Srain

An interesting and potentially historic week ahead, tropically speaking for Hawaii. The last 12 suite of operational Global guidance suggest a rather strong TS Iselle will make its approach late Thursday into Friday from an Easterly direction. While the intensity remains very uncertain, there is warmer water E of Hawaii that may keep Iselle a bit stronger and possibly allow for a steady state as it approaches. The global guidance is suggesting Julio may fair a bit better and provide for a stronger cyclone as it approaches Hawaii on Sunday from a ESE direction, slightly S of the Iselle expected track and receive the benefit of enhanced moisture throughout the column in the wake of Iselle. The intensity guidance is split between a stronger 100 kt cyclone to a near 70 kt cyclone. The NHS is taking a reasonable conservative approach and with additional data arriving particularly from the G-IV tasked missions this week, we should see some changes in what may well be two cyclones passing very near or over the Hawaiian Islands with a matter of 3-4 days later this week into the upcoming weekend.

Major Winter Storm Febraury 8th -12th Thoughts: There continues to be a lot of uncertainty regarding the upcoming weekend and early next week as a long wave trough develops across the West. What we do know is a deep trough with a Potent Winter Storm will develop across the Great Basin and Intermountain West. In fact the HPC has so little confidence in the guidance, they have tasked a NOAA G-IV Winter RECON mission to fly the Pacific and sample the environment. Across the W, wintry conditions appear likely beginning Thursday as a potent storm system moves inland along the Pacific NW/British Columbia area and drop SSE and closes off near the California/Arizona/Mexico border with temps aloft expect to drop to the -30+ range as the cold core 500mb upper low forms. Due to lack of guidance continuity, the implications of how that storm ejects from the Great Basin is the main concern for the late weekend/early next week time frame. The HPC is mentioning this morning the similarity to a Spring like storm we tend to see in late March/early April meaning a wide spread severe weather event in the warm sector that extends from Eastern New Mexico/Texas/Oklahoma and portions of Kansas with wintry weather in the cold sector N of the Polar jet. The fly in the ointment is will there be phasing with yet another short wave riding the Polar jet across Southern Canada into the Northern Plains with the active southern jet stream storm which would tend to pull down cold air from the N and collide with warm moist Gulf air to the S. The Sub tropical jet appears to come into play as well as tropical forcing increasing across the Eastern Pacific energizing the Great Basis storm We are in a somewhat zonal split flow pattern where cold air has retreated N with an active northern stream and a secondary active southern stream where this storm system will organize later this week. All in all a very active pattern is ahead and for much of the CONUS as rain chances are returning this week to the Gulf Coastal Regions with an active southern stream and the Pacific NW as the Gulf of Alaska storm moves inland. The finer details regarding the Medium Range forecast should become bit clearer later in the week as data from WSR scheduled to begin 06/0000 regarding next weekend into early next week and the sensible weather we can expect. EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD 142 AM EST MON FEB 04 2013 VALID 12Z THU FEB 07 2013 - 12Z MON FEB 11 2013 DAYS 3-5... OVERNIGHT SURFACE GRAPHICS WERE ABLE TO MAINTAIN VERY GOOD CONTINUITY WITH A BLEND OF THE 3/12Z ECMWF AND ITS ENSEMBLE MEANS...ALONG WITH SOME OF THE 3/12Z UKMET. THE 4/00Z GFS GETS TO BE A FAST OUTLIER BY FRIDAY (DAY 4) WITH THE 'CLIPPER' RACING THROUGH THE OHIO VALLEY AND OFFSHORE INTO THE WESTERN ATLANTIC. THE 4/00Z UKMET-ECMWF WERE BETTER FITS TO THE MANUAL GRAPHICS AND THE PATTERN EVOLVING VS THE 4/00Z GFS-CANADIAN. WITH MUCH OF THE 4/00Z GUIDANCE IN...THERE IS PLENTY OF SUPPORT FOR COMPLEX COASTAL WAVE DEVELOPMENT AND SECONDARY INTENSIFICATION OF A SURFACE WAVE OFF THE IMMEDIATE COASTLINE (IN THE OUTER BANKS AND BLOCK ISLAND CORRIDOR) ON FRIDAY AFTERNOON/EVENING. THE MANUAL GRAPHICS CERTAINLY ARE NOT PERFECT PROGS...BUT I DID DRAW A SFC LOW TRACK (AND INTERMEDIATE POSITION)...PASSING OVER THE BENCHMARK BEFORE 9/00Z IN THE NEIGHBORHOOD OF 1004 MB AND DEEPENING TO 996MB EAST OF HALIFAX NS AROUND 9/12Z. THIS INTERMEDIATE PROG (VALID 9/00Z) IS CLOSER TO THE 4/00Z UKMET FOR DEPTH BUT HONORS THE TRACK OF THE 3/12Z ECMWF PACKAGE AND THE 4/00Z OPERATIONAL ECMWF. THE DEEPEST SFC PRESSURE AT 983 MB AS IT ENTERS THE SW GULF OF MAINE AFTER 9/00Z MIGHT BE OVERDONE...BUT THE TRENDS FROM YESTERDAY SUPPORT ONE LAST CYCLONE (CLIPPER) BEFORE THE ARCTIC AIRMASS RETREATS AWAY FROM THE EASTERN SEABOARD. DAYS 6-7... THE MEDIUM RANGE GUIDANCE HAD A GOOD HANDLE ON THE WEST COAST TROUGH AND MODERATELY-INTENSE CYCLONE EXITING THE SOUTH CENTRAL ROCKIES NEXT WEEKEND. AS ENVISIONED A COUPLE OF DAYS AGO...THE SYSTEM HAS SLOWED A TAD...BUT WILL SWEEP SOME PACIFIC ENERGY AND A WEAK SURFACE REFLECTION ACROSS THE NORTHERN ROCKIES AND THROUGH THE NORTH DAKOTA PLAINS BEFORE THIS NORTHERN END OF THE FRONT WEAKENS IN NORTHERN MINNESOTA AND WESTERN ONTARIO. THE MANUAL H5 TRACK FOR THIS SYSTEM DOWNSTREAM OF THE FRONT RANGE WAS DRAWN WITH A 'BEST FIT' LINE FROM PUEBLO CO TO MINNEAPOLIS MN GIVEN THE VARIABILITY IN TRACK AND SPEED. THE GFS IS THE MAIN REASON THERE IS 'INTRODUCED UNCERTAINTY'. I CAN NOT REALLY FOLLOW ITS RUN TO RUN ADJUSTMENTS...BUT THE H5 TRACK IS NOT FAR FROM THE TRACK ENVISIONED FOR NEXT WEEKEND. THE WESTERN GOMEX SHOULD BE WIDE OPEN AHEAD OF THIS CYCLONE. THE ONE TREND THAT WILL NEED TO BEAR WATCHING...IS...HOW THE INTENSE WEST-NORTHWESTERLY FLOW SURGING THROUGH THE 4 CORNERS AND SOUTHERN DIVIDE REGION ON SATURDAY TRANSLATES DOWNSTREAM OVER THE SOUTHERN HIGH PLAINS OF ERN NM/WRN TX LATER ON SATURDAY AFTERNOON AND EVENING. IN SOME RESPECTS...THIS PACIFIC SYSTEM LOOKS MORE LIKE A LATE MARCH/EARLY APRIL SYSTEM... WITH A WELL-DEFINED DRY SLOT AND WARM ADVECTION WORKING NNEWD ACROSS THE TX PANHANDLE AND SOUTH CENTRAL KANSAS...AND INTO THE H5 CYCLONE'S CIRCULATION. THIS MAY END UP SHIFTING THE GULF MOISTURE EAST AND SOUTH OF THE COLD FRONT INITIALLY...AND BRIEFLY LIMIT THE PHASING OF THE LOW-LEVEL MOISTURE LIFTING ATOP THE COLD SECTOR OF THIS SYSTEM INVOF 40N LATITUDE AND BETWEEN 94W-99W LONGITUDE. LIKEWISE..A DRIER EASTERLY LOW-LEVEL FLOW IS ANTICIPATED TO BE WORKING INTO THIS SYSTEM ALONG ITS NORTHERN PERIPHERY THROUGH EARLY SUNDAY. VOJTESAK View attachment: 02042013 10Z HPC Day 7 QPF p168i.gif

All eyes turn W as the upper Ridge that has brought plentiful sunshine and a January thaw to our region breaks downs down and a deep trough and potent upper air disturbances moves onshore in California and drops SSE. At the base of that Western trough, a powerful storm system develops and attempts to close off. Further N along the British Colombia/Pacific NW Coast another potent storm system moves inland setting the stage for embedded short wave activity sliding S along the W flank of the deepening trough to our W. Moisture flowing off the Gulf returns in earnest at all levels in response to the Western trough and deepening storm across Arizona/Northern Mexico as pressures fall. The Euro and its ensembles are slower and deeper with this developing storm along with the Canadian and the GEFS. The operational GFS is a bit more progressive and a tad less stormy, but there are strong indications that the Euro idea is the more likely solution and additional Winter Storm RECON is tasked for the overnight hours tonight. Beginning Monday into Tuesday, cold air building across Western Canada is pulled S into the Great Basin while warm air with increasing Gulf moisture streams N into the Southern Plains. As we saw with the Christmas Storm, such a scenario tends to suggest winter weather in the Cold sector and a severe threat in the Warm sector. The eventual track of the upper closed cold core low will be key as to where the wintry mischief falls and exactly where the greatest threat for severe weather may unfold. Another fly in the ointment is the MJO and a noisy sub tropical jet. This is a very complex and complicated weather pattern, but the trends suggest a potent Winter Storm is ahead for next week with potential wide spread societal impacts from the West Coast into the Southern Rockies/Southern Plains on N and E into the Ohio/Tennessee Valley Regions.