Little change to Isaac, but intensification coming; Joyce forms

By: Dr. Jeff Masters , 3:13 PM GMT on August 23, 2012

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Tropical Storm Isaac is a large and impressive-looking storm on satellite images, but data from the Hurricane Hunters reveal that Isaac remains a minimal-strength tropical storm with 40 mph winds, as it heads westward across the Eastern Caribbean. An Air Force Reserve hurricane hunter aircraft which completed its mission into Isaac at 8 am EDT found top winds at the surface near 40 mph, and highest winds at their 5,000 foot flight level of 47 mph. A NOAA hurricane hunter aircraft flying at 10,000 feet has found top winds of 47 mph at that altitude. The Hurricane Hunters found a broad area of light winds with a central pressure of 1003 mb. The aircraft did not observe an eyewall trying to form, and recent microwave satellite images also show no signs of an eyewall forming. There does not appear to be much in the way of dry air near the core of Isaac, as seen on water vapor satellite loops, which is a big switch from what we've seen previously. Visible satellite loops show that Isaac has a much more symmetric circular cloud pattern, and has developed a Central Dense Overcast (CDO) of high cirrus clouds, the hallmark of an intensifying storm. These clouds have very cold cloud tops, indicating that the updrafts creating them are quite strong. An analysis of upper level winds from the University of Wisconsin CIMSS shows that an upper-level pattern of outflow supportive of significant strengthening has developed this morning, with an upper-level outflow channel now well-established to the north, and a new outflow channel opening to the south. Radar imagery from Puerto Rico shows some weak low-level spiral bands that are slowing intensifying and becoming more organized.


Figure 1. Morning radar image of Isaac taken from the Puerto Rico radar. Isaac's rain bands are weak, but are starting to take on a more spiraling shape.

Intensity forecast for Isaac
Isaac has consistently confounded predictions that it would intensify, but all the potential factors inhibiting intensification seem to have diminished to the point where intensification has to occur. Wind shear is low, 5 - 10 knots, and ocean temperatures are warm, 29°C, and these warm waters extend to great depth, giving the storm a high total heat content to work with. These factors, combined with the favorable upper-level outflow pattern and more symmetric cloud pattern, support intensification, and all of the intensity models except the HWRF model predict intensification of Isaac to a strong tropical storm or Category 1 hurricane by Friday afternoon. The latest 8 am EDT run of the SHIPS model predicts that wind shear will be light to moderate, 5 - 15 knots, for the next five days. The 11 am EDT wind probability forecast from NHC predicted a 34% chance that Isaac will become a hurricane by Friday afternoon, and a 6% chance it will be a Category 2 or stronger hurricane then. By Friday afternoon, Isaac will likely be close enough to Southwest Haiti that the inner core will be disrupted, and the storm will likely be a 45 - 55 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, and the upper-level wind pattern favorable for intensification, with low wind shear due to an upper-level anticyclone over the storm. It will probably take at least 24 hours with the storm's center over water for it to become a hurricane.

Impact of Isaac on the Islands
The south coast of Puerto Rico should see Isaac's heaviest rains and strongest winds beginning near 8 pm EDT tonight, with tropical storm-force winds of 40 - 45 mph potentially affecting the southwest portion of the island. The San Juan airport may be able to stay open during Isaac's passage, but with delays when spiral bands move overhead.

Heavy rains and tropical storm-force winds should arrive on the southern coast of the Dominican Republic late tonight, and the Santo Domingo airport will probably be closed on Friday. Rainfall amounts of 8 - 12 inches will likely affect the Dominican Republic Thursday through Saturday, creating dangerous flash floods and mudslides.

Isaac is potentially a very dangerous storm for Haiti, where 400,000 people still live outside underneath tarps in the wake of the 2010 earthquake. Heavy rains from Isaac will begin on Friday morning in Haiti, and last through Sunday. Rainfall amounts of 8 - 12 inches are possible, which will be capable of causing extreme flooding on the vegetation-denuded slopes of Haiti. It will be a major challenge to keep those Haitians living outside safe, if rainfall amounts of 5 - 10 inches occur.

Impact on Florida, Cuba, Jamaica, and the Bahamas
Florida, Cuba, Jamaica, and the Bahamas are all at risk of receiving flooding rains and high winds from Isaac. The latest set of 00Z (8 pm EDT) and 06Z (2 am EDT) model runs for Isaac are fairly unified for the coming three days, showing a west-northwestward track over Southwest Haiti and into Western Cuba. At the 4 - 5 day forecast period for Sunday and Monday, the models have come into better agreement, and have shifted west some. Our best-performing model, the ECMWF, has now shifted Isaac's path more to the east, but still is the westernmost of the models, predicting a landfall for Isaac near the Alabama/Florida border on Wednesday. While we do still have some models predicting a path up the east coast of Florida, model consensus now favors a path up the west coast of Florida through the Gulf of Mexico. The recent reformation of Isaac's center more to the south supports the idea that Isaac will take a track more to the west through the Gulf of Mexico. Since this now means a final landfall for Isaac in the Florida Panhandle is likely, the storm will probably have an extra day over water, increasing the odds that it will become a Category 2 or stronger hurricane before this final landfall. The NOAA jet is scheduled to fly into the storm this afternoon, to do a large-scale dropsonde mission to aid model forecasts. These missions can improve model forecasts by 10 - 20%, so the model runs that will be available early Friday morning should have increased reliability.

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 15% chance of receiving tropical storm-force winds and a 1% chance of receiving hurricane-force winds on Monday. The latest model tracks for Isaac suggests that the trough of low pressure pulling the storm to the north will not be strong enough to give Isaac a northeastward component of motion when it crosses Tampa's latitude. Thus, Isaac will have difficulty making a direct hit on Tampa without passing over a considerable amount of land first, making a multi-billion dollar hurricane disaster in Tampa very unlikely. I put the odds of a mass evacuation occurring during the convention at 1%; a limited evacuation of people in the Tampa Bay area living in mobile homes in low-lying areas is probably about 5 - 10 % likely. I have detailed information on Tampa's storm surge vulnerability in a post from last week.


Figure 2. Morning satellite image of Tropical Storm Joyce.

Tropical Storm Joyce forms in the Central Atlantic
The season's tenth named storm of the year, Tropical Storm Joyce, has formed in the Central Atlantic. Joyce's formation on August 23 puts 2012 in a tie for second place with 1995 for earliest formation date of the season's tenth storm. Only 2005 had an earlier appearance of the season's tenth storm, when Tropical Storm Jose formed at 2 pm EDT on August 22. None of the models show that Joyce will be a threat to the Lesser Antilles Islands, but it may be a storm that will affect Bermuda. It is possible that Joyce will complicate the track forecast for Isaac 4 - 5 days from now, when the storms may be close enough together to interact.

Jeff Masters

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1774. Maineweatherguy20023
12:09 PM GMT on August 24, 2012
My composition of interesting images

GFS with Joyce (Eastern line), Isaac (western line), Kirk (western storm), and Leslie (Eastern storm).

Taiwan typhoon waves.
Member Since: August 1, 2012 Posts: 0 Comments: 269
1773. cirrocumulus
1:00 AM GMT on August 24, 2012
Quoting Stormchaser121:
Isaac will be a western gulf storm. End of line.
Yes, I've been repeating it a lot because we have easier access to the GFS and most other models except for the ECMWF. Well, actually we have access easily from Weather Underground except that the other clusters are represented more often on many other weather websites people like to use. Yet the ECMWF is no. 1 historically. Doesn't mean it will win every time.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
1772. WetBankGuy
12:02 AM GMT on August 24, 2012
...THE GUIDANCE HAS SHIFTED A LITTLE WESTWARD IN RESPONSE


Yeah, just a little since midday. Excuse me while I jump over to Kayak and start looking for hotels.

Member Since: September 19, 2007 Posts: 0 Comments: 288
1771. BahaHurican
10:48 PM GMT on August 23, 2012
:o)
Member Since: October 25, 2005 Posts: 19 Comments: 22585
1770. Dunkman
10:27 PM GMT on August 23, 2012
The NOAA "Kermit" just found the 700mb center approx 100 miles south of the LL center. That is what everyone has been seeing on satellite.
Member Since: February 6, 2010 Posts: 0 Comments: 214
1769. Stormchaser121
10:01 PM GMT on August 23, 2012
Isaac will be a western gulf storm. End of line.
Member Since: September 2, 2011 Posts: 0 Comments: 1148
1768. RTSplayer
9:42 PM GMT on August 23, 2012
The Ridge of Gulf DOOM:


1000mb steering:



990mb:



970mb:



950mb:

Member Since: January 25, 2012 Posts: 33 Comments: 1520
1767. WindshearWillie
9:39 PM GMT on August 23, 2012


Link

Cool man
Member Since: August 10, 2009 Posts: 0 Comments: 19
1766. RTSplayer
9:36 PM GMT on August 23, 2012
LOL.

Chad Meyers took the "Multiple competing centers" route on his update.

He poked about 8 or 10 dots at random on the map...lol...
Member Since: January 25, 2012 Posts: 33 Comments: 1520
1765. evilpenguinshan
9:33 PM GMT on August 23, 2012
it's dead because there's a new blog post =p
http://www.wunderground.com/blog/JeffMasters/comm ent.html?entrynum=2200

Quoting redwagon:

See how the blog died after SECONUS became unaffected? Same with Haiti, if Isaac is perceived to be just a ~rainmaker there will be no fever pitch.
Member Since: March 20, 2012 Posts: 0 Comments: 507
1764. redwagon
9:29 PM GMT on August 23, 2012
Quoting hurricanehunter27:
. Like I said nothing has happened yet so you can't call it a tragity. If we called things tragities based on potential destruction everyday could be considered a tragity.

See how the blog died after SECONUS became unaffected? Same with Haiti, if Isaac is perceived to be just a ~rainmaker there will be no fever pitch.
Member Since: August 4, 2007 Posts: 0 Comments: 3278
1763. evilpenguinshan
9:24 PM GMT on August 23, 2012
interesting that they wouldn't tag it as 'suspect data' if that's the case...looking at their altitude (30,000ft ), I don't know if the winds would be higher or lower at flight level. beyond my knowledge XD
you could very well be correct. this storm is like ernesto 2.0 - keeping everybody guessing...


Quoting TropicalAnalystwx13:

The rain rate is pretty high, and the flight level winds are lower than the surface winds, which is another sign of it being contaminated.
Member Since: March 20, 2012 Posts: 0 Comments: 507
1762. TropicalAnalystwx13
9:21 PM GMT on August 23, 2012
In the West Pacific:

Member Since: July 6, 2010 Posts: 113 Comments: 32531
1761. TropicalAnalystwx13
9:18 PM GMT on August 23, 2012
Quoting evilpenguinshan:
he seems to be strengthening, at least on the SW side of the storm...

Time: 20:54:30Z
Coordinates: 15.2167N 69.0167W
Acft. Static Air Press: 299.2 mb (~ 8.84 inHg)
Acft. Geopotential Hgt: 9,698 meters (~ 31,818 feet)
Extrap. Sfc. Press: -
D-value: 524 meters (~ 1,719 feet)
Flt. Lvl. Wind (30s): From 39° at 30 knots (From the NE at ~ 34.5 mph)
Air Temp: -28.4°C* (~ -19.1°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 34 knots (~ 39.1 mph)
SFMR Peak (10s) Sfc. Wind: 52 knots (~ 59.8 mph)
SFMR Rain Rate: 18 mm/hr (~ 0.71 in/hr)

The rain rate is pretty high, and the flight level winds are lower than the surface winds, which is another sign of it being contaminated.
Member Since: July 6, 2010 Posts: 113 Comments: 32531
1760. evilpenguinshan
9:17 PM GMT on August 23, 2012
he seems to be strengthening, at least on the SW side of the storm...

Time: 20:54:30Z
Coordinates: 15.2167N 69.0167W
Acft. Static Air Press: 299.2 mb (~ 8.84 inHg)
Acft. Geopotential Hgt: 9,698 meters (~ 31,818 feet)
Extrap. Sfc. Press: -
D-value: 524 meters (~ 1,719 feet)
Flt. Lvl. Wind (30s): From 39° at 30 knots (From the NE at ~ 34.5 mph)
Air Temp: -28.4°C* (~ -19.1°F*)
Dew Pt: -*
Peak (10s) Flt. Lvl. Wind: 34 knots (~ 39.1 mph)
SFMR Peak (10s) Sfc. Wind: 52 knots (~ 59.8 mph)
SFMR Rain Rate: 18 mm/hr (~ 0.71 in/hr)
Member Since: March 20, 2012 Posts: 0 Comments: 507
1759. RTSplayer
9:09 PM GMT on August 23, 2012
Same deal:

Left side of the cone is what I think is most likely going to be the actual track.




Edit: ignore the curve at the end for now.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
1758. interstatelover7165
9:03 PM GMT on August 23, 2012

000
WTNT34 KNHC 232055
TCPAT4

BULLETIN
TROPICAL STORM ISAAC ADVISORY NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 PM AST THU AUG 23 2012

...ISAAC CONTINUING WEST-NORTHWESTWARD...NEW WARNINGS AND WATCHES
FOR THE BAHAMAS AND CUBA...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...16.0N 67.1W
ABOUT 180 MI...285 KM SSW OF SAN JUAN PUERTO RICO
ABOUT 255 MI...405 KM SE OF SANTO DOMINGO DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF THE BAHAMAS HAS ISSUED A TROPICAL STORM WARNING
FOR THE SOUTHEASTERN BAHAMAS INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS AND THE TURKS AND CAICOS ISLANDS.

THE GOVERNMENT OF CUBA HAS ISSUED A TROPICAL STORM WATCH FOR THE
CUBAN PROVINCES OF CAMAGUEY...LAS TUNAS...GRANMA...HOLGUIN...
SANTIAGO DE CUBA...AND GUANTANAMO.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* SOUTH COAST OF DOMINICAN REPUBLIC FROM ISLA SAONA WESTWARD TO THE
HAITI-DOMINICAN REPUBLIC SOUTHERN BORDER
* HAITI

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BRITISH VIRGIN ISLANDS
* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS
* NORTH COAST OF DOMINICAN REPUBLIC FROM THE HAITI-DOMINICAN
REPUBLIC NORTHERN BORDER EASTWARD TO NORTH OF ISLA SAONA
* SOUTHEASTERN BAHAMAS INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS AND THE TURKS AND CAICOS ISLANDS

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE CUBAN PROVINCES OF CAMAGUEY...LAS TUNAS...GRANMA...HOLGUIN...
SANTIAGO DE CUBA...AND GUANTANAMO.

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE
AND PROPERTY SHOULD BE RUSHED TO COMPLETION.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

INTERESTS IN JAMAICA...THE REMAINDER OF CUBA...THE REMAINDER OF THE
BAHAMAS...SOUTH FLORIDA...AND THE FLORIDA KEYS SHOULD MONITOR THE
PROGRESS OF ISAAC.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL
WEATHER SERVICE FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO
YOUR AREA OUTSIDE THE UNITED STATES...PLEASE MONITOR PRODUCTS
ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL STORM ISAAC WAS
LOCATED NEAR LATITUDE 16.0 NORTH...LONGITUDE 67.1 WEST. ISAAC IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 16 MPH...26 KM/H...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH SATURDAY. ON THE
FORECAST TRACK...THE CENTER OF ISAAC WILL APPROACH THE SOUTH COAST
OF THE DOMINICAN REPUBLIC TONIGHT...MOVER NEAR OR OVER THE SOUTH
COAST OF THE DOMINICAN REPUBLIC AND HAITI ON FRIDAY...AND APPROACH
SOUTHEASTERN CUBA FRIDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/H...WITH HIGHER
GUSTS. STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...AND
ISAAC COULD BECOME A HURRICANE AS IT NEARS THE DOMINICAN REPUBLIC
AND HAITI ON FRIDAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES...220 KM
MAINLY TO THE NORTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE BASED ON HURRICANE HUNTER
AIRCRAFT AND BUOY DATA IS IS 1003 MB...29.62 INCHES. NOAA BUOY
42059 RECENTLY REPORTED A PRESSURE OF 1004.1 MB...29.65 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE STILL POSSIBLE OVER PORTIONS OF
PUERTO RICO AND THE U.S. AND BRITISH VIRGIN ISLANDS THIS EVENING.
HURRICANE CONDITIONS ARE STILL POSSIBLE OVER PORTIONS OF THE
DOMINICAN REPUBLIC BY FRIDAY...AND OVER PORTIONS OF HAITI FRIDAY OR
FRIDAY NIGHT. TROPICAL STORM CONDITIONS ARE EXPECTED OVER THE
SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS ISLANDS BY LATE
FRIDAY. TROPICAL STORM CONDITIONS ARE POSSIBLE OVER SOUTHEASTERN
CUBA BY SATURDAY.

RAINFALL...TOTAL RAINFALL ACCUMULATIONS OF 8 TO 12 INCHES...
WITH MAXIMUM AMOUNTS OF 20 INCHES...ARE POSSIBLE OVER HISPANIOLA.
THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES. TOTAL RAIN ACCUMULATIONS OF 2 TO 4 INCHES...WITH MAXIMUM
AMOUNTS OF 6 INCHES OVER HIGHER TERRAIN...ARE POSSIBLE OVER PUERTO
RICO AND THE VIRGIN ISLANDS. TOTAL RAIN ACCUMULATIONS OF 4 TO 8
INCHES ARE POSSIBLE OVER THE NORTHERN WINDWARD ISLANDS AND THE
LEEWARD ISLANDS.

STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS
3 TO 5 FEET ABOVE NORMAL TIDE LEVELS IN AREAS OF ONSHORE WINDS ALONG
THE COAST OF HISPANIOLA. STORM SURGE IN PUERTO RICO...AS WELL AS
THE U.S. AND BRITISH VIRGIN ISLANDS WILL GRADUALLY SUBSIDE TONIGHT.
NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES.

SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL AFFECT THE
WINDWARD ISLANDS...LEEWARD ISLANDS...VIRGIN ISLANDS...AND PUERTO
RICO DURING THE NEXT COUPLE OF DAYS. PLEASE CONSULT PRODUCTS FROM
YOUR LOCAL WEATHER OFFICE FOR MORE INFORMATION.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...800 PM AST.
NEXT COMPLETE ADVISORY...1100 PM AST.

$$
FORECASTER BEVEN


Didn't see if it was already posted, so here,and if it was, reminder.
Member Since: August 18, 2011 Posts: 0 Comments: 994
1757. SrChiefFan1
9:00 PM GMT on August 23, 2012
Quoting SFLWeatherman:
From Firsthand Weather


Dislike...
Member Since: September 18, 2010 Posts: 0 Comments: 74
1756. TropicalAnalystwx13
9:00 PM GMT on August 23, 2012
Member Since: July 6, 2010 Posts: 113 Comments: 32531
1755. TropicalAnalystwx13
8:58 PM GMT on August 23, 2012
TROPICAL STORM ISAAC DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
500 PM AST THU AUG 23 2012

LOCATING THE CENTER OF ISAAC IS A BIT PROBLEMATIC THIS AFTERNOON.
WHILE THE CYCLONE HAS A LARGE AND WELL-DEFINED OUTER
CIRCULATION...THE INNER CORE HAS NOT CONSOLIDATED AND THERE ARE
STILL MULTIPLE VORTICITY CENTERS ROTATING AROUND THE MEAN CENTER.

HIGHLIGHTING THE ISSUE ARE DATA FROM NOAA BUOY 42059...WHICH HAS
REPORTED 25-30 KT SOUTHWESTERLY WINDS AT A POSITION SOUTHWEST OF
THE LATEST HURRICANE HUNTER AIRCRAFT FIXES...WHICH IN TURN WERE
SOUTH OF THE CENTER TRACKED IN THE PREVIOUS ADVISORY. THE INITIAL
POSITION IS A BLEND OF ALL THESE FEATURES. THE INITIAL INTENSITY
REMAINS 35 KT BASED ON THE HURRICANE HUNTER DATA.

THE SOMEWHAT UNCERTAIN INITIAL MOTION IS 285/14. THE TRACK MODEL
GUIDANCE IS IN GOOD AGREEMENT THAT ISAAC SHOULD MOVE GENERALLY
WEST-NORTHWESTWARD FOR THE NEXT 48-72 HR...AND THIS PART OF THE NEW
FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS TRACK. AFTER THAT
TIME...THE GUIDANCE HAS SHIFTED A LITTLE WESTWARD IN RESPONSE TO
THE GLOBAL MODELS FORECASTING THE WEAKNESS IN THE SUBTROPICAL RIDGE
TO BE SOMEWHAT FARTHER WEST THAN BEFORE.
THE ECMWF IN PARTICULAR
HAS MADE A SIGNIFICANT SHIFT...SHOWING A WEST-NORTHWESTWARD MOTION
INTO THE CENTRAL GULF OF MEXICO BY DAY 5. DESPITE THE GENERAL
WESTWARD SHIFT...THE HWRF AND CANADIAN MODELS STILL CALL FOR ISAAC
TO MOVE UP THE FLORIDA PENINSULA. THUS... SIGNIFICANT UNCERTAINTY
REMAINS ABOUT THE THREAT ISAAC POSES TO FLORIDA AND OTHER PORTIONS
OF THE GULF COAST. THE 96-120 HR POINTS HAVE BEEN SHIFTED A LITTLE
WESTWARD FROM THE PREVIOUS ADVISORY AND LIE NEAR THE CENTER OF THE
GUIDANCE ENVELOPE AND THE CONSENSUS MODELS.

IN THE SHORT TERM...THE STRUCTURE OF ISAAC SUGGESTS THAT ONLY SLOW
STRENGTHENING IS LIKELY. HOWEVER...THE ENVIRONMENTAL CONDITIONS
ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE
CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.
WHILE THE OFFICIAL
FORECAST NO LONGER SHOWS IT...ISAAC COULD REACH HURRICANE INTENSITY
ABOUT THE TIME IT MAKES LANDFALL IN HISPANIOLA BETWEEN 24-36 HR.
AFTER THAT...PASSAGE OVER HISPANIOLA AND CUBA SHOULD CAUSE SOME
WEAKENING. THE INTENSITY FORECAST SHOWS STRENGTHENING OVER THE GULF
OF MEXICO...AND THE CURRENT 120 HR INTENSITY COULD BE CONSERVATIVE
IF THE GLOBAL MODEL UPPER-LEVEL WIND FORECASTS VERIFY.
THE NEW
INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS FORECAST AND REMAINS
STRONGER THAN THE INTENSITY CONSENSUS.

THE NOAA G-IV JET AND AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
ARE CURRENTLY CONDUCTING A SYNOPTIC SURVEILLANCE MISSION AROUND
ISAAC. THE DATA WILL BE AVAILABLE FOR THE 0000 UTC MODEL RUNS.


FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 16.0N 67.1W 35 KT 40 MPH
12H 24/0600Z 16.6N 69.0W 40 KT 45 MPH
24H 24/1800Z 17.5N 71.5W 50 KT 60 MPH
36H 25/0600Z 18.9N 74.0W 60 KT 70 MPH
48H 25/1800Z 20.3N 76.2W 55 KT 65 MPH...INLAND
72H 26/1800Z 23.0N 80.0W 50 KT 60 MPH...OVER WATER
96H 27/1800Z 25.5N 83.0W 65 KT 75 MPH
120H 28/1800Z 28.5N 85.5W 75 KT 85 MPH

$$
FORECASTER BEVEN
Member Since: July 6, 2010 Posts: 113 Comments: 32531
1754. hurricanehunter27
8:58 PM GMT on August 23, 2012
Quoting redwagon:

If the chaos criminals sensed the population was about to go chaotic, they'd have perfect cover to loot, etc.
. Like I said nothing has happened yet so you can't call it a tragity. If we called things tragities based on potential destruction everyday could be considered a tragity.
Member Since: July 22, 2010 Posts: 1 Comments: 3851
1753. TropicalAnalystwx13
8:55 PM GMT on August 23, 2012
TROPICAL STORM ISAAC FORECAST/ADVISORY NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
2100 UTC THU AUG 23 2012

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

THE GOVERNMENT OF THE BAHAMAS HAS ISSUED A TROPICAL STORM WARNING
FOR THE SOUTHEASTERN BAHAMAS INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS AND THE TURKS AND CAICOS ISLANDS.

THE GOVERNMENT OF CUBA HAS ISSUED A TROPICAL STORM WATCH FOR THE
CUBAN PROVINCES OF CAMAGUEY...LAS TUNAS...GRANMA...HOLGUIN...
SANTIAGO DE CUBA...AND GUANTANAMO.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* SOUTH COAST OF DOMINICAN REPUBLIC FROM ISLA SAONA WESTWARD TO THE
HAITI-DOMINICAN REPUBLIC SOUTHERN BORDER
* HAITI

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BRITISH VIRGIN ISLANDS
* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS
* NORTH COAST OF DOMINICAN REPUBLIC FROM THE HAITI-DOMINICAN
REPUBLIC NORTHERN BORDER EASTWARD TO NORTH OF ISLA SAONA
* SOUTHEASTERN BAHAMAS INCLUDING THE ACKLINS...CROOKED
ISLAND...LONG CAY...THE INAGUAS...MAYAGUANA...AND THE RAGGED
ISLANDS AND THE TURKS AND CAICOS ISLANDS

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* THE CUBAN PROVINCES OF CAMAGUEY...LAS TUNAS...GRANMA...HOLGUIN...
SANTIAGO DE CUBA...AND GUANTANAMO.

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE
AND PROPERTY SHOULD BE RUSHED TO COMPLETION.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.

INTERESTS IN JAMAICA...THE REMAINDER OF CUBA...THE REMAINDER OF THE
BAHAMAS...SOUTH FLORIDA...AND THE FLORIDA KEYS SHOULD MONITOR THE
PROGRESS OF ISAAC.

TROPICAL STORM CENTER LOCATED NEAR 16.0N 67.1W AT 23/2100Z
POSITION ACCURATE WITHIN 40 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT 14 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1003 MB
MAX SUSTAINED WINDS 35 KT WITH GUSTS TO 45 KT.
34 KT.......120NE 60SE 0SW 90NW.
12 FT SEAS..500NE 60SE 0SW 360NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 16.0N 67.1W AT 23/2100Z
AT 23/1800Z CENTER WAS LOCATED NEAR 15.9N 66.4W

FORECAST VALID 24/0600Z 16.6N 69.0W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...120NE 60SE 0SW 90NW.

FORECAST VALID 24/1800Z 17.5N 71.5W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 25NE 0SE 0SW 25NW.
34 KT...130NE 50SE 30SW 100NW.

FORECAST VALID 25/0600Z 18.9N 74.0W
MAX WIND 60 KT...GUSTS 75 KT.
50 KT... 40NE 20SE 0SW 40NW.
34 KT...140NE 60SE 40SW 120NW.

FORECAST VALID 25/1800Z 20.3N 76.2W...INLAND
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 40NE 20SE 0SW 30NW.
34 KT...140NE 60SE 40SW 120NW.

FORECAST VALID 26/1800Z 23.0N 80.0W...OVER WATER
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 30NE 20SE 0SW 20NW.
34 KT...140NE 60SE 40SW 120NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 175 NM
ON DAY 4 AND 225 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY

OUTLOOK VALID 27/1800Z 25.5N 83.0W
MAX WIND 65 KT...GUSTS 80 KT.

OUTLOOK VALID 28/1800Z 28.5N 85.5W
MAX WIND 75 KT...GUSTS 90 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 16.0N 67.1W

NEXT ADVISORY AT 24/0300Z

$$
FORECASTER BEVEN
Member Since: July 6, 2010 Posts: 113 Comments: 32531
1752. HoustonTxGal
8:50 PM GMT on August 23, 2012
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1751. HoustonTxGal
8:48 PM GMT on August 23, 2012
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1750. HoustonTxGal
8:48 PM GMT on August 23, 2012
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1749. A4Guy
8:47 PM GMT on August 23, 2012
you can tell when everyone is over at the NHC site refreshing their browser every 5 seconds because the blog slows to a crawl....
Member Since: June 23, 2006 Posts: 0 Comments: 668
1748. redwagon
8:47 PM GMT on August 23, 2012
Quoting hurricanehunter27:
. How can you call it a tragedy when nothing has happened yet?

If the chaos criminals sensed the population was about to go chaotic, they'd have perfect cover to loot, etc.
Member Since: August 4, 2007 Posts: 0 Comments: 3278
1747. ProgressivePulse
8:45 PM GMT on August 23, 2012
Isaac is still very tilted, Now N to S

200mb


500mb


850mb
Member Since: August 19, 2005 Posts: 5 Comments: 5452
1746. HoustonTxGal
8:44 PM GMT on August 23, 2012


12z Euro
Member Since: September 18, 2007 Posts: 0 Comments: 1074
1745. Maineweatherguy20023
8:43 PM GMT on August 23, 2012
Quoting cirrocumulus:


Yeppers.

Confusing i think its elongated.
Member Since: August 1, 2012 Posts: 0 Comments: 269
1744. hurricanehunter27
8:43 PM GMT on August 23, 2012
Quoting jonelu:
News is reporting that many in Haiti still have no idea that Isaac is on the way. What a tragedy. It puts things in perspective.
. How can you call it a tragedy when nothing has happened yet?
Member Since: July 22, 2010 Posts: 1 Comments: 3851
1743. TropicalAnalystwx13
8:43 PM GMT on August 23, 2012
BULLETIN
TROPICAL STORM JOYCE ADVISORY NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102012
500 PM AST THU AUG 23 2012

...JOYCE LOSING ORGANIZATION...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...15.9N 42.5W
ABOUT 1280 MI...2060 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES
Member Since: July 6, 2010 Posts: 113 Comments: 32531
1742. Maineweatherguy20023
8:42 PM GMT on August 23, 2012
Quoting Buhdog:


Not to pick sides...but you tagged River guy for being off topic during a storm for what it's worth. Pot...Meet Kettle.

Sure is a weird looking trough over FL eh?



High shear there too??
Member Since: August 1, 2012 Posts: 0 Comments: 269
1741. A4Guy
8:42 PM GMT on August 23, 2012
one frustrating and confounding storm, that's for sure.
Member Since: June 23, 2006 Posts: 0 Comments: 668
1740. Maineweatherguy20023
8:41 PM GMT on August 23, 2012
Quoting HurricaneHunterJoe:
Has Isaac done a u-turn and is now heading east?

NO NO NO NO NO
Member Since: August 1, 2012 Posts: 0 Comments: 269
1739. Buhdog
8:40 PM GMT on August 23, 2012
Quoting Tazmanian:




i have a idea whats send JFV and jason out there and they can tell us what the storm is doing


Not to pick sides...but you tagged River guy for being off topic during a storm for what it's worth. Pot...Meet Kettle.

Sure is a weird looking trough over FL eh?


Member Since: July 30, 2005 Posts: 1 Comments: 960
1738. Catgypsy
8:37 PM GMT on August 23, 2012
Quoting LargoFl:
I just need to know..This isnt gonna happen?


How's your beer supply ?
Member Since: June 22, 2012 Posts: 0 Comments: 21
1737. Maineweatherguy20023
8:37 PM GMT on August 23, 2012
Quoting ChaseyChasinStorms:
Good afternoon all. I was just thinking, wouldn't it be CRAZY if the Euro is right and Isaac does come up the Louisiana/MS border (just like Katrina did) on the 7th Anniversary of Katrina, next week on Wednesday, August 29th, 2012???

Unlikely but possible. that would be the timeframe...
Member Since: August 1, 2012 Posts: 0 Comments: 269
1736. oracle28
8:36 PM GMT on August 23, 2012
Quoting interstatelover7165:
I had an interesting thought recently- if tropical entities could talk, what do you think they would say?


They would say "You guys have no idea where I'm going" or "I'm dizzy from the Coriolos effect, I gotta sit down"
Member Since: July 25, 2008 Posts: 0 Comments: 596
1735. RTSplayer
8:35 PM GMT on August 23, 2012
Quoting angiest:


I personally don't see anything resembling a COC in the base velocity scans out of PR.


That's because there isn't.

The real CoC is so far to the SSW that it is starting to exit the long range radar, which is twice the radius of the base wind velocity tool.


So you will not see the real CoC on base velocity tool at PR...ever...because it's too far west and south...


The feature some people have noticed is a swirl caused by feeder bands of different velocities passing one another. Sometimes this appears to be a circulation, even on base reflectivity, and it's just nothing.

In this case, the base reflectivity is deceiving your eyes, sort of like a hub-cab spinning backwards even though in reality it spins forwards, when you turn on base velocity you can see this has no circulation at all in that location, as all the winds to the S of the alleged rotation are in fact moving away from the radar, when given it's position, if it were a circulation, it should be blowing back towards the radar.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
1734. Maineweatherguy20023
8:34 PM GMT on August 23, 2012
Quoting HurricaneDean07:

THE CENTER IS LOCATED AT 15.7 NORTH. RECON CONFIRMS THIS. ITS NOT MOVING WSW, DUE WEST. OR ANYTHING THAT YOU THINK.

WHAT YOU SEE IS A BUNCH OF BS. All the time.

Finished venting...
Now you can meet my Ignore list. along with your little friend that is thinking the same bs as you.

Then where is it moving. It is NOT stationary...
Member Since: August 1, 2012 Posts: 0 Comments: 269
1733. wunderkidcayman
8:34 PM GMT on August 23, 2012
Quoting WPBHurricane05:


I don't know. Looks like that spin could be heading right toward the Cayman Islands.


;)


dude please stop it I did not mention one time Cayman Islands

Quoting wunderkidcayman:
that spin on PR radar is not the LLCOC guys

nope no cayman here

so stop it

that one S of PR is liekly to be a weak spin that is dying or dead

new one is SW nearer to 15N
Member Since: June 13, 2009 Posts: 2 Comments: 12557
1732. cirrocumulus
8:34 PM GMT on August 23, 2012
Quoting MississippiWx:


The "center" you are referring to is also moving rapidly due west and very far to the north. It is more than likely a lobe rotating around a common center, just as the case has been for a while now.


Yeppers.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
1731. GTcooliebai
8:33 PM GMT on August 23, 2012
Quoting interpreter:
Still looks mostly west still. No turn deteced to NW or WNW.
hmm??? Let me see who should I listen to, I think I'll go with the NHC which says WNW for now.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1730. atl134
8:33 PM GMT on August 23, 2012
Quoting mojofearless:


How is that funny, fellow Louisianian? I've been watching the Euro for days - it had NOLA in the crosshairs for a number of runs, and now it's showing more of a panhandle hit. Which is east last time I checked. Furthermore, the GFS has shifted west over the past few days. So what am I missing here? I did actually sleep, so maybe I missed something.


The 12z Euro today has it making landfall in Louisiana. Perhaps you were looking at the 00z run this morning which was farther east.
Member Since: July 27, 2010 Posts: 0 Comments: 83
1729. cirrocumulus
8:32 PM GMT on August 23, 2012
Quoting Tazmanian:
new Vortex Message about 7 minutes old



Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 23rd day of the month at 20:14Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)
Storm Number & Year: 09L in 2012
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 7
Observation Number: 13
A. Time of Center Fix: 23rd day of the month at 19:20:20Z
B. Center Fix Coordinates: 15°40'N 66°34'W (15.6667N 66.5667W)
B. Center Fix Location: 193 miles (310 km) to the S (190°) from San Juan, Puerto Rico (USA).
C. Minimum Height at Standard Level: 1,451m (4,760ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 35kts (~ 40.3mph)
E. Location of the Estimated Maximum Surface Wind: 64 nautical miles (74 statute miles) to the NE (36°) of center fix
F. Maximum Flight Level Wind Inbound: From 145° at 29kts (From the SE at ~ 33.4mph)
G. Location of Maximum Flight Level Wind Inbound: 66 nautical miles (76 statute miles) to the NE (36°) of center fix
H. Minimum Sea Level Pressure: 1004mb (29.65 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 17°C (63°F) at a pressure alt. of 1,524m (5,000ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 17°C (63°F) at a pressure alt. of 1,524m (5,000ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 17°C (63°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Radar, Wind and Pressure
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 10 nautical miles
Remarks Section:
Maximum Flight Level Wind: 47kts (~ 54.1mph) in the east quadrant at 18:12:00Z
Maximum Flight Level Temp: 18°C (64°F) which was observed 31 nautical miles (36 statute miles) to the NNE (25°) from the flight level cente


Thanks Taz.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
1728. jonelu
8:32 PM GMT on August 23, 2012
News is reporting that many in Haiti still have no idea that Isaac is on the way. What a tragedy. It puts things in perspective.
Member Since: October 31, 2007 Posts: 2 Comments: 884
1727. chevycanes
8:31 PM GMT on August 23, 2012
kermit back up in the air.
Member Since: August 6, 2007 Posts: 0 Comments: 693
1726. interpreter
8:31 PM GMT on August 23, 2012
Quoting GTcooliebai:
Looks like Isaac is starting to move more poleward?

Link
Still looks mostly west still. No turn deteced to NW or WNW.
Member Since: July 30, 2010 Posts: 0 Comments: 158
1725. snotly
8:31 PM GMT on August 23, 2012
About to start raining in Haiti
Member Since: August 27, 2005 Posts: 0 Comments: 686
1724. scott39
8:30 PM GMT on August 23, 2012
Isaac isnt even a teenager in respects to devolopement. The Eastern Caribbean is notorious for limiting the maturing of a TC. Isaac is not dealing with the dry air very well for right now. The reason the models blow it up in the GOM, is because the enviroment will allow Isaac to mature to a strong hurricane. This is what the EURO has seen all along. Dont expect any significant developement of Isaac until Saturday at the earliest....or may wait until it reaches the GOM.
Member Since: June 13, 2009 Posts: 0 Comments: 6894

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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.