Tropical Depression Isaac:

[srainhoutx]

Morning e-mail from Jeff:

New tropical depression forms in the Atlantic Ocean 645 miles East of the Leeward Islands.

Tropical Storm Warnings are issued for the Leeward Islands

Tropical Storm Watches are issued for the US/British Virgin Islands and Puerto Rico.

Discussion:
The well defined low pressure system that has been crossing the Atlantic for the past several days has developed enough deep convection overnight to be classified as at TD. The system clearly has a large circulation envelop on visible images with deep convection on its SW side this morning. The system appears to be undergoing a bit of northeasterly wind shear which is keeping thunderstorms removed to the SW side of the circulation. Additionally dry air is lurking to the NE and W of the system, but its large circulation should help to protect the developing inner core from much dry air penetration.

Track:
The depression is located south of a deep layer ridge of high pressure over the central Atlantic Ocean and this will result in a W to WNW track for the next 72 to 96 hours. This will bring the system across the Leeward and Windward Islands on Wednesday and then south of Puerto Rico and Hispaniola late this week. After 72 hours the system will begin to reach the western edge of the sub-tropical ridge over the Atlantic and a fairly decent short wave trough is forecast to dig SE from the Midwest into the central Gulf coast. This should induce a more WNW or NW motion in the days 4-5 time period toward Cuba. Model guidance is actually in very good agreement with the GFS, GFDL, and HWRF fairly close on track through 96 hours. The ECMWF is slower and more westward while the CMC is far to the right in the longer range. The GFS has been consistent over the past 24 hours with this general track reasoning. The current NHC track is a little to the west of the multi model consensus at 120 hours.

Intensity:
Except for the current shear and potential for dry air intrusion, conditions appear favorable for intensification. Most of the models bring this to a tropical storm in the next 12 -24 hours, if it is already not one currently. Suspect the large circulation will take a little bit of time to consolidate and build an inner core so will follow a slow but steady intensification in the next 48 hours and then more rapid increases beyond. One big caveat to the intensity is the potential for land interaction in the 72-120 hour time period with the islands of Hispaniola and Cuba. Any slight deviation of the forecast track could bring the system deeper across these islands which would slow intensification and likely result in some weakening. The current track brings the system just south of these islands and continues over warm waters…so it makes sense currently to follow the stronger intensity guidance at the longer range (the LGEM and SHIPS). Both make the system a major hurricane, while the GFDL, HWRF, GFS, and ECMWF do not show anywhere near as much intensification, but this is likely due to the models indicating more land interaction. Current NHC forecast brings the system to just below major hurricane status at 96 and 120 hours. Forecast intensity in the longer range is fairly low confidence.

96L:
Another area of well defined low pressure has developed about 450 miles SW of the Cape Verde Islands. Thunderstorms activity has increased with this system overnight and conditions appear favorable for development into a tropical cyclone in the next 48 hours. NHC currently gives the system at 60% chance of formation in the next 48 hours.

Forecast Track Guidance:

[kellybell4770]

I know it is way too soon to predict too far out however, are they thinking that this storm will continue back out into the Atlantic after it crosses Florida or do they think it could swing around into the Gulf?

[srainhoutx]

I know it is way too soon to predict too far out however, are they thinking that this storm will continue back out into the Atlantic after it crosses Florida or do they think it could swing around into the Gulf?

The general thinking is anywhere from Upper Texas Coast to the Bahamas as of this time. It's way too soon to know with any certainty exactly where a future Isaac may head.

[srainhoutx]

HPC Update:

PRELIMINARY UPDATE...

USED THE 00Z/21 ECENS MEAN TO UPDATE THE PRELIMINARY FRONTS AND
PRESSURES FOR DAYS 3 THROUGH 7. THE ECENS MEAN SHARED MORE IN
COMMON WITH THE VARIOUS GLOBAL DETERMINISTIC MODELS THAN THE GEFS
MEAN...THE SAID DETERMINISTIC GUIDANCE SHOWING ENOUGH SPREAD
THROUGH THE PERIOD TO NOT TRUST THEIR DETAILS. EXTRAPOLATED THE
09Z/21 NATIONAL HURRICANE CENTER FORECAST FOR THE DEPICTION OF
TROPICAL DEPRESSION NINE...WHICH WOULD TAKE THE SYSTEM TOWARD THE
FLORIDA PENINSULA DAYS 6 AND 7. WILL REFINE THE TRACK OF THIS
POTENTIAL HURRICANE DURING THE MIDDAY COORDINATION CALL.

[JackCruz]

I don't think this will be a threat to our area. This is Florida's. But anything can happen....

[unome]

look at day 7 in the loop (other images are not updated as of yet) http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html

I'll bet Tampa's getting nervous...

HPC Update:

PRELIMINARY UPDATE...

USED THE 00Z/21 ECENS MEAN TO UPDATE THE PRELIMINARY FRONTS AND
PRESSURES FOR DAYS 3 THROUGH 7. THE ECENS MEAN SHARED MORE IN
COMMON WITH THE VARIOUS GLOBAL DETERMINISTIC MODELS THAN THE GEFS
MEAN...THE SAID DETERMINISTIC GUIDANCE SHOWING ENOUGH SPREAD
THROUGH THE PERIOD TO NOT TRUST THEIR DETAILS. EXTRAPOLATED THE
09Z/21 NATIONAL HURRICANE CENTER FORECAST FOR THE DEPICTION OF
TROPICAL DEPRESSION NINE...WHICH WOULD TAKE THE SYSTEM TOWARD THE
FLORIDA PENINSULA DAYS 6 AND 7. WILL REFINE THE TRACK OF THIS
POTENTIAL HURRICANE DURING THE MIDDAY COORDINATION CALL.

[srainhoutx]

look at day 7 in the loop (other images are not updated as of yet) http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html

I'll bet Tampa's getting nervous...

9 days out I'm not so sure that anyone other than those folks in the Caribbean Islands need to be 'nevrous' about this potential threat. As we saw with Ike, things will change as time goes on...

http://www.nhc.noaa.gov/archive/2008/gr ... p_5W.shtml

[djmike]

It still amazes me that this far out, people continue to think they know where landfall will occur just by whichever way the 5 day track is pointing....I can remember several storms that had tracks (and the models) pointing towards the entire Gulf coast states before final landfall was determined. Take IKE for example.... Everyone in FL needs to chill for the time being and just keep an eye on the storm.

[Belmer]

One thing is for sure, TD9 is already a huge storm. If it misses a lot of the major islands, this could and will be a dangerous storm wherever it hits.

[srainhoutx]

BULLETIN
TROPICAL DEPRESSION NINE ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM AST TUE AUG 21 2012

...TROPICAL DEPRESSION MOVING QUICKLY WESTWARD TOWARD THE LESSER
ANTILLES...NEW WARNINGS ISSUED...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...15.1N 52.8W
ABOUT 580 MI...930 KM E OF GUADELOUPE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 20 MPH...32 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES


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

THE GOVERNMENT OF CURACAO HAS ISSUED A TROPICAL STORM WARNING FOR
SABA...ST. EUSTATIUS...AND ST. MAARTEN.

THE GOVERNMENT OF FRANCE HAS ISSUED A TROPICAL STORM WARNING FOR
MARTINIQUE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* MARTINIQUE
* DOMINICA
* GUADELOUPE AND THE SURROUNDING ISLANDS...AND ST. MARTIN
* ST. KITTS...NEVIS...ANTIGUA...MONTSERRAT...ANGUILLA...AND BARBUDA
* SABA...ST. EUSTATIUS...AND ST. MAARTEN

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* BRITISH VIRGIN ISLANDS
* PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S. VIRGIN ISLANDS

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 IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...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 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL DEPRESSION NINE
WAS LOCATED NEAR LATITUDE 15.1 NORTH...LONGITUDE 52.8 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 20 MPH...32 KM/H...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS.
ON THE FORECAST TRACK...THE CYCLONE SHOULD MOVE THROUGH THE
CENTRAL LESSER ANTILLES WEDNESDAY AFTERNOON OR EVENING...AND EMERGE
OVER THE EASTERN CARIBBEAN SEA BY THURSDAY MORNING.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...AND
THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM LATER TODAY.
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO
INVESTIGATE THE DEPRESSION THIS AFTERNOON.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE WARNING
AREA BY WEDNESDAY AFTERNOON...MAKING OUTSIDE PREPARATIONS DIFFICULT
OR DANGEROUS.

RAINFALL...TOTAL RAIN ACCUMULATIONS OF 4 TO 8 INCHES ARE POSSIBLE
OVER THE NORTHERN WINDWARD ISLANDS AND THE LEEWARD ISLANDS. TOTAL
RAIN ACCUMULATIONS OF 1 TO 3 INCHES WITH MAXIMUM AMOUNTS OF 6
INCHES ARE POSSIBLE OVER PUERTO RICO AND THE VIRGIN ISLANDS.

STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 1
TO 3 FEET ABOVE NORMAL TIDE LEVELS IN THE NORTHERN LEEWARD ISLANDS.
NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES.

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


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...200 PM AST.
NEXT COMPLETE ADVISORY...500 PM AST.

$$
FORECASTER BEVEN

TROPICAL DEPRESSION NINE DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM AST TUE AUG 21 2012

A BURST OF CONVECTION CONTINUES JUST SOUTH OR SOUTHWEST OF THE
CENTER OF TROPICAL DEPRESSION NINE...ALTHOUGH THE OVERALL COVERAGE
HAS DECREASED DURING THE PAST FEW HOURS. SATELLITE INTENSITY
ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM SAB. BASED ON THESE
DATA AND THE RELATIVELY HIGH PRESSURE OF 1010 MB AT NOAA BUOY
41040...THE INITIAL INTENSITY REMAINS 30 KT. AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE
DEPRESSION THIS AFTERNOON.

THE INITIAL MOTION REMAINS 270/17. THE DEPRESSION IS LOCATED SOUTH
OF A DEEP-LAYER SUBTROPICAL RIDGE THAT IS FORECAST TO REMAIN INTACT
FOR THE NEXT 72 HR...WHICH SHOULD KEEP THE CYCLONE MOVING GENERALLY
WESTWARD AS SHOWN BY THE TIGHTLY CLUSTERED TRACK MODEL GUIDANCE.
AFTER THAT...THE GLOBAL MODELS ARE FORECASTING A SHORTWAVE TROUGH
TO DIG SOUTHWARD OVER THE SOUTHEASTERN U.S. AND THE GULF OF
MEXICO...WHICH IS EXPECTED TO WEAKEN THE RIDGE ACROSS FLORIDA AND
THE BAHAMAS. THIS SHOULD ALLOW THE CYCLONE TO TURN WEST-
NORTHWESTWARD AND SLOW DOWN ACROSS THE NORTH-CENTRAL CARIBBEAN SEA.
THE GUIDANCE SHOWS MORE SPREAD DURING THIS PERIOD...WITH THE UKMET
ON THE RIGHT EDGE SHOWING THE CYCLONE MOVING ALONG THE NORTHERN
COAST OF HISPANIOLA...AND THE ECMWF AND GFS ON THE LEFT EDGE
SHOWING THE SYSTEM PASSING SOUTH OF HISPANIOLA. THE NEW FORECAST
TRACK IS SIMILAR TO THE PREVIOUS TRACK THROUGH 72 HR...THEN IS A
LITTLE TO THE RIGHT OF THE PREVIOUS TRACK AFTER THAT. THE TRACK IS
IN BEST AGREEMENT WITH A BLEND OF THE GFS AND ECMWF MODELS.

THE DEPRESSION IS CURRENTLY EXPERIENCING LIGHT/MODERATE
NORTHEASTERLY VERTICAL WIND SHEAR. THIS SHOULD DIMINISH DURING THE
NEXT 24 HR OR SO...LEAVING THE CYCLONE IN A FAVORABLE ENVIRONMENT
FOR DEVELOPMENT. THE NEW INTENSITY FORECAST IS THE SAME AS THE
PREVIOUS FORECAST THROUGH 72 HR...SHOWING THE SYSTEM BECOMING A
TROPICAL STORM IN 12 HR AND A HURRICANE IN 48 HR. AFTER 72
HR...THE FORECAST TRACK BRINGS THE SYSTEM CLOSER TO HISPANIOLA AND
CUBA THAN THE PREVIOUS TRACK. BASED ON THIS...THE INTENSITY
FORECAST DURING THAT TIME HAS BEEN LOWERED BY 5-10 KT.


FORECAST POSITIONS AND MAX WINDS

INIT 21/1500Z 15.1N 52.8W 30 KT 35 MPH
12H 22/0000Z 15.2N 55.3W 35 KT 40 MPH
24H 22/1200Z 15.5N 58.4W 40 KT 45 MPH
36H 23/0000Z 15.9N 61.5W 50 KT 60 MPH
48H 23/1200Z 16.2N 64.6W 65 KT 75 MPH
72H 24/1200Z 17.0N 70.0W 80 KT 90 MPH
96H 25/1200Z 18.5N 74.0W 90 KT 105 MPH...INLAND
120H 26/1200Z 20.5N 77.5W 85 KT 100 MPH...OVER WATER

$$
FORECASTER BEVEN

[srainhoutx]

Code: Select all

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT TUE 21 AUGUST 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 22/1100Z TO 23/1100Z AUGUST 2012
         TCPOD NUMBER.....12-094

I.  ATLANTIC REQUIREMENTS 
    1. TROPICAL DEPRESSION NINE
       FLIGHT ONE --TEAL 73--        FLIGHT TWO --NOAA 42--
       A. 22/1800Z, 23/0000Z         A. 23/0000Z
       B. AFXXX 0309A CYCLOME        B. NOAA2 0409A CYCLONE
       C. 22/1600Z                   C. 22/2000Z
       D. 15.7N 60.0W                D. 15.9N 61.5W
       E. 22/1730Z TO 23/0000Z       E. 22/2130 TO 23/0330Z
       F. SFC TO 15,000 FT           F. SFC TO 15,000 FT

       FLIGHT THREE --TEAL 71--      FLIGHT FOUR --NOAA 42--
       A. 23/0600Z, 1200Z            A. 23/1200Z
       B. AFXXX 0509A CYCLONE        B. NOAA2 0609A CYCLONE
       C. 23/0400Z                   C. 23/0800Z
       D. 16.0N 63.0W                D. 16.2N 64.6W
       E. 23/0530Z TO 23/1200Z       E. 23/0900Z TO 23/1430Z
       F. SFC TO 15,000 FT           F. SFC TO 15,000 FT

    2. SUCCEEDING DAY OUTLOOK:
       A. CONTINUE 6-HRLY FIXES. 
       B. A NOAA P-3 MISSION AT 23/2000Z AND 24/0800Z.
       C. A G-IV SYNOPTIC FLOW MISSION AT 23/1730Z.
    3. REMARK: INVEST MISSION IN THE GULF OF MEXICO FOR
       21/1600Z CANCELED BY NHC AT 21/0930Z.

[srainhoutx]

The 12Z GFS Ensembles have made a fairly significant shift W into the Gulf. The ensemble mean had been Florida and the Bahamas prior to the 12Z output today...

[wxman57]

They're more in line with the operational GFS run now. Just west of the FL Peninsula. Interesting week ahead...

[biggerbyte]

This far out the models are completely useless. The only purpose they serve, at this stage, is to provide most likely landfall, given today's data input, and what "might" happen tomorrow.

Although I suspect landfall to be LA, east, let us not forget what happened with Ike. The models, and many Pro Mets said no way for Texas. Most everyone forecasted it to go inland well east of here. All that did were following the models. Until this system is somewhere around Cuba, I'm not predicting anything.

[srainhoutx]

They're more in line with the operational GFS run now. Just west of the FL Peninsula. Interesting week ahead...

Yes sir. It certainly appears that way. The 12Z Operational Euro has made a shift a bit W as well...

[Snowman]

I just arrived at Tulane University in New Orleans to start college a couple of days ago. I am kind of concerned about this storm....

[jasons2k]

Yikes, hopefully this isn't "Isaac's Storm" redux. That's almost a little too creepy.

[srainhoutx]

1004.9 extrap on the second center pass with TS force winds near 40 mph. Perhaps we have enough to upgrade to Isaac.

[desiredwxgd]

Once this one takes off he is gonna be a big one....

Steve, check your private message.

[srainhoutx]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 21st day of the month at 19:08Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 307)
Tropical Depression: Number 9 (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 09
A. Time of Center Fix: 21st day of the month at 18:58:40Z
B. Center Fix Coordinates: 15°20'N 53°20'W (15.3333N 53.3333W)
B. Center Fix Location: 448 miles (722 km) to the ENE (70°) from Bridgetown, Barbados.
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 40kts (~ 46.0mph)
E. Location of the Estimated Maximum Surface Wind: 20 nautical miles (23 statute miles) to the ENE (61°) of center fix
F. Maximum Flight Level Wind Inbound: From 146° at 44kts (From between the SE and SSE at ~ 50.6mph)
G. Location of Maximum Flight Level Wind Inbound: 21 nautical miles (24 statute miles) to the ENE (60°) of center fix
H. Minimum Sea Level Pressure: 1005mb (29.68 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23°C (73°F) at a pressure alt. of 242m (794ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 25°C (77°F) at a pressure alt. of 246m (807ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 25°C (77°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, Pressure and Temperature
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 0 nautical miles
Remarks Section - Remarks That Were Decoded...
Maximum Flight Level Wind: 44kts (~ 50.6mph) in the northeast quadrant at 18:51:00Z
Sea Level Pressure Extrapolation From: Below 1,500 feet
Remarks Section - Additional Remarks...
PRELIMINARY, DO NOT RETRANSMIT