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Today is the last day of the 2021 Atlantic Hurricane Season. 8 landfalls including Ida, but no landfalls in the late season.
Days since last H. Landfall - US: Any 80 (Nicholas) , Major: 95 (Ida) Florida - Any: 1149 (Michael) Major: 1149 (Michael)
 


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MikeCAdministrator
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Re: Gulf Low [Re: Unregistered User]
      #85465 - Thu May 21 2009 01:17 PM

It's not political. The surface low is still very weak, and definitely nowhere near named or depression status. It may get re-tagged as an invest area tonight or tomorrow if the surface low persists.

Water temps in the direction its moving get cooler, although general shear is decreasing. The movement is pretty slow, however.


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danielwAdministrator
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Re: Gulf Low [Re: MikeC]
      #85466 - Thu May 21 2009 02:11 PM

Over the last 5 to 6 hours the visible satellite shots together with the IR enhanced imagery seem to indicate that the LOW might... might be trying to close off the center. At present the IR enhancement reveals an approximate 30 to 35% segment that continues to encircle the center. Starting at the southeastern side of the center and circling counterclockwise around toward the northwestern side of the center.
Probably have to run a 6-8 hour loop to see the development as it is very slow.

NWS Slidell,LA radar is beginning to indicate showers in MS as far north as the 31degree north latitude line at Poplarville/ Lumberton,MS.

East GOM Buoy 42003 at 17Z indicating pressure at 1006.5mb winds SE or 120deg at 16gusts to 19kts peak gust to 23kts.


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Storm Hunter
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Re: Gulf Low [Re: danielw]
      #85467 - Thu May 21 2009 02:58 PM

well the low is easy to track now... and i think there still a 15-25kt shear right above the low at the surface.. should weaken over night, i would expect.. there clearly is a nw dift/movement today... a bit it is slow.. so eratic movement should be noted... i would expect this to get tagged again, atleast an Invest with a new number.. since this is clearly a not the original low from the bahama's...

Track the LOW with Vis

--------------------
www.Stormhunter7.com ***see my flight into Hurricane Ike ***
Wx Data: KFLPANAM23 / CW8771
2012== 23/10/9/5 sys/strms/hurr/majh



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JoshuaK
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Re: Gulf Low [Re: Storm Hunter]
      #85468 - Thu May 21 2009 04:44 PM

According to the Satellite visible loop and other data, it appears that there are two different circulation centers associated with this system. The more defining one is located at 26N 87W as of this posting time (4:41PM EST) and consists of a mid to low level circulation, and is crawling west. The second circulation center, consisting of a high level circulation, is located at 27.5N 86W and is again crawling west.

The system is looking a little better today, but is still a long ways off from developing into anything significant. Although there is still some dry air present, the last few water vapor slides in the loops shows the dry air pocket in the central GOM closing up as more moisture works in from the west.


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scottsvb
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Re: Gulf Low [Re: JoshuaK]
      #85470 - Fri May 22 2009 12:33 AM

The system is 70% cold core...low level tropical moisture is being pulled north...but its COC is cold core. This doesnt have enough things going for it to become a subtropical storm.. I said 25% chance last night...and I'm sticking with that. The water infront of this is cooler in the mid 70s...right now its near 80 as of 6z Fri. Even though I dont think this will make a subtropical depression....tropical moisture from the lower levels along with the unstable cold core low in the mid levels will produce T-storms out as far as Florida..with this coming ashore in Louisiana.

Side note... models are persistant in the GFS,ECMWF and NOGAPS on keeping pressures low in the bahamas and florida... a low may develop again near Cuba, southern Bahamas, or near Andros Island again and move north along the east coast of Florida early next week... 30% chance this will happen cause its too far out to actually really care. Don't want to say this has a chance cause windshear will be high until it reaches the northern Bahamas and Florida.. Water temps are marginal...but this will be more tropical like 90L and not what is in the GOM right now....if there is anything at all!


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HCW
Storm Tracker


Reged: Fri
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Re: Gulf Low [Re: scottsvb]
      #85473 - Fri May 22 2009 11:22 AM

This area is now invest 90L again. Shouldn't this have been given a new number since it is not the remnants of 90L ? Looks like it's running out of time and will be inland tomorrow morning and not worth sending recon into. James N Mobile

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Marknole
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Reged: Sun
Posts: 45
Loc: Wacissa, FL
Re: Gulf Low [Re: HCW]
      #85474 - Fri May 22 2009 03:20 PM

From "Nearly nil chance of development" to this (NWS Tallahassee AFD, 2:30 PM):

SHWRS/ TSTMS INCREASING WHERE MOIST DEEP SELY FLOW WILL
ADVECT NWWD FROM GULF AND BE PERIODICALLY ENERGIZED BY SEVERAL
IMPULSES OF ENERGY ROTATING NEWD ON THE EAST SIDE OF LOW. LATEST
SATELLITE PIX HINT AT DEVELOPMENT OF A CIRCULATION.

Tropical airmass in place here in the Big Bend, along with distinct banding features. Certainly warm enough SST's over the central gulf. Any information from the met's?


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Storm Hunter
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Re: Gulf Low [Re: Marknole]
      #85475 - Fri May 22 2009 05:13 PM

i think there was a mid to upper level low that spun around the northern part of the low level low and caused some decent wind shear yesterday and today... if you look at WV loops in the last 24 hrs... it spins right off the Florida Phn coast tracking NW... its much weaker now.. which i think is opening the door some now with 90L... afternoon SPECIAL TROPICAL WEATHER OUTLOOK was made again... only given a 30% chance of a tropical low... Air Force Recon on standby again form a flight tmrw... heck it should be really close to AFB tmrw, i wouldn't be susprised if they flew one mission just to test out equipment/etc. The door is closing on the low now... its running out of water and time... this afternoon... a few storms have fired over center... but shear tears them apart... Close up Vis Right now over the NW Florida, there is a nice band of showers and storms along I-10. Can feel the tropical air mass up this way!



--------------------
www.Stormhunter7.com ***see my flight into Hurricane Ike ***
Wx Data: KFLPANAM23 / CW8771
2012== 23/10/9/5 sys/strms/hurr/majh



Edited by Storm Hunter (Fri May 22 2009 05:15 PM)


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LoisCane
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Re: Gulf Low [Re: scottsvb]
      #85476 - Fri May 22 2009 06:14 PM

I know we are watching the low in the gulf but am wondering if the models are looking at the area of persistent rain in the Carib that has caused flooding and loss of life in Haiti this week?


Another very complicated system in the GOM and imagine after the planes go in we will have a better idea of what is really going on.

Hard to tell but if it does form.. close in there is very little time to warn anyone.

Bill Read worries on this a lot and have heard him talk at conferences where he points out most close in Gulf storms develop and hit land way under 72 hours which is the time frame we try to warn people. As they often say, a bull in the china shop even though right now it doesn't look like much of a bull.

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Hugh
Senior Storm Chaser


Reged: Fri
Posts: 1060
Loc: Okaloosa County, Florida
Re: Gulf Low [Re: Storm Hunter]
      #85478 - Fri May 22 2009 07:16 PM

Quote:

Air Force Recon on standby again form a flight tmrw... heck it should be really close to AFB tmrw, i wouldn't be susprised if they flew one mission just to test out equipment/etc. The door is closing on the low now... its running out of water and time... this afternoon... a few storms have fired over center... but shear tears them apart...





This is a bit reminiscent of T.S. Edouard that formed last year, just off the coast of Mobile. It was largley ignored by the NHC as a non-tropical low until suddenly someone decided to send a recon out and it found to be organized enough to be a tropical depression, then strengthened to a tropical storm before moving inland. The difference with Edouard was that it was moving basically due west, while this thing is moving toward the coast. So it might very well run out of real estate, but in the post-season analysis, I would be shocked if it were not designated at least a depression.

--------------------
Hugh

Eloise (1975) - Elena and several other near misses (1985) - Erin & Opal (1995) - Ivan (2004)


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Storm Cooper
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Re: Gulf Low [Re: Hugh]
      #85479 - Fri May 22 2009 07:54 PM

You never know...... STWO...

a broad area of low pressure is centered over the gulf of mexico
about 200 miles south of pensacola florida. satellite imagery
indicates that the associated showers and thunderstorms continue to
increase this evening. additional development of this system is
possible, and a tropical depression could form before the low
moves inland over the northern gulf coast on saturday. an air
force reserve hurricane hunter aircraft will investigate the low
tomorrow, if necessary. there is a medium chance(30 to) 50
percent, of this system becoming a tropical cyclone during the
next 48 hours. regardless of development, heavy rains and
occasionally gusty winds are expected along portions of the
northern gulf coast tonight and saturday, and interests in this
area should monitor the progress of the system.

--------------------
Hurricane Season 2017 13/7/1


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cieldumort
Moderator


Reged: Mon
Posts: 2112
Loc: Austin, Tx
Re: Gulf Low [Re: Storm Cooper]
      #85483 - Sat May 23 2009 12:57 AM

Invest 90L is still running a little bit dry in 3 out of 4 quadrants, but that could end within the next 24 hours as convection keeps blowing up at least in the northeastern quad, helping to mix out the dry air still present from its days as a purely extra-tropical low.

There has been some speculation as to whether or not this system should have been re-tagged 91L. It seems like a reasonable debate, but one that is purely academic as to whether or not the feature actually becomes an officially number or named cyclone in the 2009 records.

As a matter of interesting discussion, 90L was originally identified as the mid-level cyclone near eastern Cuba which was associated with a surface trough. This feature has since become intertwined with the former extra-tropical low and associated frontal boundary which had been stalled out over Florida.

As of tonight, pressures within the surface low that is Invest 90L continue falling a bit, and persistent, deep convection continues building about its center of circulation. Winds are now running sustained above 20 knots over a fairly big area, but no doubt due in no small part to the pressure gradient from the higher pressure over the southeast, more than anything else, so far.

Due to 90L's proximity to land, it would only be reasonable for NHC to exercise a little bit of caution and indeed send a recon out in there Saturday, if 90L has not yet improved in structure dramatically overnight, such that they would even be inclined to assign it a TC/STC number without any additional data from recon.

Regardless of whether 90L earns itself an officiated status or not, this system has a history of dumping copious rains over a large area of real estate, and now is once again partially responsible for plenty of gusty winds. Holiday plans right along and off the coast, and holiday travel in this entire area, should certainly be made with some extra consideration.


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Bloodstar
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Re: Gulf Low [Re: MikeC]
      #85484 - Sat May 23 2009 01:04 AM

I don't know about you folks, but I'm starting to think this storm may make it over the hump and get classified as Ana. The convection is looking better, if still lopsided, and is a (shallowish) warm core system. Bouy 42364 recorded 35kt sustained winds at 400 UTC, but that was also around 400 feet above sea level, so it's not representative of winds at the surface, even so, it's still showing some stronger winds just above the surface.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2020
U. Arizona PhD program starting August 2022


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danielwAdministrator
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Reged: Wed
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Loc: Hattiesburg,MS (31.3N 89.3W)
Re: Gulf Low [Re: Bloodstar]
      #85485 - Sat May 23 2009 02:11 AM

TROPICAL WEATHER DISCUSSION...UPDATED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI MAY 22 2009

...UPDATED TO INCLUDE SPECIAL FEATURE SECTION...

...SPECIAL FEATURE...
A 1007 MB SURFACE LOW IS LOCATED NEAR 27N87W...OR ABOUT 175 NM
SOUTH OF PENSACOLA FLORIDA. A SURFACE TROUGH EXTENDS FROM THE
SURFACE LOW TO THE N YUCATAN PENINSULA NEAR 21N87W. LOW LEVEL
CONVERGENCE NEAR THE SURFACE LOW AND SURFACE TROUGH...AS WELL AS
UPPER LEVEL DIFFLUENCE E OF AN ASSOCIATED UPPER LOW NEAR
28N88W...ARE SUPPORTING NUMEROUS SHOWERS AND THUNDERSTORMS
ACROSS THE GULF N OF 23N E OF 89W....INCLUDING THE COASTAL
WATERS ACROSS THE N AND E GULF. THE TIGHT SURFACE PRESSURE
GRADIENT BETWEEN THE SURFACE LOW AND A SURFACE RIDGE OVER THE SE
CONUS IS SUPPORTING WIND SPEEDS OF 20 TO 25 KT AROUND THE LOW
ACROSS N PORTIONS OF THE MIDDLE GULF. THE SURFACE LOW IS
FORECAST TO MOVE NORTHWARD DURING THE NEXT DAY AND BE LOCATED
NEAR 30N89W AS A 1008 MB SURFACE LOW AT 23/1800 UTC. ADDITIONAL
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE...AND A TROPICAL
DEPRESSION COULD FORM BEFORE THE LOW MOVES INLAND OVER THE
NORTHERN GULF COAST ON SATURDAY. IF NECESSARY...AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT WILL INVESTIGATE THE LOW
TOMORROW. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
REGARDLESS OF DEVELOPMENT...HEAVY RAINS AND OCCASIONALLY GUSTY
WINDS ARE EXPECTED ALONG PORTIONS OF THE NORTHERN GULF COAST
TONIGHT AND SATURDAY. INTERESTS IN THIS AREA SHOULD MONITOR THE
PROGRESS OF THE SYSTEM.
bold emphasis added~danielw

Buoy Data
64 S DAUPHIN ISL 0445Z air73 sea74 VRB 29kt/gusts to 35kts 1005.5F 13 feet/ 8 seconds


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mbfly
Weather Guru


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Loc: Mobile, Alabama
Re: Gulf Low [Re: danielw]
      #85486 - Sat May 23 2009 08:49 AM

Good morning from a very soggy and windy Dauphin Island, Alabama! It has been raining heavily and steady since about 1 am . Some occasional thunder and some pretty strong wind gusts . I haven't braved going outside; just sittin' here looking out the window and watching it blow. At least I don't see Jim Cantore in my yard, so that's good!!

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JoshuaK2
Unregistered




Re: Gulf Low [Re: danielw]
      #85487 - Sat May 23 2009 11:55 AM

According to the latest AtlaOne Floater image on vis, infra, and watvap, it appears the low now has a closed off circulation, and should meet all qualifying needs to be classified as Trop Storm Ana, with 41 mph sustained winds being reported on the Alabama coastline. They shouldn't hold off on naming the thing just because it's over land now.

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Storm Hunter
Veteran Storm Chaser


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Loc: Panama City Beach, Fl.
Re: Gulf Low [Re: Unregistered User]
      #85488 - Sat May 23 2009 12:01 PM

it was close on becoming a TD... it appears that the low made landfall along the MS/Al border in the last hr. This morning a nice CDO fired off just south of Mobile. This low was pretty close to being a TD i think.

--------------------
www.Stormhunter7.com ***see my flight into Hurricane Ike ***
Wx Data: KFLPANAM23 / CW8771
2012== 23/10/9/5 sys/strms/hurr/majh



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danielwAdministrator
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Re: Gulf Low [Re: Unregistered User]
      #85489 - Sat May 23 2009 04:30 PM

The typical definition of a "closed low" is defined by Recon finding winds from at least 4 different directions nearly perpendicular to their flight path.
I.e. flying from the SW to the NE quadrant the wind would be from the NW in the SW Quad and shift to blowing from the SE in the NE Quadrant. These are rough estimates:
NW Quad = NE wind
SW Quad = NW wind
SE Quad = SW wind
NE Quad = SE wind

After flying the INVEST pattern they will make the determination of whether the Low has "closed off".
Typical patterns are the "Delta" pattern and the "Alpha" pattern. You can probably Google the NHOP and find a diagram of each pattern.
Recon flies a "leg" in one direction until the wind shifts. They then turn and fly until the next wind shift and repeat the pattern until they can " close it off"

You can use satellite imagery to some extent for closing a low. But radar and recon are much better.


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cieldumort
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Re: Gulf Low [Re: danielw]
      #85490 - Sat May 23 2009 05:16 PM

Quote:

The typical definition of a "closed low" is defined by Recon finding winds from at least 4 different directions nearly perpendicular to their flight path.




I'll take exception with the above description, as I think it is confusing and irrelevant in this situation, as recon never went into 90L. But while recon never flew 90L, the feature has pretty much been closed off for several days. Recon is helpful, if not sometimes critical, when a system is far out at sea. However, once a given feature approaches land, ground and sea-based anemometers can be clustered together in enough abundance, as to get a very clear picture of what is going on at the surface. That has been the case with 90L for at least the past 18 or so hours .

90L struggled to retain deep convection over a significant portion of its LLC. Around 2AM last night, NHC increased their three-tiered guidance to a "High" probability of an upgrade, but by the time 5AM came around, the deepest convective flare-up with an associated MCV was back to being displaced to the LLCs northeast, after what looks to have been a brief pairing-up earlier in the overnight hours.

The same sort of situation occurred once again as 90L made landfall, with a short blast of apparent mid and low level co-location. This, too, did not fare well for long.

The wind speed/pressure relationship at the surface , closed surface low, warmer core, and other determinants do argue that 90L was riding the line, and that post-season reanalysis may deem it reasonable to include it in the official count, but as with many things, some calls are just more subjective than others.



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danielwAdministrator
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Re: Gulf Low [Re: Unregistered User]
      #85492 - Mon May 25 2009 08:17 AM

Closed Low
A low pressure area with a distinct center of cyclonic circulation which can be completely encircled by one or more isobars or height contour lines. The term usually is used to distinguish a low pressure area aloft from a low-pressure trough. Closed lows aloft typically are partially or completely detached from the main westerly current, and thus move relatively slowly (see Cutoff Low).

http://forecast.weather.gov/glossary.php?word=CLOSED%20LOW

A closed low has several characteristics. Closed lows tend to be deep pressure systems with one or more height contours encircling them on the analysis charts at all levels in the troposphere. A closed low is occluded and vertically stacked. Because the low is closed, it does not generate much PVA and NVA. The vort max will be near the center of rotation. It is difficult to get a windflow that produces vorticity advection because the vorticity isopleths for the most part are parallel to the height contours. The weather associated with closed lows tends to be cloudy with showers in the vicinity of the low's center. Closed lows are often slow movers but can move quickly if they are embedded within the jet stream. Cloudy and rainy weather can persist with the slow movers. Thermal advection tends to be weak with closed lows since they are occluded. A special case of the closed low is the cut-off low. A cut-off low moves slowly since the jet stream winds aloft are displaced away from the low and are thus not able to move it along.

http://www.theweatherprediction.com/habyhints/200/

closed low—A low that may be completely encircled by an isobar or contour line.
(This means an isobar or contour line of any value, not necessarily restricted to those arbitrarily chosen for the analysis of the chart.) Strictly, all lows are closed. However, in weather-map analysis terminology, this designation is used commonly in two respects: 1) on surface charts, to distinguish a low from a trough, especially as a low develops within the trough; and 2) on upper-level charts, to accentuate the fact that the circulation is closed, especially at levels and over latitudes where such an occurrence is unusual. The definition of closed high is analogous.

http://amsglossary.allenpress.com/glossary/search?id=closed-low1

http://www.google.com/search?hl=en&q="closed+Low"&aq=f&oq=&aqi=g1

Most of the Closed Low definitions require a vertically stacked system. Learn something new everyday.


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