Potentially dangerous 92L steadily developing; Igor nears hurricane strength
A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies to the north and west of 92L, and this dry air could interfere with development at times over the next few days.
Figure 1. Morning satellite image of 92L.
Track forecast for 92L
The disturbance is moving west-northwest at 11 mph, and steering currents favor a continuation of this motion for the next three days. Model support for development is scattered. The GFS and NOGAPS models do not develop 92L. The GFDL and ECMWF models predict development, with a track taking 92L into Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)
Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. Water temperatures are certainly warm enough to support development. The main detriment to intensification is likely to be dry air, and 92L could wrap in some of the dry air to its northwest at times, slowing down development. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.
Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.
Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-northwest in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic on Tuesday and Wednesday. This should allow Igor to pass several hundred miles to the northeast of the Lesser Antilles. In the longer range, Igor may be a threat to Bermuda, and has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 10% for Bermuda and 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.
Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.
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This may be my only post today; I'll have a new post Sunday morning.
Jeff Masters
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Home Depot too. At least the ones in Florida you can buy them.
.LONG TERM...7 PM MONDAY THROUGH SATURDAY...A BROAD AND ELONGATED
MID LEVEL RIDGE WILL REMAIN ANCHORED OVER DEEP SOUTH TX FOR MUCH
OF THIS UPCOMING WEEK MAINTAINING GENERALLY ABOVE NORMAL TEMPS.
THE OVERALL MOISTURE VALUES WILL BE FAIRLY LACKING FOR MUCH OF THIS
UPCOMING WEEK WHICH WILL LIKELY LIMIT THE CONV POTENTIAL. HOWEVER
LOOKING EAST INTO THE THE EASTERN CARIB SEA NHC CONTINUES TO MONITOR
A BROAD AREA OF LOW PRESSURE FOR POSSIBLE DEVELOPMENT. THE LATEST
ECMWF AND GFS INDICATE THAT THIS FEATURE WILL CONTINUE MOVING WEST
TOWARDS THE YUCATAN PENINSULA EVENTUALLY MOVING INTO THE SW GULF
OF MEX ON THURS. THE ECMWF SHOWS STRONGER DEVELOPMENT OF THIS
FEATURE VERSUS THE GFS WHICH SHOWS A BROADER LESS DEVELOPED SURFACE
LOW. REGARDLESS OF THE LEVEL OF DEVELOPMENT OF THIS FEATURE EXPECT
SOME DEEPER TROPICAL MOISTURE TO START ADVECTING ACROSS DEEP SOUTH
TX ON FRI AND SAT RESULTING IN SOME BETTER CONV POTENTIAL LATE IN
THE EXTENDED RANGE PERIOD. RUN TO RUN CONSISTENCY WITH THE LATEST
GFS MEX MOS TEMPS AND POPS IS PRETTY GOOD AND MODEL TO MODEL
COMPARISON BETWEEN THE GFS AND ECMWF ALSO SHOWS DECENT CONSISTENCY.
WILL LEAN CLOSE TO THE GFS MEX MOS TEMPS AND POPS IN THE 3 TO 7
DAY RANGE. PLEASE REFER TO THE LATEST OUTLOOK AND FORECASTS FROM
NHC CONCERNING THE PROGRESS OF THIS SYSTEM IN THE CARIB SEA.
MARINE...TODAY THROUGH 7 PM MONDAY...AT 1 AM BUOY 20 REPORTED EAST
SOUTHEAST WINDS AT 12 KNOTS WITH GUSTS TO 14 KNOTS AND SEAS AT 2
FEET WITH A 5 SECOND PERIOD. THE WINDS WILL CONTINUE LIGHT TO
MODERATE FROM THE SOUTHEAST TO EAST THE NEXT FEW DAYS. THE SEAS WILL
REMAIN LOW THROUGH MONDAY. THE EXTENDED MARINE FORECAST PERIOD
CONDITIONS WILL DEPEND GREATLY ON THE OVER MOVEMENT AND DEVELOPMENT
OF THE BROAD SURFACE LOW IN THE EASTERN CARIB SEA. A STRONGER MORE
NORTHWARD TRACKING SYSTEM WILL RESULT IN HIGHER WINDS AND SEAS
TOWARDS NEXT WEEKEND WHILE A WEAKER MORE SOUTHWARD SYSTEM WILL
HAVE MUCH LESS OF AN IMPACT ON THE LOWER TX MARINE CONDITIONS. FOR
NOW WILL GO WITH A MORE CONSERVATIVE WIND AND SWELL FORECAST FOR
THE LATER MARINE PERIODS. AT THIS TIME NO SCA CONDITIONS EXPECTED.
&&
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Yea, those things are great for more than just tropical weather. I have one for when the fronts start coming through. Sometimes they have some nasty weather as you know.
If I am understanding this correctly pressure supports a TD but winds only 30mph. Pressure drop should be a sign of organization happening. Correct ?
92LINVEST.25kts-1007mb-157N-707W
Link
92L looking better ATM.
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