African disturbance 92L chugs west; California fires generating significant pollution

By: Dr. Jeff Masters , 1:40 PM GMT on July 02, 2008

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A strong tropical wave (Invest 92L) is a few hundred miles off the coast of Africa, south of the Cape Verde Islands. This low has the potential to develop into a tropical depression later this week as it moves westwards at 15-20 mph. The low is under about 5-10 knots of wind shear, which is favorable for development. Sea Surface Temperatures are about 28°C, which is about 2-3°C above average for this date, and well above the 26°C threshold for tropical storm formation. There is not much African dust or dry air near the storm, but the low appears much as it did yesterday, with little heavy thunderstorm activity. The low has plenty of spin, as seen on this morning's QuikSCAT pass (Figure 1). One 35 mph (30 knot) wind vector was noted to the southwest of the storm's center in the QuikSCAT data, so 92L is kicking up some strong winds. There aren't really any negatives for development, except for climatology--there has never been a tropical depression that has formed east of 34° longitude in the first half of July (see the first image I posted in my July Atlantic hurricane outlook). NHC is giving a medium (20-50% chance) that 92L will develop into a tropical depression by Friday afternoon. All the models are developing this system into a tropical depression by Saturday. Wind shear is forecast by the SHIPS model to remain below 10 knots for the next four days, and the waters will stay warm (above 26°C) for the next 2-3 days of 92L's life. None of the computer models foresee that 92L will become a threat to land, and it currently appears that the storm will recurve in the middle of the Atlantic Ocean, east of Bermuda.


Figure 1. QuikSCAT image of 92L from 3:12am EDT Wed July 2, 2008. Image credit: Paul Chang, NOAA/NESDIS/ORA.

California fires cause significant air pollution
It was a destructive April, May, and June for fires in California, with 889,000 acres burned (71% of this acreage since June 20!) This is over five times the acreage burned during the same months in 2007. Satellite-detected fires from April through June this year totaled over 13,000, compared to only 1,200 during the same time period in 2007. These fires have caused many cities in the state to exceed the EPA's daily standard of 35 µg/m3 for particulate air pollution (Figure 2).


Figure 2. Location of all satellite-detected fires from last year (left panel) and this year (right panel) for the months of April through June, along with the number of days when surface particle pollution exceeded EPA's daily standard in several major cities in California. Image credit: Environmental Protection Agency (EPA), National Aeronautics and Space Administration (NASA).

Air quality is improving this week in California due to the onset of west-southwesterly winds aloft that have enhanced mixing and dispersion in the atmosphere. The moist flow of air off the ocean has brought fog and raised humidity levels, aiding firefighting efforts. However, with fire season's peak still months away, expect many more fires and significant pollution episodes later this summer.

Jeff Masters

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657. WeatherfanPR
8:31 PM GMT on July 02, 2008
93L naaaahhh, by the Navy, are u kidding me!!!
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656. reedzone
8:29 PM GMT on July 02, 2008
Yep I updated my comment there.. sorry guys lol
93L it is! Notice this invest was that wave that some people thought would develop in the middle of the ocean. Big time shear from the TUTT should destroy it but weirder things have happened.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
655. CybrTeddy
8:30 PM GMT on July 02, 2008
We have 93L from that wave we were watching.
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654. Tazmanian
1:07 PM PDT on July 02, 2008
93L is on the navy site
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653. nash28
4:29 PM EDT on July 02, 2008
93L huh??? Can't wait for the model runs on this one:-)
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652. Drakoen
8:29 PM GMT on July 02, 2008
We have 93L near Barbados. The NHC must be interested.
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651. Drakoen
8:28 PM GMT on July 02, 2008
644. jphurricane2006 8:26 PM GMT on July 02, 2008
looks like we have Invest 93L now lol

lol ok ok Drak, your right, got my ZZZZs mixed up


lol it's not a problem. It's easy to get confused. The NHC time change confused me which is why I thought they were doing TWO with advisories lol. Too much confusion...
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650. atmoaggie
8:20 PM GMT on July 02, 2008
Afternoon Drak! I thought observations actually followed universal time, unlike model runs (as in with a weather observation/portion of data, 18z is actually 2 PM, subtract 4 hours, etc.). I know the models don't exactly use universal time (you don't see GFS running at 2 PM; 18z usually is released at around 6:00 PM, aka. 18:00). Are you trying to say that data collected at 18z (2:00 PM eastern) goes into the 18z model run (hence the name?). Just asking for a clarification for future reference. Sorry if I'm not making any sense.

Also, GFS goes through a data assimilation cycle for 3(?) hours. The model is held up to allow as many observations as possible to be incorporated. This is why NAM, for example, comes out much closer to the model start time. GFS is intentionally held back for the obs with the expectation that slight errors in the first 3 hours being corrected by real obs lends a better result in a 7 day or 10 day forecast.

Trying to find the documentation, but I haven't the time at the moment...
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649. WeatherfanPR
8:27 PM GMT on July 02, 2008
93L naaaahhh, by the Navy, are u kidding me!!!
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648. TerraNova
3:25 PM EST on July 02, 2008
639. reedzone 3:24 PM EST on July 02, 2008

The Navy site is a joke today.

However, unlike in the previous incident, the FTP data server the NCEP/NWS operates has been updated with 93L. Link

Coordinates = 13.4N, 59.7W
Winds = 20 kts
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647. nrtiwlnvragn
4:26 PM EDT on July 02, 2008
AL 93 2008070218 BEST 0 134N 597W 20 0 DB
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645. cchsweatherman
8:24 PM GMT on July 02, 2008
Good afternoon all! Looks like the NAVY may be declaring another invest. NAVY site has Invest 93L. By the way, reedzone, give them sometime. They have to get a floater on the system and they need to process the information. It looks like they may be declaring an invest for the feature moving through the Central Lesser Antilles.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
643. nrtiwlnvragn
4:24 PM EDT on July 02, 2008
invest_al932008.invest
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641. Drakoen
8:24 PM GMT on July 02, 2008
637. jphurricane2006 8:20 PM GMT on July 02, 2008
actually the NHC issues advisories at 5 and 11

they issue the TWO and TWD at 2 and 8


How could they use the 00z runs for the 11:00pm advisory if the 00Z runs haven't even come out yet?
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640. stoormfury
8:15 PM GMT on July 02, 2008
TERRA NOVA
this wave had rotation since yesteday when it was about 600 mile seast of barbados. but because of the influence of the tutt it was not able to organise. if it had not bee for the tutt the system would interesting andmore emphasis would have place in this area than off the coast of Africa
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639. reedzone
8:21 PM GMT on July 02, 2008
Hmm thought this was a trick but it isn't. The feature that Tampaspin and others have been pointing to has been tagged 93L. Shear is too hostile for things to get going but interesting to say.....

Link
Member Since: July 1, 2008 Posts: 13 Comments: 7437
638. TerraNova
3:20 PM EST on July 02, 2008
627. primez 3:10 PM EST on July 02, 2008
Hey, I think I spotted a tornado today just south of East Islip over the Great South Bay on Long Island. How do I report it?


Call your local national weather service office (the National Weather Service in Upton, NY).
Website
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636. OUSHAWN
8:14 PM GMT on July 02, 2008
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
246 PM CDT WED JUL 2 2008

.DISCUSSION...
SCATTERED SHRA/TSRA AFFECTING THE SRN HALF OF THE CWA THIS AFTN
AND CONTINUING TO WORK ITS WAY SLOWLY NORTHWARD. WILL MAINTAIN
20-30 POPS FOR MOST AREAS FOR EARLY EVENING ACTIVITY. LITTLE
CHANGE IS EXPECTED FOR THE NEXT COUPLE OF DAYS. A VERY WEAK UPPER
LOW WILL REMAIN OVER SOUTH TX...AND KEEP CONDITIONS FAVORABLE FOR
SCATTERED DIURNAL CONVECTIVE DEVELOPMENT. GPSMET DATA CONTINUES TO
SHOW A RATHER SHARP MOISTURE GRADIENT ACROSS THE AREA...WITH PWS
RANGING FROM AROUND AN INCH OVER THE NE ZONES TO JUST OVER 2
INCHES IN THE MATAGORDA BAY AREA. EACH DAY WILL SEE SCATTERED
SHRA/TSRA DEVELOP OVER THE OFFSHORE WATERS AFTER MIDNIGHT...THEN
WORK ITS WAY ONSHORE DURING THE LATE NIGHT/EARLY MORNING HOURS.
ACTIVITY WILL SPREAD INLAND DURING THE DAY...WITH THE SEABREEZE
SERVING AS A FOCUS FOR DEVELOPMENT. WILL MAINTAIN HIGHEST POPS (50
PCT) FOR AREAS SOUTH/SOUTHWEST OF HOUSTON WHERE DEEPEST MOISTURE
WILL REMAIN IN PLACE...TAPERING DOWN TO 20S OVER THE FAR NORTH.
GFS FORECASTS THE RIDGING TO STRENGTHEN A BIT OVER THE WEEKEND
ALONG WITH A SLIGHT LOWERING OF MOISTURE LEVELS. HOWEVER...ECMWF
KEEPS THE DEEPER MOISTURE IN PLACE OVER SOUTH TX. MODEL SOUNDINGS
SHOW CONTINUATION OF NO CAPPING ALONG WITH CONVECTIVE TEMPS IN THE
UPPER 80S SATURDAY/SUNDAY. WILL SCATTERED DEVELOPMENT EACH DAY THIS
WEEKEND...BUT COVERAGE SHOULD BE LESS THAN ON THURSDAY/FRIDAY.
LATEST GFS SHOWS A SURGE OF DEEPER MOISTURE ORIGINATING OVER THE
NW CARIBBEAN AND PUSHING INTO SE TX BEGINNING ON MONDAY ALONG
WITH THE DEVELOPMENT OF ANOTHER INVERTED TROUGH AT 500 MB. THE
OTHER MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT WITH THIS SCENARIO.
EXPECT AN INCREASE IN CONVECTIVE COVERAGE AGAIN BY TUESDAY/WEDNESDAY
OF NEXT WEEK...AND HAVE BUMPED POPS UPWARD IN FORECAST.


Again we will have plenty of mositure coming in but another inverted trough will keep shear high and stop anything from developing.
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635. nrtiwlnvragn
4:15 PM EDT on July 02, 2008
623. jphurricane2006

NHC forecast cycle

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634. TerraNova
3:13 PM EST on July 02, 2008
622. Drakoen 3:05 PM EST on July 02, 2008

Thanks Drak/JP.
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633. Drakoen
8:10 PM GMT on July 02, 2008
You guys are making it more difficult than it is. When you are looking at the 18z run at 00hr you are looking at the atmoshpere at 18z of that day. The NHC issues advisories at 2:00pm and 8:00pm as the 12z runs go with the 2:00pm and the 12z runs with the 8:00pm. The model output come out later after the intial data. You don't see the 00Z runs being used at 8:00pm since they come out later than that.
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632. stoormfury
7:49 PM GMT on July 02, 2008
well it has been a seesaw as to whether it is 92L or TD2 some sites had it as a TD and was withdrawn, bottom line we are still with 92Lat this hour.
the system is large with its LLC more to the east of the convection. it is slowly organising and it will take sometime in doing so,. The loger it takes to get it's act together more west it goes and closer to tat magic 40deg line when it should be making that turn. i am in total disagreement with most of the models. this system which is moving at 13 mphwill still be a shallow system wich will move with the low level flow well pass 40deglong. although wind shear is about 10-15 mph the ssinthe CATL is about 27degc which is not that too favourable for rapid intesification. there is a ares of dry air ahead of the system betwen 40-50deg long which might be an inhibitor, but the system is so large that it can moisten that area aheadof it. wind shear will be low in the CATL for the next five days and there indications that the shear inthe CARIB is forecast to weaken
my take on this system is that it will slowly develop into astrong tropical storm for the most and it will track west or even south of west for a time before getting close to the islands time is the deciding factor and i believe most of the models are basing their tracks on what cimatolgy has done in the past and forget alot of new things are now happenning in this era or tropical storm activity.
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631. TheWeatherMan504
8:12 PM GMT on July 02, 2008
again the NHC will color it red before they upgrade it to a TD.
Member Since: May 18, 2008 Posts: 2 Comments: 1042
630. TerraNova
3:05 PM EST on July 02, 2008
The feature approaching the islands is visible on radar out of the Windwards. If you loop it you can see a bit of surface rotation. Quickscat missed the area. It's moving into a region of unfavorable wind shear (with the TUTT analyzed at the 500mb level across the Northwestern Carribean).

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628. FLWeatherFreak91
4:09 PM EDT on July 02, 2008
Just to let you guys know... the US now has a bear market.... Pretty important piece of info. for any of you following the horrible stock situation. Back to the wx now.
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627. primez
8:07 PM GMT on July 02, 2008
Hey, I think I spotted a tornado today just south of East Islip over the Great South Bay on Long Island. How do I report it?
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626. CybrTeddy
8:06 PM GMT on July 02, 2008
Aye Drak, but what about 11 PM?
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622. Drakoen
8:04 PM GMT on July 02, 2008
620. TerraNova 8:03 PM GMT on July 02, 2008
609. Drakoen 2:50 PM EST on July 02, 2008
The 18z runs typically go with the 8:00pm advisories as the 12z runs go with the 2:00pm advisories since the model outputs are 5-6 hours later. It won't become a tropical depression today.

Afternoon Drak! I thought observations actually followed universal time, unlike model runs (as in with a weather observation/portion of data, 18z is actually 2 PM, subtract 4 hours, etc.). I know the models don't exactly use universal time (you don't see GFS running at 2 PM; 18z usually is released at around 6:00 PM, aka. 18:00). Are you trying to say that data collected at 18z (2:00 PM eastern) goes into the 18z model run (hence the name?). Just asking for a clarification for future reference. Sorry if I'm not making any sense.


Yes that's what I am saying.
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621. weathermanwannabe
4:01 PM EDT on July 02, 2008
616. IKE 4:00 PM EDT on July 02, 2008 Gotcha; I clicked on Tally on the map (where I am at for the next two days) instead of Defuniak...Well, Tally is currently at 30% for tommorow but I think that will go up in the Big Bend region as well to 40 or 50%...
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620. TerraNova
2:58 PM EST on July 02, 2008
609. Drakoen 2:50 PM EST on July 02, 2008
The 18z runs typically go with the 8:00pm advisories as the 12z runs go with the 2:00pm advisories since the model outputs are 5-6 hours later. It won't become a tropical depression today.


Afternoon Drak! I thought observations actually followed universal time, unlike model runs (as in with a weather observation/portion of data, 18z is actually 2 PM, subtract 4 hours, etc.). I know the models don't exactly use universal time (you don't see GFS running at 2 PM; 18z usually is released at around 6:00 PM, aka. 18:00). Are you trying to say that data collected at 18z (2:00 PM eastern) goes into the 18z model run (hence the name?). Just asking for a clarification for future reference. Sorry if I'm not making any sense.
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618. Drakoen
8:00 PM GMT on July 02, 2008
613. jphurricane2006 7:57 PM GMT on July 02, 2008
that to me doesnt make much sense drak

why wouldnt the 18Z go with the 2pm, since 18Z IS 2pm


The models take a while to interpret the data. You'll notice the 18z runs don't come out at 18Z.
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617. ClearH2OFla
3:56 PM EDT on July 02, 2008
StormW thank you for your great report as always.
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616. IKE
2:58 PM CDT on July 02, 2008
602. weathermanwannabe 2:38 PM CDT on July 02, 2008
593. IKE 3:25 PM EDT on July 02, 2008

Hey Ike; the GOM is a good example right now of the less than exact timing of Mother Nature; our "offical" rain pops in North Florida, from Tally NNW, are still currently in the 20% range for the next several days, but, that "front" in the Northern Gulf has stalled out already, and, starting to lift up already as a warm front; betcha they increase the rain pops again by this evening......If shear were lower in the Gulf right now, it would also be a different story perhaps.....


I've got a 40% chance tomorrow and Friday...50% on Saturday.....
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614. OUSHAWN
7:54 PM GMT on July 02, 2008
Something has to give sooner or later in the GOM. There is so much energy out there and the only thing keeing us all from turning our attention there is the shear...of course that's a very big and potent reason. The thing is I haven't seen anything pointing to the shear relaxing in the gulf anytime soon. I still have a weird feeling all that moisture will not go away quietly.
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612. reedzone
7:53 PM GMT on July 02, 2008
Great blog analysis StormW, worded perfectly.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
610. Nolehead
7:48 PM GMT on July 02, 2008
jp, yep you nailed it with accuweather...DIRTY LAUNDRY!!
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609. Drakoen
7:48 PM GMT on July 02, 2008
606. jphurricane2006 7:47 PM GMT on July 02, 2008
of course they do lol, anything to keep it further south and more of a threat to the US and that is usually what Accuweather is thinking

also um Drak, 18Z is 2pm, just because that said AL92L and not TD, doesnt meant it cant become one before the end of the night


The 18z runs typically go with the 8:00pm advisories as the 12z runs go with the 2:00pm advisories since the model outputs are 5-6 hours later. It won't become a tropical depression today.
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608. TheWeatherMan504
7:46 PM GMT on July 02, 2008
603. jphurricane2006 7:41 PM GMT on July 02, 2008
kman I have been saying that for 2 days lol

larger circulations take longer to organize, we all know that


A good example was Hurricane Helene in 2006. had a large circulation and it took a while to get well organized but when it did it became a 125 mph monster i think at one point it had TS force wind extening 690 miles from the center.
Member Since: May 18, 2008 Posts: 2 Comments: 1042

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