Disturbance 90L brings heavy rain to Puerto Rico; major pollution in California
A surface low pressure system (90L) just east of Puerto Rico is moving to the west at 5-10 mph. This low is entangled with an upper-level low pressure system that is bringing about 30 knots of wind shear, so no development is likely today. Long range radar out of Puerto Rico shows bands of heavy rain hitting the islands and surrounding waters, but these bands are not well-organized. Satellite loops show most of the heavy thunderstorm activity is to the northeast of the low's center of circulation, and high wind shear is keeping this thunderstorm activity disorganized. This morning's QuikSCAT pass missed 90L.
Figure 1. Latest satellite image of 90L. Image credit: NOAA.
The surface low is expected to separate from the upper level low tonight and move west-southwest or southwest across Puerto Rico, bringing the threat of heavy rain and flooding to the island. Recent rains have left large areas of interior and western Puerto Rico at or near saturation, and mudslides were reported yesterday in Utuado. Flooding problems and mudslides are likely across Puerto Rico and the Virgin Islands Friday and Saturday, and this is shaping up to be the most significant rain event of the fall wet season thus far for Puerto Rico.
On Friday and Saturday, 90L will move westward along or just south of Hispaniola, bringing heavy rain, flash flooding, and possible mudslides to that island. The ECMWF and NOGAPS models predict that wind shear will drop to 10-20 knots by Friday night, which may allow some slow development of the disturbance if the center remains over water. The GFS model keeps wind shear 20-30 knots through the period, and does not develop 90L. By Saturday, the storm will near Jamaica, and the ECMWF and NOGAPS models predict a tropical depression will form by Sunday. Steering currents grow weak on Monday, and the storm could stall out for many days in the Western Caribbean, in an area of low wind shear and high heat content waters. This may allow the system to intensify into a hurricane. The eventual fate of this system is highly uncertain, since steering currents will be so weak. Those of you planning to travel to the Western Caribbean next week should keep a close watch on this system. NHC has not scheduled any flights into 90L yet.
It is possible that wind shear and passage over the islands will sufficiently disrupt this disturbance so that it does not develop. However, surface pressures have fallen 2-3 mb over most of the Western Caribbean the past two days, and there is a good chance that a new area of disturbed weather will develop. One such disturbance formed yesterday south of Haiti, but has since dissipated. Unsettled rainy weather can be expected to affect much of the Western Caribbean over the coming week.
California's fires
Surface maps show that the high pressure system that brought this week's strong Santa Ana winds to Southern California has now moved east and is over Colorado. The Santa Ana winds have ceased over California, and only light winds with afternoon sea breezes are expected today and for the next seven days. No precipitation is expected for at least the next week. The combination of light winds and lack of rain will make for a serious air pollution hazard in the region, until the fires are extinguished. There is still plenty of smoke over the ocean waters (Figure 2) that will get blown back over land by afternoon sea breezes over the next week.
Figure 2. Visible satellite image at 1:45 pm PDT Wednesday October 24, showing a huge area of smoke over the Pacific Ocean. Some of this smoke is being blown northward (top of image), and is expected to move over northern California and northern Nevada over next two days. This northward-moving smoke is being lifted by the flow around an approaching low pressure system, and is not expected to affect air quality near the surface. However, the smoke just offshore San Diego and Los Angeles will remain near the surface, and some of it will be pushed back over land by afternoon sea breezes. Image credit: NASA.
Jeff Masters
with all the smoke in the air the moon last night was looking like holloween.
Reader Comments
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Yet another season which proves it's not the number that form, it's the number that make landfall . ..
Cool links! Sure does look like a tropical system on sat and radar! Care to comment StormW? Dr. Masters? Would like to hear your takes on this one!
This looks like the one to watch on the short term.
There is building convection, closing circulation, low shear and it looks like the convection north of Panama is sending a jet of energy that way.
Hmmm .. . .
West carrib system lookin more impressive with each new pic. Gonna be interesting to see how they play out with each other. Combine maybe? Perhaps do the "Fuji" dance in the Carrib? I do love watching these things, I just don't want 'em to hurt anyone.
SMALL UPPER LOW REMAINS IN THE NW CARIBBEAN NEAR 18N82W COVERING
THE AREA FROM 14N-21N BETWEEN 80W-86W.
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1015 AM EDT FRI 26 OCTOBER 2007
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 27/1100Z TO 28/1100Z OCTOBER 2007
TCPOD NUMBER.....07-154
I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK: POSSIBLE LOW LEVEL
INVEST NEAR 16.5N 75.0W AT 28/1800Z.
Conditions at 42056 as of
(9:50 am EDT)
1350 GMT on 10/26/2007: Unit of Measure: English Metric Time Zone: Station Local
Wind Direction (WDIR): N ( 360 deg true )
Wind Speed (WSPD): 10.0 m/s
Wind Gust (GST): 12.0 m/s
Wave Height (WVHT): 1.9 m
Dominant Wave Period (DPD): 6 sec
Average Period (APD): 5.7 sec
Mean Wave Direction (MWD): NNE ( 21 deg true )
Atmospheric Pressure (PRES): 1012.7 mb
Pressure Tendency (PTDY): +1.5 mb ( Rising )
Link
Most interesting potential w/ the WCar ULL right now is whether it will stick around long enough to spin down. Well, it has some rainmaking potential too.
National Weather Service
THE AREA OF LOW PRES
NEAR PUERTO RICO IS EXPECTED TO CONTINUE W AND REACH THE W
CARIBBEAN SUN THROUGH TUE BUT RIGHT NOW THERE IS GREAT
UNCERTAINTY TO ANY POTENTIAL DEVELOPMENT. THERE IS A CHANCE THAT
WINDS COULD INCREASE AROUND THE LOW ITSELF...BUT THIS EVENT
APPEARS TO HAVE A GREATER CHANCE TO BE A GRADIENT WIND EVENT
WITH THE STRONGEST WINDS WELL TO THE NW OVER THE GULF OF MEXICO.
Looks like it is moving south now.
.LONG TERM [MONDAY THROUGH THURSDAY]...LOOKING MORE LIKE OCTOBER IN
THE LONG TERM AS WE REMAIN DRY...WITH TEMPERATURES STARTING OUT
RIGHT AROUND NORMAL AND THEN SLOWLY CLIMBING ABOVE NORMAL MID WEEK.
FORECAST AREA WILL REMAIN BETWEEN SURFACE HIGH PRESSURE ACROSS THE
SOUTHERN STATES...AND LOW PRESSURE ACROSS THE SOUTHERN GULF OF
MEXICO...SO IT COULD BE BREEZY AT TIMES MONDAY AND TUESDAY...AGAIN
ESPECIALLY ALONG THE COAST. /22
&&
.MARINE...HIGH PRESSURE WILL SETTLE OVER THE NORTH CENTRAL GULF
THROUGH TODAY THEN BECOME REINFORCED FROM THE NORTHWEST TONIGHT AND
CONTINUE THROUGH MONDAY MORNING. AS A RESULT A LIGHT NORTHERLY WIND
FLOW CAN BE EXPECTED THIS EVENING THEN STEADILY BUILDING FROM THE
NORTH LATE TONIGHT CONTINUING THROUGH EARLY NEXT WEEK. WITH THIS...A
SMALL CRAFT ADVISORY WILL LIKELY BE REQUIRED OVER THE WEEKEND. GUSTS
TO GALE FORCE COULD BE POSSIBLE ALSO FOR THE OFFSHORE WATERS SUNDAY
NIGHT. WINDS SHIFT MOSTLY NORTHEAST BY TUESDAY IN RESPONSE TO HIGH
PRESSURE TO THE NORTH SHIFTING EAST AND A DEVELOPING AREA OF LOW
PRESSURE MOVING INTO THE LOWER GULF. RAIN CHANCES INCREASE OVER THE
MARINE AREA SUN THROUGH MIDWEEK AS THE AREA OF LOW PRESSURE BEGINS
TO SLOWLY EMERGE OVER THE SE GULF. /32
I still think that ULL would have to hang around for a while for us to see any tropical / surface development, though.
1008mb surface low has formed in conjunction with the ULL due west of the caymans, about 100 miles
Link please
tropical system over southern france!?
Visible Satellite of Europe
http://www.sat24.com/images.php?country=eu&type=last&303070
Regional Radar Loop of Europe
http://www.meteox.co.uk/h.aspx?r=&jaar=-3&soort=loop1uur
Sub-tropical, not common for this area of the MED this time of year, but certainly not rare; there were two in the MED last week, one south of Italy and the other in nearly the exact location of the one your pointing out; that one produced TS winds on the coast as it EXITED the mainland
Interesting, utila, but not necessarily surprising. Conditions there are about the best overall for development right now. That's why we've been saying if 90L hangs on to get into that "box" it's more likely to develop.
I still think that ULL would have to hang around for a while for us to see any tropical / surface development, though.
Thanks. It looks like this area is building up and there will be some interaction with the convection N of Panama. There is not much movement.
I agree with you regarding the BOX. Location, location, location.
http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8sht.html
(Sorry, my browser still won't do the link thingy. Please cut and paste.)
This low pressure will continue to move slowly west or west northwest over the next few days, bringing more showers and thunderstorms into the Caribbean. While upper-level winds are currently inhibiting any tropical cyclone formation, they will lessen as the low moves west, and therefore it bears watching for some possible slow development.
This is per The Weather Channel update at 5 this morning. Maybe they need to pay attention to the NHC because they are stating it is moving WSW. I know I don't have a meterology degree but I can even tell its moving WSW not WNW or West.
1008mb surface low has formed in conjunction with the ULL due west of the caymans, about 100 miles
When was this?
The low center is now near 17N 68W and the ball of heavy convection that was close to it last night is now completely gone.
It appears to be moving at a fairly good clip and this combined with shear is obviously contributing to its inability to generate any convection over or near the COC
It will need to slow, or shear will need to relax significantly ( or both ! ) if it is to have a real shot at becoming a TD IMO
Naked swirls can only last so long even with a low surface pressure before they open up into a wave
OMG.....OMG....THE BOXES
See? I told you...LOL
Couple of things to note from an electrics standpoint.
1. Note the onshore flow over where the fires are in SoCal. There's no Pac high coupling anything right now. No cold core coupling, either in the Pacific.
2. North of system look at high pressure. That's the wheel that will right turn any storm toward the US. This looks to be a beautiful coupled large scale region with fair weather and then in large circle convection all around it and all associated with strikes largely in south america.
3. Space weather is favorable w/ solar winds dropping below 500 km/sec:
http://www.sec.noaa.gov/ace/Mag_swe_24h.gif
4. QBO neg thus favorable for Atlantic formation.
5. Bloom activity now showing up in east Florda, previously along Bahamas and then, of course, south of there near Caracus Venezuela. The latter is probably more important, becuase most of the displacement currents powering 16 come from South America with that bloom area in the conductive pathway to the storm.
6. Consider La Nina connotation. Remember that the colder SSTs are for each degF there is a one percent drop in conductivity. What that means is that with these heavy diurnal pulses of lightning, between about 22 UT and about 3 UT, there is no place for that current to couple out west to the tropics. So that leaves the bulk of the cloud microphysics affects to take place elsewhere. We also have seen very little in the EPAC, the Pacific high that brought the Santa Ana is done and the cold cores in teh Pacific are done. There is nothing left but the Atlantic. Also keep in mind that the source of the displacement current will be less global--as less leaking also means less from other parts of the world coming to the coupled region, excluding what comes off of the African coast--that's another current pathway. So, as pretty much expected, this upgrade to a tropical depresssion comes during peak strikes. Don't be surprised, OTOH, to see it weaken as peak strike period ends.
7. I'll throw this in but we have a full moon and that seems to have correlated with Atlantic tropical storm activity this year. Not exactly sure what that means to this point.
http://www.methanemike.com
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