUT AT LEAST BEARS WATCHING GIVEN THAT THE
SYSTEM IS BROAD...HAS BEEN SLOW TO ORGANIZE...AND WILL BE
INTERACTING WITH THE LARGER ISLANDS AT THE WESTERN END OF THE
ANTILLES.

...ISAAC EXPECTED TO MOVE INTO THE MID-SOUTH BY NEXT FRIDAY...

THE WESTERLIES ACROSS THE NORTHERN PACIFIC ARE NORTH OF WHAT IS
NORMAL FOR LATE AUGUST. THIS FORCES ENERGY TO POOL DOWNSTREAM,
ACROSS THE PACIFIC NORTHWEST, WITH DOWNSTREAM TROUGHING EXPECTED
ACROSS THE NORTHEAST AND A WARM CORE RIDGE EXPECTED TO WAVER IN
POSITION AND STRENGTH BETWEEN THE CENTRAL ROCKIES AND CENTRAL
PLAINS. THE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE IS IN GOOD
AGREEMENT ON THESE GENERAL IDEAS. THE MODEL CHOICE THIS PERIOD
WAS PARTIALLY CONSTRAINED BY THE LATEST NATIONAL HURRICANE CENTER
(NHC) FORECAST FOR ISAAC, WHICH RESEMBLED THE 12Z UKMET THROUGH
THURSDAY MORNING. A 00Z GFS/00Z ECMWF COMPROMISE WAS USED
THEREAFTER, WITH INPUT RECEIVED FROM NHC REGARDING TROPICAL
SYSTEMS AT 17Z. THE 06Z/12Z GFS AND 12Z CANADIAN SOLUTIONS HAD TO
BE THROWN OUT BY DEFAULT.
THIS LED TO REASONABLE CONTINUITY WITH
THE MID-MORNING PRESSURES.



LOL.."pick a model..any model"..
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HPC

TROPICAL CYCLONE ISAAC
======================
THE 06Z/12Z GFS AND 12Z CANADIAN RECURVE THE SYSTEM QUICKER
THROUGH THE MID-ATLANTIC STATES THAN THE OTHER GUIDANCE, WHILE THE
00Z/12Z ECMWF AND ITS ENSEMBLE MEAN SHOW STRONGER RIDGING ACROSS
THE PLAINS/MIDWEST WHICH KEEPS THE SYSTEM ON A SLOWER AND MORE
WESTERLY TRAJECTORY. THE QUICKER SOLUTION CANNOT BE RULED OUT AS
THE PREFERRED MODEL BLEND DROPS ENERGY FROM THE WESTERLIES AROUND
THE NORTHWEST SIDE OF ISAAC, CLOSING OFF A MID TO UPPER LEVEL LOW
ACROSS TEXAS BY NEXT THURSDAY AND FRIDAY. THIS DEVELOPMENT WOULD
EFFECTIVELY SHIFT THE COL IN THE STEERING PATTERN SO FAR SOUTH
THAT ISAAC WOULD HAVE LITTLE CHOICE BUT TO RECURVE AROUND THE
PERIPHERY OF THE SUBTROPICAL RIDGE, INITIALLY LURED BY A BREAK IN
THE RIDGE ACROSS THE UPPER OHIO VALLEY TUESDAY (SIMILAR TO DEBBY
IN LATE JUNE BUT FARTHER TO THE WEST). HEAVY CORE RAINFALL WITH
AREAL AVERAGE AMOUNTS OF 8-9 INCHES ARE EXPECTED ACROSS SOUTHERN
FLORIDA/THE FLORIDA KEYS/THE FLORIDA PANHANDLE WITH THE SYSTEM
THROUGH WEDNESDAY MORNING PER THE 15Z NHC TRACK, WITH LESSER
AMOUNTS OF 3-5 INCHES POSSIBLE ACROSS THE SOUTHEAST AND MID-SOUTH
BY NEXT FRIDAY NEAR ITS TRACK, ITS DRAPING FRONTAL BOUNDARY ACROSS
THE SOUTHEAST, AND WITHIN ITS MAIN INFLOW BAND FROM THE GULF OF
MEXICO ON ITS EASTERN SIDE. LOCAL AMOUNTS OF 12-16 INCHES ARE
POSSIBLE BOTH WITHIN ITS CENTRAL DENSE OVERCAST (CDO) AND WHERE
ITS MAIN INFLOW BAND SETS UP AND PIVOTS, WHICH COULD BE AS FAR
EAST AS GEORGIA. THE CURRENT SIZE AND FORECAST TRACK FOR ISAAC
RESEMBLE HURRICANE DENNIS OF 2005, THOUGH SOMEWHAT TO THE EAST
AFTER LANDFALL. CENTRAL GEORGIA REMAINS IN AN EXCEPTIONAL,
LONG-DURATION DROUGHT SO THEY COULD USE THE RAINFALL. NORTHEAST
FLORIDA AND SOUTHERN GEORGIA WERE SATURATED FROM BERYL AND DEBBY
AS WELL AS SYNOPTICALLY-DRIVEN RAINFALL EVENTS DURING THE PAST
SEVERAL DAYS, SO THE RAIN WOULD BE PROBLEMATIC IN THAT AREA.
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Since NHC and NWS Miami share the same facilities in South Dade the latest discussion out of NWS Miami should give us some clue of what NHC is thinking for the 5pm advisory.

HW will likely be posted now for both the keys and S Florida from Broward-Collier southward

TSW north of this line to central Florida
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people on this blog bashing the NHC are an amusement to me....
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Quoting Levi32:


I "should" graduate here Spring 2014, but then I may have to move to Florida and not actually start school there until I have been living there a year and gotten residency. Out-of-state tuition is out of the question.


As smart as you are, they should give you a scholarship.
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I know Isaac is strengthening, but I just dont see a good satelitte pic from rainbow.
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HPC

...TROPICAL STORM ISAAC...

THE TRACK OF ISAAC IN THE 12Z NAM NOW MORE CLOSELY RESEMBLES THE
MAJORITY OF GUIDANCE...WHEREAS EARLIER NAM RUNS HAD BEEN FAR TO
THE RIGHT. IN THIS RUN...HOWEVER...THE STRUCTURE IS MUCH
DIFFERENT. MOST OF THE MODELS INDICATE A BROAD AREA OF SURFACE LOW
PRESSURE...AND PERHAPS A SECOND LOCAL PRESSURE MINIMUM SOUTHWEST
OF THE TRACK CENTER-LINE. THE NAM NOW SHOWS THE MORE SOUTHWESTERN
MINIMUM BECOMING EQUAL TO THE ORIGINAL CENTER...AND THEN BECOMING
DOMINANT AS THE SYSTEM CROSSES CUBA. THIS NOTION IS NOT REFLECTED
IN THE OTHER MODELS...BUT AT LEAST BEARS WATCHING GIVEN THAT THE
SYSTEM IS BROAD...HAS BEEN SLOW TO ORGANIZE...AND WILL BE
INTERACTING WITH THE LARGER ISLANDS AT THE WESTERN END OF THE
ANTILLES.

...ISAAC EXPECTED TO MOVE INTO THE MID-SOUTH BY NEXT FRIDAY...

THE WESTERLIES ACROSS THE NORTHERN PACIFIC ARE NORTH OF WHAT IS
NORMAL FOR LATE AUGUST. THIS FORCES ENERGY TO POOL DOWNSTREAM,
ACROSS THE PACIFIC NORTHWEST, WITH DOWNSTREAM TROUGHING EXPECTED
ACROSS THE NORTHEAST AND A WARM CORE RIDGE EXPECTED TO WAVER IN
POSITION AND STRENGTH BETWEEN THE CENTRAL ROCKIES AND CENTRAL
PLAINS. THE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE IS IN GOOD
AGREEMENT ON THESE GENERAL IDEAS. THE MODEL CHOICE THIS PERIOD
WAS PARTIALLY CONSTRAINED BY THE LATEST NATIONAL HURRICANE CENTER
(NHC) FORECAST FOR ISAAC, WHICH RESEMBLED THE 12Z UKMET THROUGH
THURSDAY MORNING. A 00Z GFS/00Z ECMWF COMPROMISE WAS USED
THEREAFTER, WITH INPUT RECEIVED FROM NHC REGARDING TROPICAL
SYSTEMS AT 17Z. THE 06Z/12Z GFS AND 12Z CANADIAN SOLUTIONS HAD TO
BE THROWN OUT BY DEFAULT.
THIS LED TO REASONABLE CONTINUITY WITH
THE MID-MORNING PRESSURES.

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Quoting wxwonder1:


That is a very interesting observation. I'm wondering if Levi would have any thoughts on this? At any rate, I do hope someone has some thoughts to offer on that.


would love to hear your thoughts
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1378. FOREX
Quoting FOREX:


The local METS here in PCB disagree, but who knows. As of 15 minutes ago WJHG METS still think it will go well east of PC Beach. I'll be happy when I know for sure so I can go to the bank and start preparing.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
1055 AM EDT Fri Aug 24 2012

.NEAR TERM [Today]...
This morning`s KTAE sounding showed a PW of 1.42". Shower activity
has completely ceased over the area overnight as dry air filtered into
the area on the backside of an upper level trough located over South
Carolina. Along with the drier air and decreased cloud cover
expected today, temps should reach the lower 90s this afternoon.
With very low POPs there is only an isolated chance of any showers
this afternoon.

&&


.SHORT TERM [Saturday through Sunday]...
Low PWATs will continue through Saturday thanks to weak northerly
flow on the backside of the east coast trof. This has put us in a
generally offshore flow pattern. However this same weakness will
provide a conduit for the future motion of Issac. Despite remaining
near a weakness in the subtropical ridge or a slight mid-upper level
trough, PoPs will continue below climatology through Saturday. With
the projected path of Issac, however, increasing easterly flow from
the Atlantic will begin to increase atmospheric moisture clouds and
POPs with light precipitation over the Eastern Big Bend on Sunday
afternoon with light easterly winds over the marine areas.

&&

.PREVIOUS DISCUSSION...
555 AM EDT Fri Aug 24 2012

.LONG TERM [Sunday Night through Thursday]...Very little change in
thinking from the previous package, as the drier air which is moving
in from the NW will provide our CWA with a welcomed reprieve from
the Humidity, as well as below normal PoPs for the end of this week
and weekend. However, this will all begin to change by Monday as
Tropical Storm Isaac, which is still well out to sea in the Atlantic
to the south of Hispanola, continues on its approach through the
Caribbean and into the Gulf of Mexico. From there, it is expected to
strengthen into a Hurricane and begin to turn more towards the NW or
even NNW, with a possible landfall in the NE or NC Gulf Coast Region
on Tuesday Night or Wednesday. It is still too early to determine
the exact track, development, and intensity of Isaac, as it has been
fairly slow to develop and will likely have to encounter some
potentially disruptive higher terrain over parts of Cuba. However,
Isaac is a very large system, so it is important not to focus on the
exact track due to the uncertainties mentioned above. Also due to
its large size, Isaac is expected to have a very large envelope of
Tropical Storm force winds associated with it. Additionally,
depending on its final track and speed, Isaac may dump quite a bit
of rainfall across a good portion of our CWA, even if it does not
make a direct landfall in our area. This could be quite problematic,
since many locations across the region have received copious amounts
of rainfall during the past few weeks, which could result in lower
than normal thresholds for Flash Flooding. Therefore, all interests
in the northern Gulf of Mexico should closely monitor the progress
of Isaac and stay tuned to the latest Advisories from the National
Hurricane Center, and local forecasts and updates from the National
Weather Service in Tallahassee.


&&

.AVIATION [Through 12Z Saturday.]...
With the drier air conditions at all the aerodromes remained VFR
this morning. With low POPs only very isolated showers are expected
today.

&&

.MARINE...
Winds and seas over the coastal waters will remain on the low side
through the first 24 hours of the forecast with a very weak pressure
gradient in place. Thereafter, winds and seas will begin to slowly
increase as the gradient tightens between high pressure to the north
and Tropical Storm Isaac to the south. Expect initial small craft
advisory conditions to reach the offshore waters by late Sunday
afternoon. There remains considerable uncertainty as to the track
and intensity of Isaac. On the current forecast track, conditions
will deteriorate quickly Sunday night and remain hazardous through
the middle of next week. Mariners can check the latest hurricane
forecasts at hurricanes.gov.

&&

.FIRE WEATHER...
Even with high pressure building to our north with afternoon
dewpoints dropping into the Mid to Upper 60s, it will still not
become dry enough for Red Flag Conditions to materialize over the
next few days. Afternoon Relative Humidities should hold safely
above critical thresholds across the Tri-State area. Then, by the
early to middle portion of next week, Isaac will bring a return to
plenty of Tropical Moisture to our region, with a significant
wetting rainfall becoming more likely with time.

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.

&&

$$

SHORT TERM...Lanier
LONG TERM...Gould
AVIATION...Lanier


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The Barahona peninsula in SW Haiti has a mountain range right through it, but since that peninsula is so narrow, it probably won't weaken Issac too much. If Issac's center can run up the spine of Cuba from the SE and travel over Cuba to at least the 79 or 80 longitude area, it should be disrupted and weaken further. The amount of terrain that the storm's center will move over Cuba is uncertain, so any degree of weakening tomorrow/Sunday before moving out over open water again remains to be seen.
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Quoting midgulfmom:
OBXNCWEATHER, good post!


thank you... i have been reading yours today as well and have appreciated the discussions you've been having....

*fingers crossed for you and i*
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1375. emcf30
Quoting Jedkins01:


Yeah out of state tuition is really bad, if you did become a resident, FSU is probably one of the most reasonable schools cost wise out there, and all around a really great campus, I've visited twice now. I'm just waiting to hear back from them on my application now...


Good luck to both you and Levi.



1980 Alumni here. Loved that school

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Thanks
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OBXNCWEATHER, good post!
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Still no partial eyewall according to Vortex message.
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1371. FOREX
Quoting NOLALawyer:
Cantore has allegedly arrived on the Gulf Coast.......


Guess we will know in 36 minutes because he is scheduled to be at the expert desk at 4pm Eastern.
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Quoting GoWVU:
WOW, go to work today and get home and seems like we might be seeing a little of Issac here in Charleston SC... I think it was Levi that said this was going to be a East Coast storm?? Funny thing nothing on the local news about this shift to the east....


It will eventually come to nc/sc once it makes landfall on the panhandle of florida it will track northeast towards you
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Quoting OBXNCWEATHER:
I don't want to eat up space, but I looked and haven't seen this posted yet... I have a question/observation about something in their discussion regarding the current surface analysis... In many many many incidents past when there has been a storm moving north out of the Caribbean, I have noticed that when pressures are lower over North Carolina as it is emerging from the mountainous terrain down there, that systems quite often then begin to ride the right side of the cone of uncertainty, causing continuous rightward adjustments... I have no idea what it means, but I have been around long enough to recognize it as "something I've noticed and mentioned to myself on more than one occasion".

(P.S. for the record, those who know me know that i do not wish, doom, down, hype, or any other type of -cast, so that is not what this is :) My handle is OBXNCWEATHER, although I now live in Satellite Beach, FL, which just happens to be on the East Coast of FL...)

I hope I disclaimed enough. Just wondering if anyone else ever noticed the same pattern of lower pressures over eastern NC when a storm emerges into the W Atl or Florida Straits.

Thanks.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
256 PM EDT FRI AUG 24 2012

.DISCUSSION...
THE UPPER LEVEL PATTERN CONSISTED OF HIGH PRESSURE STRETCHING FROM
JUST OFF THE EAST COAST OF FLORIDA TO THE WESTERN ATLANTIC...A
WEAKNESS IN THE RIDGE OVER FLORIDA...WITH A WEAK LOW PRESSURE AREA
DEVELOPING OVER THE CAROLINAS AND WESTERN ATLANTIC...AND ANOTHER
HIGH OVER THE WESTERN GULF AND TEXAS. SCATTERED SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH THE WIND SURGE ARE SPREADING WEST
ACROSS MOST OF THE REGION THIS AFTERNOON. SOME STRONG WINDS 40 T0
50 MPH MAY BE POSSIBLE IN THESE STORMS. THESE
CONDITIONS...SCATTERED SHOWERS WITH EMBEDDED THUNDERSTORMS...IS
EXPECTED TO CONTINUE OVERNIGHT AND THROUGH THE DAY ON SATURDAY.

ALL EYES THEN TURN TO TROPICAL STORM ISAAC. ISAAC HAS BEGUN ITS
NORTHWEST TURN AND WILL MOVE OVER HISPANIOLA AND TOWARDS EASTERN
CUBA OVERNIGHT. ALL MODEL GUIDANCE HAS SHIFTED SIGNIFICANTLY TO
THE EAST FROM RUNS YESTERDAY. THE ECMWF IS THE FURTHEST
WEST...WITH THE STORM MOVING CLOSE TO THE CURRENT NHC OFFICIAL
FORECAST TRACK. THE OTHER MODELS NOW BRING THE STORM INTO THE
MIDDLE KEYS OR SOUTH FLORIDA. IN ADDITION...MOST OF THE MODELS
SHOW LITTLE INTERACTION WITH CUBA. THIS COULD BE VERY SIGNIFICANT
FOR SOUTH FLORIDA...BECAUSE THE STORM WOULD BE ABLE TO SPEND MUCH
MORE TIME OVER WATER. LOOKING AT THE GLOBAL MODELS AND HURRICANE
MODELS...THEY WOULD BE INDICATING A HURRICANE POSSIBLY MOVING
INTO THE MIDDLE KEYS OR SOUTH FLORIDA SUNDAY EVENING. THIS IS ALSO
SOMEWHAT FASTER THAN PREVIOUS RUNS. SO THERE IS A LOT MORE
UNCERTAINTY FOR SOUTH FLORIDA. THIS IS ONLY ONE SUITE OF MODEL
RUNS...BUT THE THREAT TO SOUTH FLORIDA LOOKS TO BE INCREASING.

GOING WITH THE OFFICIAL NHC TRACK...WE CAN START TO NARROW DOWN
SOME IMPACTS THAT MAY OCCUR TO SOUTH FLORIDA. HEAVY RAINFALL COULD BE
A MAJOR IMPACT ACROSS SOUTH FLORIDA...WITH 4 TO 8 INCHES OF RAIN
AND LOCALLY HIGHER AMOUNTS. SOUTH FLORIDA IS EXPECTED TO BE ON THE
RIGHT FRONT QUADRANT OF THE STORM...AND TROPICAL TORNADOES WOULD
ALSO BE POSSIBLE. TROPICAL STORM CONDITIONS COULD BEGIN AS EARLY
AS SUNDAY MORNING ACROSS THE COASTAL WATERS AND DEEP SOUTH
FLORIDA COASTAL AREAS. SURGE IS TOO EARLY TO DETERMINE...BUT ON
THE CURRENT TRACK...MINOR COASTAL FLOODING WOULD BE POSSIBLE ALONG
BISCAYNE BAY AND ALONG THE COLLIER COUNTY COASTLINE. KEEP IN MIND THAT
THESE IMPACTS COULD BECOME MUCH DIFFERENT IF THE STORM TRACKS TO
THE RIGHT OR LEFT...OR IF THE STORM BECOMES STRONGER THAN
CURRENTLY INDICATED.

CONDITIONS WILL SLOWLY IMPROVE FROM SOUTH TO NORTH ON MONDAY...BUT
DEPENDING ON THE TRACK OF ISAAC...RAIN BANDS MAY CONTINUE TO
AFFECT MUCH OF THE REGION THROUGH THE DAY. SOUTHERLY WINDS WILL
THEN CONTINUE ON TUESDAY...WITH CONDITIONS CONTINUING TO IMPROVE.


That is a very interesting observation. I'm wondering if Levi would have any thoughts on this? At any rate, I do hope someone has some thoughts to offer on that.
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You just put yourself in the danger zone on this blog



strong>
Quoting GoWVU:
WOW, go to work today and get home and seems like we might be seeing a little of Issac here in Charleston SC... I think it was Levi that said this was going to be a East Coast storm?? Funny thing nothing on the local news about this shift to the east....
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Can somebody paste the 3pm dicussion from the NWS out of Miami.. It's somewhat ominous as the threat for Florida is increasing...
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Interstatelover was right, at least Tropical Storm conditions for South Florida. This is an odd play out.
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1365. 7544
Quoting OBXNCWEATHER:
I don't want to eat up space, but I looked and haven't seen this posted yet... I have a question/observation about something in their discussion regarding the current surface analysis... In many many many incidents past when there has been a storm moving north out of the Caribbean, I have noticed that when pressures are lower over North Carolina as it is emerging from the mountainous terrain down there, that systems quite often then begin to ride the right side of the cone of uncertainty, causing continuous rightward adjustments... I have no idea what it means, but I have been around long enough to recognize it as "something I've noticed and mentioned to myself on more than one occasion".

(P.S. for the record, those who know me know that i do not wish, doom, down, hype, or any other type of -cast, so that is not what this is :) My handle is OBXNCWEATHER, although I now live in Satellite Beach, FL, which just happens to be on the East Coast of FL...)

I hope I disclaimed enough. Just wondering if anyone else ever noticed the same pattern of lower pressures over


eastern NC when a storm emerges into the W Atl or Florida Straits.

Thanks.


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
256 PM EDT FRI AUG 24 2012

.DISCUSSION...
THE UPPER LEVEL PATTERN CONSISTED OF HIGH PRESSURE STRETCHING FROM
JUST OFF THE EAST COAST OF FLORIDA TO THE WESTERN ATLANTIC...A
WEAKNESS IN THE RIDGE OVER FLORIDA...WITH A WEAK LOW PRESSURE AREA
DEVELOPING OVER THE CAROLINAS AND WESTERN ATLANTIC...AND ANOTHER
HIGH OVER THE WESTERN GULF AND TEXAS. SCATTERED SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH THE WIND SURGE ARE SPREADING WEST
ACROSS MOST OF THE REGION THIS AFTERNOON. SOME STRONG WINDS 40 T0
50 MPH MAY BE POSSIBLE IN THESE STORMS. THESE
CONDITIONS...SCATTERED SHOWERS WITH EMBEDDED THUNDERSTORMS...IS
EXPECTED TO CONTINUE OVERNIGHT AND THROUGH THE DAY ON SATURDAY.

ALL EYES THEN TURN TO TROPICAL STORM ISAAC. ISAAC HAS BEGUN ITS
NORTHWEST TURN AND WILL MOVE OVER HISPANIOLA AND TOWARDS EASTERN
CUBA OVERNIGHT. ALL MODEL GUIDANCE HAS SHIFTED SIGNIFICANTLY TO
THE EAST FROM RUNS YESTERDAY. THE ECMWF IS THE FURTHEST
WEST...WITH THE STORM MOVING CLOSE TO THE CURRENT NHC OFFICIAL
FORECAST TRACK. THE OTHER MODELS NOW BRING THE STORM INTO THE
MIDDLE KEYS OR SOUTH FLORIDA. IN ADDITION...MOST OF THE MODELS
SHOW LITTLE INTERACTION WITH CUBA. THIS COULD BE VERY SIGNIFICANT
FOR SOUTH FLORIDA...BECAUSE THE STORM WOULD BE ABLE TO SPEND MUCH
MORE TIME OVER WATER. LOOKING AT THE GLOBAL MODELS AND HURRICANE
MODELS...THEY WOULD BE INDICATING A HURRICANE POSSIBLY MOVING
INTO THE MIDDLE KEYS OR SOUTH FLORIDA SUNDAY EVENING. THIS IS ALSO
SOMEWHAT FASTER THAN PREVIOUS RUNS. SO THERE IS A LOT MORE
UNCERTAINTY FOR SOUTH FLORIDA. THIS IS ONLY ONE SUITE OF MODEL
RUNS...BUT THE THREAT TO SOUTH FLORIDA LOOKS TO BE INCREASING.

GOING WITH THE OFFICIAL NHC TRACK...WE CAN START TO NARROW DOWN
SOME IMPACTS THAT MAY OCCUR TO SOUTH FLORIDA. HEAVY RAINFALL COULD BE
A MAJOR IMPACT ACROSS SOUTH FLORIDA...WITH 4 TO 8 INCHES OF RAIN
AND LOCALLY HIGHER AMOUNTS. SOUTH FLORIDA IS EXPECTED TO BE ON THE
RIGHT FRONT QUADRANT OF THE STORM...AND TROPICAL TORNADOES WOULD
ALSO BE POSSIBLE. TROPICAL STORM CONDITIONS COULD BEGIN AS EARLY
AS SUNDAY MORNING ACROSS THE COASTAL WATERS AND DEEP SOUTH
FLORIDA COASTAL AREAS. SURGE IS TOO EARLY TO DETERMINE...BUT ON
THE CURRENT TRACK...MINOR COASTAL FLOODING WOULD BE POSSIBLE ALONG
BISCAYNE BAY AND ALONG THE COLLIER COUNTY COASTLINE. KEEP IN MIND THAT
THESE IMPACTS COULD BECOME MUCH DIFFERENT IF THE STORM TRACKS TO
THE RIGHT OR LEFT...OR IF THE STORM BECOMES STRONGER THAN
CURRENTLY INDICATED.

CONDITIONS WILL SLOWLY IMPROVE FROM SOUTH TO NORTH ON MONDAY...BUT
DEPENDING ON THE TRACK OF ISAAC...RAIN BANDS MAY CONTINUE TO
AFFECT MUCH OF THE REGION THROUGH THE DAY. SOUTHERLY WINDS WILL
THEN CONTINUE ON TUESDAY...WITH CONDITIONS CONTINUING TO IMPROVE.


hmmmmmmm thanks interesting read there
Member Since: May 6, 2007 Posts: 0 Comments: 6676
Quoting A4Guy:


Oh my god...will you please stop?
Why do keep arguing with the NHC?

No matter how hard you try, you cannot will the storm to roll over your house. It doesn't work. Many have tried, and all have failed.
LOL!!! glad you make that comment!! that was about time!!! to stop the continue disrespect for the hard working PROFESSIONAL METS at the NHC,this people from the CI are truly something else!!!.
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1363. wn1995


my latest isaac forecast track. Pretty similar to the last, nothing much to add.
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Quoting mcluvincane:


Doesn't look that dry on water vapor

Not dry, but drier. Seeing a big strip of white inside these things indicates that they are struggling with dry air.

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Quoting ncstorm:


because apparently the SE only consists of Florida..LOL..but yeah, the Carolinas and points northward was the original target for the Conus when the GFS started showing Isaac..dont be surprised if it comes back to that scenario..


lol hey ncstorm... i would second that... there are quite a few times i remember sitting on Hatteras Island watching the GFS go right back to it's original forecast days out and come close to verifying...

i'm sure the entire pattern was different (i would be interested if anyone knows), but Floyd comes to mind....
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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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