[ChaserUK]

TROPICAL STORM GORDON DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082012
1100 AM AST THU AUG 16 2012

VISIBLE SATELLITE IMAGERY INDICATES TIGHTLY CURVED CONVECTIVE BANDS
HAVE FORMED AROUND A SMALL CENTRAL DENSE OVERCAST...WHICH INDICATES
THAT GORDON IS STRENGTHENING. SATELLITE INTENSITY ESTIMATES ARE
T3.0 FROM TAFB...T2.5 FROM SAB...AND T2.7 ADT FROM UW-CIMSS. GIVEN
THE MID-LEVEL BANDED EYE FEATURE NOTED IN A 16/1143 UTC SSMIS
MICROWAVE IMAGE...THE INITIAL INTENSITY HAS BEEN INCREASED TO 45
KT...WHICH IS SUPPORTED BY THE 45-KT TAFB INTENSITY ESTIMATE.

GORDON IS RECURVING TO THE NORTHEAST...AND THE INITIAL MOTION IS NOW
045/14 KT. THE CYCLONE HAS ROUNDED THE SUBTROPICAL RIDGE AXIS AND
WILL BE MOVING INTO THE MID-LATITUDE WESTERLIES DURING THE NEXT
12-24 HOURS. AS A RESULT...GORDON SHOULD GRADUALLY TURN TOWARD THE
EAST THROUGH 72 HOURS. AFTER THAT TIME...THE CYCLONE IS EXPECTED TO
LIFT OUT TOWARD THE NORTHEAST AHEAD OF A DIGGING SHORTWAVE TROUGH
AND BE NEAR THE AZORES ISLANDS IN ABOUT 4 DAYS. THE NHC MODEL
GUIDANCE IS TIGHTLY PACKED AROUND THE PREVIOUS FORECAST TRACK...
SO ONLY MINOR TWEAKS WERE MADE FOR THIS ADVISORY.

SATELLITE IMAGERY INDICATES THAT UPPER-LEVEL OUTFLOW HAS BECOME WELL
ESTABLISHED IN ALL QUADRANTS...ESPECIALLY IN THE NORTHEASTERN
SEMICIRCLE. THE VERTICAL SHEAR IS FORECAST TO REMAIN FAVORABLE FOR
ABOUT THE NEXT 36 HOURS AND WARM SEA-SURFACE TEMPERATURES OF AT
LEAST 27C LIE AHEAD OF THE CYCLONE. AS A RESULT OF THESE FAVORABLE
CONDITIONS...STEADY INTENSIFICATION SEEMS REASONABLE ALTHOUGH DRY
MID-LEVEL AIR IS BEGINNING TO ENCROACH FROM THE WEST. BY 48
HOURS...WESTERLY WIND SHEAR AND DRY AIR ENTRAINMENT ARE EXPECTED TO
SHARPLY INCREASE...WHICH SHOULD ACT TO PUT A BRAKE ON THE
STRENGTHENING PROCESS. AS GORDON APPROACHES THE AZORES IN 4 DAYS...
THE SYSTEM COULD MERGE WITH A FRONTAL SYSTEM AND TRANSITION INTO A
STRONG EXTRATROPICAL CYCLONE. THE INTENSITY FORECAST IS IDENTICAL
TO THE PREVIOUS ADVISORY...AND IS CLOSE TO INTENSITY CONSENSUS
MODEL...IV15.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 33.3N 53.8W 45 KT 50 MPH
12H 17/0000Z 34.3N 51.8W 50 KT 60 MPH
24H 17/1200Z 34.9N 48.3W 55 KT 65 MPH
36H 18/0000Z 34.9N 44.5W 60 KT 70 MPH
48H 18/1200Z 34.8N 40.6W 65 KT 75 MPH
72H 19/1200Z 35.6N 32.7W 60 KT 70 MPH
96H 20/1200Z 37.9N 25.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 21/1200Z 40.4N 19.0W 45 KT 50 MPH...POST-TROP/EXTRATROP


COULD be a real threat to the Azores either tropical or extrop?

[ChaserUK]

also interesting what Gordon 2006 ended up doing as an extrop system to the UK and parts of Europe too.

......The remnants of Gordon affected the United Kingdom with strong winds, including gusts to 60 mph (97 km/h) in the Isles of Scilly off the southwest coast and 81 mph (130 km/h) on the mainland.[1] The storm system produced heavy precipitation and thunderstorms that caused localized flooding. Wainfleet, Lincolnshire recorded 1.66 in (42.2 mm) of rainfall, of which almost half fell within the span of an hour.[23] High winds delayed rail service,[24] and in Dawlish, the rail line was damaged by coastal flooding. More than 1,000 homes were left without power in Truro, Cornwall.[25] The storm brought moist air northward that contributed to record warm temperatures across portions of the UK.[26]

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This post has been edited by ChaserUK: 16 August 2012 - 17:20

[Dave W]

Very intetesting Matthew .. could throw the proverbial spanner in the models works!

[PJB]

Gordon could bring some heavy rain and wind to the Azores. Big differences in the model handling thereafter - and this having an impact on subsequent model evolution.

[Dave W]

Yes .. whilst the GFS 12Z op run and about half the others fizzle development out NW of Corunna - another 50% actually run this as a developing low up towards Brest by HH120 but just 1 picked up on any resultant heavy rain..

[ChaserUK]

Indeedy, a couple of models have a much more pronounced N component to them...

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[skizzo3]

This is quite unusual, but the tropical storm (now a hurricane category 1) is heading towards the Azores. Fortunately its not expected to hit Portugal.





IM Portugal has already issued red alert for the oriental group of islands. Waves are expected to reach 14-16m in height, truly frightening.



Hope it doesn't get too chaotic over there

[Dave K]

It's expected to weaken slightly back to a Severe Tropical Storm tomorrow. It will be the first time since 2009 the Azores have been hit by a TS ( Grace ). In 2006 a Hurricane Gordon affected the Azores and and the remnants of the storm went on to hit Ireland Northern Ireland causing quite a lot of damage.

http://www.wundergro...l?entrynum=2191

[skizzo3]

The difference is hardly significant though. We'll have to wait and see.

[Dave K]

 skizzo3, on 18 August 2012 - 18:00, said:

The difference is hardly significant though. We'll have to wait and see.

No, not much comfort for the people in the Azores, we can hope it passes by over the ocean.

[skizzo3]

It is now category 2

[P.K.]

Yes looks like they've now got it down as 90kts at 18Z (although the intermediate advisory at that time held it at 70kts).

[ChaserUK]

Such a coincidence that the Azores will be affected by a second Gordon with only one other inbetween I think. Gordon is on the Bracknell +72 hrs now - just love seeing tropical systems on those charts for some reason.

[Uskys]

 ChaserUK, on 18 August 2012 - 19:48, said:

Such a coincidence that the Azores will be affected by a second Gordon with only one other inbetween I think. Gordon is on the Bracknell +72 hrs now - just love seeing tropical systems on those charts for some reason.

Yes ... its surreal seeing them on the fax, its named on as Gordon there from +48 to +60, then at +72 is "post gordon" ... and yesterdays +120 as ex-gordon.

[ChaserUK]

You know we could get a Cat 3 before weakening in 12 hours - that's only another 6mph sustained windspeeds to achieve!

[ChaserUK]

Oh very nearly Cat 3 last night - increased to 110mph now dropped back to 106mph - marginally better for the Azores but not much.

[Sam Jowett]

It will be interesting to see if Gordon decays over the cooler waters as models predict. In recent history, the hurricanes/tropical storms that have resided in the warm waters near the SW European coast seem to have acted atypically in terms of decay. This may be coincidental in terms of interaction with the mid-latitude forcing and stronger coriolis effect, causing a baratropic storm to sustain itself longer than clasically expected. We shall see if recent history repeats itself...

[ChaserUK]

 Sam Jowett, on 19 August 2012 - 10:39, said:

It will be interesting to see if Gordon decays over the cooler waters as models predict. In recent history, the hurricanes/tropical storms that have resided in the warm waters near the SW European coast seem to have acted atypically in terms of decay. This may be coincidental in terms of interaction with the mid-latitude forcing and stronger coriolis effect, causing a baratropic storm to sustain itself longer than clasically expected. We shall see if recent history repeats itself...

I have been thinking the same. Tropical systems that reach this part of the world do seem to buck normal behaviour patterns! Vince obviously springs to mind! Not being an expert like you guys - would the models base the behaviour on tropical systems overall or would they take into account tropical systems in this part of the world also?

This post has been edited by ChaserUK: 19 August 2012 - 10:47

[Dave K]

Auto-translation from Portuguese with a little correction

Quote

Hurricane Gordon, which passed the Azores in the early hours of today, has now turned into a tropical storm and is moving away from the islands, said Lusa meteorologist Peter Mata "It's a tropical storm, now it's moving away from the archipelago. In terms of precipitation there is practically no more rainfall from the storm," said meteorologist. According to the same source, one can still feel strong wind gusts in Santa Maria, northwest, and São Miguel, in the northeast.

Stating that the Hurricane "came closer than to Santa Maria than Sao Miguel," Pedro Mata said maximum values ​​recorded at stations of the Meteorological Institute a gust of 143 km / h in Santa Maria and a rainfall of 70 litres/m2.

In San Miguel, including the airport station in Ponta Delgada, the maximum wind gust reached 95 km / h in terms of rainfall was recorded a value of 80 litres/m2 in the northeast.

"It is natural that there are higher gusts in the eastern part of the island, which has been the most affected, but we have no station there," said the weatherman.

Anticipating that the next few hours there will continue to experience strong gusts, both in Santa Maria and São Miguel, Pedro Mata believes gradually wind intensity will decrease too.

"We do not think that in Santa Maria, the values ​​that exceed those already reached overnight," he said.

[Dave W]

All models do decay the system by late Tuesday , we shall see..