Tropical Storm Danny Spaghetti Model, Satellite Image Reveal a Girly-Man August 28, 2009

TS Danny Visible Image not much to look at with exposed center 19:45Z 08.28.09

Danny Rainbow IR 1945Z 08.28.09

Tropical Storm Danny is a girly-man.  It has some pretty robust convection but its well east of the center.  By Friday afternoon the low level circulation was completely exposed and the hurricane hunter reported a central pressure at a pedestrian 1007 mb.  It’s also running out of time for development.  As a deep trof starts to invade the eastern two thirds of the nation,  southwesterly winds ahead of the trof will increase and end any chance for upper level support.  That upper trof that has been plaguing Danny from the beginning just never went away as the models had been thinking.  The storm spent most of the day drifing to the west, which the models also never figured out, but with all of the convection going on east, it may be trying to reform a center. By late in the day, it started a more northern drift.  Either way, the modeling data does not call for real significant increase in intensity as it moves up the Southeast and mid Atlantic coasts.  So, the National Hurricane Center isn’t even bothering to change the tropical storm watch for the outer banks of North Carolina to a warning.  If it reforms farther east, then there is almost no chance of it affecting the US.  But, the conventional models all still run it along the Carolina coast.  It quickly loses its tropical characteristics, which never really fully developed anyway.  But, in this case its a so what situation because the models want to run it along the Northeast Coast and have it deepen from its current 1007 mb down to about 994mb and then move it into Nova Scotia.  So, there could be some heavy rain, gusty winds and high seas…in some regards similar to Bill except the seas probably won’t be running as high. 

Atlantic View 20:45Z 08.28.09 Invest 94L Not Quite as Impressive as Prior Day

There is another tropical cyclone trying to get going way out about 300 miles WSW of the Cape Verde Islands. That one has some potential and its farther south than previous cyclones that have formed of late.  That would decrease the potential for it getting caught up in any unseasonal trofs that move into the Atlantic.  But, its way out there and there are lots of possibilities. At this point, I would almost hazard a suggestion that it has a better chance of adversely affecting the US than Danny…but it so far out that one can’t really say that so I won’t. 9 of  15 tropical cyclone models make it a Tropical Storm in 48 hours with 6 of those eventually making it a hurricane, two claiming Cat 2.  We’ll see. Man proposes, God disposes.

TS Danny Spagetti Models 18Z 082809

TS Danny Spaghetti Model Tracks 18Z 082809

5pm TS Danny NHC Forecast Track 08.28.09

WTNT45 KNHC 282035
TCDAT5
TROPICAL STORM DANNY DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
500 PM EDT FRI AUG 28 2009

AFTER STALLING EARLIER THIS AFTERNOON…THE CENTER OF DANNY IS
FINALLY MOVING SLOWLY NORTHWARD OR NORTH-NORTHEASTWARD. DATA FROM AN
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST THAT DANNY IS
STILL A MINIMAL TROPICAL STORM…BASED ON A 33-KT OBSERVATION FROM
THE SFMR IN THE SOUTHEASTERN QUADRANT.

THE INTENSITY FORECAST SHOWS THE POSSIBILITY FOR A LITTLE
STRENGTHENING IN THE SHORT TERM…AS THE INCREASING UPPER-LEVEL
DIVERGENCE COULD SUPPORT THE REDEVELOPMENT OF CONVECTION NEAR THE
CENTER. HOWEVER…BY 24 HOURS…DANNY WILL BE MOVING INTO A VERY
UNFAVORABLE ENVIRONMENT FOR A TROPICAL CYCLONE…WITH THE SHIPS
MODEL SHOWING WIND SHEAR INCREASING TO 35 KT BY THAT TIME. BY 36
HOURS…DANNY WILL BE OVER SSTS OF NEAR 20C…AND INTERACTING WITH
THE DEEP-LAYER BAROCLINIC TROUGH OVER THE EASTERN U.S.  MOST OF
THE LATEST GLOBAL MODELS AND PHASE SPACE DIAGRAMS SHOW THAT DANNY
WILL BE EXTRATROPICAL BY THAT TIME. THERE IS THE POTENTIAL FOR SOME
INTENSIFICATION OF DANNY LATE IN THE FORECAST PERIOD AS AN
EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC.

THE GUIDANCE WAS INITIALIZED WITH A LONG TERM MOTION OF 315/08…
AND REMAINS IS GOOD AGREEMENT ON THE RAPID ACCELERATION OF DANNY
NORTHWARD AND NORTH-NORTHEASTWARD. IN FACT…THE MODEL SPREAD IS
SMALLER NOW THAN IT WAS EARLIER TODAY. THE OFFICIAL TRACK IS SLOWER
THAN THE MODEL CONSENSUS THROUGH MOST OF THE PERIOD DUE TO THE SLOW
INITIAL MOTION. FROM 24 TO 36 HOURS…THE NEW FORECAST IS SHIFTED
TO THE RIGHT OF THE PREVIOUS FORECAST TRACK…BUT DANNY IS STILL
EXPECTED TO MOVE CLOSE TO THE SOUTHEASTERN COAST OF NEW ENGLAND AND
APPROACH NOVA SCOTIA IN 36-48 HOURS.

DATA FROM THE AIRCRAFT SUGGEST THAT THE ONLY 34-KT WINDS ARE LOCATED
IN THE SOUTHEASTERN QUADRANT. THE LACK OF WINDS ON THE WEST SIDE OF
DANNY LESSEN THE THREAT FOR TROPICAL STORM WIND REACHING THE NORTH
CAROLINA OUTER BANKS. HOWEVER…THE WATCH IS LEFT IN PLACE IN CASE
THE WIND FIELD BECOMES BETTER DEFINED ON THE WESTERN SIDE OF DANNY.
AS DANNY BECOMES EXTRATROPICAL…ITS EXPANDING WIND FIELD MAY
IMPACT THE COAST OF NEW ENGLAND. THESE POTENTIAL IMPACTS WILL BE
HANDLED WITH GALE WARNINGS AND OTHER PRODUCTS ISSUED BY LOCAL NWS
OFFICES IN THAT REGION.

FORECAST POSITIONS AND MAX WINDS

INITIAL      28/2100Z 30.4N  75.4W    35 KT
12HR VT     29/0600Z 32.7N  75.8W    40 KT
24HR VT     29/1800Z 37.3N  73.2W    40 KT
36HR VT     30/0600Z 41.9N  68.2W    40 KT…EXTRATROPICAL
48HR VT     30/1800Z 46.5N  61.4W    40 KT…EXTRATROPICAL
72HR VT     31/1800Z 50.5N  49.5W    40 KT…EXTRATROPICAL
96HR VT     01/1800Z 53.0N  35.0W    45 KT…EXTRATROPICAL
120HR VT     02/1800Z 55.0N  22.0W    50 KT…EXTRATROPICAL

$$
FORECASTER BRENNAN

Tropical Storm Danny Satellite Images Show Better Organization-Spaghetti Model Persistent August 27, 2009

Tropical Storm Danny 1415Z 08.27.09

TS Danny Spaghetti Model 12Z 08.27.09

TS Danny Spaghetti Model Intensity 12Z Thu

NHC Fcst Track 11am Thursday

Tropical Storm Danny Water Vapor 12Z 08.27.09

Tropical Storm Danny continues to have problems as it is still sandwiched between upper level lows.  This has resulted in upper winds coming together which is the opposite of what you need for a hurricane to develop.  Consequently, it doesn’t look very good.  But, Dr. Jack Beven at the National Hurricane Center reports late this morning that the overall circulation is getting better looking.  But, I see, and he notes, that the convection and best stuff is generally disjointed to the north and northeast of the center of low level circulation.  Now, over the next day or so, the upper level lows will move out and an upper level high is expected to take its place over the top of Danny.  That is the chance that it needs to develop and become better organized. 

Tropical Storm Danny 14:45Z Dvorak 08.27.09

Now, the official forecast calls for Danny to start to move north and stay just off the east coast as it develops into a minimal hurricane.  However, previously there was only one model that had the storm scraping the US coast.  Now there are three.  The Canadian model has been the most consistent in this regard.  The other two are the US Navy NOGAPS and the more conventional NAM.  The tropical models do not suggest this.  But, I am wondering if, since the storm has not truly been tropical in nature, if the non-tropical storms initially have a better handle on the system.  Also, the storm keeps on either reforming or drifting farther west than what the tropical models have been calling for.  This is why I am still of the mind that the storm may in fact at least partially move along the Carolina coast.  On the other hand, if this guy lolligags out in the ocean much longer, another big, unseasonable trof like the one that caught Bill will be digging into the Ohio Valley and will pick it up before it ever gets to the coast.  There is a consensus among the models that the storm will deepen as it moves northward and gets even with the middle of the Atlantic coast.   They also point toward an impact on Nova Scotia.  However, there are some problems  with  the developmental scenario brought forth by the models that conflict with conventional wisdom as Dr. Beven points out at the bottom of the post.

Canadian Model 996 mb Low near Hattaras valid Friday Evening derived 00Z Thu

Danny Visible Satellite Image 1445Z 08.27.09

WTNT45 KNHC 271449
TCDAT5
TROPICAL STORM DANNY DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
1100 AM EDT THU AUG 27 2009

DANNY HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING.  THE
LOW-LEVEL CIRCULATION LOOKS BETTER DEFINED THAN IT DID YESTERDAY…
AND THE CONVECTION IS CLOSER TO THE CENTER.  THAT BEING SAID…THE
CENTER IS STILL EXPOSED…THE CONVECTION HAS MORE OF A LINEAR
CHARACTER THAN THE CURVED BANDS CHARACTERISTIC OF A TROPICAL
CYCLONE…AND THE STRONGEST WINDS ARE STILL WELL REMOVED FROM THE
CENTER.  THE INITIAL INTENSITY IS HELD AT 50 KT PENDING THE NEXT
AIR FORCE RESERVE HURRICANE HUNTER MISSION AT 18Z…ALTHOUGH RECENT
QUIKSCAT DATA SUGGESTS THIS COULD BE A LITTLE GENEROUS.

THE EXPOSED LOW-LEVEL CENTER HAS BEEN MOVING ALMOST DUE WESTWARD FOR
THE PAST FEW HOURS.  IT IS UNCLEAR IF THIS IS REPRESENTATIVE OF THE
ACTUAL MOTION OF DANNY OR A SHORT-TERM TREND.  SO…THE INITIAL
MOTION IS AN UNCERTAIN 310/11.  DESPITE THE PROBLEMATIC INITIAL
MOTION…THE TRACK GUIDANCE MODELS ARE IN EXCELLENT AGREEMENT THAT
DANNY SHOULD TURN NORTHWARD OVER THE NEXT 24-36 HR IN ADVANCE OF A
COMPLEX DEEP-LAYER TROUGH MOVING INTO THE EASTERN UNITED STATES.
AFTER THAT…THE STORM SHOULD ACCELERATE NORTHEASTWARD INTO THE
WESTERLIES…PASSING NEAR OR OVER NEW ENGLAND AND THE CANADIAN
MARITIMES ON ITS WAY INTO THE NORTH ATLANTIC.  THE
NAM…NOGAPS…AND CANADIAN MODELS ARE ON THE LEFT SIDE OF THE
GUIDANCE ENVELOPE… CALLING FOR THE CENTER TO PASS NEAR CAPE
HATTERAS AND THEN OVER NEW ENGLAND.  THE GFS…GFDL…AND HWRF ARE
ON THE RIGHT SIDE…CALLING FOR THE CENTER TO STAY OFFSHORE UNTIL
IT REACHES NOVA SCOTIA.  THE NEW FORECAST TRACK IS ADJUSTED TO THE
LEFT OF THE PREVIOUS TRACK FOR THE FIRST 48 HR BASED ON THE INITIAL
POSITION AND MOTION…AND IT LIES DOWN THE MIDDLE OF THE GUIDANCE
ENVELOPE.  WHILE THE FORECAST TRACK DOES NOT CURRENTLY SHOW DANNY
MAKING LANDFALL IN THE UNITED STATES…ADDITIONAL MOTION TO THE
LEFT OF THE TRACK COULD BRING THE CENTER NEAR OR OVER THE U. S.
EASTERN SEABOARD.

DANNY IS CURRENTLY IN AN AREA OF UPPER-LEVEL CONFLUENT FLOW
ASSOCIATED WITH THE PERSISTENT CYCLONIC SHEAR AXIS SEEN IN WATER
VAPOR IMAGERY.  THE LARGE-SCALE MODELS FORECAST THIS FEATURE TO BE
REPLACED BY AN UPPER-LEVEL ANTICYCLONE DURING THE NEXT 24-30 HR…
AND IF THIS VERIFIES IT WILL GIVE DANNY ITS BEST CHANCE TO
STRENGTHEN.  BASED ON THIS…THE INTENSITY FORECAST CALLS FOR DANNY
TO STRENGTHEN DURING THE 24-48 HR PERIOD…WITH A PEAK INTENSITY OF
65 KT.  THE GUIDANCE AGREES THAT DANNY SHOULD START LOSING TROPICAL
CHARACTERISTICS AND INTENSITY AFTER 48 HR AS IT BECOMES EMBEDDED IN
A STRONG BAROCLINIC ENVIRONMENT.  OVERALL…THE INTENSITY FORECAST
IS IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS…WITH THE PEAK
INTENSITY BELOW THAT OF THE HWRF AND GFDL MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL      27/1500Z 27.5N  73.1W    50 KT
12HR VT     28/0000Z 28.7N  73.9W    50 KT
24HR VT     28/1200Z 30.3N  74.5W    55 KT
36HR VT     29/0000Z 33.2N  74.3W    60 KT
48HR VT     29/1200Z 36.9N  72.4W    65 KT
72HR VT     30/1200Z 45.0N  64.5W    60 KT…EXTRATROPICAL
96HR VT     31/1200Z 50.0N  53.0W    45 KT…EXTRATROPICAL
120HR VT     01/1200Z 52.5N  37.0W    30 KT…EXTRATROPICAL

$$
FORECASTER BEVEN

Tropical Storm Danny Spaghetti Model, Discussion-East Coast, Halifax Wary August 26, 2009

Tropical Storm Danny 9:18:45Z 08.26.09

Tropical Storm Danny NHC forecast Track 11am 08.26.09

For a more recent update on Tropical Storm Danny, CLICK HERE

As hinted in a previous post, Invest 92L has indeed become Tropical Storm Danny.  The initial model runs are still holding pretty much on line.   That is some want to take it as a tropical storm or even a weak hurricane into North Carolina and then along the US coast with some deepening to as low as 985 mb somewhere between Washington DC and New York City.  Others want to have the storm brush the Carolina coast and hug the East Coast of the US and deepen before moving just east of Halifax, Nova Scotia.  Still others want to keep the storm offshore altogether before it runs into Nova Scotia.  Andrea in Halifax…all the models have it affecting you in some manner…But…

Danny Water Vapor 9:17:45Z 08.26.09

There is some consensus as to the notion that another big fat trof digs down into the Ohio Valley by the end of the week.  That is pretty much a very good bet.  That will turn the storm north as the Atlantic ridge just hasn’t had enough time to broaden westward again following the last big trof that dug down and turned Bill.  But, this guy is still a bit sandwiched between a pair of upper lows.  That is lousy for development.  The morning water vapor image sucks.  The Dvorak image is a little better.  Typically, an under developed system may not always follow the flow as decisively as a fully developed storm.  This guy is still gaining tropical characteristics but does have a developing low level circulation.  So, this guy may have more of a westward component initially. than a fully developed storm would.  It will have an opportunity to develop.  Mostl likely it only gets to Cat 1 status because as the trof quickly approaches, it will get into an increasing flow of southwesterly winds ahead of the trof. That will accelerate it northward and eventually north north eastward. It should also mess up any upper level support that it can get.  So, while some models want to make it get stronger than Cat 1, the good environment for that to happen probably won’t be around long enough. 

Tropical Storm Danny Dvorak Image 9:18:45Z 08.26.09

Bottom line is that Danny is here.  There is a good chance that it will become a hurricane.  There is a pretty fair chance that it will get deeper as it moves up the east coast.  There is a good chance that it will hit Nova Scotia, perhaps with a greater impact than Bill had.  There is a fair chance that at least the fringes will affect the east coast from the South Carolina/North Carolina border northward and there is something approaching a fair chance that there is a landfall in the US for a time from say the SC/NC border to Wilmington and then perhaps stay inland through Virginia before it re-emerges just offshore.  Lot of variables at this time. 

Tropical Storm Danny Spaghetti Model 12Z 08.26.09

Tropical Storm Danny Spaghetti Intensity Model 12Z 08.26.09

Canadian Model Fri Eve-Hurricane Danny Near NC Outer Banks

TROPICAL STORM DANNY DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL052009
1100 AM EDT WED AUG 26 2009

SATELLITE IMAGERY SHOWS THAT THE AREA OF DISTURBED WEATHER EAST OF
THE BAHAMAS HAS DEVELOPED A WELL-DEFINED LOW-LEVEL CIRCULATION…
WITH REPORTS FROM A NOAA HURRICANE HUNTER AIRCRAFT INDICATING THE
SYSTEM WAS BEST DEVELOPED BELOW 12000 FT.  QUIKSCAT DATA AND A FEW
OBSERVATIONS FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER SHOW
TROPICAL STORM-FORCE WINDS OCCURRING NORTH AND NORTHEAST OF THE
CENTER…WHICH IS THE BASIS FOR THE INITIAL INTENSITY OF 40 KT.
THE STORM HAS BEEN TANGLED UP WITH AN UPPER-LEVEL LOW FOR THE PAST
24 HR…AND THE STRUCTURE AS MUCH RESEMBLES A SUBTROPICAL CYCLONE
AS A TROPICAL CYCLONE.  HOWEVER…CYCLONE PHASE ANALYSES FROM
FLORIDA STATE UNIVERSITY SUGGEST THAT DANNY IS MARGINALLY MORE
TROPICAL THAN SUBTROPICAL…HENCE THE DESIGNATION OF TROPICAL
STORM.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 295/16.  DANNY IS ON THE
NORTH SIDE OF A MID/UPPER-LEVEL LOW CENTERED OVER HISPANIOLA AND
SOUTHWEST OF A MID/UPPER-LEVEL RIDGE CENTER EAST OF BERMUDA.
THIS PATTERN SHOULD STEER DANNY GENERALLY NORTHWESTWARD WITH
DECELERATION FOR THE NEXT 24-36 HR.  AFTER THAT…THE LARGE SCALE
MODELS AGREE THAT A MID/UPPER-LEVEL TROUGH SHOULD DEVELOP OVER THE
GREAT LAKES…WITH A MID/UPPER-LEVEL LOW OVER THE GULF COAST STATES
MOVING EASTWARD OR NORTHEASTWARD.  THIS EVOLUTION SHOULD CAUSE
DANNY TO TURN NORTHWARD AND THEN RECURVE INTO THE WESTERLIES.
WHILE THE MODELS AGREE ON THE SCENARIO…THERE IS ENOUGH SPREAD IN
THE TRACK GUIDANCE TO MAKE IT UNCERTAIN WHAT LAND AREA DANNY MAY
AFFECT.  THE NAM AND THE CANADIAN MODELS FORECAST DANNY TO MAKE
LANDFALL IN EASTERN NORTH CAROLINA IN ABOUT 72 HR AND MOVE UP THE
U. S. EASTERN SEABOARD…WHILE THE GFS…HWRF… AND GFDL SHOW A
MORE EASTERLY TRACK THAT KEEPS DANNY OFFSHORE UNTIL IT REACHES THE
CANADIAN MARITIMES.  THE FORECAST SPLITS THE DIFFERENCE BETWEEN
THESE EXTREMES AND IS A LITTLE TO THE LEFT OF THE MODEL CONSENSUS.
THE FORECAST TRACK IS ROUGHLY PARALLEL TO THE U. S. EAST COAST…AND
ANY DEVIATION FROM THE TRACK COULD MAKE A LARGE DIFFERENCE IN WHAT
AREAS GET IMPACTED BY DANNY.  THEREFORE…IT IS IMPORTANT NOT TO
FOCUS TOO MUCH ON THE EXACT FORECAST TRACK.

THE INTENSITY FORECAST IS PROBLEMATIC.  WATER VAPOR IMAGERY SHOWS
UPPER-LEVEL LOWS NORTH AND SOUTH OF DANNY CONNECTED BY A CYCLONIC
SHEAR AXIS.  THIS IS NOT A IDEAL PATTERN FOR STRENGTHENING…AND
THE LARGE-SCALE MODELS SUGGEST IT MAY TAKE 24-36 HR FOR THE
ENVIRONMENT TO BECOME MORE FAVORABLE.  BASED ON THIS AND THE
CURRENT ORGANIZATION OF THE STORM…THE INTENSITY FORECAST CALLS
FOR SLOW STRENGTHENING FOR THE FIRST 36 HR.  IT THEN SHOWS A FASTER
STRENGTHENING FROM 36-48 HR AS CONDITIONS BECOME MORE FAVORABLE.
AFTER 48 HR…STRONG UPPER-LEVEL SOUTHWESTERLY WINDS ASSOCIATED
WITH THE EASTERN U. S. TROUGHS ARE EXPECTED TO CAUSE INCREASED
SHEAR AND THE BEGINNING OF EXTRATROPICAL TRANSITION.  THE INTENSITY
FORECAST THUS CALLS FOR DANNY TO REACH 65 KT IN 72 HR…THEN BECOME
EXTRATROPICAL BY 96 HR.  THE INTENSITY FORECAST IS IN BEST
AGREEMENT WITH THE SHIPS AND LGEM MODELS.  HOWEVER…IT IS WEAKER
THAN THE FORECASTS OF THE GFDL AND HWRF.

FORECAST POSITIONS AND MAX WINDS

INITIAL      26/1500Z 24.9N  70.3W    40 KT
12HR VT     27/0000Z 25.8N  72.0W    40 KT
24HR VT     27/1200Z 26.8N  73.6W    45 KT
36HR VT     28/0000Z 28.1N  74.5W    50 KT
48HR VT     28/1200Z 30.1N  75.2W    60 KT
72HR VT     29/1200Z 36.0N  73.5W    65 KT
96HR VT     30/1200Z 45.0N  67.0W    65 KT…EXTRATROPICAL
120HR VT     31/1200Z 52.0N  53.0W    60 KT…EXTRATROPICAL

$$
FORECASTER BEVEN