ATL: TROPICAL DEPRESSION BONNIE - DISCUSSION

[brunota2003]

Wow...it is so weak on the west side, would it even classify as a tropical cyclone? I know one of the criteria is a well defined LLC, and the last set of obs doesn't even break 10 knots at flight level, not to mention a lot of the winds are pointing in the WRONG direction for a closed llc.

Here is the latest image (no VDM yet...):



The next set still shows no well defined LLC (and one could even argue the winds are so weak, they are veering, so the LLC could of opened up)



And now we have a VDM:

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 23rd day of the month at 08:03Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 305)
Storm Number & Year: 03L in 2010
Storm Name: Bonnie (flight in the North Atlantic basin)
Mission Number: 4
Observation Number: 10
A. Time of Center Fix: 23rd day of the month at 7:37:00Z
B. Center Fix Coordinates: 24°06'N 78°20'W (24.1N 78.3333W)
B. Center Fix Location: 92 miles (147 km) to the SW (223°) from Nassau, Bahamas.
C. Minimum Height at Standard Level: 1,497m (4,911ft) at 850mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 34kts (~ 39.1mph)
E. Location of the Estimated Maximum Surface Wind: 59 nautical miles (68 statute miles) to the ENE (57°) of center fix
F. Maximum Flight Level Wind Inbound: From 128° at 41kts (From the SE at ~ 47.2mph)
G. Location of Maximum Flight Level Wind Inbound: 67 nautical miles (77 statute miles) to the NE/ENE (56°) of center fix
H. Minimum Sea Level Pressure: 1009mb (29.80 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,526m (5,007ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 19°C (66°F) at a pressure alt. of 1,530m (5,020ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 18°C (64°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 and Pressure
N. Fix Level: 850mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 0 nautical miles
Remarks Section:
Maximum Flight Level Wind: 41kts (~ 47.2mph) in the northeast quadrant at 7:15:50Z
Maximum Flight Level Temp: 19°C (66°F) which was observed 6 nautical miles to the E (81°) from the flight level center

[somethingfunny]

This is interesting....



The Vortex is around 24N. But if you look at the long-range Miami radar....something peculiar is showing at 25N, west of the westernmost tip of Andros Island.



Recon hasn't gone there yet.

[brunota2003]

Yeah, you're telling me! I'm watching these roll in and am still not sure what to think about it...

[tgenius]

So I just woke up and was like "where is the rain"?!? Then looking at radar this really does look like it's going to be about an afternoon rainstorm once it finally gets here.

[Florida1118]

TS Watches Just posted for N. Gulf coast. good luck to you!

[Ground_Zero_92]

So I just woke up and was like "where is the rain"?!? Then looking at radar this really does look like it's going to be about an afternoon rainstorm once it finally gets here.

I'm visiting my parents in South Miami Heights an was thinking the same thing when I looked at the radar presentation. In fact, I've seen thunderstorms look more ominous than Bonnie looks on radar so far. Hope She stays that way!

[brunota2003]

The first part of the discussion is the most telling:

000
WTNT43 KNHC 230859
TCDAT3
TROPICAL STORM BONNIE DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
500 AM EDT FRI JUL 23 2010

THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING BONNIE
HAS FOUND LITTLE CHANGE IN STRENGTH. THE AIRCRAFT HAS MEASURED A
PEAK 850 MB FLIGHT-LEVEL WIND OF 42 KT...BELIEVABLE SFMR WINDS OF
34 KT...AND A MINIMUM PRESSURE OF 1008 MB. THESE DATA SUPPORT
MAINTAINING AN INITIAL INTENSITY OF 35 KT. THE AIRCRAFT DATA
SUGGEST THAT THE CIRCULATION HAS BECOME LESS DEFINED AS FEW WEST
OR NORTHWEST WINDS WERE FOUND. IF THIS TREND CONTINUES...IT IS
POSSIBLE FOR BONNIE TO DEGENERATE TO AN OPEN TROUGH. FOR NOW...THE
OFFICIAL FORECAST ASSUMES THAT BONNIE WILL BE ABLE TO MAINTAIN A
CLOSED CIRCULATION AND REMAIN A TROPICAL CYCLONE. AS BONNIE PASSED
THROUGH THE CENTRAL BAHAMAS...AN OBSERVING SITE ON STANIEL CAY
REPORTED A SUSTAINED WIND OF 37 KT.

THE AIRCRAFT FIXES SHOW THAT BONNIE IS MOVING FASTER AND HAS TURNED
WEST-NORTHWESTWARD. THE INITIAL MOTION ESTIMATE IS 295/16. BONNIE
IS FORECAST TO MAINTAIN THIS GENERAL HEADING DURING THE NEXT DAY OR
SO AS IT MOVES AROUND THE SOUTHWESTERN SIDE OF A MID- TO UPPER-
LEVEL RIDGE CENTERED OVER THE CAROLINAS. THE TRACK GUIDANCE IS
GOOD AGREEMENT DURING FIRST 48 HOURS...BUT THERE IS SOME SPREAD IN
THE GUIDANCE AFTER LANDFALL ALONG THE NORTHERN GULF COAST. THE
GUIDANCE IS NOTICEABLY FASTER...WHICH MAY BE IN PART FROM THE MORE
WESTWARD INITIAL LOCATION. THE NEW NHC TRACK IS SIMILAR TO THE
PREVIOUS TRACK BUT IS FASTER THAN THE PREVIOUS ADVISORY. THIS
REQUIRES THE ISSUANCE OF TROPICAL STORM WATCHES FOR A PORTION OF
THE NORTHERN GULF COAST.

THE UPPER-AIR ENVIRONMENT AHEAD OF BONNIE IS LESS THAN IDEAL FOR
STRENGTHENING. BONNIE IS EXPECTED TO REMAIN UNDER THE INFLUENCE OF
MODERATE TO STRONG SOUTHEASTERLY SHEAR DUE TO THE FLOW BETWEEN AN
UPPER-LEVEL LOW OVER THE GULF OF MEXICO AND THE AFOREMENTIONED
RIDGE. THE UPPER-LEVEL FLOW IS FORECAST BY THE GLOBAL MODELS TO
WEAKEN IN 36-48 HOURS...WHICH COULD ALLOW FOR SOME STRENGTHENING OF
BONNIE. THE OFFICIAL FORECAST IS BETWEEN THE MORE AGGRESSIVE
SHIPS/LGEM GUIDANCE AND THE HWRF/GFDL MODELS WHICH SHOWS LITTLE...
IF ANY...INTENSIFICATION.


FORECAST POSITIONS AND MAX WINDS

INITIAL 23/0900Z 24.1N 78.6W 35 KT
12HR VT 23/1800Z 25.0N 81.0W 40 KT
24HR VT 24/0600Z 26.2N 84.1W 40 KT
36HR VT 24/1800Z 27.6N 86.9W 45 KT
48HR VT 25/0600Z 28.8N 89.1W 45 KT
72HR VT 26/0600Z 31.5N 92.0W 25 KT...INLAND
96HR VT 27/0600Z 34.5N 93.0W 20 KT...POST-TROP/REMNT LOW
120HR VT 28/0600Z...DISSIPATED

$$
FORECASTER BROWN/LANDSEA

[johngaltfla]

Thankfully this isn't going to be much of a storm. I was going to go to Bonita to help a friend move his boat, but I'll bet he changes his mind after seeing it did not intensify at all overnight. Be thankful this didn't form in late August/Early September folks.

[TampaFl]

5:00AM Postion - Map courtesy http://www.BoatUS.com

[brunota2003]

Recon is currently inbound, the next couple of sets of obs should hold the minimum pressure and the wind shift. Will be curious to see what they find this time.

[brunota2003]

so far a minimum pressure of 1009.3 mb. There was no wind shift where they measured that, the winds were from basically SSE to SSW the entire time.

[floridasun78]

THE AIRCRAFT DATA
SUGGEST THAT THE CIRCULATION HAS BECOME LESS DEFINED AS FEW WEST
OR NORTHWEST WINDS WERE FOUND. IF THIS TREND CONTINUES...IT IS
POSSIBLE FOR BONNIE TO DEGENERATE TO AN OPEN TROUGH. (( this could be not tropical storm??)) plane having hard time finding low it more stronger on sat pic

[Florida1118]

Well, There goes all there Advisories out the window...All this Drama for 40? Well, At least B. is off the list.

[brunota2003]

Well, There goes all there Advisories out the window...All this Drama for 40? Well, At least B. is off the list.

Actually, they said an observing site recorded winds of 37 knots earlier today...so assuming it doesn't do anything further, and the anemometer is sited correctly, I could see them bumping Bonnie to 40 knots in the post storm report.


Also, recon has found winds from SE to SSW...nothing closing the low off yet.

[Florida1118]

So, Its Do or die for Bonnie now. Personally, Im hoping for the Die one but you know... How much longer are the Recon guys there?

[brunota2003]

Not sure...but so far we've found winds from 104 to 218 degrees. Or from ESE to SSW. They are literally circling around, probably going "Um...where'd the center go? Oh well, open trough it is!"

Looking at the POD, I believe they have roughly another 2 hours left on station...it said 05Z to 12Z, and it is about 10Z now.

[hiflyer]

They stay up much longer than that and I will be finding a dropsonde in my back yard! grin. Radar shows she is booking into land rapidly. Clear of Andros and in the Gulf Stream just offshore SE Florida. At current rate of advance this could be over on the coast by noon around here as far as the rain shield is concerned.

[brunota2003]

I've always thought it'd be cool to have a dropsonde land in your yard that the AF dropped. Recon is continuing to book it to the NE...not sure what they see, maybe a feature in the convection, or they want to set up for another pass. Still have not found a closed circulation.

[ravyrn]

DISCLAIMER: This is my personal opinion and is in no way an official forecast.

It seems Bonnie is closing back in on the ULL in the gulf. Its getting squished between the ULL and the ridge. With its current presentation, I imagine it may just be some rain showers with undesirable easterly gusts hitting land somewhere between Biloxi and Pensacola.

[Florida1118]

If this does survive and has A closed Low, Could someone explain this to me?
http://www.srh.noaa.gov/tbw/
Why RIGHT on the water next to the coast there is a TS Warnings but land, there is nothing?