Personal forecasts for tropical storm GABRIELLE

[Matt-hurricanewatcher]

Subtropical storm GABRIELLE
9-7-2007
9pm est
Forecast one

...A subtropical storm forms over the western Atlatnic...


...Recon found a broad LLC with the low pressure over the western Atlantic today. At the time of the reports or around 3-4 hours ago at the time there was only broad LLC. Latest satellite images show a westly flow of the clouds around the base of the developing LLC. This is a strong sign that this low pressure area has developed a weak "closed" LLC near 30.2-30.4 north/72 west. Because of the broad wind field, and the fact it is disorganized. We have no choice but to put this system as a subtropical storm.


Over the last few days a trough has been effecting this system,,,this trough has lifted out. With a cut off ULL southwest of the system has been cutting off slowly over the last 24 hours. In which has made for lower shear over the system. Shear appears to be around 15-20 knots at this moment. While the ULL is moving west-southwestward, expect the tropical cyclone to move west-northwest over the next 24-36 hour, around a 'strong' high pressure to its north. The ULL is centered near 29.5 north/74 west...Still effecting the system with some shear. So only slow development is being forecasted over the next 6-12 hours. With a west-northwest movement...Afterwards we have to watch for the trough over the central United states, this system is being forecasted by the hurricane and global models, to help weaken the high and push it eastward. Which should turn the system northwest into NC around 42-48 hours...The Gfdl shows a landfall into SC/NC it is the leftward of the model sweet. The main part of the hurricane model think a run at the outterbanks of NC. We will call for a track into land 35.5 north/77.5-78 west.

The enviroment should slowly become more favorable for development of the cyclone. In fact once the ULL moves out of the way shear should drop to arond 12-15 knots, and with the gulf stream. We are forecasting the system to strengthen into a strong tropical storm by landfall.

Forecast
0 40 knots
6 45 knots
12 45 knots tropical
24 55 knots
36 60 knots
48 55 knots inland over NC.
72 50 knots moving out to sea
96 55 knots becoming extratropical
120 40 knots extra tropical

Forecaster Matthew





The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.



Post all personal forecast...

[Coredesat]

S2K Disclaimer: The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My Disclaimer: These products are unofficial and are not certified by any Regional Specialized Meteorological Centre, Tropical Cyclone Warning Centre, or any official forecasting agency and may be subject to large errors. Refer to their products for official updates.

My forecasts can be found in full at http://core-cyclone.livejournal.com

Forecast #1 - 0300 UTC 08 September 2007

...Subtropical Storm Gabrielle forms off the Carolina coast...

Estimated Position: 30.5°N 72.7°W (confidence poor)
Est. Maximum Sustained Winds: 40 knots (45 mph)
Est. Minimum Pressure: 1010 hPa
Movement: WNW at 8 knots

DISCUSSION

Despite the lack of any well-defined low-level circulation center, the low pressure area off the Carolina coast has strong enough winds and convection associated with it to be classified Subtropical Storm Gabrielle (07L) by the NHC. Despite several swirls on shortwave IR satellite imagery, the actual circulation center is in the middle of a crescent-shaped mass of broken convection just east of an upper-level low (shown as the leftmost swirl in the loop). Convection has been wrapping better around the upper-level low, which is shearing the system and giving it its strange appearance.

Air Force reconnaissance observations earlier indicated surface winds of 40 knots, and despite a Dvorak estimate of T2.0/2.0 from TAFB and a Hebert-Poteat estimate of ST1.5/1.5 from SAB, the intensity for this forecast is set at 40 knots, for lack of a better indicator of the system's intensity - and I am not going to make any up.

Gabrielle is currently being steered around the upper-level low toward the Carolinas. An approaching cold front should cause the system to recurve toward the northeast after 48 hours, but the system should make landfall before then. I am currently not expecting the system to transition to a full tropical storm prior to landfall unless it becomes better organized, though this is certainly possible as Gabrielle encounters warmer waters and slightly lower shear.

Little change in strength is forecast over the next 24 hours, with some gradual strengthening to 48 hours due to decreasing shear. The track is along the lines of the global model, GFDL, and HWRF consensus. Interaction with the front should initiate extratropical transition by the end of the forecast period.



FORECAST POSITIONS AND MAX WINDS

Init...30.5°N 72.7°W...40 kt
12 hr...31.3°N 74.3°W...40 kt
24 hr...32.7°N 75.6°W...45 kt
36 hr...34.4°N 76.3°W...50 kt
48 hr...36.6°N 75.7°W...45 kt...inland
72 hr...39.0°N 72.0°W...35 kt...becoming extratropical

[cheezyWXguy]

Amateur Forecast 1
12:00AM CDT


...GABRIELLE FORMS OFF EAST COAST TONIGHT...

DISTURBANCE INVEST 99L HAS ACQUIRED SUFFICIENT CHARACTERISTICS TO BE NAMED SUBTROPICAL. ON TOP OF THAT, RECON EARLIER REPORTED FLIGHT LEVEL WINDS OF 48KT, REDUCING TO ABOUT 40KTS AT THE SURFACE, EQUATING TO TROPICAL STORM FORCE WINDS. THUS THE SEVENTH NAMED STORM OF THE 2007 SEASON IS BORN.

GABRIELLE HAS A FAIRLY POOR-DEFINED CIRCULATION CENTER AT THE MOMENT, VOID OF MUCH, IF ANY, DEEP CONVECTION. HOWEVER...CONDITIONS ARE IMPROVING GRADUALLY, WITH SHEAR AND DRY AIR ON TE DECREASE. DUE TO THE FORECASTING OF CONDITIONS CONTINUING TO IMPROVE OVER THE NEXT FEW DAYS, GABRIELLE IS FORECAST TO SLOWLY STRENGTHEN OVER THE NEXT 24 HOURS, WITH A STEADIER STRENGTHENING THEREAFTER UNTIL LANDFALL, BRINGING GABRIELLE TO A CATEGORY 1 HURRICANE. ON TOP OF THAT, THE SYSTEM IS FORECAST TO TRANSITION OVER COMPLETELY TO TROPICAL OVER THE NEXT 12-24 HOURS.

UNLIKE MANY STORMS THIS YEAR SO FAR, THE FORECAST IS FAIRLY CONFIDENT, WITH AN INITIAL MOVEMENT OF WNW TO NW OVER THE NEXT 24HOURS, FOLLOWED BY A TURN TO THE N DURING DAY 2, WITH A RECURVE OUT TO SEA AFTER LANDFALL ON NORTH CAROLINA. MODEL GUIDANCE IS IN DECENT AGREEMENT, SO I HAVE PUT MY FORECAST TRACK IN THE GENERAL CENTER OF THE GUIDANCE, BETWEEN A HARMLESS RECURVE OUT TO SEA OR A LANDFALL ON THE NC/SC BORDER.


FORECASTER: CHRIS

INTENSITY FORECAST FOR 07LGABRIELLE:
TIME, MAX WINDS(KT)
0HR-40KT,1011MB
12HR-45KT
24HR-50KT
36HR-60KT
48HR-70KT...INLAND
72HR-50KT...OVER WATER, BECOMING EXTRATROPICAL
96HR-50KT...EXTRATROPICAL





Map courtesy of http://www.wunderground.com

[Matt-hurricanewatcher]

Subtropical storm GABRIELLE
1am est
9-8-2007
Forecast 2#


Latest satellite shows that Gabrielle has developed a well defined LLC near 30.5 north/73.5 west...This LLC has become organized and has formed convection to its north and west over the last few hours. This system appears to be moving at near 280 or just north of west over the last few hours.

Both Gfs/Gfdl phase at FSU shows the system has slowly become more tropical. And also the shear level is now around 10 knots based on Cimss shear maps. That is very favorable for tropical cyclone development. This system is very close to becoming tropical based on the data I've put up. Also the tightness of the system is a big sign. Over the next 12-24 hours as the system moves over the Gulf stream and the shear reminds half way favorable, we expect strengthing. We now forecast this storm to become a 70 knot hurricane by 36 hours...In a hurricane into NC.


Tropical storm Gabrielle has been moving west-northwest over the last few hours around the base of a high pressure to its north. The frontal/trough is moving through the great lakes area currently...This system will be the thing that helps to form the weakness in the ridge of high pressure around 36-48 hours. 00z Gfs shows the system moving westward or west-northwest through the next 24 hours...Followed by a weakness by the trough forming at 500-700 mililbars after 36 hours. This should help the system to turn more northwestward as a large part of the tropical models do currently appear to catch. Landfall around 38-42 hours appears to be the time frame,,,we are holding onto our forecast of a landfall from the last forecast. Maybe slightly north. The flow ahead of the trough should after 60 hours speed the system out to sea. The latest 00z Gfdl shows a more northward track into the outterbanks of NC. Landfall around 54 hours...This all has to do with how fast the trough moves eastward, and how strong the high pressure will be. We don't think this high pressure will break down as fast as some of the faster models think...In fact we are more inline with the Gfs currently, but slightly more north. The CMC/Ukmet 00z does offer support to the latest GFDL Latest 850 maps put the ridge at 1587 height at 850 millibars just north of the outterbanks, with the trough at least another 12-24 hours from seriously effecting this ridge. This ridge extends up to 300 millibars...So its pretty strong. That is why we forecast a more inland path into NC.

Forecast
0 45 knots 30.6 north/73.5 west
6 50 knots 30.9 north/74.2 west
12 55 knots 31.3 north/75.3 west
24 60 knots 33.5 north/76.5 west
36 70 knots 34.2 north/77.5 west
48 55 knots 35.6 north/77.4 west Inland
72 60 knots 36.8 north/74.5 west
96 50 knots extratropical

Forecaster Matthew


The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Matt-hurricanewatcher]

Tropical storm Gabrielle
forecast 3#
9am est
9-8-2007


...Gabrielle appears to becoming tropical while moving northwestward...

...Latest shows convection trying to build over a well defined LLC, but with shear still pushing it to the northwest quad. Ship reports and quickscat have reported 35 knots for ship/40 knots for quickscat. Strength is kepted at 45 knots with yesterdays 42 knot surface wind from recon, and the 48 knot flight level. Even so we do expect it could be pretty close to it now. Sab shows 2.5t for 35 knots and tropical. The wind field is slightly in larged to the north, but that is normal for a system with a high to the north. Recon will be in the system over the next few hours.

Latest models show the ridge forming a weakness much faster then last forecasts thinking...This system is already moving into the northeastern united states. In which case is weaking the ridge of high pressure. So most of the hurricane model sweet has moved to a skim of the cyclone off the outterbanks of NC. Also the system is .6 degree's north of forecast at 6 hours. So forecast track is shifted northward through out the track. Also we are forecasting the ridge to break down enough to allow the system to follow class to the core of the hurricane sweet...We feel that they have a good idea at this time on track,,,Already on layer means on cimss the high is setting up at 300-500 millibars slightly northeast of the system. That is why it is starting to move more northward. We are still going to make landfall near 35.7 north into the outterbanks...After that the trough should speed it out into the Atlatnic. In which it will become extratropical. The last 2 runs of the models have been showing this...In finally we have the brains to go with it. Make no mistake we busted on telling the strength of the ridge.

We are forecasting also less strengthing because the system is going to make landfall earlier. Also the enviroment does not look nearly as favorable. We take it to just under cane strength at 24-30 hours. With a landfall near 32-38 hours...Then a movement northeastward out to sea. It would not suprize me if it does not make landfall, that there could be a short time from that it could strengthen more. Heck its possible if shear keeps up we maybe to high with the wind, at least for the first 24 hours.

Forecast
0 31.5/74.2 45 knots
6 32.3/74.9 50 knots
12 33.1/75.3 55 knots
24 34.5/75.8 60 knots
36 35.4/75.2 50 knots
48 36.5/73.8 55 knots
72 38.0/68 50 knots extratropical

Forecaster Matthew


The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Next forecast at 6pm pst/9pm est

[Derek Ortt]

lol at signing forecasts with one's first name

It is OK to use one's last name at the end of a forecast

[Coredesat]

S2K Disclaimer: The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My Disclaimer: These products are unofficial and are not certified by any Regional Specialized Meteorological Centre, Tropical Cyclone Warning Centre, or any official forecasting agency and may be subject to large errors. Refer to their products for official updates.

Forecast #2 - 1800 UTC 08 September 2007

...Gabrielle approaching North Carolina with little change in strength...

Estimated Position: 31.5°N 74.2°W (confidence good)
Est. Maximum Sustained Winds: 40 knots (45 mph)
Est. Minimum Pressure: 1009 hPa
Movement: NW at 8 knots

DISCUSSION

Gabrielle (07L) has increased somewhat in organization overnight, though it is still not quite tropical in nature. A well-defined low-level circulation center has finally developed, but it is completely exposed with the nearest convection confined to the NW quadrant about 2 degrees away from the center. Vapor imagery shows dry air intrusion into the circulation, though there is some modest outflow in the NW quadrant. Shear has decreased slightly, but there is significant dry air suppressing convection on all other sides of the system. Latest estimates were ST2.5/2.5 from TAFB (H-P) and T2.5/2.5 from SAB. A recon mission is currently underway, but at the moment there does not seem to be any reason to change the intensity of 40 kt.

Gabrielle is nearing the western edge of the subtropical ridge, and as such recurvature toward the north and northeast should occur within the next 24 hours or so. The model guidance has shifted eastward since the previous forecast, and the current forecast now calls for recurvature over the Outer Banks of North Carolina. The system should begin extratropical transition by the end of the forecast period. Transition to tropical is now forecast to occur in 24 hours or so, but given the system's current appearance this may not occur if convection does not develop closer to the center.



FORECAST POSITIONS AND MAX WINDS

Init...31.5°N 74.2°W...40 kt...subtropical
12 hr...33.0°N 75.2°W...40 kt...subtropical
24 hr...34.5°N 75.7°W...45 kt...tropical
36 hr...35.9°N 75.4°W...45 kt...tropical
48 hr...37.3°N 74.0°W...50 kt...tropical
72 hr...39.5°N 70.5°W...50 kt...becoming extratropical

[Stephanie]

Great jobs with the personal forecasts AND remembering to use the disclaimer.

[Matt-hurricanewatcher]

Tropical storm Garrielle
9-8-2007
5pm pst/8pm est
forecast 4

...Tropical storm moving towards the outterbanks....

...Recon found a weaker but tropical system today. With only 39 knots flight level, telling me that most of that higher winds was caused by the high to the north yesterday. Also a pressure of 1009 millibars. Sab 2.5t.

The system will be moving over the gulf stream and the shear should be low enough for some strengthen. So strengthen is being forecast over the next 12 hours. Followed by steady state after 24-36 hours as the system moves out to sea.


The system has turned north-northwestward over the last few hours, in fact the ridge has shifted east and is helping pull the system northward with the frontal system moving into the northeastern united states. Overall shear is down to around 8-10 knots over the tropical cyclone...In should stay that way for the next 12-18 hours, but afterwards expect the frontal system to increase shear over the system. High is set up from 500-850 millibars almost south to north to the east of the system now...There is no choice but to forecast this system to move northward over the next 24 hours. In fact with the little ridging that is still in place, it will likely track just off shore the outterbanks. This is looking at the flow patterns that still show a weak high just north of the system, but this high should be breaking down as the trough moves to its north. The hurricane models have not shifted much eastward from the 12z to the 18z. The latest Gfdl trys to turn it back westward with a landall into the NC/SC border. I say the gfdl has not done very well this season. It stinks. I will discount it. Based on current trends we will shift to just off the outterbanks or just near of the Bamm/Bamms/Bamd hurricane models. The global models keep it northward ahead of the frontal system...With Gfs/Gfdl/hw showing a north-northeastward east of long island by 60 hours. The hurricane models forecast a turn more east-northeastward. In which we are going closer with.


0 32.8 north/74.9 west 40 knots
6 33.7 north/75.2 west 50 knots
12 34.6 north/75.5 west 55 knots
24 35.8 north/75.6 west 55 knots
36 36.4 north/74.3 west 50 knots
48 37.2 north/72.5 west 50 knots
72 40.3 north/67.2 west 50 knots extratropical

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[JonathanBelles]

viewtopic.php?p=1625960#p1625960

Posted there ^^

[Matt-hurricanewatcher]

Tropical storm Gabrielle
9-9-2007
1am pst/4am est
forecast 5

...Tropical storm gabrielle weakens to a 35 knot tropical storm as it turns more north-northwestward off NC.

The recon found that Gabrielle pressure is down to 1004.8 millibars but with peak flight level winds of 41 knots or 37 mph at the surface. We are assuming that stronger winds are in the western quad under the convection. The center is also west of the forecasted track near 33.39 north/75.54 west based on recon data as of a hour ago. The core temperature difference from inside to outside the cyclone is fair from inside to outside or around 4c differences. That is fairly healthy.

Overall the shear is around 8-10 knots over the core of the cyclone. But it appears that it is stronger based on the fact that the core is northeast part of the convection. Based on shear maps from cimss shear should only increase over the next 24-36 hours as the the trough moves into the area. Between 36-60 hours as its being kicked out to the north atlatic, the system as it is moving with the shear could strengthen again. In that is being forecasted.

300z stream layer maps show that we still have a high to the north of the cyclone. But most of the high pressure area appears to have pushed east of the cyclone. The main trough axis is now moving into the great lakes area, at 700-850 millibar level. As you get up to 300-500 millibars the high to the north is even weaker. So the cyclone is expected to turn more to the north over the next 6-12 hours. Latest hurricane models bams,bamd shows a movement through the outterbanks, while the bamm shows a movement farther inland at 00z. The newer 06z hurricane models show a more soild track into the outterbanks. We will forecast this to maybe go another .2-.4 west at tops and with a mostly northward track into the outterbanks with in 18-24 hours. Followed by a track north-northeastward and then finally northeastward out into the north Atlatic. The latest 00z Gfdl seems also to be more inline with the hurricane models...In shows this making landfall over the outterbanks in 24 hours. Followed by a northeast movement into the north Atlantic. So our idea's have strong support.


Forecast
0 35 knots 33.5 north/76 west
6 40 knots 34.2 north/76.2 west
12 45 knots 34.7 north/76.4 west
24 45 knots 35.2 north/76.4 west
36 50 knots 36.8 north/74.3 west
48 55 knots 37.9 north/69 west
72 40 knots 40.2 morth/64.5 west extratropical




The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Coredesat]

S2K Disclaimer: The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

My Disclaimer: These products are unofficial and are not certified by any Regional Specialized Meteorological Centre, Tropical Cyclone Warning Centre, or any official forecasting agency and may be subject to large errors. Refer to their products for official updates.

Forecast #3 - 0900 UTC 09 September 2007

...Gabrielle approaching the Carolina coast with little change in strength...

Estimated Position: 33.8°N 76.3°W (fair: GOES-FLOATER IR2/IR4)
Est. Maximum Sustained Winds: 40 knots (45 mph)
Est. Minimum Pressure: 1004 hPa
Movement: NNW at 8 knots

DISCUSSION

Gabrielle (07L) became a fully tropical storm yesterday evening, but has struggled mightily since then. Convection is now sheared to the southwest of the apparent center, with the exception of a band extending north from the convective mass. The system has a tilted appearance on shortwave IR satellite imagery; the mid-level circulation is being impacted by strong mid-level shear. Dry air ahead of the incoming trough to the west is also inhibiting the convection and limiting it to the southwest quadrant. Based on recon observations of 53 kt at flight level, the intensity remains 40 kt.

The position creates a slight problem with the forecast track - a new center may be forming closer to the convection. If this is the case, the track may be slightly to the west of the forecast provided here. Aside from that, there is little change to the previous forecast reasoning except for less strengthening and a slight shift to the west. However, if the center reforms, the system could strengthen more than forecast, though given its proximity to land any extra strengthening should be negligible.



FORECAST POSITIONS AND MAX WINDS

Init...33.8°N 76.3°W...40 kt
12 hr...35.4°N 76.2°W...45 kt...inland
24 hr...37.0°N 75.1°W...40 kt...over water
36 hr...38.3°N 73.3°W...40 kt
48 hr...39.5°N 70.9°W...40 kt
72 hr...41.5°N 66.0°W...35 kt...extratropical

[Matt-hurricanewatcher]

Tropical storm Gabrielle
Forecast 6#
9-9-2007
4pm pst/7pm est


....Gabrielle over NC moving northward; to move back into the Atlatnic ocean in the next 6 hours. 35.9 north/76.2 west...

As the system was making landfall the recon found 66 knot flight level winds. With surface winds at 55 knots...The system has weaken since that time. With reports of 35-40 knot winds over NC/outterbanks. We are holding the system at 40 knos for this forecast. With a possible slow restrengthing once it turns more northeastward out to sea, before it becomes extratropical after 48 hours.

Strong northly shear is over Gabrielle, blowing the convectoin to the south of the cirulation. This shear is expected to stay over the system as long as its moving north or north-northeastward for the next 24 hours at least.


Ridging is gone to the north of the cyclone, with the ridge fully formed east the cyclone. A northly track should be expected for the next 6-12 hours, followed by the trough moving into the northeastern United states catching the system and pulling it more northeastward after 24 hours. The gfs and Gfdl shows fairly slow movement of the cyclone over the next 24 hours. And more northward...Followed by a more east-northeastward motion once the trough catches it. The 12z Gfdl is to far east in its placement of the cyclone.


0 35.9 north/76.2 west 40 knots
6 36.4 north/76.0 west 40 knots
12 36.9 north/74.8 west 45 knots
24 38.2 north/73.2 west 45 knots
36 39.5 north/70.5 west 50 knots
48 40.0 north/63.5 west 40 knots
Extratropical

[Matt-hurricanewatcher]

Tropical depression Gabrielle
forecast 7#
9-10-2007
3:30am pst/6:30am est


...Gabrielle weakens to a depression as it moves northeastward over the western Atlantic.


...Over the last 6 hours gabrielle has be void of all convection. Now reports show tropical storm force winds any more. But over the last few shots it has formed a single small area of convection. If that keeps up and redevelops as gabrielle gets picked up by trough over the next 6-12 hours, this system could restrengthen. But for now this will be the last forecast issued, unless it does so.