Cristobal Discussion Thread

TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014
500 PM AST SAT AUG 23 2014

The Air Force Reserve Hurricane Hunter aircraft investigating the
disturbance near the southeastern Bahamas found a well-defined
circulation this afternoon. Even though the convective presentation
is somewhat ragged, there is enough organization to classify the
system as a tropical cyclone. The intensity is set to 30 kt based
on flight level wind data from the aircraft and an earlier ASCAT
pass, and the central pressure of 1005 mb is based on a recent
surface observation from Providenciales in the Turks and Caicos. The
SHIPS model shows light to moderate shear over the cyclone for the
next couple of days, which should allow for intensification given
that the cyclone will be moving over waters of 29 to 30C. The NHC
forecast shows slow strengthening in the first 24 to 36 hours as
the cyclone organizes. Global models show more favorable upper-
level winds over the system in a couple of days, which should allow
for strengthening to a hurricane in by 3 days. The official forecast
is close to the IVCN intensity consensus through the period.

The initial motion estimate is a relatively uncertain 310/10 given
the recent formation of the center. The cyclone should continue
moving northwestward and north-northwestward into a developing break
in the subtropical ridge cause by a mid/upper-level trough off the
U.S. east coast. As the trough begins to lift out and steering
currents weaken, a slow motion is expected in 36 to 48 hours. Then
as a subtropical ridge rebuilds to the east of the cyclone later in
the period, the system is expected to turn northward and then
northeastward. However, there is significant disagreement in
the timing and sharpness of the turn in this and previous dynamical
model cycles. Currently the GFDL and GFS are along the western
edge of the guidance envelope showing a more westward track and
a slower motion at day 5. The ECMWF, GEFS mean, and HWRF show a
sharper turn and a more northeastward motion by day 5 on the east
side of the guidance envelope. The NHC forecast is near the TVCA
multi-model consensus through most of the period and a little to the
left of it at day 5. Given the spread in the guidance and the recent
formation of the system, confidence in the details of the track
forecast is lower than normal.

FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 21.8N 72.3W 30 KT 35 MPH
12H 24/0600Z 22.9N 73.6W 35 KT 40 MPH
24H 24/1800Z 24.0N 74.4W 40 KT 45 MPH
36H 25/0600Z 24.6N 74.8W 45 KT 50 MPH
48H 25/1800Z 25.0N 75.0W 55 KT 65 MPH
72H 26/1800Z 26.5N 76.0W 65 KT 75 MPH
96H 27/1800Z 29.0N 77.5W 65 KT 75 MPH
120H 28/1800Z 32.0N 76.5W 70 KT 80 MPH

$$
Forecaster Brennan

Lets see what the 18z gfs has to say should be starting soon

So far the 18z GFS is close to the 12z. I won't be posting images unless there's a drastic change.

Tonight's 00z runs will contain all the recon data from today.

It's very unorganized on the 18z GFS. It's still stalled at 78 hours northeast of the Bahamas, but it's not stacked at all. The mid level vorticity is still in the southern Bahamas.

2nd VDM is northwest of the 1st:


Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 23rd day of the month at 22:05Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 301)

Mission Purpose: Investigate fourth suspect area (flight in the North Atlantic basin)

Mission Number: 4

Observation Number: 14
A. Time of Center Fix: 23rd day of the month at 21:44:40Z
B. Center Fix Coordinates: 21°47'N 72°21'W (21.7833N 72.35W)
B. Center Fix Location: 81 miles (131 km) to the WNW (286°) from Cockburn Town, Turks and Caicos Islands (GBR).
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 19kts (~ 21.9mph)
E. Location of the Estimated Maximum Surface Wind: 45 nautical miles (52 statute miles) to the SW (225°) of center fix
F. Maximum Flight Level Wind Inbound: From 244° at 7kts (From the WSW at ~ 8.1mph)
G. Location of Maximum Flight Level Wind Inbound: 49 nautical miles (56 statute miles) to the SW (225°) of center fix
H. Minimum Sea Level Pressure: 1005mb (29.68 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 24°C (75°F) at a pressure alt. of 340m (1,115ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 24°C (75°F) at a pressure alt. of 341m (1,119ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 21°C (70°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 1,500 feet
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 10 nautical miles
Remarks Section:
Maximum Flight Level Wind: 30kts (~ 34.5mph) which was observed 66 nautical miles (76 statute miles) to the NW (312°) from the flight level center at 21:03:30Z

Maximum Flight Level Wind Outbound: 29kts (~ 33.4mph) which was observed 41 nautical miles (47 statute miles) to the NE (46°) from the flight level center at 21:56:00Z

Sea Level Pressure Extrapolation From: Below 1,500 feet
Maximum Flight Level Temp: 25°C (77°F) which was observed 10 nautical miles (12 statute miles) to the SW (219°) from the flight level center