A LARGE AREA OF DISTURBED WEATHER...ASSOCIATED WITH TWO TROPICAL
WAVES...IS CENTERED ABOUT 800 MILES EAST OF THE WINDWARD ISLANDS.
SHOWERS AND THUNDERSTORMS IN THIS AREA ARE CURRENTLY
DISORGANIZED...BUT UPPER-LEVEL WINDS ARE FORECAST TO BE MARGINALLY
FAVORABLE FOR DEVELOPMENT AS THE SYSTEM MOVES WEST-NORTHWESTWARD
AROUND 15 MPH. THERE IS A MEDIUM CHANCE...30 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
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--------------------------------------------------------------------------------
Date(UTC): 2010/09/30 11:32
Author: Ryan Torn
Submitted at(UTC): 2010/09/30 12:00
--------------------------------------------------------------------------------
Current Conditions/Review of Yesterday's Forecast:
NHC upgraded TD16 to TS Nicole at 1500 UTC yesterday; however,
by 2100 UTC this system was downgraded to a non-tropical system
and will not be discussed here. PGI48L and PGI51L appear to
have merged together and are now designated PGI51L. The
ensemble has been predicting for this system to get close to
genesis criteria for the past three forecast cycles, though to
date, there does not appear to be any increase in the
circulation of this system during the past couple of days,
though there is plenty of convection. The initial position of
this system within the ensemble is just to the north of the
consensus. PGI49L has not shown much sign of getting better
organized since moving off the African coast. The ensemble has
been more bearish about the development of this system relative
to PGI51L because it encounters more shear as it moves to the
NW. The ensemble has the pouch fairly close to the consensus at
the initial time, but there is a lot of spread.
DAY 1 (Next 24 hours) Outlook:
PGI49L continues to move to the northwest during the first
period of the forecast, with position variance stretched in the
E-W direction. There is a slow increase in the midtropospheric
circulation in all ensemble members; however, the OW values
remain nearly constant and near 1. PGI51L is predicted to be
over the windward islands by 24 h, with larger position variance
stretched in the NE-SW direction. The circulation values
associated with this system are predicted to nearly double
during this 24 h period, with the OW values becoming much
greater than zero.
DAY 2 (24 - 48 hours) Outlook:
PGI49L continues to drift to the NW during this period, with the
ensemble-mean position near 17N 51W at 48 h, with large variance
stretched in the E-W direction. The circulation values continue
to increase during this period, with a few of the extreme
members reaching circulation and thickness genesis criteria by
the end of the period. PGI51L is forecast to be in the
Caribbean sea just to the south of the Virgin Islands by 48 h.
The position variance is stretched in the NW-SE direction during
this period. All of the members show continued strengthening of
this system during the period, though some members start to
level off the circulation values well below genesis criteria.
The minimum pressures associated with this system continue to
fall in all members.
Extended Outlook:
PGI49L continues along the same NW trajectory, with a large
amount of position variance in the along-track direction. The
circulation values continue to increase in the ensemble mean,
nearly reaching genesis criteria by 72 h, though there is a
large amount of spread with some members decaying by 72 h and
others showing a robust TS. This is an excellent case for
initial condition sensitivity calculations given the large
uncertainty. PGI51L is nearly stationary during this period,
with some slow drift to the NW toward Hispaniola and Puerto
Rico. The position variance is stretched in the E-W direction
within the ensemble. The ensemble-mean circulation and
thickness anomaly values continue to increase during this period
and both exceed genesis criteria by 72 h. There are also a
number of members that predict these two metrics will remain
below genesis criteria, so this is also an uncertain forecast,
though it should be noted that the ensemble has been aggressive
with trying to develop this into a TD for the past three days,
thus I am not sure how much I trust this forecast.
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I don't know why people want big storms to hit their house. Other forums always have people from especially Florida who get "dissapointed" when storms don't develop big (Nicole) or miss their house.
Yes this system is destined for recurve but it could be a close watch for the east coast/Carribean Sea.
A rather complicated setup for 97L. The PREDICT Team thoughts...
Yesterday, the models suggested that PGI48L had weakened and
that PGI51L to the west was the only trackable pouch out of the
two. However, since late yesterday, the real atmosphere began
being uncooperative and convection flared in the PGI48L
vicinity.
The models still indicate that PGI48L is very weak, to the point
of being only an OW max in one or more models.
To complicate matters, the relatively stronger PGI49L/97L is
closing in from the east. I'm guessing that the basic storyline
is: As 97L moves in, it will absorb whatever is left of PGI48L
and then PGI51L. The result may be stationary or even eastward
tracks for the weaker, western pouches, but the models don't
really show that now.
The one other possible scenario is portrayed by ECMWF: PGI49L
weakens as it moves west, and the tiny PGI48L strengthens as it
moves northwestward, perhaps even absorbing the remnants of
PGI49L. This seems less likely given that PGI49L/97L appears
stronger in the satellite & TPW animations, but, as I said,
convection is definitely flaring with PGI48L, too.
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DISORGANIZED SHOWERS AND THUNDERSTORMS CONTINUE IN ASSOCIATION WITH
A LARGE AREA OF DISTURBED WEATHER LOCATED ABOUT 900 MILES EAST OF
THE LESSER ANTILLES. UPPER-LEVEL WINDS ARE FORECAST TO BECOME
SOMEWHAT MORE CONDUCIVE FOR DEVELOPMENT AND THERE IS A MEDIUM
CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD OR WEST-NORTHWESTWARD
AT 15 TO 20 MPH.
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ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT FRI OCT 1 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
1. SHOWERS AND THUNDERSTORMS REMAIN DISORGANIZED IN ASSOCIATION WITH
A LARGE AREA OF DISTURBED WEATHER LOCATED ABOUT 700 MILES EAST OF
THE LESSER ANTILLES. DEVELOPMENT...IF ANY...OF THIS SYSTEM SHOULD
BE SLOW TO OCCUR...AND THERE IS A LOW CHANCE...20 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT
MOVES WESTWARD OR WEST-NORTHWESTWARD AT 15 TO 20 MPH.
2. A SURFACE TROUGH OVER THE NORTHWESTERN CARIBBEAN SEA CONTINUES TO
PRODUCE DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY. THERE IS A
LOW CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY EASTWARD OR
NORTHEASTWARD. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINS ARE
POSSIBLE DURING THE NEXT DAY OR TWO ACROSS NORTHERN CENTRAL
AMERICA...THE CAYMAN ISLANDS...EASTERN CUBA...JAMAICA...AND
HISPANIOLA.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Guidance suggests a weak vort splits and a SW Caribbean version becomes dominate. We shall see. It's late in the year 'locally', but a 'just right' upper air pattern could leave the door open for points just to our East IMO.
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BROAD AREA OF LOW PRESSURE LOCATED OVER THE EXTREME NORTHEASTERN
CARIBBEAN SEA CONTINUES TO PRODUCE A DISORGANIZED AREA OF SHOWERS
AND THUNDERSTORMS THAT EXTENDS FROM THE EASTERN CARIBBEAN SEA
NORTHEASTWARD ACROSS THE LEEWARD ISLANDS TO THE ADJACENT ATLANTIC
WATERS. UPPER-LEVEL WINDS ARE EXPECTED TO BECOME MORE CONDUCIVE
FOR DEVELOPMENT BY TUESDAY NIGHT OR WEDNESDAY AS THIS SYSTEM MOVES
GENERALLY NORTHWESTWARD AT 5 TO 10 MPH...AND THERE IS A MEDIUM
CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...LOCALLY
HEAVY RAINS ARE POSSIBLE DURING THE NEXT DAY OR TWO OVER THE
LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO RICO...AND
HISPANIOLA.
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A LOW PRESSURE AREA CENTERED JUST NORTH OF THE VIRGIN ISLANDS
CONTINUES TO BECOME BETTER DEFINED. ALTHOUGH THUNDERSTORM ACTIVITY
HAS CHANGED LITTLE DURING THE PAST SEVERAL HOURS...THIS SYSTEM HAS
THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY
OR SO AS UPPER-LEVEL WINDS GRADUALLY BECOME MORE CONDUCIVE FOR
DEVELOPMENT. THERE IS A HIGH CHANCE...60 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
NORTHWESTWARD AT 5 TO 10 MPH. REGARDLESS OF DEVELOPMENT...LOCALLY
HEAVY RAINS ARE POSSIBLE DURING THE NEXT DAY OR TWO OVER THE
LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO RICO...AND
HISPANIOLA.
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A WELL-DEFINED LOW PRESSURE SYSTEM CENTERED ABOUT 140 MILES NORTH OF
SAN JUAN PUERTO RICO IS PRODUCING A LARGE BAND OF CLOUDINESS AND
THUNDERSTORMS OVER THE NORTHEASTERN CARIBBEAN SEA...PUERTO RICO...
THE VIRGIN ISLANDS...AND THE LEEWARD ISLANDS...AND EXTENDING
NORTHWARD OVER THE ATLANTIC OCEAN FOR SEVERAL HUNDRED MILES.
UPPER-LEVEL WINDS ARE GRADUALLY BECOMING MORE CONDUCIVE FOR
DEVELOPMENT...AND THIS SYSTEM COULD BECOME A SUBTROPICAL OR
TROPICAL DEPRESSION DURING THE NEXT DAY OR SO. THERE IS A HIGH
CHANCE...80 PERCENT...OF THIS SYSTEM BECOMING A SUBTROPICAL OR
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
NORTHWESTWARD AT 5 TO 10 MPH. LOCALLY HEAVY RAINS AND GUSTY WINDS
WILL BE POSSIBLE OVER THE LEEWARD ISLANDS...THE VIRGIN ISLANDS...
AND PUERTO RICO DURING THE NEXT DAY OR TWO.
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It looks as if it would become a SubTropical system, at least temporarily, due to the upper low to the west of it, but the low is expected to loose its influence on the developing system in the next couple days. It's destined on going out to sea.
The little feature south of Hispaniola looks interesting too, but no invest or mention on TWO yet.
SUBTROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010
500 AM AST WED OCT 06 2010
SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE NORTH OF
PUERTO RICO HAS DEVELOPED BANDS OF DEEP AND CURVED CONVECTION IN
THE NORTHERN AND EASTERN QUADRANTS. IN ADDITION...NIGHT VISIBLE
IMAGES SUGGEST THAT THE CENTER HAS BECOME BETTER-DEFINED SINCE
YESTERDAY. SATELLITE CLASSIFICATIONS ARE A TROPICAL 2.0 FROM
TAFB...AND A SUBTROPICAL 1.5 FROM TAFB. WHILE THE LOW IS NOT FAR
FROM BEING MORE TROPICAL THAN SUBTROPICAL...ITS CURRENT LARGE
RADIUS OF MAXIMUM WINDS...AT LEAST 120 N MI...AND ITS ENTANGLEMENT
WITH AN UPPER LOW LEAD ME TO START THE SYSTEM AS A SUBTROPICAL
DEPRESSION. THE INITIAL WINDS ARE SET TO 30 KT...IN AGREEMENT WITH
A FEW SHIP AND BUOY OBSERVATIONS DURING THE PAST SEVERAL HOURS.
MOST OF THE MODEL GUIDANCE SHOW THE UPPER-LEVEL LOW TO THE
WEST-SOUTHWEST OF THE DEPRESSION MOVING SLOWLY SOUTHEASTWARD AND
WEAKENING OVER THE NEXT DAY OR SO. THIS SHOULD ALLOW THE
DEPRESSION TO MOVE ON THE NORTHERN SIDE OF THAT LOW...WHICH WOULD
PLACE IT INTO A MORE FAVORABLE AREA FOR STRENGTHENING WITH LIGHTER
WIND SHEAR. SINCE THE SYSTEM IS OVER WARM WATERS AND THE MODELS
WEAKEN THE UPPER-LEVEL LOW...TRANSITION TO A TROPICAL CYCLONE SEEMS
LIKELY IN A DAY OR SO. BECAUSE OF THE CURRENT STRUCTURE OF THE
CYCLONE...ONLY A SLOW INTENSIFICATION IS EXPECTED BECAUSE IT COULD
TAKE SOME TIME TO SHED ALL OF ITS SUBTROPICAL CHARACTERISTICS.
VERTICAL WIND SHEAR IS LIKELY TO INCREASE IN A COUPLE OF DAYS...
WHICH WILL PROBABLY HALT ANY STRENGTHENING AFTER THAT TIME. THE
NHC INTENSITY FORECAST IS ON THE LOW SIDE OF THE GUIDANCE GIVEN THE
INITIAL SUBTROPICAL STRUCTURE...AND IS GENERALLY BETWEEN THE MODEL
CONSENSUS AND THE LGEM.
BEST ESTIMATE OF INITIAL MOTION IS ABOUT 325/7. THE DEPRESSION IS
MOVING NORTHWESTWARD BETWEEN THE UPPER-LEVEL LOW AND A LARGE RIDGE
OVER THE CENTRAL ATLANTIC OCEAN. THE RIDGE SHOULD BE ERODED AWAY
IN A DAY OR TWO BY A SERIES OF MID-LATITUDE TROUGHS MOVING ACROSS
THE WESTERN ATLANTIC OCEAN. THIS PATTERN SHOULD CAUSE THE SYSTEM
TO SLOW DOWN BY LATE TONIGHT...THEN TURN TOWARD THE NORTHEAST AND
ACCELERATE BY EARLY FRIDAY DUE TO THE INCREASING MID-LATITUDE FLOW.
OVERALL THE MODEL AGREEMENT IS PRETTY GOOD FOR A WEAK SYSTEM AND
THE NHC FORECAST IS NEAR OR SLIGHTLY EAST OF THE DYNAMICAL MODEL
CONSENSUS. EXTRATROPICAL TRANSITION SEEMS LIKELY BY 96 HR...IF NOT
SOONER...AS DEPICTED BY MOST OF THE GLOBAL MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 06/0900Z 22.2N 67.0W 30 KT
12HR VT 06/1800Z 23.0N 67.7W 35 KT
24HR VT 07/0600Z 23.6N 68.0W 40 KT
36HR VT 07/1800Z 24.2N 67.5W 45 KT
48HR VT 08/0600Z 25.0N 66.1W 45 KT
72HR VT 09/0600Z 28.0N 60.5W 45 KT
96HR VT 10/0600Z 32.0N 50.0W 40 KT...POST-TROP/EXTRATROP
120HR VT 11/0600Z 36.5N 37.5W 35 KT...POST-TROP/EXTRATROP
FORECASTER BLAKE
