| Hurricane Watch Team |

000
WTNT33 KNHC 152033
TCPAT3
BULLETIN
TROPICAL STORM BILL ADVISORY NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
500 PM AST SAT AUG 15 2009

...TROPICAL STORM BILL...THE SECOND TROPICAL STORM OF THE SEASON
FORMS IN THE FAR EASTERN ATLANTIC...

SATELLITE IMAGES INDICATE THAT TROPICAL DEPRESSION TWO HAS
STRENGTHENED AND HAS BECOME TROPICAL STORM BILL..THE SECOND NAME
CYCLONE OF THE SEASON. AT 500 PM AST...2100 UTC...THE CENTER OF
THE TROPICAL STORM WAS LOCATED NEAR LATITUDE 11.3 NORTH...LONGITUDE
35.2 WEST OR ABOUT 820 MILES...1320 KM...WEST-SOUTHWEST OF THE CAPE
VERDE ISLANDS.

BILL IS MOVING TOWARD THE WEST NEAR 16 MPH...26 KM/HR. A GRADUAL
TURN TO THE WEST-NORTHWEST IS EXPECTED DURING THE NEXT FEW DAYS.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 40 MPH...65
KM/HR...WITH HIGHER GUSTS. SOME STRENGTHENING IS FORECAST DURING
THE NEXT 24 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB...29.65 INCHES.

...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...11.3N 35.2W
MAXIMUM SUSTAINED WINDS...40 MPH
PRESENT MOVEMENT...WEST OR 265 DEGREES AT 16 MPH
MINIMUM CENTRAL PRESSURE...1004 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.

$$
FORECASTER AVILA

---

Hurricane Watch - Tropical Storm Ana tracking thread.
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| Hurricane Watch Team |

---

Hurricane Watch - Tropical Storms Ana & Bill tracking threads.
Note: This poster does not respond to off-board emails.

| Hurricane Watch Team |

000
WTNT43 KNHC 160247
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 PM AST SAT AUG 15 2009

SATELLITE IMAGES CONTINUE TO SHOW THAT BILL IS GRADUALLY BECOMING
BETTER ORGANIZED WITH NUMEROUS CONVECTIVE BANDING FEATURES.
HOWEVER...THE CYCLONE LACKS AN INNER CORE AND DEEP CONVECTION NEAR
THE CENTER. INITIAL INTENSITY IS KEPT AT 35 KNOTS WHICH IS A BLEND
OF THE DVORAK CLASSIFICATIONS AND QUIKSCAT DATA. WITH THE
CONDUCIVE ENVIRONMENT AHEAD...BILL IS FORECAST TO BECOME A
HURRICANE IN A COUPLE OF DAYS AND BECOME EVEN STRONGER THEREAFTER.
THIS IS CONSISTENT WITH SHIPS AND BOTH THE GFDL/HWRF MODEL PAIR.

BILL IS MOVING WESTWARD OR 270 DEGREES AT 14 KNOTS. THE CYCLONE IS
WELL-EMBEDDED IN THE TROPICAL TRADE WINDS AND WILL CONTINUE ON THIS
GENERAL TRACK WITH A GRADUAL TURN TO THE WEST-NORTHWEST. THE ECMWF
WAS THE LEADER SHOWING A GRADUAL NORTHWARD TREND AHEAD OF A TROUGH
OVER THE EASTERN UNITED STATES A FEW RUNS AGO. NOW...THE REST OF
THE MODELS...WITH THE EXCEPTION OF THE UK MODEL...ARE FOLLOWING THE
ECMWF TUNE...AND ALL TURN BILL MORE THE WEST-NORTHWEST AND NORTHWEST
BY THE END OF THE FORECAST PERIOD. BASED ON THIS SHIFT IN THE
GUIDANCE...THE OFFICIAL FORECAST WAS ALSO SHIFTED A LITTLE
NORTHWARD AND IS IN THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE
ENVELOPE.


FORECAST POSITIONS AND MAX WINDS

INITIAL 16/0300Z 11.3N 36.6W 35 KT
12HR VT 16/1200Z 11.2N 38.7W 40 KT
24HR VT 17/0000Z 12.0N 41.5W 50 KT
36HR VT 17/1200Z 12.8N 44.0W 55 KT
48HR VT 18/0000Z 14.0N 47.0W 65 KT
72HR VT 19/0000Z 15.5N 52.5W 75 KT
96HR VT 20/0000Z 18.0N 58.5W 85 KT
120HR VT 21/0000Z 21.0N 64.0W 95 KT

$$
FORECASTER AVILA

---

Hurricane Watch - Tropical Storms Ana & Bill tracking threads.
Note: This poster does not respond to off-board emails.

Statement as of 5:00 am AST on August 16, 2009

the center of Bill has been difficult to find this morning...and a
0419 UTC AMSR-E pass indicated that it has either slowed down or
has been re-forming closer to the deep convection. Dvorak
T-numbers are now 3.0 from TAFB and 2.5 from SAB...so the initial
intensity is raised to 40 kt. Bill is expected to gradually
strengthen over the next couple of days...and the official forecast
follows the upward trend noted in the intensity guidance. Bill is
now expected to reach major hurricane status by day 5...but it
should be noted that the 100 kt shown in the forecast is still
below the intensity consensus and well below the HWRF model. This
is to account for increased vertical shear that may develop by days
4 and 5...as indicated in the SHIPS guidance.
The initial motion is an uncertain 270/11. Bill is expected to
gradually gain latitude and turn to the west-northwest over the
next few days. The new suite of model guidance has shifted a
little north of the previous guidance envelope as most of the
models appear to be showing the development of a deep mid- to
upper-level trough over the eastern United States at the end of the
forecast period. Most of the models...with the exception of the
UKMET as a southern outlier...are in remarkably good agreement
through day 5.

Forecast positions and Max winds

initial 16/0900z 11.4n 37.2w 40 kt
12hr VT 16/1800z 11.8n 39.3w 45 kt
24hr VT 17/0600z 12.5n 41.9w 50 kt
36hr VT 17/1800z 13.4n 44.7w 60 kt
48hr VT 18/0600z 14.3n 47.5w 70 kt
72hr VT 19/0600z 16.5n 53.0w 85 kt
96hr VT 20/0600z 19.0n 58.5w 95 kt
120hr VT 21/0600z 22.0n 64.0w 100 kt

$$
forecaster Berg

Statement as of 11:00 am AST on August 16, 2009

Bill is displaying a beautiful curved band pattern on satellite
imagery this morning with a new burst of convection occurring near
the center. A 0808 UTC Quikscat pass showed maximum winds of at
least 45 kt...and Dvorak satellite intensity estimates are between
45-55 kt. The initial intensity is set to 50 kt as a blend of the
above data.

A series of microwave passes and visible images have confirmed that
the center has shifted a little bit to the north and the initial
motion is about 285/14. A continued west-northwest motion is
expected for the new few days due to subtropical ridging to the
north of Bill. All of the global models besides the UKMET show
the tropical cyclone moving to the north of the Leeward Islands as a
break in the ridge forms at about 65w. Model guidance has shifted
to the northeast this morning...and the official forecast follows
that trend.

Environmental conditions appear favorable for continued
intensification due to light shear and warm waters. SSTs begin to
rise more significantly in a couple of days and the NHC intensity
forecast could be conservative after that time. All reliable
guidance shows this system eventually becoming a major hurricane...
though at differing time periods with the statistical guidance
showing it happening earlier than the dynamical models. The NHC
forecast is raised from the previous one...and is in good agreement
with the SHIPS/lgem through 72 hours. The intensity forecast is
leveled off after 96 hours due the possibility of westerly shear
developing...as suggested by the GFS/ECMWF models.

The Quikscat pass from this morning showed that the wind field with
Bill has expanded...and consequently the initial 12 ft seas and
forecast wind radii are larger than the previous forecast.

Forecast positions and Max winds

initial 16/1500z 12.1n 38.4w 50 kt
12hr VT 17/0000z 12.6n 40.4w 60 kt
24hr VT 17/1200z 13.4n 43.1w 70 kt
36hr VT 18/0000z 14.3n 45.9w 80 kt
48hr VT 18/1200z 15.2n 48.6w 90 kt
72hr VT 19/1200z 17.5n 54.0w 100 kt
96hr VT 20/1200z 20.5n 59.0w 105 kt
120hr VT 21/1200z 24.0n 63.5w 105 kt

$$
forecaster Blake

Statement as of 5:00 PM AST on August 16, 2009

satellite images show that Bill has developed a central dense
overcast along with impressive banding and outflow. These features
suggest that the storm continues to intensify. Satellite intensity
estimates from TAFB/SAB have increased to t3.5...55 kt on the
Dvorak scale and this value will be used for the initial wind
speed.
Bill is moving toward the west-northwest or 285/14. This general
motion is expected for the next couple of days as a subtropical
ridge should remain firm to the north of the tropical cyclone.
Thereafter...a couple of evolutions to the synoptic pattern seem
possible. The first...favored by the GFS/ECMWF/GFDL/HWRF...shows a
mid-latitude shortwave diving into the subtropical ridge...causing
it to break around 65w. This leads to a northwest motion of Bill
in about three days. The other solution...shown by the
NOGAPS/UKMET...is that the hurricane bypasses the first break and
continues moving toward the west-northwest...eventually turning
northwest at the end of the forecast due to a large mid-latitude
trough approaching the eastern United States. The official
forecast is shifted a little bit to the right at the end...in
deference to the highly-skilled models in the former solution.
Water vapor images show that the hurricane is on the south side of
an upper high with little shear likely for the next several days.
In combination with warm SSTs...there is no reason not to forecast
continued strengthening of Bill. In fact...the SHIPS rapid
intensification index shows a 38 percent chance of a 30 kt increase
in winds during the next 24 hours. All reliable models continue to
show this system becoming a major hurricane...with the
GFDL/HWRF/GFDN models forecasting Bill to reach category four
strength by day 5. However...there is some evidence in the global
model fields that the upper-level winds will become less favorable
after 72 hours with some southwesterly shear developing as Bill
becomes displaced from an upper-level high. The official forecast
will show the intensity leveling off after that time due to that
possibility. The NHC intensity forecast is close to the previous
forecast and is similar to the SHIPS model.

Forecast positions and Max winds

initial 16/2100z 12.8n 40.0w 55 kt
12hr VT 17/0600z 13.4n 42.1w 65 kt
24hr VT 17/1800z 14.2n 45.0w 75 kt
36hr VT 18/0600z 15.0n 47.7w 85 kt
48hr VT 18/1800z 16.0n 50.4w 95 kt
72hr VT 19/1800z 18.5n 55.5w 105 kt
96hr VT 20/1800z 22.0n 60.5w 105 kt
120hr VT 21/1800z 26.5n 65.0w 105 kt

$$
forecaster Blake

| Hurricane Watch Team |

000
WTNT43 KNHC 170253
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 PM AST SUN AUG 16 2009

INFRARED SATELLITE IMAGERY REVEALS AN IMPRESSIVE MASS OF DEEP
CONVECTIVE TOPS TO -80C WITHIN A CENTRAL DENSE OVERCAST...ALONG
WITH AN EXPANDING UPPER-LEVEL OUTFLOW. A LONG...WELL-DEFINED BAND
CONNECTED TO THE ITCZ IS NOTED IN THE SOUTHERN SEMICIRCLE...WHILE
LESSER BANDING COILS AROUND THE NORTHERN HALF OF THE CIRCULATION.
DVORAK T-NUMBERS ARE 3.5 AND 4.0 FROM SAB AND TAFB...RESPECTIVELY.
TAKING THE MEAN OF THESE INTENSITY ESTIMATES...THE ADVISORY WIND
SPEED IS SET AT 60 KT.

RECENT SATELLITE CENTER FIXES ARE SOMEWHAT UNCERTAIN BUT YIELD AN
INITIAL MOTION ESTIMATE OF 290/17...REPRESENTING A SLIGHTLY FASTER
FORWARD SPEED THAN BEFORE. UNDER THE INFLUENCE OF SUBTROPICAL
RIDGING TO THE NORTH...BILL IS EXPECTED TO MAINTAIN A GENERAL
WEST-NORTHWEST HEADING FOR THE NEXT 48-72 HOURS. WITH LITTLE
SPREAD IN THE CURRENT MODEL CYCLE THROUGH THIS TIME...THE OFFICIAL
TRACK DEVIATES LITTLE FROM THE PREVIOUS ADVISORY. THEREAFTER...
MODEL GUIDANCE IS IN GOOD AGREEMENT THAT A RATHER SUBSTANTIAL BREAK
IN THE SUBTROPICAL RIDGE SHOULD DEVELOP ROUGHLY ALONG 60W...WHICH
SHOULD RESULT IN A MORE NORTHWESTWARD COURSE. MOST OF THE MODEL
SOLUTIONS HAVE SHIFTED FARTHER NORTH FROM THE PREVIOUS RUNS...AND
SO HAS THE MODEL CONSENSUS. ONLY THE UKMET FAVORS A MORE
WEST-NORTHWESTWARD PATH AND APPEARS AS THE LONE...SOUTHERN OUTLIER
AMONGST THE REMAINDER OF THE GLOBAL MODELS. THE OFFICIAL FORECAST
IS ADJUSTED NORTH OF THE PREVIOUS ONE...ESPECIALLY BEYOND 96
HOURS...BASED ON THE LATEST GUIDANCE.

EVEN THOUGH ENVIRONMENTAL SHEAR IS QUITE LOW...BILL HAS BEEN
TRACKING OVER MARGINAL SEA SURFACE TEMPERATURES AND WATERS ARE NOT
FORECAST TO WARM FURTHER UNTIL AFTER 24 HOURS. INTERESTINGLY...THE
GFDL/HWRF SHOW A NEARLY FLAT INTENSIFICATION RATE FOR THE NEXT DAY
OR TWO...PERHAPS UNDERSCORING THE TEPID THERMODYNAMIC CONDITIONS. IT
SHOULD BE NOTED...HOWEVER...THAT THE SHIPS RAPID INTENSITY INDEX
SHOWS A 41% CHANCE OF A 30 KT INTENSITY INCREASE DURING THE NEXT 24
HOURS. THEREAFTER...THE GUIDANCE IS IN GOOD AGREEMENT THAT LOW
SHEAR AND WARMING WATERS SHOULD PREVAIL FOR BILL...ALLOWING THE
CYCLONE TO EVOLVE INTO A MAJOR HURRICANE OVER THE FORECAST PERIOD.
THE OFFICIAL FORECAST IS CLOSEST TO THE SHIPS MODEL GUIDANCE...
WHICH PREDICTS A FAIRLY STEADY RATE OF DEVELOPMENT OVER THE NEXT
FEW DAYS. TOWARD THE END OF THE FORECAST PERIOD...THE GLOBAL
MODELS HAVE BEEN HINTING AT INCREASING WESTERLY SHEAR AS BILL
OUTRUNS FAVORABLE ANTICYCLONIC FLOW TO THE SOUTHEAST.
ACCORDINGLY...THE OFFICIAL INTENSITY FORECAST SHOWS SLIGHT
WEAKENING NEAR THE END OF THE PERIOD.

FORECAST POSITIONS AND MAX WINDS

INITIAL 17/0300Z 13.4N 41.7W 60 KT
12HR VT 17/1200Z 14.1N 43.7W 70 KT
24HR VT 18/0000Z 14.9N 46.5W 80 KT
36HR VT 18/1200Z 15.8N 49.2W 85 KT
48HR VT 19/0000Z 16.8N 51.8W 95 KT
72HR VT 20/0000Z 19.7N 56.8W 105 KT
96HR VT 21/0000Z 23.5N 61.5W 105 KT
120HR VT 22/0000Z 28.1N 65.5W 100 KT

$$
FORECASTER KIMBERLAIN/PASCH

---

Hurricane Watch - Tropical Storms Ana & Bill tracking threads.
Note: This poster does not respond to off-board emails.