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Somerset Squall

Hurricane Nadine

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Tropical Depression 14L has formed midway between the Eastern Caribbean and the Cape Verde Islands. The depression has a well defined LLC but convection is not looking to healthy as present as 14L is ingesting a large amount of the dry air from the west. 14L is eventually expected to overcome this, especially as shear is low which will prevent the dry air making significant intrusions into the centre once the depression has formed an inner core. Sea temps support strengthening too, and NHC expect 14L to become a hurricane in a few days time. 14L looks to move northwestward, then north then northeastward around a the subtropical ridge to it's northeast. 14L should not be a threat to land.

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A FISH but models have shown it near the Azores and Spain which could be interesting.

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Looks like they want to send all the remnants of thier activity towards us this year:

201214N_7F.png

trackmap_storm2.jpg

models_storm2.jpg

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Interesting track shown by the GFS model taking Nadine towards the Azores/Canary Islands, SST's are pretty warm in this part of the world which could be enough to maintain Nadine a TS status a fair distance should she take this route across the Atlantic. Or she could just get ripped apart by shear...

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Looks like Nadine will recurve quite sharply which puts the Azores at risk as others have said. Nadine looks impressive on satellite imagery, and now has sustained winds of 50kts. Some impressive banding features are wrapping well into the defined circulation, which is an indicator of a maturing storm in a low shear environment. Looks to become a hurricane pretty soon by the looks of things.

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Nadine seems to be doing fairly well compared to the other storms in the deep tropics this season. Also, random fact: no "N" storm in the Atlantic has ever exceeded Category 1 strength.

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Nadine seems to be doing fairly well compared to the other storms in the deep tropics this season. Also, random fact: no "N" storm in the Atlantic has ever exceeded Category 1 strength.

Thats because its much slower than the others at this stage so no structural core issues. It has a ULL to the north east enhancing outflow and a front to the west steering it towards the Azores High which it will travel underneath enhancing inflow. So long as it avoids the ULL to the north east then it could be formidable.

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Nadine seems to take a sharp right in 117 hours but I'm not sure how much of her current energy she will retain on her journey back across the Atlantic?

201214N_7G.png

Tropical Storm NADINE: Probability of Cat 1 or above winds to 117 hours lead

models_storm2.jpg

trackmap_storm2.jpg

wv_satellite_storm2_1.jpg

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GFDL doesn't have her taking such a sharp right turn:

1.track.current.png

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Looks from GFS to be set to curve back towards Spain and only make extratropical transition not long before it reaches there (check the North Atlantic modelled wind speed!), then possibly heading north towards southern UK. Could be quite eventful if that happens...or it could follow the due north track west of the Azores high and fizzle out over the Labrador Sea. Very much worth keeping a keen eye on for now though.

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Another one of a series of Atlantic storms that we may have affect us this year. NASA have been checking Nadine out with a drone:

NASA drone spies on tropical storm Nadine

Overnight, tropical depression 14 (TD14) gained enough intensity to earn the name Nadine, the 14th tropical storm of the 2012 Atlantic hurricane season. Our tropical weather expert, Brian McNoldy says he could only find two others years in 160 years of records in which the 14th storm formed sooner: 1936 and 2011.

Nadine is on a projected path that threatens no land area according to the National Hurricane Center, but a NASA field campaign is taking full advantage of this storm to get deeper insight into how hurricanes develop and intensify.

On Tuesday, NASA sent an unmanned Global Hawk into TD14/Nadine on a 26 hour mission to sample the storm’s environment. It is the longest continuous period a storm has ever been investigated, considerably longer than the capabilities of manned Air Force Hurricane Hunter planes. Climate Central’s Andrew Freedman put it this way: “To put that [26 hour flight] in further perspective, the longest regularly scheduled passenger flight is between Singapore and Newark, N.J., which clocks in at a comparatively paltry 18 hours and 55 minutes.â€

drone-flight.jpg

One of two Global Hawks NASA is using to investigate tropical weather systems (NASA) The drone that gazed down on Nadine is one of two Global Hawks NASA will dispatch from Wallops Island, Va. to collect data on tropical systems through early October and again in 2013 and 2014.

The planes are operated from ground control stations at Wallops and Dryden Flight Research Center at Edwards Air Force Base, Calif. The mission is formally known as the Hurricane and Severe Storm Sentinel (HS3). Reaching altitudes as high as 60,000 feet, the Hawks can fly above the highest-penetrating storms, while its suite of cutting-edge instruments can sense the air all the way down to the ocean surface.

The two Hawks contain several sensors to take measurements - one focusing on the storm environment, the other - the “over storm Hawk†- which hones in on storm attributes like wind and rain rates.

The Environmental Global Hawk

“The primary objective of the environmental Global Hawk is to describe the interaction of tropical disturbances and cyclones with the hot, dry and dusty air that moves westward off the Saharan desert and appears to affect the ability of storms to form and intensify,†said Scott Braun, a NASA research meteorologist.

The suite of instruments includes:

* A Cloud Physics Lidar (CPL), which measures clouds structure and aerosols (dust, sea salt and smoke particles)

* A scanning high-resolution interferometer sounder (S-HIS), which can sense temperatures and water vapor from the surface through the atmosphere

* The Advanced Vertical Atmospheric Profiling System (AVAPS), which ejects small sensors tied to parachutes (cool!) to measure winds, temperature and humidity

drone.jpg

The Over Storm Hawk

“Instruments on the ‘over-storm’ Global Hawk will examine the role of deep thunderstorm systems in hurricane intensity change, particularly to detect changes in low-level wind fields in the vicinity of these thunderstorms,†said Braun.

The suite of instruments includes:

* The High Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), which measures cloud structure and winds in three dimensions

* The High-Altitude MMIC Sounding Radiometer (HAMSR), which uses microwave wavelengths to measure temperature, water vapor, and precipitation from the top of the storm to the surface

* A Hurricane Imaging Radiometer (HIRAD) which measures surface winds and rain rates

It’s too soon to evaluate how much valuable information this mission is collecting compared to manned aircraft such as Hurricane Hunters. But Climate Central’s Freedman says if the mission proves successful, the Hawks “might one day replace some of those conventional planes as a mainstay of hurricane recon work.â€

http://www.washingtonpost.com/blogs/capital-weather-gang/post/nasa-drone-spies-on-tropical-storm-nadine/2012/09/12/18401d74-fce5-11e1-8adc-499661afe377_blog.html

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I'd be inclined to discard the GDFL on the basis that the globals have been extremely consistent in ending up near the Azores (whether it just weakens or gets picked up is another question).

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I'd be inclined to discard the GDFL on the basis that the globals have been extremely consistent in ending up near the Azores (whether it just weakens or gets picked up is another question).

Must admit GFDL has thrown up some strange tracks recently, almost as if there was no human intervention?

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Nadine is not yet a hurricane. The intensity has steadied at 60kts, just below hurricane strength. It appears shear and dry air have been affecting Nadine over the last 18hrs. The window for strengthening is closing, as shear will rise further in a couple days time. Nadine still may become a hurricane within that time.

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201214N.png

nadine5day2.gif

024006P_sm.gif

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SEPTEMBER 14 2012...2:42 AM EDT...

Tropical Storm Nadine has stopped strengthening in the last 24 hours...therefore avoiding hurricane strength. The tropical cyclone could threaten the Azores beyond 5 days out...so interests in the Azores should monitor the progress of this system. See Nadine special feature section below for further details.

Sep_14_2012_0045Z.png

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0126Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

Sep_14_2012_0015Z.png

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM NADINE...

Track-wise...once again as in the previous two discussions...the short-term NHC recorded storm track has a slight leftward angle with respect to the NHC track forecast. The NHC short-term track forecast has continued to require ever-so-slight leftward shifts in the last 24 hrs...and therefore I am predicting another such slight leftward shift as shown by my forecast track in Figure 1 below. This means I am currently slightly left of NHC for the short-term track forecast.

With that said...in order for my and the NHC's short-term track forecast to verify...Nadine would have to turn straight north in the next 24 hours. Nadine is probably strong/tall enough in structure to "feel" steering influence from the paragraph P4 upper vorticity to the SW and paragraph P2 W Atlantic cut-off upper vortex to the NW. Along ex-Leslie's long front...a broad western Atlantic surface low is forming with the support of paragraph P2 W Atlantic cut-off upper vortex peripherial divergence. For the next 24 hrs...00Z GFS still develops a new low-level ridge west of Nadine which I surmise is from upper convergence as Nadine's upper outflow clashes with paragraph P7 Caribbean-to-C Atlc upper ridge. This low-level ridge prevents Nadine from progressing further westward...so Nadine has would have no choice but to go straight north while attracted toward the western Atlantic low to the NW. All of the facts in this paragraph support Nadine tracking straight north by 24 hours from now.

The steering picture still gets more complicated for the timeframe that is now between 24 and 48 hrs...with Nadine between the western Atlantic low to her west...paragraph P2 W Atlantic low-level ridge arriving to her north...the paragraph P6 low-level ridge to her southeast...and the ex-Isaac deep-layered vortex (paragraph P5) to her northeast. With all this conflicting steering...I honestly prefer to keep Nadine stationary between 24 and 48 hrs. But because the models and NHC forecast still want to move Nadine faster to the NE than what I am thinking for that timeframe...I still show some NE progress (but still slower than the NHC forecast).

After 48 hrs...00Z GFS shows a shortwave fragment of paragraph P2 upper trough re-enforcing the ex-Isaac deep-layered vortex...which helps drag Nadine eastward towards it. But what really inclines me to agree with an eastward motion by that time is that the low-level ridge to her north getting knocked out by the paragraph P1 upper trough. Coupled with paragraph P6 low-level ridge to her south and re-enforced ex-Isaac deep-layered vortex to her east...it makes sense to show eastward motion after 48 hrs. I support an increasingly slowing eastward track between 48 and 120 hrs (which makes me even further behind the NHC track forecast)...due to Nadine catching up to what is now the paragraph P2 W Atlantic low-level ridge which will be in the NE Atlantic by this timeframe. In fact...I would prefer to stall out the track towards 120 hrs with the ex-Isaac vortex diminishing...leaving Nadine trapped in a narrowing gap between the paragraph P6 low-level ridge to the south and NE Atlantic low-level ridge. Interestingly...this morning's 00Z GFS prefers to reverse the track WNW away from the Azores after 120 hrs (not shown in Figure 1). I suppose 00Z GFS is giving more credence to the NE Atlantic low-level ridge which should be stronger than the paragraph P6 low-level ridge by that time.

Due to uncertainty beyond 120 hrs and Nadine being closer to the Azores by that time...interests in the Azores should still watch Nadine even though there are emerging scenarios as posed above that suggest the Azores would have no impact.

Sep_14_2012_TSNadineForecast.png

Figure 1: My forecast for Tropical Storm Nadine created this morning.

Intensity-wise...Nadine has stopped strengthening in the last 24 hrs...maintaining a flat intensity of 70 mph max sustained winds (just below hurricane force). This is contrary to earlier intensity forecasts which made Nadine a hurricane by now. In hindsight...it appears all prior forecasts ignored the western upper outflow blockage that Nadine is currently experiencing from paragraph P4 upper vorticity. At this time...I no longer expect Nadine to ever become a hurricane...but the NHC suggests Nadine will have a fast enough eastward track such that it is buried below a more favorable upper outflow environment beneath an upper ridge wave just ahead of the paragraph P1 upper trough. In fact...the NHC suggests Nadine becoming a hurricane later on by day 5. Because of my Nadine track forecast continuing to show a slower eastward progression than NHC's...I still prefer being below the NHC intensity guidance with the assumption that Nadine will be closer to the westerly shear of the paragraph P1 upper trough. I slightly weaken Nadine to 60 mph max winds by 11 PM Saturday as the westerly shear initially hits Nadine...then I keep Nadine modeled as a steady-state tropical storm balanced by unfavorable paragraph P1 upper trough westerly shear over her west half and favorable upper ridge wave outflow over her east half. This is contrary to my earlier handling of Nadine...which showed continuous long-term weakening...but now I do not want to stray too far away from the newly-elevated NHC intensity guidance for day 5.

The impact swath in Figure 1 is initialized based on the 11 PM EDT NHC tropical storm wind radius. The impact swath remains generally the same size thru the forecast period due to the flat intensity forecast. Note the rightward bias in the initial impact swath (with respect to forecast track)...due to the upper outflow blockage caused by paragraph P4 upper vorticity limiting the activity in the west half of Nadine. The impact swath is drawn with the assumption that Nadine remains lopsided like this thru the forecast period...especially with potential westerly vertical shear from the incoming paragraph P1 upper trough later on.

...MID-LATITUDES DISCUSSION...

P1...Upper trough and surface frontal system in mid-latitude westerlies has entering the upper-left corner of above atmo birdseye chart. The surface front is advancing into the eastern US...which curls into a frontal cyclone that has ejected northeastward from Hudson Bay and toward Greenland in last 24 hrs. Warm air advection ahead of the front supports upper ridge wave over the NE US and Atlantic Canada. Upper convergence of the upper trough supports a 1030 mb low-level ridge building over the central US. Finally...a fragment of this upper trough has dropped off a cut-off upper vortex over the SW US.

P2...Upper trough has advanced from W Atlantic and into the north Atlantic in last 24 hrs...and its eastern divergence supports the still-strong remnant low of Leslie which has zipped NE toward northern Europe and out of the scope of the above atmo birdseye chart. Even though Ex-Leslie has exited the picture...it should be noted she will continue to bring elevated winds and surf to the Atlantic high seas shipping lanes as she heads toward northern Europe. The associated surface frontal zone tailing from ex-Leslie is stretched across the central Atlantic and the Bahamas. Elsewhere...the western upper convergence of the upper trough used to support large area of dry air and a 1029 mb surface ridge over the W Atlantic...but now is supported by SE convergence of upper ridge mentioned in paragraph P1. The upper trough has left behind a new cut-off upper vortex over the W Atlantic in last 24 hrs. Another old fragment of this upper trough remains cut-off...now located over the SE US/Gulf of Mexico area.

P3...To the southeast of ex-Leslie...the remnant of Michael has continued NE along the cold front extending from ex-Leslie...also out of the scope of the above birdseye charts like ex-Leslie. Ex-Michael appeared intermittently in HPC analyses to the east of S Greenland...but now has also left the scope of the HPC analyses. I am currently assuming that ex-Michael has lost its identity within the larger low pressure field of ex-Leslie.

P4...Cut-off upper vorticity remains in the open Atlantic...still established as SW-NE upper trough squeezed between the Caribbean-to-C Atlc upper ridge cell and upper ridge cell toward Africa (both cells mentioned in paragraph P7). An embedded upper vortex is currently just N of Puerto Rico.

P5...While currently positioned just south of the Azores...remnant deep-layered low of Isaac is turning slowly northwestward toward break in paragraph P6 and P7 lower and upper ridges...the break generated by paragraph P2 mid-latitude system.

P6...Atlantic surface ridge has been eroded out of the western Atlantic as ex-Leslie's Atlantic cold front continues advances in. Its remaining eastern Atlantic portion is supported by the SE convergence of lengthy paragraph P7 Caribbean-to-C Atlc upper ridge cell. Easterly flow on the south side of this surface ridge is helping to waft pockets of Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...

P7...Upper ridging across the tropical Atlantic persists. The Caribbean to Central Atlantic upper ridge cell has been stretched into the NE Atlantic toward Europe thanks to low-level warm air advection ahead of the ex-Leslie (paragraph P2) system. Like a mid-latitude upper ridge wave...southeastern convergence of this Caribbean-to-C Atlc upper ridge supports pockets of dry air in the Caribbean and east of the Lesser Antilles. Remainder of the upper ridging is located toward the west coast of Africa and above Tropical Storm Nadine.

P8...The tropical wave SW of the Cape Verde Islands in the previous discussion is now midway between the Lesser Antilles and Cape Verde Islands. Its t-storm cluster has slightly increased in the last 24 hrs...but so far is embedded in straight upper easterly flow on the south side of paragraph P7 upper ridging. Until the t-storm latent heat release increases to support an embedded warm core upper outflow structure in the upper ridge...not considering this an area for tropical development. It is also headed toward paragraph P7 dry air and less favorable paragraph P4 upper vorticity.

P9...Satellite imagery suggests a tropical wave has emerged from the west coast of Africa and into the waters SE of the Cape Verde Islands. The t-storm activity is not as impressive as it was earlier when it was along the African coast.

http://www.wundergro...ml?entrynum=196

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Tropical Storm Nadine has lingered at just below hurricane strength, but is expected to meet less favorable conditions as it turns northeast, away from the U.S. The storm had maximum sustained winds of 70 mph as of 5 a.m. Friday, little changed from the day before, when the storm was expected to soon become a hurricane. That strengthening has now been pushed off to Monday, though forecasters say it's going to become more difficult for the storm.

Nadine was about 800 miles northeast of the Virgin Islands and other northern Leeward Islands, and 765 miles east-southeast of Bermuda. It's not expected to impact any land until perhaps it reaches the Azores in the middle of the Atlantic around Thursday. If it does reach hurricane status, it would be the eighth Atlantic storm this season to do so, the upper bounds of the estimate NOAA made in early August.

Forecasters are eyeing one other tropical system off the South American coast, but give it only a 10 percent chance of forming into a tropical cyclone in the next 48 hours. The heart of hurricane season is all but over, lasting from mid-August to mid-September. But the risk of tropical storms extends through October.

http://www.baltimore...0,1318495.story

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Nadine becomes hurricane in Atlantic, away from US

MIAMI -- The U.S. National Hurricane Center says Nadine has become a hurricane in the Atlantic Ocean, but that it poses no threat to land. Nadine's maximum sustained winds late Friday were 75 mph (121 kph), making it a Category 1 hurricane.

Nadine is centered about 725 miles (1167 kilometers) east of Bermuda and is moving north-northeast at 14 mph (23 kph), taking it farther away from the U.S. Nadine is the eighth hurricane of the Atlantic season.

In the Pacific, Tropical Storm Kristy is slowly weakening with maximum sustained winds near 75 mph (121 kph). Kristy is centered about 275 miles (443 kilometers) west-southwest of the southern tip of Mexico's Baja California and is northwest at 9 mph (14 kph).

http://www.sacbee.co...l#storylink=cpy

Nadine, a storm in the Atlantic Ocean, strengthened to become the eighth hurricane of the year in the region, according to the National Hurricane Center.

The category 1 hurricane, weakest on the Saffir-Simpson hurricane wind scale which goes to category 5, has sustained winds of 75 miles per hour (120 kilometers per hour), and is located about 725 miles east of Bermuda, according to an advisory issued yesterday at 11 p.m. New York time.

http://www.bloomberg...tic-season.html

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She's struggled but is officially just a hurricane:

WTNT34 KNHC 150243

TCPAT4

BULLETIN

HURRICANE NADINE ADVISORY NUMBER 15

NWS NATIONAL HURRICANE CENTER MIAMI FL AL142012

1100 PM AST FRI SEP 14 2012

...NADINE BECOMES THE EIGHTH HURRICANE OF THE ATLANTIC SEASON...

SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION

-----------------------------------------------

LOCATION...30.0N 52.8W

ABOUT 725 MI...1170 KM E OF BERMUDA

ABOUT 1570 MI...2530 KM WSW OF THE AZORES

MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H

PRESENT MOVEMENT...NNE OR 25 DEGREES AT 14 MPH...22 KM/H

MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES

WATCHES AND WARNINGS

--------------------

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

DISCUSSION AND 48-HOUR OUTLOOK

------------------------------

AT 1100 PM AST...0300 UTC...THE CENTER OF HURRICANE NADINE WAS

LOCATED NEAR LATITUDE 30.0 NORTH...LONGITUDE 52.8 WEST. NADINE IS

MOVING TOWARD THE NORTH-NORTHEAST NEAR 14 MPH...22 KM/H. A TURN

TOWARD THE NORTHEAST AND A SLIGHT DECREASE IN FORWARD SPEED ARE

EXPECTED BY SATURDAY MORNING...FOLLOWED BY AN ACCELERATION TOWARD

THE EAST SATURDAY NIGHT AND SUNDAY.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 75 MPH...120 KM/H...

WITH HIGHER GUSTS. NADINE IS A CATEGORY ONE HURRICANE ON THE

SAFFIR-SIMPSON HURRICANE WIND SCALE. LITTLE CHANGE IN STRENGTH IS

FORECAST DURING THE NEXT 48 HOURS.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 35 MILES...55 KM...FROM

THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO

230 MILES...370 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 985 MB...29.09 INCHES.

HAZARDS AFFECTING LAND

----------------------

NONE.

NEXT ADVISORY

-------------

NEXT COMPLETE ADVISORY...500 AM AST.

FORECASTER BRENNAN

http://www.nhc.noaa.gov/text/refresh/MIATCPAT4+shtml/120843.shtml

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Yep Coast, Nadine has finally made it and is a 65kt hurricane this morning. Shear continues to impact the system, and I don't see Nadine getting all that stronger. NHC expect a peak of 70kts which I think is a good assessment given the continued shear over Nadine. Waters will get progressively cooler by day 4/5 as Nadine stops moving eastwards and instead lifts northeastwards as it approches the Azores. Nadine should be a weakening tropical storm on it's approach to these islands.

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Depending on who you chose to follow, it looks like she's heading for The Azores:

models_storm2.jpg

trackmap_storm2.jpg

201214N.png

201214N_7G.png

Hurricane NADINE: Probability of Cat 1 or above winds to 117 hours lead

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Nadine's eastward motion continues to be slightly faster than the previous forecasts even though those forecasts upped the pace of the eastward track. Therefore it would seem my updated forecast in Figure 1 should be another rightward adjustment for all forecast points. However...my previous forecasts had a southward bias for the timeframe that is the next 24 hours as I saw no reason to bend the track to the north until later on...but Nadine is turning more northward already. Since the NHC has adjusted their track a bit southward...I suppose it is time for me to adjust my track northward and meet the NHC in the middle...therefore agreeing with the NHC forecast track for the first 48 hours. In the end...my northward adjustment does not require me to have a rightward adjustment despite the initial faster than expected eastward motion. Also...Nadine's eastward track is finally slowing down.

The developing slowdown in Nadine's eastward track is the result of resistance from the Atlantic high seas low-level ridge (end of paragraph P2) entering NE Atlantic. The developing northward deflection in the track is the result of the paragraph P5 low-level ridge already bridging with the NE Atlantic low-level ridge...the bridge forming at a location east of Nadine. I begin disagreeing with the NHC track forecast in between 48 and 60 hours....when I think Nadine will wiggle left toward a low-level ridge weakness associated with what is now the 1001 mb low in paragraph P2. As the weakness passes by to the north between 60 and 72 hrs...I believe Nadine will then wiggle back rightward while trying to link with that weakness.

The aforementioned 1001 mb system and its upper trough approach Nadine while decomposing into into two upper vortices...thanks to strong and deep-layered ridge developing in warm air advection ahead of the paragraph P1 frontal system. The first is a cut-off deep-layered vortex west of Nadine (which could become a subtropical cyclone as mentioned in the intro of this full discussion). The second is an upper vortex to the north which now appears to have the potential to drag Nadine eastward between 72 and 96 hrs. The strength of the deep-layered ridge in the 00Z GFS causes it to shoot this second upper vortex southward such that Nadine would whirl counter-clockwise about the upper vortex in between 96 and 120 hrs.

Intensity-wise...Nadine in the last 24 hrs has weakened to a 70 mph max wind tropical storm as I previously forecasted...so I maintain the weakening rate I showed in my previous forecast. The developing slowdown in track for the next 24 hours should allow the less shearing (more favorable) north Atlantic upper ridge wave...propped up by warm air advection ahead of the paragraph P2 1001 mb low...to catch up to and overspread Nadine...so I flatten the weakening rate during this time. This warm air advection should cause the new and unfavorable shortwave upper trough W of Nadine to diminish as remarked in paragraph P4. I accelerate the weakening rate (faster than the NHC shows) by 48 to 96 hrs as Nadine's forecast track crosses the 26 deg C isotherm into cooler waters...and experiences unfavorable SW vertical shear delivered by the two upper vortices mentioned in the above track forecast discussion. I suppose the NHC shows a slower weakening rate as they expect Nadine to more gradually transition into a non-tropical low supported by divergence from this shearing SW jet...but alternatively I see Nadine in unfavorable upper converence on the SW and south sides of the northern upper vortex. In fact...I don't see Nadine receiving supportive upper divergence until it enters the east side of the northern upper vortex in between 96 and 120 hrs...which is finally when I flatten the weakening rate. I agree with the NHC on a non-tropical Nadine by 120 hrs.

Sep_17_2012_TSNadineForecast.png

The impact swath in Figure 1 is initialized based on the 11 PM EDT NHC tropical storm wind radius...which I lean rightward with respect to the storm track by 48 to 96 hrs to account for a forecasted increase in SW vertical shear for that timeframe. The swath is also shrunken to represent a weakening Nadine in the latter part of the forecast. My swath only covers the western and central Azores at this time...but could easily cover all of the Azores if the radius of the counter-clockswise loop track at 96 to 120 hrs becomes larger...or if Nadine's wind field actually grows or maintains size if the more vigorous above-discussed NHC intensity forecast verifies.

http://www.wundergro...ml?entrynum=200

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Tropical Storm Turns Away From U.S.; Kristy, Lane Far Off Mexico

Tropical Storm Nadine, the 14th named system of the Atlantic hurricane season that runs through November, has turned east-northeastward and away from the U.S. and Caribbean.

Nadine was 675 miles (1,085 kilometers) southwest of the Azores with winds of 70 miles per hour, the Miami-based National Hurricane Center said in a 5 a.m. Atlantic time advisory. Tropical Depression Kristy off Mexico’s Pacific coast is forecast to become a remnant low today. The system was 630 miles west-northwest of southern Baja California with winds of 35 mph. Further west, Lane strengthened to a Category 1 hurricane on the five-step Saffir-Simpson scale, according to the NHC. It is 1,160 miles west-southwest of the tip of Baja, moving north- northwest and posing no threat to land.

http://www.bloomberg...off-mexico.html

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Nadine is still spinning away, making it's way to the Azores. Nadine peaked at 70kts but has slowly weakened over the last day or so back to 55kts, as dry air wraps into Nadine's LLC and waters gradually cool. Increasing shear along with cold waters near the Azores is expected to force Nadine to become extratropical in a few days time. However, Nadine is not expected to continue to move northeast past the Azores, and instead could move back southwards into warmer water. The NHC mention the possibility of Nadine transitioning back to a tropical cyclone in about 5 days. It will be interesting to see if Nadine manages this.

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The NHC mention the possibility of Nadine transitioning back to a tropical cyclone in about 5 days. It will be interesting to see if Nadine manages this.

:good:

TS Nadine

Tropical storm Nadine is slowly weakening and turning extra-tropical as she heads toward the Azores. Satellite appearance shows the transition from tropical to post-tropical due to shear and cooler waters. Currently Nadine has 60mph winds, has a 989mb pressure, and is moving NE at 9mph. Convection has been trying to cover the center back up and over the past few hours has been having more success. This convection is weak though and the environment doesn't favor strengthening. Nadine should maintain strength or even weaken slightly over the next 5 days. The track is what will be very difficult. Models are very split on exactly where Nadine will go and if she will be tropical or non-tropical. Nadine should continue to go NE until she gets near the Azores and then, as most models indicate, turn around and head toward the south. Nadine could go SW and turn tropical, go S and slowly turn tropical, or go SE and possibly stay extra-tropical. No matter where Nadine exactly tracks she will bring squally weather to the Azores. Nadine will also most likely be alive for a while before either dying off or getting picked up by a trough. People in the Azores need to be preparing for possible TS conditions

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http://www.wunderground.com/blog/wxchaser97/comment.html?entrynum=31

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Well make your mind up!!!

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Tropical Storm NADINE: Probability of tropical storm winds to 117 hours lead

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