Tropical Depression Isaac:

[srainhoutx]

RECON data suggests that Isaac is still suffering from some southerly shear. The center appears elongated S to N and is not yet vertically stacked. The first visible imagery does suggest that Isaac is developing convection in the southern semi circle, but dry air to the E and S has kept development in check.

[unome]

Tropical Overshooting Tops - IR Images from CIMSS

explanation from CIMSS' site:
The TOTs are used as a proxy indicator to analyze vigorous convection trends in tropical disturbances that may become incipient tropical cyclones. Preliminary research has indicated some skill in using the TOT product as a predictor of TC genesis and rapid intensification in the Atlantic Ocean (Pacific Ocean analysis incomplete).



close-up loop: http://cimss.ssec.wisc.edu/goes_r/provi ... on_PG.html

basin loop: http://cimss.ssec.wisc.edu/goes_r/provi ... ation.html

[srainhoutx]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 27th day of the month at 13:03Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number & Year: 09L in 2012
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 25
Observation Number: 13
A. Time of Center Fix: 27th day of the month at 12:31:10Z
B. Center Fix Coordinates: 25°50'N 84°52'W (25.8333N 84.8667W)
B. Center Fix Location: 195 miles (313 km) to the WSW (254°) from Fort Myers, FL, USA.
C. Minimum Height at Standard Level: 1,342m (4,403ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 54kts (~ 62.1mph)
E. Location of the Estimated Maximum Surface Wind: 61 nautical miles (70 statute miles) to the SE (140°) of center fix
F. Maximum Flight Level Wind Inbound: From 199° at 40kts (From the SSW at ~ 46.0mph)
G. Location of Maximum Flight Level Wind Inbound: 94 nautical miles (108 statute miles) to the SE (130°) of center fix
H. Minimum Sea Level Pressure: 989mb (29.21 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,525m (5,003ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 22°C (72°F) at a pressure alt. of 1,523m (4,997ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 19°C (66°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Open, 09-24, RAGGED
M. Eye Shape & Diameter: Circular with a diameter of 32 nautical miles (37 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 3 nautical miles
Remarks Section:
Maximum Flight Level Temp: 22°C (72°F) which was observed 12 nautical miles (14 statute miles) to the SSE (158°) from the flight level center

[unome]

72-hr QPE from NMQ (National Mosaic & Multi-Sensor QPE) http://nmq.ou.edu/

from their website:
The NMQ project is a joint initiative between the National Severe Storms Laboratory, Federal Aviation Administration, National Weather Service/Office of Hydrologic Development, the Office of Climate, Water and Weather Services and the University of Oklahoma Cooperative Institute in Mesoscale Meteorolgical Studies.

The NMQ serves as an international testbed for research, development, evaluation and science to operations infusion of high resolution 3D Mosiac of multiple radars and radar networks for model assimilation and aviation applications, Quantitative Precipitation Information (QPI) including Multiple Sensor Quantitative Precipitation Estimation (MSQPE) and Very Short Term Quantitative Precipitation Forecasts (VSTQPF) for the monitoring and warnings of floods and flash floods and in support of comprehensive hydrology and ecosystem modeling.


latest available 72-hr period

[srainhoutx]

12Z Tracks & Intensity. The 12Z tracks suggest a SE Louisiana cluster with a few further W with a general heading NW after making landfall. The intensity guidance suggest a Cat 1 with only the HWRF suggesting a Cat 2 status.

[Rip76]

At the current location in the gulf, it would be real tough to go against the NHC now.
Maybe while Isaac is pulling all of the moisture out of Texas, we'll get a few showers in Houston...

I need to quit watching loops... I thought I just saw a wobble to the west.

[srainhoutx]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 27th day of the month at 13:48Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Storm Number & Year: 09L in 2012
Storm Name: Isaac (flight in the North Atlantic basin)
Mission Number: 25
Observation Number: 17
A. Time of Center Fix: 27th day of the month at 13:25:40Z
B. Center Fix Coordinates: 25°57'N 85°06'W (25.95N 85.1W)
B. Center Fix Location: 207 miles (332 km) to the WSW (257°) from Fort Myers, FL, USA.
C. Minimum Height at Standard Level: 1,346m (4,416ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 63kts (~ 72.5mph)
E. Location of the Estimated Maximum Surface Wind: 12 nautical miles (14 statute miles) to the W (274°) of center fix
F. Maximum Flight Level Wind Inbound: From 10° at 41kts (From the N at ~ 47.2mph)
G. Location of Maximum Flight Level Wind Inbound: 23 nautical miles (26 statute miles) to the W (271°) of center fix
H. Minimum Sea Level Pressure: 990mb (29.23 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 20°C (68°F) at a pressure alt. of 1,521m (4,990ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 22°C (72°F) at a pressure alt. of 1,525m (5,003ft)
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 (Undecoded): RAGGED
M. Eye Shape & Diameter: Circular with a diameter of 26 nautical miles (30 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 2 nautical miles
Remarks Section:
Maximum Flight Level Wind: 55kts (~ 63.3mph) in the northeast quadrant at 9:58:30Z

[MontgomeryCoWx]

Strengthening and still moving wnw

[TXStormjg]

Strengthening and still moving wnw

And, if this direction continues, I see landfall a bit further west. Duh!! Anyway, I am hoping for landfall more west mainly because it hits the swamp areas more. I don't want to see NOLA slammed again, and I don't want to go days without power! Just my two cents.

[MontgomeryCoWx]

Still think a Morgan City to Houma landfall

[unome]

great update from Jim Williams at http://hurricanecity.com/ , really easy to understand http://www.youtube.com/watch?v=RPvRhD3l ... e=youtu.be

[weatherrabbit]

maybe "old school" watching pressure trends along the coast....

http://forecast.weather.gov/product.php ... &version=1

[srainhoutx]

While the NAM is not a reliable tropical model, there are some 'hints' via the 12Z NAM WRF/NMM that the ridging to the N of Isaac will begin to have some influence and the trough is not as strong suggesting a potential for some W to WNW drifting as Isaac makes its approach to the Houma/Morgan City Louisiana Area. I only mention this from a synoptic setup potential...

[unome]

maybe "old school" watching pressure trends along the coast....

http://forecast.weather.gov/product.php ... &version=1

not old-school - just educated ! NHC has a link for 24-hr pressure change in their "Analysis Tools" on the left side of their home page - here's the current graphic, showing pressures rising over TX & lowering in the eastern gulf



this site is good for monitoring pressures also: http://sailwx.info/wxobs/pressure.phtml

click an area to zoom in (on a map at the link, not below)

[wxman57]

GFDL looks like a direct hit for us here in Houston. How reliable has the GFDL been this year?

Somewhere between terrible and awful. I don't think we'll see anything in SE TX from Isaac. Slight chance a few bands of showers/storms drift in from the NE on Wednesday.

[Portastorm]

GFDL looks like a direct hit for us here in Houston. How reliable has the GFDL been this year?

Somewhere between terrible and awful. I don't think we'll see anything in SE TX from Isaac. Slight chance a few bands of showers/storms drift in from the NE on Wednesday.

The 6z GFS suggests between 1/2 and 1 inch of rain for Harris County in the next five days. That was a slightly increased amount compared to the 0z run which showed a quarter to a half inch of rainfall.

[Rip76]

Wow... to the NW at 22mph

sorry, news lady said 22.
it's 14...

[srainhoutx]

BULLETIN
TROPICAL STORM ISAAC ADVISORY NUMBER 26
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1000 AM CDT MON AUG 27 2012

...ISAAC MOVING WEST-NORTHWESTWARD OVER THE EASTERN GULF OF
MEXICO...POSES SIGNIFICANT STORM SURGE THREAT TO THE NORTHERN GULF
COAST...


SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...26.1N 85.3W
ABOUT 250 MI...400 KM S OF APALACHICOLA FLORIDA
ABOUT 310 MI...500 KM SE OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...988 MB...29.18 INCHES


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

ALL TROPICAL STORM WARNINGS HAVE BEEN DISCONTINUED EAST AND SOUTH OF
AUCILLA RIVER FLORIDA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* EAST OF MORGAN CITY LOUISIANA TO DESTIN FLORIDA...INCLUDING
METROPOLITAN NEW ORLEANS...LAKE PONTCHARTRAIN...AND LAKE MAUREPAS

A HURRICANE WATCH IS IN EFFECT FOR...
* INTRACOASTAL CITY TO MORGAN CITY LOUISIANA

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* EAST OF DESTIN FLORIDA TO THE AUCILLA RIVER
* INTRACOASTAL CITY TO MORGAN CITY LOUISIANA

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* EAST OF SABINE PASS TO WEST OF INTRACOASTAL CITY LOUISIANA

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 HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE
WITHIN THE WATCH AREA.

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.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED BY
YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1000 AM CDT...1500 UTC...THE CENTER OF TROPICAL STORM ISAAC WAS
LOCATED NEAR LATITUDE 26.1 NORTH...LONGITUDE 85.3 WEST. ISAAC IS
MOVING TOWARD THE NORTHWEST NEAR 14 MPH...22 KM/H...AND THIS GENERAL
MOTION IS EXPECTED TO CONTINUE TODAY WITH A GRADUAL DECREASE IN
FORWARD SPEED. A TURN TOWARD THE NORTHWEST IS EXPECTED BY TUESDAY.
ON THE FORECAST TRACK...THE CENTER OF ISAAC WILL MOVE OVER THE
EASTERN GULF OF MEXICO TODAY AND APPROACH THE NORTHERN GULF COAST
IN THE HURRICANE WARNING AREA ON TUESDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 65 MPH...100 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48
HOURS...AND ISAAC IS EXPECTED TO BECOME A HURRICANE BEFORE REACHING
THE NORTHERN GULF COAST.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB...29.18 INCHES.


HAZARDS AFFECTING LAND
----------------------
STORM SURGE...THE COMBINATION OF A STORM SURGE AND THE TIDE WILL
CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING
WATERS. THE WATER COULD REACH THE FOLLOWING DEPTHS ABOVE GROUND IF
THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE...

* SOUTHEAST LOUISIANA...MISSISSIPPI...AND ALABAMA...6 TO 12 FT
* SOUTH-CENTRAL LOUISIANA...3 TO 6 FT
* FLORIDA PANHANDLE...3 TO 6 FT
* FLORIDA WEST COAST INCLUDING APALACHEE BAY...1 TO 3 FT

THE DEEPEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST IN AREAS OF
ONSHORE FLOW. SURGE-RELATED FLOODING DEPENDS ON THE RELATIVE TIMING
OF THE SURGE AND THE TIDAL CYCLE...AND CAN VARY GREATLY OVER SHORT
DISTANCES. FOR INFORMATION SPECIFIC TO YOUR AREA...PLEASE SEE
PRODUCTS ISSUED BY YOUR LOCAL WEATHER SERVICE OFFICE. NEAR THE
COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE AND DANGEROUS WAVES.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO SPREAD NORTHWARD
INTO THE FLORIDA BIG BEND AREA AND THE FLORIDA PANHANDLE IN THE
TROPICAL STORM WARNING AREA TONIGHT.

TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE NORTHERN GULF
COAST IN THE HURRICANE WARNING AREA LATER TONIGHT...WITH HURRICANE
CONDITIONS EXPECTED ON TUESDAY.

RAINFALL...ISAAC IS EXPECTED TO PRODUCE ADDITIONAL RAIN
ACCUMULATIONS OF 1 TO 3 INCHES OVER THE FLORIDA PENINSULA...WHERE
ISOLATED MAXIMUM STORM TOTAL AMOUNTS OF 15 INCHES ARE POSSIBLE.
TOTAL RAINFALL AMOUNTS OF 6 TO 12 INCHES...WITH MAXIMUM AMOUNTS OF
18 INCHES...ARE POSSIBLE IN SOUTHEASTERN LOUISIANA...SOUTHERN
MISSISSIPPI...SOUTHERN ALABAMA AND THE WESTERN FLORIDA PANHANDLE.

TORNADOES...ISOLATED TORNADOES ARE POSSIBLE IN CENTRAL AND
NORTHERN FLORIDA TODAY...AND ALONG THE NORTHERN GULF COAST TONIGHT
AND TUESDAY.

SURF...DANGEROUS SURF AND RIP CURRENT CONDITIONS WILL CONTINUE TO
AFFECT THE FLORIDA COASTLINE AND THE FLORIDA KEYS DURING THE NEXT
DAY OR SO...AND BEGIN TO AFFECT PORTIONS OF THE NORTHERN GULF COAST
LATER TODAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...100 PM CDT.
NEXT COMPLETE ADVISORY...400 PM CDT.

$$
FORECASTER STEWART

[MontgomeryCoWx]

It's 14 mph not 22

[srainhoutx]

TROPICAL STORM ISAAC DISCUSSION NUMBER 26
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1000 AM CDT MON AUG 27 2012

DATA FROM THE TAMPA AND KEY WEST DOPPLER RADARS...AND FROM AIR FORCE
RESERVE AND NOAA RECONNAISSANCE AIRCRAFT DATA INDICATE THE INNER
CORE STRUCTURE AND INTENSITY OF ISAAC HAS CHANGED LITTLE SINCE THE
PREVIOUS ADVISORY. A RAGGED EYE FEATURE HAS OCCASIONALLY APPEARED
IN THESE DATA...BUT IT HAS BEEN UNABLE TO PERSIST. THE CENTRAL
PRESSURE HAS DECREASED TO AROUND 987-988 MB...BUT THIS HAS NOT
RESULTED IN ANY INCREASE IN THE WIND SPEEDS. THE PREVIOUS INTENSITY
OF 55 KT IS BEING MAINTAINED FOR THIS ADVISORY BASED ON THE RECON
WIND DATA.

THE INITIAL MOTION ESTIMATE IS 305/12. NO SIGNIFICANT CHANGE WAS
MADE TO THE PREVIOUS FORECAST TRACK. THE LATEST 12Z UPPER-AIR DATA
INDICATE 20-40 METER HEIGHT RISES AT THE 500 MB AND 400 MB LEVELS
ACROSS THE SOUTHEASTERN AND SOUTH-CENTRAL U.S....WHICH SUGGESTS
THAT THE SUBTROPICAL RIDGE TO THE NORTH OF ISAAC HAS STRENGTHENED
SLIGHTLY. THIS WOULD SUPPORT A NORTHWESTWARD TO WEST-NORTHWESTWARD
MOTION UNTIL LANDFALL IN ABOUT 36-48 HOURS...AND THIS MOTION IS
SUPPORTED BY THE NHC MODEL CONSENSUS. AFTER 48 HOURS...HOWEVER...
THE MODEL GUIDANCE IS WIDELY DIVERGENT WITH A SPREAD OF MORE THAN
500 N MI BETWEEN THE GFS ON THE LEFT AND THE ECMWF ON THE RIGHT.
THE FORECAST TRACK AT DAYS 3-5 IS ALSO SIMILAR TO THE PREVIOUS
ADVISORY AND LIES CLOSE TO THE MODEL CONSENSUS...BUT THIS IS A LOW
CONFIDENCE FORECAST AT THOSE TIME PERIODS.

THE LACK OF STRENGTHENING APPEARS TO TO BE DUE TO THE
LARGER-THAN-AVERAGE WIND RADII...WHICH HAVE YET TO CONTRACT
INWARD...ALONG WITH THE PERIODIC ENTRAINMENT OF DRY MID-LEVEL AIR
FROM THE EASTERN SEMICIRCLE INTO THE INNER-CORE REGION. UNTIL THE
DRY AIR MIXES OUT...EROSION OF THE INNER-CORE CONVECTION WILL
LIKELY CONTINUE UNTIL ISAAC APPROACHES THE NORTH-CENTRAL GULF COAST
IN ABOUT 24 HOURS. AT THAT TIME...INCREASED FRICTIONAL EFFECTS FROM
THE GULF COAST LAND MASS IS EXPECTED TO CONTRIBUTE TO AN INCREASE
IN CONVECTION IN THE NORTHEAST QUADRANT...WHICH COULD ENABLE THE
STRENGTHENING PROCESS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY AND IS SLIGHTLY ABOVE THE INTENSITY
CONSENSUS MODEL IV15.

BECAUSE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER...IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK.

FORECAST POSITIONS AND MAX WINDS

INIT 27/1500Z 26.1N 85.3W 55 KT 65 MPH
12H 28/0000Z 27.1N 86.8W 65 KT 75 MPH
24H 28/1200Z 28.3N 88.4W 70 KT 80 MPH
36H 29/0000Z 29.3N 89.6W 80 KT 90 MPH
48H 29/1200Z 30.2N 90.5W 70 KT 80 MPH...INLAND
72H 30/1200Z 31.9N 91.7W 40 KT 45 MPH...INLAND
96H 31/1200Z 35.2N 92.3W 25 KT 30 MPH...INLAND
120H 01/1200Z 39.3N 91.3W 20 KT 25 MPH...INLAND

$$
FORECASTER STEWART